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  • Articles  (324)
  • Oxford University Press  (324)
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  • ICES Journal of Marine Science  (121)
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  • 1
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    The reactions of shoaling adult cod to a pelagic trawl: implications for commercial trawling (2012)
    Oxford University Press
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    Publication Date: 2012-02-17
    Description: Rosen, S., Engås, A., Fernö, A., and Jörgensen, T. 2012. The reactions of shoaling adult cod to a pelagic trawl: implications for commercial trawling. – ICES Journal of Marine Science, 69: 303–312. The reactions of shoaling adult Atlantic cod to a pelagic trawl were measured during fishing off the north coast of Norway. Cod remaining in the trawl track dived at rates as fast as 0.35 m s –1 following vessel passage and swam away from the vessel, in the direction of the approaching trawl, at an average rate of 0.6 m s –1 . They did not attempt to swim ahead of the trawl as documented previously, but passed into the lower half of the trawl entrance and swam slowly in the direction of trawling at a rate of 0.2–0.5 m s –1 as the trawl's greater speed through water carried them deeper into the trawl. Shoals compressed vertically once inside the trawl, suggesting that packing density increased at least fourfold. Fish remained in the lower part of the trawl as they moved through its tapered section towards the codend, with little to no clearance above the bottom panel, but significant clearance beneath the top panel. Catches were sufficient to support commercial harvest, and the behaviour observed suggests that changes in trawl design and fishing strategy might improve fuel economy and species selectivity.
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  • 2
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    Common large-scale responses to climate and fishing across Northwest Atlantic ecosystems (2012)
    Oxford University Press
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    Publication Date: 2012-02-17
    Description: Shackell, N. L., Bundy, A., Nye, J. A., and Link, J. S. 2012. Common large-scale responses to climate and fishing across Northwest Atlantic ecosystems. – ICES Journal of Marine Science, 69: 151–152. Investigating whether there were common biological responses to climate and fishing across seven Northwest Atlantic ecosystems, a minimum/maximum autocorrelation factor analysis of biological indicators for each region revealed a common primary multivariate trend of a rapid change during the 1980s and early 1990s. There was a strong common pattern in the biological indicators responsible for the primary multivariate temporal trend in the five more northerly regions: an increase in the abundance of phytoplankton, an increase in biomass at mid-trophic levels, and a decline in predatory groundfish size. The common associations between patterns and drivers were fishing indices and the Atlantic Multidecadal Oscillation, but all associations weakened when co-varying drivers were held constant. The results are consistent with known long-term effects of intense fishing, such as a decline in average fish size and changes in species composition. Less fishing pressure has allowed some regions to recover to former predatory biomass levels since the late 1990s, but the bulk of the biomass consists of fewer species. However, fishing was not the only driver, and a more mechanistic understanding of how the climate affects lower trophic levels is needed to contextualize climate effects in heavily fished ecosystems.
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  • 3
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    Regional metier definition: a comparative investigation of statistical methods using a workflow applied to international otter trawl fisheries in the North Sea (2012)
    Oxford University Press
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    Publication Date: 2012-02-17
    Description: Deporte, N., Ulrich, C., Mahévas, S., Demanèche, S., and Bastardie, F. 2012. Regional métier definition: a comparative investigation of statistical methods using a workflow applied to international otter trawl fisheries in the North Sea. – ICES Journal of Marine Science, 69: 331–342. The European Common Fisheries Policy recognizes the importance of accounting for heterogeneity in fishing practices, and métier-based sampling is now at the core of the EU Data Collection Framework. The implementation of such an approach would require Member States to agree on the standard regional métier definitions and on practical rules to categorize logbook records into métiers. Several alternative approaches have been used in the past to categorize landings profiles, but no consensus has yet emerged. A generic open-source workflow is developed to test and compare a selection of methods, including principal components analysis (PCA), hierarchical agglomerative clustering (HAC), K -means, and Clustering LARge Applications (CLARA), and to provide simple allocation rules. This workflow is applied to a unique regional dataset consisting of bottom-trawl logbooks of five North Sea countries. No method proved to be infallible, but combining PCA with either CLARA or HAC performed best. For 2008, a hierarchical classification with 14 species assemblages is proposed. Discriminant analysis proved more robust than simple ordination methods for allocating a new logbook record into an existing métier. The whole approach is directly operational and could contribute to defining more objective and consistent métiers across European fisheries.
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  • 4
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    A reassessment of trends in the North Sea Large Fish Indicator and a re-evaluation of earlier conclusions (2012)
    Oxford University Press
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    Publication Date: 2012-02-17
    Description: Greenstreet, S. P. R., Rogers, S. I., Rice, J. C., Piet, G. J., Guirey, E. J., Fraser, H. M., and Fryer, R. J. 2012. A reassessment of trends in the North Sea Large Fish Indicator and a re-evaluation of earlier conclusions. – ICES Journal of Marine Science, 69: 343–345. Previous analysis of the Large Fish Indicator, the basis for the North Sea "fish communities" EcoQO, suggested a strong recovery between 2001 and 2008. Discovery of a mistake in this earlier analysis now suggests that this recovery is not as strong as first thought, but reanalysis of the corrected data still supports the majority of conclusions drawn in the original paper.
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  • 5
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    Classification of fish and non-fish acoustic tracks using discriminant function analysis (2012)
    Oxford University Press
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    Publication Date: 2012-02-17
    Description: Xie, Y., Michielsens, C. G. J., and Martens, F. J. 2012. Classification of fish and non-fish acoustic tracks using discriminant function analysis. – ICES Journal of Marine Science, 69: 313–322. Hydroacoustic data acquired for estimating fish populations contain information on both fish and non-fish targets, so sonar technicians traditionally rely on their knowledge of fish behaviour and experience with hydroacoustics to remove non-fish targets from the hydroacoustic data. This process is often labour-intensive and time-consuming, making real-time assessment of fish populations difficult. Simple solutions are not always available for all circumstances. However, the split-beam sonar data collected in the lower Fraser River, British Columbia, Canada, showed distinct signatures between actively swimming fish and non-fish objects such as drifting debris, surface bubbles, and stationary objects in the water column and off the river bottom. Acoustic tracks of fish and non-fish targets were characterized by differentiable statistical patterns that were amenable to discriminant function analysis (DFA). An application of DFA to segregate fish and non-fish targets detected by a split-beam sonar system in the lower Fraser River is presented, characteristics of user-identified fish and non-fish acoustic tracks being utilized as learning samples for the DFA. Also, a method to rank the discriminating power of individual variables is presented, providing guidance for constructing efficient and effective discriminant functions with variables that offer high discriminating power. The DFA yielded classification accuracies of 96% for fish and 91% for non-fish tracks and reduced the manual sorting time by 50–75%.
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  • 6
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    Declining silicate concentrations in the Norwegian and Barents Seas (2012)
    Oxford University Press
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    Publication Date: 2012-02-17
    Description: Rey, F. 2012. Declining silicate concentrations in the Norwegian and Barents Seas. – ICES Journal of Marine Science, 69: 208–212. Since 1990, a decline in silicate concentrations together with increasing salinities has been observed in the Atlantic water of the Norwegian and Barents Seas. This decline in silicate has been found to be related to the relative proportion in which eastern and western source water masses from the northeastern North Atlantic enter the Norwegian Sea.
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  • 7
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    Integrated risk analysis for rare marine species impacted by fishing: sustainability assessment and population trend modelling (2012)
    Oxford University Press
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    Publication Date: 2012-02-17
    Description: Zhou, S., Milton, D. A., and Fry, G. C. 2012. Integrated risk analysis for rare marine species impacted by fishing: sustainability assessment and population trend modelling. – ICES Journal of Marine Science, 69: 271–280. Risk assessment and conservation management of rare species are challenging due to a lack of data. We developed an integrated risk assessment approach to assess human impact on population sustainability of rare species. The approach involved two components: a quantitative sustainability assessment coupled with modelling trends in relative abundance. Both components took nil catches into account through zero-inflated statistical distributions that simultaneously modelled the zero and non-zero catches separately in submodels. The sustainability assessment used detection–non-detection data for population estimation and linked sustainability to easily collected life-history traits. This component provides an assessment of population sustainability at one point in time. The trend modelling applied zero-inflated negative binomial models to temporal trends in density and dispersion of species. It provided a complement to the static sustainability assessment. We applied this integrated approach to assess the risk to 14 species of rare, protected sea snakes incidentally caught in the Australian Northern Prawn Fishery. This approach can be applicable for risk assessment of many species with limited abundance data, a large number of absences and some presence–absence information only.
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  • 8
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    Feeding the world: what role for fisheries? (2012)
    Oxford University Press
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    Publication Date: 2012-02-17
    Description: Frid, C. L. J., and Paramor, O. A. L. 2012. Feeding the world: what role for fisheries? – ICES Journal of Marine Science, 69: 145–150. Fisheries (wild capture and aquaculture) deliver more than 110 million tonnes of food and around 15% of the dietary protein to the 7 billion people currently living on the planet. With the global population expected to peak at 9 billion by 2050, and 〉80% of global fish stocks currently fully or overexploited (and aquaculture is at least in part dependent on capture fisheries), the contribution of fisheries looks set to decline. The challenge is therefore determining how better management, an ecosystem perspective, and more efficient utilization of fisheries waste can support fisheries products continuing to contribute significantly to "feeding the world" up to and beyond the population peak.
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  • 9
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    Cormorant diet in relation to temporal changes in fish communities (2012)
    Oxford University Press
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    Publication Date: 2012-02-17
    Description: Boström, M. K., Östman, Ö., Bergenius, M. A. J., and Lunneryd, S-G. 2012. Cormorant diet in relation to temporal changes in fish communities. – ICES Journal of Marine Science, 69: 175–183. The stomach contents of 229 great cormorants ( Phalacrocorax carbo sinensis ) shot between March and October 2009 along the Swedish east coast were analysed for differences in diet between gender, age, and breeding phase. Sticklebacks ( Gasterosteus aculeatus and Pungitius pungitius ) were the most common prey, followed by eelpout ( Zoarces viviparus ), herring ( Clupea harengus membras ), and cyprinids (Cyprinidae). Diet did not differ between age and gender, but changed over the breeding season. The different phases explained around 10% of the total variation in stomach content between cormorants, suggesting no major shift in diet over the breeding season. The diet of cormorants in 2009 was compared with the results of a study conducted in the same area in 1992. There were evident changes in the diet between 1992 and 2009, with less perch ( Perca fluviatilis ) and cyprinids and more eelpout and herring in 2009. This change in diet could partly be related to changes in the fish community. The seasonal changes in diet composition of whole stomachs were less notable than in many previous studies, but long-term changes in the fish communities may induce changes in cormorant diet. It is clearly important to use stomach contents in areas with many small fish species for a comprehensive assessment of cormorant diet.
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  • 10
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    Use of the otolith shape analysis in stock identification of anglerfish (Lophius piscatorius) in the Northeast Atlantic (2012)
    Oxford University Press
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    Publication Date: 2012-02-17
    Description: Cañás, L., Stransky, C., Schlickeisen, J., Sampedro, M. P., and Fariña, A. C. 2012. Use of the otolith shape analysis in stock identification of anglerfish ( Lophius piscatorius ) in the Northeast Atlantic. – ICES Journal of Marine Science, 69: 250–256. The geographical variability in the anglerfish Lophius piscatorius otolith shape was investigated to examine biological evidence for the current separation into Northern and Southern stocks of L. piscatorius established in the Southwest European waters (Southern Shelf area) by the International Council for the Exploration of the Sea (ICES). In all, 629 otoliths of L. piscatorius (12–90 cm total length) from commercial fishing and research surveys were collected in two consecutive years, 2008 and 2009. The otolith shape was compared between stocks for differences in univariate descriptors using non-parametric analysis of covariance, as well as elliptical Fourier shape descriptors, through a metric multidimensional scaling and a linear discriminant analysis (LDA). The differences found in the otolith shape between Northern and Southern stocks were not large enough to hold the current status of L. piscatorius regarding stock definition in the Southern Shelf area, although homogeneous mixing between both stocks is not expected as there were significant differences between three univariate descriptors and the LDA was significant. These results are in agreement with the previous L. piscatorius stock identification studies (genetics, body morphology, and migratory behaviour), which do not support the current separation of these stocks but found substructures within the area.
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  • 11
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    Recruitment depressions in North Sea herring (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
    Description: Corten, A. 2013. Recruitment depressions in North Sea herring. – ICES Journal of Marine Science, 70:1–15. Two periods of sustained low recruitment have been observed in North Sea herring in recent history; one from 1971 to 1979 and one that started in 2002 and continued up until the most recent year for which information is available (2010). This paper compares both periods of recruitment depression and considers the possible causes for each of them. The first depression (1971–1979) has been commonly ascribed to insufficient egg production by the depleted parent stock. However, recruitment to the central and northern populations was probably also affected by an environmental factor. There are indications of a reduced Atlantic inflow into the northwestern North Sea at the time of the depression. This could have affected survival of the larvae by slowing down their transport to the nursery areas in the southeastern North Sea. For the second period (2002–2010), the low recruitment has been ascribed to an increase in temperature and/or a regime shift in the ecosystem. An alternative explanation could be predation by the large stock of adult herring on its own larvae.
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  • 12
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    Review of integrated size-structured models for stock assessment of hard-to-age crustacean and mollusc species (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
    Description: Punt, A. E., Huang, T., and Maunder, M. N. 2013. Review of integrated size-structured models for stock assessment of hard-to-age crustacean and mollusc species. – ICES Journal of Marine Science, 70:16–33. Crustaceans and molluscs such as crabs, rock lobsters, prawns, abalone, and oysters constitute large and valuable fisheries. However, assessments of these species are hampered because they cannot be production aged, in contrast to many teleosts. The major data sources for these species, in addition to catch and abundance index data, are the size compositions of the catches and of any fishery-independent indices. Assessments of such species have been conducted using age-based methods of stock assessment, as well as surplus production models. However, size-structured methods are now preferred because they can make full use of size-composition data, are able to integrate multiple sources of data, and produce the types of outputs which are needed for management purposes. An advantage of size-based models over age-based models is that all processes can be size-based, and these processes can modify the (unmodelled) size-at-age distribution. We review these methods, highlighting the choices that need to be made when developing integrated size-structured stock assessments, the data sources which are typically available and how they are used for parameter estimation, and contrast a number of such assessments worldwide.
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  • 13
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    Fish avoidance of research vessels and the efficacy of noise-reduced vessels: a review (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
    Description: De Robertis, A. and Handegard, N. O. 2013. Fish avoidance of research vessels and the efficacy of noise-reduced vessels: a review. – ICES Journal of Marine Science, 70:34–45. It has long been recognized that fish can avoid approaching vessels and that these behaviours can bias fishery surveys. Underwater noise is considered the primary stimulus, and standards for research vessel noise have been established to minimize fish reactions. We review the literature on fish reactions to vessels appearing since these recommendations were made, focusing on acoustic surveys, and compare how fish react to noise-reduced and conventional vessels. Reactions to approaching vessels are variable and difficult to predict. However, the behaviour can bias acoustic abundance measurements, and should be considered when performing acoustic surveys. The few comparisons of acoustic abundance measurements from noise-reduced and conventional vessels are contradictory, but demonstrate that the sound pressure level, on which the noise-reduction criterion is based, is insufficient to explain how fish react to survey vessels. Further research is needed to identify the stimuli fish perceive from approaching vessels and the factors affecting whether fish perceiving these stimuli will react before further recommendations to reduce vessel-avoidance reactions can be made. In the interim, measurement of the biases introduced by fish avoidance reactions during surveys, and timing of surveys when fish are in a less reactive state, may reduce errors introduced by vessel avoidance.
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  • 14
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    How do cephalopods become available to seabirds: can fish gut contents from tuna fishing vessels be a major food source of deep-dwelling cephalopods? (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
    Description: Xavier, J. C., Cherel, Y., Roberts, J., and Piatkowski, U. 2013. How do cephalopods become available to seabirds: can fish gut contents from tuna fishing vessels be a major food source of deep-dwelling cephalopods? – ICES Journal of Marine Science, 70:46–49. Cephalopods are important prey for numerous seabird species. However, the physical mechanisms by which cephalopods (particularly species considered as deep-dwelling) become available to seabirds are poorly understood, and it has recently been suggested that the discarded stomachs of gutted fish captured by tuna longliners can be a major source of deep-dwelling species. Here, we identify some deep-dwelling cephalopods that appear in the diet of seabirds, review the current knowledge of their vertical distribution, and compare the stomach contents of commercially captured tuna with those of seabirds foraging in the same area. The limited available information leads us to conclude that tuna longliners are unlikely to be a major source of deep-dwelling cephalopods for seabirds. However, much more information is required on the ecology of seabird prey, particularly commercially unexploited cephalopod species, which may be obtained from scientific cruises devoted to cephalopod biological research. In addition multispecies/foodweb modelling studies may be required to explore potential interactions between seabirds, their predators and prey, and commercial fishing operations.
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  • 15
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    Age determination of Atlantic halibut (Hippoglossus hippoglossus L.) along the coast of Norway: status and improvements (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
    Description: Karlson, S., Michalsen, K., and Folkvord, A. 2013. Age determination of Atlantic halibut ( Hippoglossus hippoglossus L.) along the coast of Norway: status and improvements. – ICES Journal of Marine Science, 70:50–55. This study re-evaluates the current ageing methodology for the Atlantic halibut, Hippoglossus hippoglossus . The traditional method is through surface readings of otoliths, but, based on new experiments with different preparation treatments and techniques, a more accurate and cost-efficient procedure for the age determination of Atlantic halibut is proposed.
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  • 16
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    ITQs in Swedish demersal fisheries (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
    Description: Waldo, S., and Paulrud, A. 2013. ITQs in Swedish demersal fisheries. – ICES Journal of Marine Science, 70:68–77. Individual transferable quota (ITQ) is a management measure that is widely discussed, not least in the reform of the European Common Fisheries Policy. While the system is expected to reduce overcapacity and improve economic performance, questions are raised concerning the future of small-scale fisheries. This paper uses a model for Swedish fisheries (the Swedish Resource Rent Model for the Commercial Fisheries, SRRMCF) where the economics and fleet structure in a potential Swedish ITQ-system are analysed. The model is an optimization model based on linear programming and data from the European Union's data collection framework. The modelling approach can readily be used by other member states. Three main conclusions can be drawn on how ITQs will affect fisheries: The fishing fleet measured in number of vessels will decrease by approximately 30–50%. Profitability will increase so that the fishing industry will be able to provide competitive wages and make a financial contribution to fisheries management. The system can be designed so that small-scale fisheries are not disadvantaged.
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  • 17
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    A Metier-Sustainability-Index (MSI25) to evaluate fisheries components: assessment of cases from data-poor fisheries from southern Europe (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
    Description: Tzanatos, E., Castro, J., Forcada, A., Matic-Skoko, S., Gaspar, M., and Koutsikopoulos, C. 2013. A Métier-Sustainability-Index (MSI25) to evaluate fisheries components: assessment of cases from data-poor fisheries from southern Europe. – ICES Journal of Marine Science, 70:78–98. The present work presents an integrated comparative assessment of the sustainability of fishing tactics or métiers (combinations of area, season, fishing gear, and target species). An index, which includes biological, conservation, socioeconomic, and management criteria, was created for this purpose: the "Métier Sustainability Index" (MSI25). It was designed using the traffic lights approach and comprises 25 indicators that refer to the "health" of the fisheries. Additionally, the MSI25 provides an indication of the "certainty" of that information with regard to the data type/heterogeneity. Subsequently, the index was tested using data from six case studies (81 métiers) from the Mediterranean and the Atlantic. The index showed that 63.0% of the métiers were "sustainable", 21.0% were "unsustainable" and 16.0% were "under pressure"; 59.3% of characterizations were considered as "certain". The index evaluation showed significant differences between areas and gears. This paper considers the characteristics of the datasets used, the case management status, and the applicability of the index in improving the management of specific fisheries. Overall, the MSI25 was found to be a useful tool for the evaluation and management of highly heterogeneous fisheries and data from various sources and types.
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    A trap with a twist: evaluating a bycatch reduction device to prevent rockfish capture in crustacean traps (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
    Description: Favaro, B., Duff, S. D., and Côté, I. M. 2013. A trap with a twist: evaluating a bycatch reduction device to prevent rockfish capture in crustacean traps. – ICES Journal of Marine Science, 70:114–122. Bycatch, or the incidental capture of non-target species, occurs in fisheries around the world, with often detrimental ecological consequences. Bycatch reduction devices (BRDs) that increase catch specificity have been used successfully in some fisheries, and the development of such devices remains an important component of the global effort to reduce bycatch rates. We tested novel devices designed to exclude juvenile rockfish ( Sebastes spp.) from traps used to catch spot prawns ( Pandalus platyceros ), a commercially important species in British Columbia, Canada. The devices included reductions in trap opening sizes and novel bent-tunnel openings. Reducing trap opening size did not affect bycatch rates of rockfish or other non-target fish species. In contrast, bent-tunnel BRDs eliminated rockfish bycatch, and two of the bent-tunnel variants also excluded other fish species. However, prawn catch rates were reduced in all modified gear, and large prawns were often excluded more than small prawns. Videos recorded in situ revealed that prawn attempts to enter traps took longer and were more likely to fail in BRD-equipped than in unmodified traps. We conclude that bent-tunnel BRDs have the potential to be useful, but improvements are needed to increase prawn catch to levels similar to that of unmodified traps.
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    Effects of a large-scale and offshore marine protected area on the demersal fish assemblage in the Southwest Atlantic (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
    Description: Alemany, D., Iribarne, O. O., and Acha, E. M. 2013. Effects of a large-scale and offshore marine protected area on the demersal fish assemblage in the Southwest Atlantic. – ICES Journal of Marine Science, 70:123–134. There are few extensive and offshore located marine protected areas (MPAs) in the world oceans and their performance is still being debated. We evaluated the effects of a large-scale offshore MPA located on the Southwest Atlantic Patagonian Shelf (43°S 63°W) on the demersal fish assemblage. Compliance of the Patagonian MPA was assessed by analysing eight years of satellite vessel monitoring system (VMS; 2000–2008) data, which showed compliance and fishing effort concentrated near the protection boundaries. MPA effects were studied by employing a five year database collected by a scientific research vessel in protected and fishing locations, before and after the MPA establishment. We assessed 152 scientific trawling stations using multivariate analysis of fish assemblage structure, fish abundance (discriminating target and non-target species), and mean size and proportion of juveniles of the target species (Argentine hake, Merluccius hubbsi ). The identified MPA effects were a trend towards increasing abundance of the demersal fish assemblage, the target and non-target fish species, and hake juvenile size, and a higher proportion of juveniles aged 2+ inside the MPA. These positive trends support the case for offshore, large-scale MPAs.
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    Stock identification of wahoo (Acanthocybium solandri) in the Pacific and Indian Oceans using morphometrics and parasites (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
    Description: Zischke, M. T., Griffiths, S. P., Tibbetts, I. R., and Lester, R. J. G. 2013. Stock identification of wahoo ( Acanthocybium solandri ) in the Pacific and Indian Oceans using morphometrics and parasites. – ICES Journal of Marine Science, 70:164–172. The wahoo ( Acanthocybium solandri ) is an increasingly important by-product species of tropical pelagic fisheries worldwide. However, specific management of the species is currently hindered by a dearth of information on basic biology and stock structure. This study examined the stock structure of wahoo using morphometric characters and parasite fauna from fish collected in three regions of the western Pacific, and one region in each of the eastern Pacific and eastern Indian Oceans. Similar morphometric measurements and parasite abundance of wahoo collected off eastern Australia suggest they may form part of a single phenotypic stock in the western Pacific Ocean. Morphometric measurements and parasite fauna were significantly different among wahoo from the western Pacific and eastern Pacific Oceans, suggesting multiple discrete phenotypic stocks despite genetic homogeneity. Assessing fish from a range of regions throughout the Pacific Ocean may help discriminate stock boundaries in this region. Future research using complementary techniques, such as otolith microchemistry and genetic microsatellites, may improve our understanding of the global stock structure of wahoo to suitably inform regional fishery management organizations.
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    A comparative analysis of marine fish species susceptibilities to discard mortality: effects of environmental factors, individual traits, and phylogeny (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
    Description: Benoît, H. P., Plante, S., Kroiz, M., and Hurlbut, T. 2013. A comparative analysis of marine fish species susceptibilities to discard mortality: effects of environmental factors, individual traits, and phylogeny. – ICES Journal of Marine Science, 70:99–113. Determining the sustainability of fishing mortality for discards requires information on discard amounts as well as capture and release mortality rates. Formal estimates of these rates are costly and only available for a limited number of species and fisheries. In their absence, proxies for discard mortality could inform risk assessments of fishing mortality sustainability for discarded species. Here, time-to-mortality (TM) was assessed for 48 marine fish species exposed to air following capture during an annual multi-species bottom-trawl survey. Species-specific estimates of TM were related qualitatively to more formal estimates of discard mortality from commercial fisheries, confirming the use of TM as a proxy. The effects on TM of species and individual traits, phylogenetic similarity (proxy for traits not explicitly included in the analysis) and environmental factors related to capture were also assessed. Much of the observed individual variability was explained by intraspecific and interspecific positive relationships between body size and TM. Sedentary species and those lacking a gas bladder or deciduous scales had greater TM. Effects of phylogeny and capture depth and temperature were also found. This study demonstrates how reliable proxies of discard mortality rate can be readily obtained in the field or estimated from relevant covariates.
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    Habitat selection by hooded seals (Cystophora cristata) in the Northwest Atlantic Ocean (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
    Description: Andersen, J. M., Wiersma, Y. F., Stenson, G. B., Hammill, M. O., Rosing-Asvid, A., and Skern-Maurizen, M. 2013. Habitat selection by hooded seals ( Cystophora cristata ) in the Northwest Atlantic Ocean. – ICES Journal of Marine Science, 70:173–185. We examined annual habitat use for 65 hooded seals (32 adult females, 17 adult males, and 16 juveniles) equipped with satellite relay data loggers (SRDLs) in spring or summer during five field seasons (2004–2008). A combined approach using first passage time (FPT) analysis and a generalized additive model (GAM) was applied to test for habitat selection, with a focus on environmental parameters of depth, slope, ice, sea surface temperature (SST), and chlorophyll. The models were run on adult males, adult females, and juveniles separately, and the results identified SST, depth, and chlorophyll as the most important factors influencing habitat selection across all categories. Furthermore, males and females preferred similar habitat conditions, but were separated geographically, and by depth, at various times of the year. Males appeared to be more localized in their habitat use patterns, focusing their search effort in areas of complex seabed relief such as Baffin Bay, Davis Strait, and the Flemish cap, while females concentrated their search effort along shelf areas (e.g. the Labrador shelf). These findings support our hypothesis that hooded seals prefer areas where topography and oceanographic processes create favourable foraging conditions.
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  • 23
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    Movements and site fidelity of harbour seals (Phoca vitulina) in Kattegat, Denmark, with implications for the epidemiology of the phocine distemper virus (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
    Description: Dietz, R., Teilmann, J., Andersen S. M. Rigét, F., and Olsen, M. T. 2013. Movements and site fidelity of harbour seals ( Phoca vitulina ) in Kattegat, Denmark, with implications for the epidemiology of the phocine distemper virus. – ICES Journal of Marine Science, 70:186–195. Twenty-seven harbour seals were caught and tagged at the island of Anholt in central Kattegat, Denmark, the epicentre of the phocine distemper virus (PDV) outbreaks in 1988 and 2002 that killed 50–60% of the populations. The satellite tagging shows that harbour seals from Anholt moved widely across Kattegat with a maximum distance of 249 km from the tagging haul-out site. Overall, females travelled over a wider area compared with males [90% kernel home range (KHR) females, 5189 km 2 ; males, 3293 km 2 ). KHR calculated for yearlings (6414 km 2 ) is larger than for subadults (2534 km 2 ), which again is larger than for adult seals (1713 km 2 ), showing a strong site fidelity, indicating limited gene flow between haul-out sites. Distances moved and home range sizes increased across autumn, peaked in February–March, and decreased through spring. During the breeding season in spring, all seals were very stationary around Anholt. The onset of the PDV epizootics in 1988 and 2002 took place when the Anholt harbour seals congregate on the Island during April. Anholt seal were also documented to have contact with infected seal locations at Hesselø, Læsø, and the Swedish west coast, although this contact takes place during winter prior to the documented summer outbreaks.
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    On the use of omnidirectional sonars and downwards-looking echosounders to assess pelagic fish distributions during and after midwater trawling (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
    Description: Stockwell, J. D., Weber, T. C., Baukus, A. J., and Jech, J. M. 2013. On the use of omnidirectional sonars and downwards-looking echosounders to assess pelagic fish distributions during and after midwater trawling. – ICES Journal of Marine Science, 70:196–203. Small pelagic fish can play an important role in the structure and function of ecosystems, and there is increasing interest in their non-market value. At the scale of fish aggregations, however, the impact of fishing has received relatively little attention, with most effort devoted to impacts of vessel and gear avoidance on stock size estimates. We used concurrent deployment of a downwards-looking echosounder (Simrad ES60 system) and an omnidirectional sonar (Simrad SP90 system) during commercial pairtrawling operations for Atlantic herring ( Clupea harengus ) in the Gulf of Maine to examine their potential for studying the impacts of fishing on herring aggregations. We compared a number of aggregation metrics to illustrate similarities and differences between the two systems, and then qualitatively examined their properties during and after pairtrawling events to illustrate potential applications. Our results suggest that using both downwards-looking and omnidirectional systems provides complementary information on fish aggregation metrics. Future applications of these systems in before–after–control-impact (BACI) designs may help inform management agencies when evaluating potential impacts of fishing at the time and space scales of pelagic fish aggregations.
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    A distorted wave Born approximation target strength model for Bering Sea euphausiids (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
    Description: Smith, J. N., Ressler, P. H., and Warren, J. D. 2013. A distorted wave Born approximation target strength model for Bering Sea euphausiids. – ICES Journal of Marine Science, 70:204–214. Acoustic surveys monitor euphausiid populations in the Bering Sea because of their importance as prey for walleye pollock and other organisms. Various scattering models exist to convert acoustic backscatter data to estimates of euphausiid numerical density or biomass, but a target strength (TS) model specific to Bering Sea euphausiids has not been available. This study parameterized a distorted wave Born approximation (DWBA) scattering model using physical (length and body shape) and material (density contrast, g , and sound speed contrast, h ) properties measured from live euphausiids. All model parameters (length, shape, material properties, orientation) were evaluated for their effect on predicted TS. A polynomial function was used to describe animal shape and produced smaller TS estimates compared to a taper function, as is traditionally used in DWBA scattering models of euphausiids. Animal length was positively correlated with TS, but variations in other parameters (including material properties and orientation) also produced large changes in TS. Large differences in TS between estimates calculated using measured versus literature material property values caused large variations in acoustic estimates of euphausiid numerical densities (animals m –3 ) which emphasizes the importance of collecting site-specific g and h measurements when possible.
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    Fitting a non-parametric stock-recruitment model in R that is useful for deriving MSY reference points and accounting for model uncertainty (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
    Description: Cadigan, N. G. 2013. Fitting a non-parametric stock–recruitment model in R that is useful for deriving MSY reference points and accounting for model uncertainty. – ICES Journal of Marine Science, 70:56–67. Modelling the relationship between parental stock size and subsequent recruitment of fish to a fishery is often required when deriving reference points, which are a fundamental component of fishery management. A non-parametric approach to estimate stock–recruitment relationships is illustrated using a simulated example and nine case studies. The approach preserves compensatory density dependence in which the recruitment rate monotonically decreases as stock size increases, which is a basic assumption of commonly used parametric stock–recruitment models. The implications of the non-parametric estimates on maximum sustainable yield (MSY) reference points are illustrated. The approach is used to provide non-parametric bootstrapped confidence intervals for reference points. The efficacy of the approach is investigated using simulations. The results demonstrate that the non-parametric approach can provide a more realistic estimation of the stock–recruitment relationship when informative data are available compared with common parametric models. Also, bootstrap confidence intervals for MSY reference points based on different parametric stock–recruitment models often do not overlap. The confidence intervals based on the non-parametric approach tend to be much wider, and reflect better uncertainty due to stock–recruit model choice.
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    The role of behavioural flexibility in a whole of ecosystem model (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
    Description: van Putten, I. E., Gorton, R. J., Fulton, E. A., and Thebaud, O. 2013. The role of behavioural flexibility in a whole of ecosystem model. – ICES Journal of Marine Science, 70:150–163. The predictive accuracy of complex fisheries models developed to anticipate the effects of changing fishery regulations appears to depend on a solid understanding of the processes and feedback systems linking biological and physical information to resource user. Many fisher decisions are modelled in the human component of the models, including inertia, or location choice flexibility. We unpack a whole of ecosystem system model and explore how location choice flexibility in fleet behaviour (sticking to the same seasonal and spatial distribution of fishing) affects outcomes such as catches and income levels and variability. Our analysis shows that the interpretation is not straightforward, and the relationship between behavioural flexibility and income level and income variability has to be considered in the context of three main fleet characteristics: profitability; how diversified the fleet is; and growing or declining target species biomass. We contend that making behavioural flexibility sensitive to the health of the stock and fleet profitability could potentially improve accuracy of large whole of ecosystem models such as Atlantis.
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    Allometric relations and consequences for feeding in small pelagic fish in the Bay of Biscay (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
    Description: Bachiller, E. and Irigoien, X. 2013. Allometric relations and consequences for feeding in small pelagic fish in the Bay of Biscay. – ICES Journal of Marine Science, 70:232–243. The body size of fish is an important factor in determining their biology and ecology, as predators eat prey smaller than themselves. Predator mouth size restricts the availability of possible prey. In this paper we provide the allometric relationships of eight common, small pelagic fish species in the Bay of Biscay. In addition, we describe the predator-prey size ratios for different species, and we determine changes in their ratio-based trophic-niche breadth with increasing body size. Results suggest that gape size does not totally determine the predator-prey size ratio distribution, but predators use the entire available prey size range, including the smallest. As they grow they simply incorporate larger prey as their increased gape size permits. Accordingly, a large degree of overlap was found in the diet composition in terms of size and predator-prey ratios, even between fish of different sizes. Of the species studied, only horse mackerels seem to be clearly specialized in relatively large prey.
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    Ecosystem status and functioning: searching for rules of thumb using an intersite comparison of food-web models of Northeast Atlantic continental shelves (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
    Description: Lassalle, G., Lobry, J., Le Loc'h, F., Mackinson, S., Sanchez, F., Tomczak, M. T., and Niquil, N. 2013. Ecosystem status and functioning: searching for rules of thumb using an intersite comparison of food-web models of Northeast Atlantic continental shelves. – ICES Journal of Marine Science, 70:135–149. This work aimed to provide a better understanding of how the structure and function of marine ecosystems and trophic control mechanisms influence their response to perturbations. Comparative analysis of Ecopath models of four Northeast Atlantic ecosystems was used to search for rules of thumb defining the similarities and differences between them. Ecosystem indicators, related to the ecology of species interactions, were derived from these models and compared. Two main questions were addressed. (i) What are the main energy pathways and mechanisms of control? (ii) Do these ecosystems exhibit the widespread and potentially stabilizing food-web structure such that top predators couple distinct energy pathways? A strong bentho-pelagic coupling operated over the Bay of Biscay Shelf, while energy reached higher trophic levels mostly through pelagic compartments, in northern areas. Zooplankton was demonstrated to be trophically important in all ecosystems, acting as a regulator of the abundance of small pelagic fish. A latitudinal pattern in flow control was highlighted by this analysis, with a significant contribution of top-down effect at higher latitudes. This top-down control of the Baltic Sea, combined with the fact that this ecosystem did not exhibit the potentially stabilizing two-channel structure, suggested a non-stable environment.
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    Community N2 fixation and Trichodesmium spp. abundance along longitudinal gradients in the eastern subtropical North Atlantic (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
    Description: Fernández, A., Graña, R., Mouriño-Carballido, B., Bode, A., Varela, M., Domínguez-Yanes, J. F., Escánez, J., de Armas, D., and Marañón, E. 2013. Community N 2 fixation and Trichodesmium spp. abundance along longitudinal gradients in the eastern subtropical North Atlantic. – ICES Journal of Marine Science, 70:223–231. We have determined planktonic community N 2 fixation, Trichodesmium abundance, the concentration and vertical diffusive flux of phosphate, and satellite-derived estimates of atmospheric concentration of dust along two longitudinal transects in the eastern subtropical North Atlantic during November 2007 and from April–May 2008. Trichodesmium abundance was particularly low (〈3 trichome l –1 ) during the spring 2008 cruise, when low sea surface temperatures were recorded and vertical stratification was less marked. However, community N 2 fixation was always measurable, albeit low compared with other regions of the tropical Atlantic. The average, vertically-integrated N 2 fixation rate was 1.20 ± 0.48 µmol N m –2 d –1 in autumn 2007 and 8.31 ± 3.31 µmol N m –2 d –1 in spring 2008. The comparison of these rates of diazotrophy with the observed Trichodesmium abundances suggests that other, presumably unicellular, diazotrophs must have contributed significantly to community N 2 fixation, at least during the spring 2008 cruise. Satellite data of atmospheric dust concentration suggested similar rates of atmospheric deposition during the two surveys. In contrast, vertical diffusive fluxes of phosphate were 5-fold higher in spring than in autumn (14.2 ± 12.1 µmol P m –2 d –1 and 2.8 ± 2.6 µmol P m –2 d –1 , respectively), which may have stimulated N 2 fixation. These findings agree with the growing view that N 2 fixation is a more widespread process than the distribution of Trichodesmium alone may suggest. Our data also suggest a role for phosphorus supply in controlling the local variability of diazotrophic activity in a region subject to relatively high atmospheric inputs of iron.
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    A correction to "Assessment of goose barnacle (Pollicipes pollicipes Gmelin, 1789) stocks in management plans: design of a sampling program based on the harvesters' experience" (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
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    In situ target strength estimates of visually verified orange roughy (2012)
    Oxford University Press
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    Publication Date: 2012-12-12
    Description: Macaulay, G. J., Kloser, R. J., and Ryan, T. E. 2013. In situ target strength estimates of visually verified orange roughy. – ICES Journal of Marine Science, 70:215–222. The first estimates of orange roughy ( Hoplostethus atlanticus ) target strength at 38 and 120 kHz with visual verification were obtained from a self-contained echosounder and video camera system affixed to a demersal trawl towed through dense aggregations of spawning orange roughy. Mean target strength estimates were obtained from 24 tracks of orange roughy containing 83 echoes. The mean target strength at 38 kHz was –52.0 dB with a 95% confidence interval of –53.3 to –50.9 dB for fish with a mean length of 33.9 cm. At 120 kHz the mean target strength was –47.9 dB (confidence interval of –48.8 to –46.4 dB). This work makes two significant advances: in situ TS measurements have been made that can be confidently attributed to orange roughy, and using a trawl to herd orange roughy past the system resolved the previously intractable problem of fish avoidance.
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    Demersal fish biodiversity: species-level indicators and trends-based targets for the Marine Strategy Framework Directive (2012)
    Oxford University Press
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    Publication Date: 2012-10-13
    Description: Greenstreet, S. P. R., Rossberg, A. G., Fox, C. J., Le Quesne, W. J. F., Blasdale, T., Boulcott, P., Mitchell, I., Millar, C., and Moffat, C. F. 2012. Demersal fish biodiversity: species-level indicators and trends-based targets for the Marine Strategy Framework Directive. – ICES Journal of Marine Science, 69: 1789–1801. The maintenance of biodiversity is a fundamental theme of the Marine Strategy Framework Directive. Appropriate indicators to monitor change in biodiversity, along with associated targets representing "good environmental status" (GES), are required to be in place by July 2012. A method for selecting species-specific metrics to fulfil various specified indicator roles is proposed for demersal fish communities. Available data frequently do not extend far enough back in time to allow GES to be defined empirically. In such situations, trends-based targets offer a pragmatic solution. A method is proposed for setting indicator-level targets for the number of species-specific metrics required to meet their trends-based metric-level targets. This is based on demonstrating significant departures from the binomial distribution. The procedure is trialled using North Sea demersal fish survey data. Although fisheries management in the North Sea has improved in recent decades, management goals to stop further decline in biodiversity, and to initiate recovery, are yet to be met.
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    Environmental effects on recreational squid jigging fishery catches (2012)
    Oxford University Press
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    Publication Date: 2012-10-13
    Description: Cabanellas-Reboredo, M., Alós, J., Palmer, M., and Morales-Nin, B. 2012. Environmental effects on recreational squid jigging fishery catches. – ICES Journal of Marine Science, 69: 1823–1830. Experimental fishing sessions simulating the operating procedures of the recreational fishery for the European squid that operates at inshore Palma Bay (Balearic Islands, Spain) were conducted to investigate the effects of environmental variables on squid catches. The catch per unit of effort (cpue) of recreational-like jigging sessions showed a seasonal pattern (higher cpue during colder months). Two alternative hypotheses can explain such a pattern. First, squid could migrate inshore during colder months to seek spatio-temporal windows within which the sea temperature maximize spawning success. Second, the timing of the seasonal reproductive peak and the growth rate of any given cohort would result in a higher percentage of squid whose body size is greater than the gear-specific vulnerability threshold during the colder months. The combination of environmental variables that maximized cpue was a low sea surface temperature, a low windspeed, low atmospheric pressure, and days close to the new moon. A specific period of the day, narrowly around sunset, favoured the catches. Within this narrow period, the sunlight is still sufficient to allow the recreational fishing lures to be effective, and the squid have already shifted to a more active pattern of movement characteristic of the night-time period.
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    Lengths at maturity and conversion factors for skates (Rajidae) around the British Isles, with an analysis of data in the literature (2012)
    Oxford University Press
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    Publication Date: 2012-10-13
    Description: McCully, S. R., Scott, F., and Ellis, J. R. 2012. Lengths at maturity and conversion factors for skates (Rajidae) around the British Isles, with an analysis of data in the literature. –ICES Journal of Marine Science, 69: 1812–1822. Biological data on skates (Rajidae) from around the British Isles were collected between 1992 and 2010. The relationship between total length and weight for nine species ( Amblyraja radiata , Dipturus batis- complex, Leucoraja fullonica , L. naevus , Raja brachyura , R. clavata , R. microocellata , R. montagui , and R. undulata ) are provided for each sex and ICES ecoregion (when significantly different). Conversion factors for disc width to total length are provided. The lengths at first maturity and of the largest immature skates are reported for each sex, and the lengths at 50% maturity are estimated. Spatial differences in the length at maturity of R. clavata (females only) and L. naevus (both sexes) were observed. The lengths at maturity are discussed in relation to the results of earlier studies, and methodological differences are considered to have influenced reputed decreases in the length at maturity. A more standardized approach to collecting and reporting maturity information is required if potential spatial differences and temporal changes are to be investigated.
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    Assessment of goose barnacle (Pollicipes pollicipes Gmelin, 1789) stocks in management plans: design of a sampling program based on the harvesters' experience (2012)
    Oxford University Press
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    Publication Date: 2012-10-13
    Description: Parada, J. M., Outeiral, R., Iglesias, E., and Molares, J. 2012. Assessment of goose barnacle ( Pollicipes pollicipes Gmelin, 1789) stocks in management plans: design of a sampling program based on the harvesters' experience. – ICES Journal of Marine Science, 69: 1840–1849. Management plans of coastal marine resources require a wealth of information on socioeconomic topics, harvesting activities, population dynamics, and stock status. Moreover, the information provided by technical experts must take into account the needs of the managers. It must also adapt to schedules to serve a useful purpose. In many cases, the methodologies used by research teams are not directly applicable as they may be too complicated, aimed at specific objectives related to basic scientific work, or too costly to apply to long-term monitoring of extensive shellfish beds. Also, rocky coastlines exposed to heavy wave action preclude the use of sampling techniques that involve time-consuming data collection. This paper proposes a quick and simple methodology for gathering data in the field, based on the knowledge of the harvesters, to obtain stock assessments in keeping with their information needs. This methodology uses coverage percentage as an abundance index and weighting factor for the biometric information gathered from 50 specimens in each sampling. The sampling design uses the knowledge of the harvesters to define homogeneous strata. The results are in agreement with both the scientific-technical knowledge and the harvesters' knowledge of the populations being analysed.
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    Collapse of allis shad, Alosa alosa, in the Gironde system (southwest France): environmental change, fishing mortality, or Allee effect? (2012)
    Oxford University Press
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    Publication Date: 2012-10-13
    Description: Rougier, T., Lambert, P., Drouineau, H., Girardin, M., Castelnaud, G., Carry, L., Aprahamian, M., Rivot, E., and Rochard, E. 2012. Collapse of allis shad, Alosa alosa , in the Gironde system (southwest France): environmental change, fishing mortality, or Allee effect? – ICES Journal of Marine Science, 69: 1802–1811. At the end of the 20th century the allis shad population in the Gironde was the largest in Europe. During the first decade of the 21st century, catches declined dramatically by two orders of magnitude, and a fishery moratorium was implemented in 2008. This deterioration in the status of the stock was confirmed by three independent assessments (abundance of juveniles and of potential and effective spawners). Three hypotheses on the cause of the collapse were examined: (i) an environmental change in freshwater and/or in the estuary; (ii) an increase in marine and/or estuarine mortality; and (iii) the presence of an Allee effect. Changes in flow, temperature, and water quality over the period were inconclusive, but remain a possible causative factor. The instantaneous rate of marine (mean: 0.7 year –1 , s.e. 0.1 year –1 ) and estuarine (mean: 2.6 year –1 , s.e. 0.1 year –1 ) mortalities showed no trend between 1991 and 2003. Nevertheless, the past high estuarine (fishing) mortalities combined with a demographic Allee effect in the reproduction dynamics could explain the population collapse and hamper the stock recovery under the moratorium. This conclusion is, however, tentative as it was not possible to prove the presence of the density-dependent mechanism associated with the demographic Allee effect.
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    Atlantic cod (Gadus morhua) feed during spawning off Newfoundland and Labrador (2012)
    Oxford University Press
    Details
    Publication Date: 2012-10-13
    Description: Krumsick, K. J., and Rose, G. A. 2012. Atlantic cod ( Gadus morhua ) feed during spawning off Newfoundland and Labrador. – ICES Journal of Marine Science, 69: 1701–1709. We test a current assumption that Atlantic cod ( Gadus morhua ) off Newfoundland and Labrador, Canada, do not feed during the protracted spawning season (March–September). Stomach contents were analysed from 10 473 cod from four Northwest Atlantic Fisheries Organization regions (2J, 3K, 3L, and 3Ps) over 9 years from which gonads were also analysed to determine sex and maturity status. Adult cod in spawning condition did feed in all regions, usually at rates equivalent to or even greater than non-spawning fish and juveniles. Both sexes fed during spawning, though females consumed lesser amounts. Regional differences were evident. The total fullness index was greater in the northern (2J) than the southern (3Ps) region, with no consistent differences between spawners and non-spawners. The most southerly region (3Ps) exhibited the greatest prey diversity, the northern region (2J) the least. Shrimp was the major diet item in the northern regions. Capelin, zooplankton, crab, and other fish increased in importance to the south. Differences in prey items between non-spawning and spawning individuals of both sexes were possibly related to spawning behaviour. Models using consumption rates should not assume that cod do not feed during the protracted spawning season in these waters.
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    Feeding hotspots for four northwest Atlantic groundfish species (2012)
    Oxford University Press
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    Publication Date: 2012-10-13
    Description: Methratta, E.T., and Link, J.S. 2012. Feeding hotspots for four northwest Atlantic groundfish species. — ICES Journal of Marine Science, 69: 1710–1721. We used predator distribution and stomach content data to estimate the annual per capita rate of consumption for four representative predator species from the northwestern Atlantic Ocean, and considered how consumption is influenced by depth, bottom salinity, sediment grain size, location variables, and species-specific diet components. We found that geographic variables and species-specific prey resources were significantly associated with consumption rates, a pattern consistent with predator-prey theory. Prey categories comprised of fish were particularly important for a more mobile predator (silver hake Merluccius bilinearis) , whereas benthic invertebrate prey were consistently important for a more sedentary predator (little skate Raja erinacea ). Hotspots in consumption rates that overlap with particular prey resources were highlighted by the significance of location variables (longitude) for winter flounder Pseudopleuronectes americanus , silver hake, little skate, and sea raven Hemitripterus americanu s. Depth was an important explanatory factor for consumption by little skate, but the explanatory value of abiotic habitat factors was low for the other three species. Greater emphasis on species-specific food habits, migratory patterns, and ecological interactions at the synoptic scales relevant to fisheries is needed for fisheries management.
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    Cusk (Brosme brosme) and climate change: assessing the threat to a candidate marine fish species under the US Endangered Species Act (2012)
    Oxford University Press
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    Publication Date: 2012-10-13
    Description: Hare, J.A., Manderson, J.P., Nye, J.A., Alexander, M.A., Auster, P.J., Borggaard, D.L., Capotondi, A.M., Damon-Randall, K.B., Heupel, E., Mateo, I., O'Brien, L., Richardson, D.E., Stock, C.A., and Biege, S.T. 2012. Cusk ( Brosme brosme ) and climate change: assessing the threat to a candidate marine fish species under the US Endangered Species Act. – ICES Journal of Marine Science, 69: 1753–1768. In the Northwest Atlantic Ocean cusk ( Brosme brosme ) has declined dramatically, primarily as a result of fishing activities. These declines have led to concern about its status, which has prompted reviews under the US Endangered Species Act and the Canadian Species at Risk Act. Changes in distribution and abundance of a number of marine fish in the Northwest Atlantic have been linked to climate variability and change, suggesting that both fishing and climate may affect the status of cusk. Our goal was to evaluate potential effects of climate change on Northwest Atlantic cusk distribution. Coupling a species niche model with the output from an ensemble of climate models, we projected cusk distribution in the future. Our results indicate cusk habitat in the region will shrink and fragment, which is a result of a spatial mismatch between high complexity seafloor habitat and suitable temperature. The importance of habitat patch connectivity for cusk is poorly understood, so the population-level consequences of climate-related habitat fragmentation are uncertain. More broadly, climate change may reduce appropriate thermal habitat and increase habitat fragmentation for other cold-water species in the region; thereby, increasing the potential for regional overexploitation and extirpation.
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    Is spawning time of marine fish imprinted in the genes? A two-generation experiment on local Atlantic cod (Gadus morhua L.) populations from different geographical regions (2012)
    Oxford University Press
    Details
    Publication Date: 2012-10-13
    Description: Otterå*, H., Agnalt, A-L., Thorsen, A., Kjesbu, O.S., Dahle, G., and Jørstad, K. 2012. Is spawning time of marine fish imprinted in the genes? A two-generation experiment on local Atlantic cod ( Gadus morhua L.) populations from different geographical regions. – ICES Journal of Marine Science, 69: 1722–1728. Spawning time (onset of spawning) in Atlantic cod ( Gadus morhua L.) was monitored in an experimental setup and combined with modelled spawning time estimates from the wild. The experiment broodstock were collected from several geographical areas and kept in a common environment. Their spawning times in 2004 were compared with the spawning times of their daughters in 2009 and 2010. Daughter spawning time was highly correlated with that of the mother, indicating genetic regulation of spawning time. However, large individual variation in spawning time was observed. The modelling data suggests a north-south gradient in onset of spawning along the Norwegian coast, driven by differences in temperature, i.e. later dates of spawning in the north.
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    Spatio-temporal variability in western Baltic cod early life stage survival mediated by egg buoyancy, hydrography and hydrodynamics (2012)
    Oxford University Press
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    Publication Date: 2012-10-13
    Description: Hinrichsen, H-H., Hüssy, K., and Huwer, B. 2012. Spatio-temporal variability in western Baltic cod early life stage survival mediated by egg buoyancy, hydrography and hydrodynamics. – ICES Journal of Marine Science, 69: 1744–1752. To disentangle the effects of different drivers on recruitment variability of marine fish, a spatially and temporally explicit understanding of both the spawning stock size and the early life stage dynamics is required. The objectives of this study are to assess the transport of western Baltic cod early life stages as well as the variability in environmentally-mediated survival along drift routes in relation to both spatial (within and between different spawning areas) and temporal (interannual and seasonal) dynamics. A spatially and temporally highly-resolved biophysical model of the Baltic Sea was used to describe mortalities and survival success of eggs and yolk-sac larvae—represented by individual, virtual drifters—as predicted proportions of drifters that either died due to bottom contact or lethal temperatures, or that survived up to the end of the yolk-sac larval stage. The environmental conditions allowing survival of cod and yolk-sac larvae indicate that favourable conditions predominately occurred during the late spawning season, while minimum survival rates could be expected from January to March. The spatial analysis of different spawning areas revealed highest survival chances in the Kattegat, intermediate survival in the Great Belt, and only low survival in the Sound, Kiel Bay and Mecklenburg Bay.
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  • 43
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    Condition indices of Atlantic cod (Gadus morhua) biased by capturing method (2012)
    Oxford University Press
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    Publication Date: 2012-10-13
    Description: Ovegård, M., Berndt, K., and Lunneryd, S-G. 2012. Condition indices of Atlantic cod ( Gadus morhua ) biased by capturing method. – ICES Journal of Marine Science, 69: 1781–1788. In studies evaluating the condition and general health status of fish stocks, the method used for catching the fish is seldom considered as a factor of importance. In this study, condition indices were compared between cod caught in pots, gillnets, and on hooks in the same geographical area. The results showed that cod ( Gadus morhua ) caught on baited gear types (pots and hooks) generally displayed a lower condition and an older age (i.e. suggesting a lower growth rate) compared to cod caught in gillnets. It is unclear whether these results merely illustrate divergent behavioural responses in fish originating from one single population, or if these divergent behavioural components represent distinct subpopulations displaying different mean conditions and growth rates. Regardless of the underlying causes, the results not only show that parts of the Baltic cod stock are in extremely poor condition, they also indicate that different gear types used in the same area could target similar-sized conspecifics exhibiting large differences in condition and size-at-age. The potential impact of the difference in condition between the pots and other gear types could hamper the implementation of the cod pot as a potentially seal-safe and sustainable fishing method.
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    Sexual dimorphism in size, age, maturation, and growth characteristics of boarfish (Capros aper) in the Northeast Atlantic (2012)
    Oxford University Press
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    Publication Date: 2012-10-13
    Description: Hüssy, K., Coad, J. O., Farrell, E. D., Clausen, L. W., and Clarke, M. W. 2012. Sexual dimorphism in size, age, maturation, and growth characteristics of boarfish ( Capros aper ) in the Northeast Atlantic – ICES Journal of Marine Science, 69: 1729–1735. Boarfish ( Capros aper ) have, in recent years, become of increasing commercial importance due to their apparent increase in abundance in the Northeast Atlantic. This study presents detailed biological information relevant to understanding stock structure and dynamics. Boarfish are a long-lived species that reach a maximum age of 〉30 years. The size distribution is skewed towards larger sizes, as expected from an unexploited stock with sexual dimorphism, where females are, on average, larger than males. No seasonal effects occur in size distribution and sex ratio, indicating that females and males stay together in shoals throughout the year. Females become increasingly dominant in abundance at larger sizes and older ages. There is no significant difference in length at maturity nor age at maturity between the two sexes, with L 50 = 9.7 cm and A 50 = 3.4 years. Growth is dimorphic following von Bertalanffy growth characteristics, with a common t 0 = –2.897, but significantly different K and L inf values, where females have K = 0.145 and L inf = 16.519 and males have K = 0.181 and L inf = 14.437. The sexual dimorphism in size is thus caused by sex-specific growth and longevity patterns.
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    Cod catches taken by the German recreational fishery in the western Baltic Sea, 2005-2010: implications for stock assessment and management (2012)
    Oxford University Press
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    Publication Date: 2012-10-13
    Description: Strehlow, H. V., Schultz, N., Zimmermann, C., and Hammer, C. 2012. Cod catches taken by the German recreational fishery in the western Baltic Sea, 2005–2010: implications for stock assessment and management. – ICES Journal of Marine Science, 69: 1769–1780. Next to the commercial fishery, the recreational fishery plays an important role in the removal of biomass from fish stocks. In this study, we present estimates of German recreational cod ( Gadus morhua ) catches in the western Baltic Sea between 2005 and 2010. Fishing effort was estimated using a stratified mail survey and annual sales of fishing licences. Catch per unit effort was estimated by stratified random sampling of access points and interviews about completed trips. Length distributions of cod catches were acquired by sampling recreational cod catches from charter boats and data from community fishing events. Estimates of the total cod biomass removed by the recreational fishery fluctuated between 2159 t in 2009 and 4127 t in 2005. Annual recreational fishery cod harvests accounted for a significant share of the total landings, with a yearly variation from 34 to 70% of the German commercial cod landings from the western Baltic Sea. The majority of recreational fishery cod catches were taken from private boats and charter vessels. Because of the amount and specifically the variability of the recreational catches, they are important for the assessment and management of the resource and, therefore, need to be surveyed annually.
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    Efficacy of conservation measures for the American lobster: reproductive value as a criterion (2012)
    Oxford University Press
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    Publication Date: 2012-10-13
    Description: Xu, C., and Schneider, D. C. 2012. Efficacy of conservation measures for the American lobster: reproductive value as a criterion – ICES Journal of Marine Science, 69: 1831–1839. Reproductive value takes into account both current and future value, effectively characterizing the value of an individual to the population. In this study, we use reproductive value as a criterion to evaluate the effectiveness of several conservation measures that have been undertaken or proposed for the American lobster ( Homarus americanus ) fishery in Newfoundland. These measures are slot fishing (i.e. no fishing below or above certain sizes), marine protected areas (MPAs), V-notching, and window fishing (i.e. no fishing within a size window). Reproductive value was estimated by using catch length data available from commercial fisheries and research surveys. We found that MPAs had the greatest effect, followed by V-notching and slot-fishing. MPAs resulted in an average increase of 64.9% in total reproductive value, V-notching an average increase of 18.3%, and slot fishing an average increase of 16.8%. In general, window fishing was not effective unless the size of the window was large. For instance, an average increase of 8.7% in total reproductive value would require a wide window (100–129 mm). Our results provide a scientific basis for evaluating conservation measures in a way that integrates population demographical information with information from commercial fisheries and research surveys.
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  • 47
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    Hydrographic influence on the spawning habitat suitability of western Baltic cod (Gadus morhua) (2012)
    Oxford University Press
    Details
    Publication Date: 2012-10-13
    Description: Hüssy, K., Hinrichsen, H.-H., and Huwer, B. 2012. Hydrographic influence on the spawning habitat suitability of western Baltic cod ( Gadus morhua ) – ICES Journal of Marine Science, 69: 1736–1743. Recruitment variability of marine fish is influenced by the reproductive potential of the stock (i.e. stock characteristics and abundance) and the survival of early life stages, mediated by environmental conditions of both a physical (water temperature, salinity and oxygen conditions, ocean currents) and a biological nature (i.e. food, predators). The objective of this study is to assess the importance of variability in environmental conditions within different western Baltic cod spawning grounds for egg survival. Habitat identification was based on environmental threshold levels for egg survival and development and ambient hydrographical conditions at different times during the spawning season. The long-term resolution of environmental conditions allowing survival of western Baltic cod eggs indicates that favourable conditions predominantly occurred during the late spawning season in April/May, while minimum survival rates could be expected from January to March. Unsuitable time periods and habitats exhibiting the highest mortality rates are exclusively characterized by ambient water temperatures below the critical survival threshold. Despite the strong influence of water temperature on habitat suitability, the impact of habitat suitability on recruitment was not clearly defined, suggesting that other mechanisms regulate year class strength.
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    Indicators of fishing pressure and seafloor integrity (2012)
    Oxford University Press
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    Publication Date: 2012-10-13
    Description: Piet, G. J., and Hintzen, N. T. 2012. Indicators of fishing pressure and seafloor integrity. – ICES Journal of Marine Science, 69: 1850–1858. This study calculates a suite of indicators reflecting the spatial extent of fishing and its impact on the seafloor and discusses the usefulness of these indicators to inform future management and the issues to consider. It explores several methods to calculate the indicators and shows that they can be informative to report on both fishing pressure and the status of the seafloor. However, although observed overall trends were robust against the specific method of calculation, the absolute values vary greatly with the calculation method. As both aspects are important from a policy perspective, agreement on the methodology to calculate the indicators is required. This study based on the Dutch Exclusive Economic Zone (EEZ) shows that it is possible to calculate indicators required to inform decision-makers on the pressure of fishing as well as the status of the seafloor pending a decision on the following issues: (i) choice of an appropriate grid cell resolution, (ii) use of interpolated VMS tracks instead of VMS position registrations, (iii) choice of an "intensity threshold" dependent on the benthic community recovery capacity, and (iv) the level of confidence required when assessing if an area is not impacted.
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    Integration of environmental and fishery management in Europe (2012)
    Oxford University Press
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    Publication Date: 2012-08-22
    Description: Jennings, S., and Le Quesne, W. J. F. 2012. Integration of environmental and fishery management in Europe. – ICES Journal of Marine Science, 69: . Policy drivers for integrating environmental and fishery management in Europe have never been so strong. Scientists calling for better integration now have the opportunity to help deliver it. The main challenge is providing relevant evidence on short time-scales using existing knowledge. Policies, scientists, and society largely agree that management targets should be linked to achieving sustainability, but research often fails to show when fishing impacts ‘matter’ in relation to sustainability criteria. If targets for ecosystem functions or processes are to complement more tractable targets for species and habitats, scientists will need to show why impacts ‘matter’ and when they become unsustainable. For now, and to meet ambitious and pressing policy timetables, priority should be given to developing credible targets for impacts with a high risk of compromising sustainability, rather than dissipating research and advisory effort to achieve broader coverage of state, function, and process. Impacts on sensitive species and habitats often compromise sustainability; thus, setting targets for them is a priority. Meeting these targets will often require management measures that are expected to diminish risks of other unsustainable impacts. Fast and significant progress towards integration could be achieved by incorporating measures to meet environmental targets for sensitive species and habitats into fishery management plans.
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    Size-related variation in fecundity of European eel (Anguilla anguilla) (2012)
    Oxford University Press
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    Publication Date: 2012-08-22
    Description: MacNamara, R., and McCarthy, T. K. 2012. Size-related variation in fecundity of European eel ( Anguilla anguilla) . – ICES Journal of Marine Science, 69: . Declining European eel ( Anguilla anguilla ) recruitment has focused attention on conservation of potential spawners leaving continental waters. Fecundity of wild, seaward-migrating silver-phase eels was shown to be size-related and higher than previously reported from artificial maturation experiments. Reliable information on fecundity is essential for stock modelling and future development of eel management policies.
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    Is juvenile anchovy a feeding resource for the demersal community in the Bay of Biscay? On the availability of pelagic prey to demersal predators (2012)
    Oxford University Press
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    Publication Date: 2012-08-22
    Description: López-López, L., Preciado, I., Villamor, B., Velasco, F., Iglesias, M., Nogueira, E. Gutierrez-Zabala, J. L., and Olaso, I. 2012. Is juvenile anchovy a feeding resource for the demersal community in the Bay of Biscay? On the availability of pelagic prey to demersal predators. – ICES Journal of Marine Science, 69: . The role that juvenile anchovy ( Engraulis encrasicolus ) play as a food resource for the demersal community in the southern Bay of Biscay is assessed using 21 years of anchovy abundance data and demersal predator diets. During the study period, a total of 26 fish and elasmobranch species preyed on anchovy either frequently or occasionally. Predators with a crustacean-based diet targeted the smaller anchovy individuals. The size range of anchovy juveniles (centred at 7.5–8.9 cm) was comparable to that of the largest nektonic–benthic crustaceans, but generally smaller than other demersal and pelagic fish prey. Hake ( Merluccius merluccius ) and megrim ( Lepidorhombus whiffiagonis ) were the predators that consumed the highest number of anchovy, one of the main prey items driving the variability of their diets. Anchovy consumption conformed only partially to the abundance of anchovy in the southern Bay of Biscay, suggesting that factors other than abundance might condition its availability to demersal predators. Prey size could be one of them, as the size of the anchovy preyed on proved to be significantly smaller than the individuals collected with bottom trawls. However, other factors, such as the vertical position of the shoals of anchovy juveniles, could also constrain anchovy availability to demersal predators.
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    Conservation of coastal stingrays: seasonal abundance and population structure of the short-tailed stingray Dasyatis brevicaudata at a Marine Protected Area (2012)
    Oxford University Press
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    Publication Date: 2012-08-22
    Description: Le Port, A., Lavery, S., and Montgomery, J. C. 2012. Conservation of coastal stingrays: seasonal abundance and population structure of the short-tailed stingray Dasyatis brevicaudata at a Marine Protected Area. – ICES Journal of Marine Science, 69: . Elasmobranch (shark, ray, and skate) populations around the world are in decline, and effective conservation measures are urgently needed. Marine Protected Areas (MPA) placed in locations important for key life-history stages may form part of an effective conservation strategy. In this context, we examined the seasonal abundance and population structure of the short-tailed stingray ( Dasyatis brevicaudata ) at an offshore MPA in northeastern New Zealand, and the reported use of this location as a mating ground. Diver surveys were conducted from 2004 to 2007 at the Poor Knights Islands Marine Reserve (PKIMR). During this time, we observed: (i) a substantial increase in adult and subadult numbers, particularly females during the suggested breeding season, and a corresponding increase in females bearing fresh mating scars; and (ii) large numbers of smaller (probably immature) D. brevicaudata individuals of both sexes from spring to autumn. These results suggest that the PKIMR acts as both a mating aggregation location and a nursery for this species. We suggest that for coastal stingrays such as D. brevicaudata , small MPAs may be effective at protecting key life-history stages, but that as movements outside of reserve boundaries also occur, additional management tools may also be necessary.
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    Giant mud crab (Scylla serrata): relative efficiencies of common baited traps and impacts on discards (2012)
    Oxford University Press
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    Publication Date: 2012-08-22
    Description: Butcher, P. A., Leland, J. C., Broadhurst, M. K., Paterson, B. D., and Mayer, D. G. 2012. Giant mud crab ( Scylla serrata ): relative efficiencies of common baited traps and impacts to discards. – ICES Journal of Marine Science, 69: . This study was initiated in response to a scarcity of data on the efficiency, selectivity and discard mortality of baited traps to target Scylla serrata . Five replicates of four traps, including "hoop nets", rigid "wire pots", and collapsible "round" and "rectangular" pots were deployed for 3, 6 and 24 h in two Australian estuaries. Trapped S. serrata were "discarded" into cages and monitored with controls over 3 d. All S. serrata were assessed for damage, while subsets of immediately caught and monitored individuals had haemolymph constituents quantified as stress indices. All traps retained similar-sized (8.1–19.1 cm carapace width) S. serrata , with catches positively correlated to deployment duration. Round pots were the most efficient for S. serrata and fish—mostly Acanthopagrus australis (3% mortality). Hoop nets were the least efficient and were often damaged. No S. serrata died, but 18% were wounded (biased towards hoop nets), typically involving a missing swimmeret. Physiological responses were mild and mostly affected by biological factors. The results validate discarding unwanted S. serrata for controlling exploitation, but larger mesh sizes or escape vents in pots and restrictions on hoop nets would minimise unnecessary catches, pollution and ghost fishing.
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    The development and use of a spatial database for the determination and characterization of the state of the German Baltic small-scale fishery sector (2012)
    Oxford University Press
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    Publication Date: 2012-08-22
    Description: Papaioannou, E. A., Vafeidis, A. T., Quaas, M. F., and Schmidt, J. O. 2012. The development and use of a spatial database for the determination and characterization of the state of the German Baltic small-scale fishery sector. – ICES Journal of Marine Science, 69: . Although substantial progress has been made in the acquisition and analysis of fishery data, the small-scale fishery (SSF) sector is frequently data deficient, with relevant primary data often being fragmented and incomplete. Also, in contrast to the case of the larger scale sector, a coherent methodological framework for the assessment of the SSF has, in most cases, not been formulated. In the present study, the methodology of developing a database for the German Baltic SSF sector is presented. The aim of the database is to combine fishery primary data effectively and enable the sound determination and characterization of the German Baltic SSF sector. Data used include, among others, fleet data derived from the European Community Fleet Register (CFR) database and logbook data from the German Federal Office for Agriculture and Food (BLE). The database includes information on the technical specifications of SSF vessels (length, engine power, etc.); the sector's operational range; main target species; fishing grounds; landing ports; and weight and price of landings. Results of employing the database for profiling the state of the SSF sector (in 2008) are presented. The results demonstrate the benefits of such an approach within the framework of managing coastal fish resources and fishing activities.
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    Reference points based on dynamic optimization: a versatile algorithm for mixed-fishery management with bioeconomic age-structured models (2012)
    Oxford University Press
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    Publication Date: 2012-04-10
    Description: Da Rocha, J-M., Gutiérrez, M-J., and Cerviño, S. 2012. Reference points based on dynamic optimization: a versatile algorithm for mixed-fishery management with bioeconomic age-structured models. – ICES Journal of Marine Science, 69: 660–669. Single-species management objectives may not be consistent within mixed fisheries. They may lead species to unsafe situations, promote discarding of over-quota, and/or misreporting of catches. We provide an algorithm for characterizing bioeconomic reference points for a mixed fishery as the steady-state solution of a dynamic optimal management problem. The optimization problem takes into account that: (i) species are caught simultaneously in unselective fishing operations, and (ii) intertemporal discounting and fleet costs relate to reference points to discounted economic profits along optimal trajectories. We illustrate how the algorithm can be implemented by applying it to the European northern hake stock ( Merluccius merluccius ), where fleets also capture northern megrim ( Lepidorhombus whiffiagonis ) and northern anglerfish ( Lophius piscatorius and Lophius budegassa ). We find that optimal mixed management leads to a target reference point that is quite similar to two-thirds of the F msy single-species (hake) target. Mixed management is superior to single-species management because it leads the fishery to higher discounted profits, with higher long-term spawning-stock biomass for all species. We calculate that the losses due to the use of the F msy single-species (hake) target in this mixed fishery account for 11.4% of total discounted profits.
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    Using cross-correlations to assess the relationship between time-lagged pressure and state indicators: an exemplary analysis of North Sea fish population indicators (2012)
    Oxford University Press
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    Publication Date: 2012-04-10
    Description: Probst, W. N., Stelzenmüller, V., and Fock, H. 2012. Using cross-correlations to assess the relationship between time-lagged pressure and state indicators: an exemplary analysis of North Sea fish population indicators. – ICES Journal of Marine Science, 69: 670–681. A sustainable ecosystem-based management, as postulated by the European Union-Marine Strategy Framework Directive (MSFD), requires a sound understanding of the cause–effect relationships between human pressures and ecosystem states. In this study, cross-correlations are used to introduce a protocol for the analysis of time-lagged relationships between pressure and state indicators. To perform meaningful cross-correlations, the time-series of the pressure and the state indicator should be prewhitened by fitting autoregressive integrated moving average models to the pressure indicator time-series. This study provides some theoretical examples on the implications of non-prewhitened and prewhitened cross-correlations and exemplifies the use of prewhitened cross-correlations to compare the pressure–state relationship of a well-established indicator suite vs. the relationship of a new indicator proposed under the MSFD. The established indicator suite is fishing mortality ( F ) vs. spawning-stock biomass ( SSB ), the new indicator suite is F vs. the 95% percentile of the length frequency distribution ( L 95 ). The L 95 aims to characterize the proportion of large individuals within a population. The prewhitened cross-correlations for F and SSB are significant for all four analysed species (cod, haddock, saithe, and plaice), the L 95 is correlated with F for cod, haddock, and saithe. However, the L 95 was also influenced by the annual survey catch and recruitment.
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    21st century fisheries management: a spatio-temporally explicit tariff-based approach combining multiple drivers and incentivising responsible fishing (2012)
    Oxford University Press
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    Publication Date: 2012-04-10
    Description: Kraak, S. B. M., Reid, D. G., Gerritsen, H. D., Kelly, C. J., Fitzpatrick, M., Codling, E. A., and Rogan, E. 2012. 21st century fisheries management: a spatio-temporally explicit tariff-based approach combining multiple drivers and incentivising responsible fishing. – ICES Journal of Marine Science, 69: 590–601. Traditionally fisheries management has focused on biomass and mortality, expressed annually and across large management units. However, because fish abundance varies at much smaller spatio-temporal scales, fishing mortality can potentially be controlled more effectively if managed at finer scale. The ecosystem approach requires more indicators at finer scales as well. Incorporating ecosystem targets would need additional management tools with potentially conflicting results. We present a simple, integrated, management approach that provides incentives for "good behaviour". Fishers would be given a number of fishing-impact credits, called real-time incentives (RTIs), to spend according to spatio-temporally varying tariffs per fishing day. RTI quotas and tariffs could be based on commercial stocks and ecosystem targets. Fishers could choose how to spend their RTIs, e.g. by limited fishing in high-catch or sensitive areas or by fishing longer in lower-catch or less sensitive areas. The RTI system does not prescribe and forbid, but instead allows fishers to fish wherever and whenever they want; ecosystem costs are internalized and fishers have to take them into account in their business decisions. We envisage no need for traditional landings or catch quotas for the fleets while operating under the scheme. The approach could facilitate further devolution of responsibility to industry.
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    Development and application of an agent-based model to evaluate methods for estimating relative abundance indices for shoaling fish such as Pacific rockfish (Sebastes spp.) (2012)
    Oxford University Press
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    Publication Date: 2012-04-10
    Description: Thorson, J. T., Stewart, I. J., and Punt, A. E. 2012. Development and application of an agent-based model to evaluate methods for estimating relative abundance indices for shoaling fish such as Pacific rockfish ( Sebastes spp.). – ICES Journal of Marine Science, 69: 635–647. Many marine fish, including Pacific rockfish ( Sebastes spp.), exhibit habitat-selective and shoaling behaviours, which can lead to imprecision when using survey data to estimate an annual index of stock abundance. We develop a spatial agent-based model (ABM) for Pacific rockfish, which generates data similar to those observed in existing bottom-trawl surveys and can represent various spatial and shoaling behaviours. We use the ABM to evaluate the performance of a model that uses mixture distribution methods to account for fish shoals and delta-methods to account for range expansion or contraction. This delta-mixture model is compared with conventional delta-generalized linear models (delta-GLMs) and a quantile regression delta-model. The delta-mixture increases precision by 15% relative to delta-GLMs in estimated abundance indices when shoaling behaviours are present, whereas precision is similar between delta-GLM and delta-mixture models when shoals are absent. The delta-quantile method has similar improvements over conventional delta-GLM methods, and the improved precision from delta-mixture and delta-quantile methods is decreased but not eliminated by decreased sampling intensities. These simulations represent the first evaluation of delta-mixture models for index standardization and show a substantial improvement over conventional delta-GLMs for shoaling species such as Pacific rockfish.
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    Species identification in seamount fish aggregations using moored underwater video (2012)
    Oxford University Press
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    Publication Date: 2012-04-10
    Description: O'Driscoll, R. L., de Joux, P., Nelson, R., Macaulay, G. J., Dunford, A. J., Marriott, P. M., Stewart, C., and Miller, B. S. 2012. Species identification in seamount fish aggregations using moored underwater video. – ICES Journal of Marine Science, 69: 648–659. Acoustic surveys of New Zealand deep-water seamounts often show fish aggregations up to 150 m high on the summit. Although bottom trawls on the seamount slopes catch predominantly orange roughy ( Hoplostethus atlanticus ), species composition in the midwater plumes is extremely uncertain. In June 2010, moored underwater video cameras were deployed on the summit of the Morgue seamount (summit depth 890 m), a feature that has been closed to fishing since 2001. Cameras and lights were timed to come on for 2 min every 2 h. Fish response to the mooring was monitored using vessel-mounted echosounders. Moored cameras confirmed that orange roughy were present up to 70 m above the seamount summit. Orange roughy made up 97% of the fish identified from the video. Other species observed included smooth oreo ( Pseudocyttus maculatus ), spiky oreo ( Neocyttus rhomboidalis ), deep-water dogfish, cardinalfish ( Epigonus spp.), and squid. Total along-track backscatter from the plume varied by a factor of 25 over a period of hours. Peak acoustic densities in the plume (equivalent to 20 orange roughy m –3 ) were an order of magnitude higher than peak visual estimates (0.64 orange roughy m –3 ), but relative densities between paired video and acoustic observations were generally consistent.
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    In Remembrance: John William Ramster, 1937-2011 A personal tribute (2012)
    Oxford University Press
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    Publication Date: 2012-04-10
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    Implications of using alternative methods of vessel monitoring system (VMS) data analysis to describe fishing activities and impacts (2012)
    Oxford University Press
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    Publication Date: 2012-04-10
    Description: Lambert, G. I., Hiddink, J. G., Hintzen, N. T., Hinz, H., Kaiser, M. J., Murray, L. G., and Jennings, S. 2012. Implications of using alternative methods of vessel monitoring system (VMS) data analysis to describe fishing activities and impacts. – ICES Journal of Marine Science, 69: 682–693. Understanding the spatial distribution and intensity of fishing activity is a prerequisite for estimating fishing impacts on seabed biota and habitats. Vessel monitoring system data provide information on fishing activity at large spatial scales. However, successive position records can be too infrequent to describe the complex movements fishing vessels make. High-frequency position data were collected to evaluate how polling frequency and the method of analysis influenced the estimates of fishing impact on the seabed and associated epifaunal communities. Comparisons of known positions with predictions from track interpolation revealed that the performance of interpolation depended on fleet behaviour. Descriptions and indicators of fishing intensity were influenced significantly by the analytical methods (track reconstruction, density of position records) and grid-cell resolution used for the analysis. These factors can lead to an underestimation of fishing impact on epifaunal communities. It is necessary to correct for such errors to quantify the effects of fishing on various ecosystem components and hence to inform ecosystem-based management. Polling at intervals of 30 min would provide a desirable compromise between achieving precise estimates of fishing impacts on the seabed and minimizing the cost of data collection and handling.
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    Otolith microstructure analysis to resolve seasonal patterns of hatching and settlement in western Baltic cod (2012)
    Oxford University Press
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    Publication Date: 2012-08-22
    Description: Rehberg-Haas, S., Hammer, C., Hillgruber, N., Hüssy, K., and Temming, A. 2012. Otolith microstructure analysis to resolve seasonal patterns of hatching and settlement in western Baltic cod. – ICES Journal of Marine Science, 69: . Previous studies showed that Baltic cod ( Gadus morhua ) settle to demersal life at a given size, while the annulus is formed seasonally, irrespective of size. The goal of this study was to examine the timing of check formation in juvenile Baltic cod otoliths to validate macrostructural ageing and to differentiate between true annuli and secondary structures such as settlement checks. Otoliths were collected from fish off Fehmarn Island in 2008 and 2009, and were examined for macrostructural and microstructural patterns using light and scanning electron microscopy. All fish examined were age-0. Back-calculation of hatch dates indicated hatching from April to June and from February to August in 2008 and 2009, respectively. Juveniles formed either one or two translucent rings. The first translucent ring started to form ~3 months post-hatch and was interpreted as a settlement check, since it appeared to be a function of age and/or size and not season. Deposition of the second ring began in mid October to early November irrespective of fish size and/or age, thus indicating that this ring may represent the first annulus of Baltic cod. Both rings were clearly distinguishable in individuals hatched between February and May, but were merged in those fish where settlement coincided with the seasonally formed second ring.
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    Spawning location of Norway pout (Trisopterus esmarkii Nilsson) in the North Sea (2012)
    Oxford University Press
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    Publication Date: 2012-08-22
    Description: Nash, R. D. M., Wright, P. J., Matejusova, I., Dimitrov, S. P., O'Sullivan, M., Augley, J., and Höffle, H. 2012. Spawning location of Norway pout ( Trisopterus esmarkii Nilsson) in the North Sea. – ICES Journal of Marine Science, 69: . The northern region of the North Sea (56–62°N) was sampled in February/March 2009 for eggs and in May 2010 for larvae. To aid in the identification of Norway pout stage I eggs and distinguish them from other ‘cod-like’ eggs, a Taq-Man probe was designed for this species and used here. Stage I Norway pout egg diameters collected from the field were in the range 1.03–1.28 mm and largely overlapped with the size range determined for whiting ( Merlangius merlangus ). The distribution of Norway pout stage I eggs in 2009 revealed the distribution of spawning in the North Sea and showed that it was similar to the distribution of 2 + Norway pout taken during the International Bottom Trawl Surveys (IBTS) over the same period covering the whole North Sea. The larvae sampled in 2010 were largely in the same area; however, larger larvae occurred to the south-east of the survey area, suggesting advection of young stages from the principal spawning areas in the north-western North Sea to the south-east and toward the Skagerrak.
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    Mitochondrial DNA and microsatellite genetic differentiation in the European anchovy Engraulis encrasicolus L. (2012)
    Oxford University Press
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    Publication Date: 2012-08-22
    Description: Borrell, Y. J., Piñera, J. A., Sanchez Prado, J. A., and Blanco, G. 2012. Mitochondrial DNA and microsatellite genetic differentiation in the European anchovy Engraulis encrasicolus L. – ICES Journal of Marine Science, 69: . The European anchovy Engraulis encrasicolus is currently one of the principal target species for commercial fisheries in Europe, and most stocks are overfished at present. In this work, specimens were sampled in the Bay of Biscay (Cantabrian, Basque Country, and French coasts) in 2009 and also in the Mediterranean (Adriatic Sea). Mitochondrial DNA (mtDNA; cytochrome b and 16S) was sequenced, and 14 nuclear microsatellites showing high and low levels of polymorphism were arranged in three multiplex polymerase chain reaction (PCR) systems and genotyped. Two main ancient mitochondrial clades were found. These clades are separated by 15 mutational steps and 1.7% sequence divergence, corresponding to a separation time of ~0.5 million years ago. Our results using both mtDNA and microsatellites suggest the presence of at least three genetically differentiated groups: the west Cantabrian Sea, the rest of the populations in the Bay of Biscay, and the Mediterranean. Although it is known that western Iberian Atlantic populations of E. encrasicolus may be genetically different from those of the Bay of Biscay, the results suggest that the transition between these groups may be as close as a 100 km and that a recent genetic homogenization process in the eastward area of the Bay of Biscay has probably occurred.
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    Vertical migrations of saithe (Pollachius virens) in Icelandic waters as observed with data storage tags (2012)
    Oxford University Press
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    Publication Date: 2012-08-22
    Description: Armannsson, H., and Jónsson, S. Þ. 2012. Vertical migrations of saithe ( Pollachius virens ) in Icelandic waters as observed with data storage tags. – ICES Journal of Marine Science, 69: . Knowledge of fish behaviour is important for general understanding of fish life history and responses to environmental and biological conditions. Vertical migrations can affect bottom trawl indices of the fish through their availability to the trawl and acoustic indices through changes in target strength. Here we present results based on data sets of hourly recordings of depth from 51 saithe. The data were analysed with respect to diel and seasonal differences in saithe vertical movement. Duration and extent of vertical movements were analysed with 1 min resolution, and the daily vertical range (DVR) was analysed with respect to potential use of the free vertical range (FVR). Our results show diel and seasonal differences in hourly depth changes of saithe, indicating reduced activity during night-time and in winter. Individual saithe are capable of rapid depth changes in 〈1 min, often of the same order as the maximum observed in movements of longer duration. The DVR often exceeded the FVR, and in some instances exceeded critical limits, indicating that saithe may at times only maintain neutral buoyancy near the upper limit of their daily vertical range.
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    Survey estimates of king crab (Paralithodes camtschaticus) abundance off Northern Norway using GLMs within a mixed generalized gamma-binomial model and Bayesian inference (2012)
    Oxford University Press
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    Publication Date: 2012-08-22
    Description: Hvingel, C., Kingsley, M.C.S., and Sundet, J.H. 2012. Survey estimates of king crab ( Paralithodes camtschaticus ) abundance off Northern Norway using GLMs within a mixed generalized gamma-binomial model and Bayesian inference. – ICES Journal of Marine Science, 69: . A trawl survey provides information on number and biomass of introduced king crab ( Paralithodes camtschaticus ) to the management of a fishery off the coast of Northern Norway; the annual catch quotas are largely set as a percentage of the survey estimate. A specially built sledge trawl was designed for the survey. It needs only small areas of trawlable bottom, performs well on a wide range of bottoms, and appears to have good catchability for benthic organisms. Many survey hauls catch no crabs and the non-zero catches have a highly skewed distribution. Data were therefore analysed with a compound model, in which separate predictors were fitted for the proportion of zero catches and for the catch size of the non-zero catches. The compound model was fitted by Bayesian methods using WinBUGS. The distribution of non-zero catches fitted well to a generalized gamma distribution, but with parameter values that made it approximate a lognormal distribution. Numbers of fishable crabs peaked in 2003, and total numbers in 2010 were about two-fifths of the 2003 maximum.
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    Precision in bycatch estimates: the case of tuna purse-seine fisheries in the Indian Ocean (2012)
    Oxford University Press
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    Publication Date: 2012-08-22
    Description: Amandè, M. J., Chassot, E., Chavance, P., Murua, H., Delgado de Molina, A., and Bez, N. 2012. Precision in bycatch estimates: the case of tuna purse-seine fisheries in the Indian Ocean. – ICES Journal of Marine Science, 69: . Estimating bycatch, i.e. the incidental catch of non-target marine animals and undersized individuals of target species, by raising observer data to the whole fishery is routine practice. The annual bycatch of the European tropical tuna purse-seine fishery over the period 2003–2009 was estimated at 11 590 t [95% confidence interval: (8165–15 818 t)], corresponding to 4.7% of the tuna landings. An analysis of the variability in the precision of this estimate, based on generalized linear models and Monte Carlo simulations, showed that the current sampling coverage of the tropical tuna fishery observer programme, which is 4.6% of the fishing trips, resulted in large uncertainties in bycatch estimates by species, i.e. none of the estimates have a relative root mean square error smaller than 50%. Although the overall magnitude of bycatch of the fishery appeared to be small, the current sampling coverage was insufficient to give any reliable estimate for low-occurring species, such as marine turtles, some oceanic pelagic sharks, and some billfishes. Increasing the sampling coverage would likely improve bycatch estimates. Simulation outputs were produced to help define (i) trade-offs between the priority species to be monitored, (ii) the estimation precision, (iii) expected accuracy, and (iv) the associated sampling costs.
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    Assessing the sensitivity of seabird populations to adverse effects from tidal stream turbines and wave energy devices (2012)
    Oxford University Press
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    Publication Date: 2012-08-22
    Description: Furness, R. W., Wade, H. M., Robbins, A. M. C., and Masden, E. A. 2012. Assessing the sensitivity of seabird populations to adverse effects from tidal stream turbines and wave energy devices. – ICES Journal of Marine Science, 69: . Tidal turbines and wave energy devices may affect seabird populations through collision mortality, disturbance and habitat loss. Given the pressures to harness tidal and wave energy, especially in Scottish waters, there is an urgent need to assess population-level impacts on seabird species. With a lack of deployed devices to monitor in areas of importance for seabirds, our approach uses data from scientific literature on seabird ecology and conservation importance likely to influence population vulnerability to "wet renewables" in Scottish waters. At this stage however, we can only infer likely interactions with tidal and wave devices. We identify black guillemot, razorbill, European shag, common guillemot, great cormorant, divers and Atlantic puffin as the species most vulnerable to adverse effects from tidal turbines in Scottish waters. We identify divers as the species most vulnerable to adverse effects from wave energy devices in Scottish waters. Wave energy devices seem likely to represent a lesser hazard to seabirds than tidal turbines, and both forms of energy capture seem likely to represent a lower hazard to seabirds than offshore wind farms (wind-power plants). The indices developed here for Scottish seabird populations could be applied to populations elsewhere. This approach will help in identifying likely impacts of tidal and wave energy deployments on seabirds, and in optimizing deployment of resources for compulsory environmental monitoring.
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    A quantitative comparison of the diets of sympatric pelagic sharks in gulf and shelf ecosystems off southern Australia (2012)
    Oxford University Press
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    Publication Date: 2012-08-22
    Description: Rogers, P. J., Huveneers, C., Page, B., Hamer, D. J., Goldsworthy, S. D., Mitchell, J. G., and Seuront, L. 2012. A quantitative comparison of the diets of sympatric pelagic sharks in gulf and shelf ecosystems off southern Australia. – ICES Journal of Marine Science, 69: . Predator–prey dynamics represent an important determinant in the functioning of marine ecosystems. This study provides the first quantitative investigation of the diets of sympatric pelagic shark species in gulf and shelf waters off southern Australia. Stomachs of 417 sharks collected from fishery catches between 2007 and 2011 were examined, including 250 bronze whalers, 52 shortfin makos, 49 dusky sharks, 39 smooth hammerheads, and 27 common threshers. Dusky sharks had the highest dietary diversity of the five species examined. We found overlap in the consumption of cephalopods, small pelagic teleosts, crustaceans, and benthic teleosts in bronze whalers, dusky sharks, and smooth hammerheads, and preliminary evidence of specialization in the highly migratory species, the common thresher and the shortfin mako. Findings were discussed and compared with previous studies in other temperate marine ecosystems. This study will significantly improve the understanding of the ecological roles of these top predators in the gulf and shelf habitats off southern Australia, and enhance the ecosystem models being developed for this unique bioregion.
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    Modelling in-season pulses of recruitment and hyperstability-hyperdepletion in the Loligo gahi fishery around the Falkland Islands with generalized depletion models (2012)
    Oxford University Press
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    Publication Date: 2012-08-22
    Description: Roa-Ureta, R. H. 2012. Modelling in-season pulses of recruitment and hyperstability-hyperdepletion in the Loligo gahi fishery around the Falkland Islands with generalized depletion models. – ICES Journal of Marine Science, 69: . The time-series of daily catch, fishing effort, and mean body mass of the summer fishing seasons of the squid, Loligo gahi , in the Falkland Islands from 1990 to 2009 are investigated with generalizations of depletion models that account for in-season pulses of recruitment (i.e. open populations) and non-linear relationships between catch as the response variable, and effort and abundance as the predictor variables. Two main results were found. First, stock dynamics are more complex than assumed by Leslie–Davis or De Lury depletion models, because in most years, there are several major in-season recruitment pulses, sometimes even larger than the pre-season pulse, contradicting the basic assumption of a decline in catch rates over the fishing season. Second, the fishery operates under a regime of hyperstability—catch rates decline slower than abundance—at low stock abundance and hyperdepletion—catch rates decline faster than abundance—at intermediate and high stock abundance. The hyperdepleted regime is far more prevalent, a result attributed to the availability of refuges from fishing operations, which may lower the abundance threshold to pass from the low-abundance hyperstable regime to the higher-abundance hyperdepleted regime.
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    Modelling the abundance of grey seals (Halichoerus grypus) along the Norwegian coast (2012)
    Oxford University Press
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    Publication Date: 2012-08-22
    Description: Øigård, T. A., Frie, A. K., Nilssen, K. T., and Hammill, M. O. 2012. Modelling the abundance of grey seals ( Halichoerus grypus ) along the Norwegian coast. – ICES Journal of Marine Science, 69: . An age-structured population dynamics model of the Norwegian grey seal ( Halichoerus grypus ) population has been developed. The model is of a Bayesian character in the sense that priors for various parameters were used. Model runs indicated an increase in the abundance of the total Norwegian grey seal population during the last 30 years, suggesting a total of 8740 (95% confidence interval: 7320–10 170) animals in 2011. A total catch of 707 (95% confidence interval: 532–882) grey seals would maintain the population size at the 2011 level. Model runs suggest that current catch levels will likely result in a reduction in the population size in Sør-Trøndelag and Nord-Trøndelag counties, and an increase in the population size in Rogaland, Nordland, Troms, and Finnmark counties. The model runs assumed that 80% of the seals taken in Rogaland came from the UK and that 50 and 55% of the catches in Troms and Finnmark, respectively, were immigrants from Russia.
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    Environmental and fisheries effects on Gracilechinus acutus (Echinodermata: Echinoidea) distribution: is it a suitable bioindicator of trawling disturbance? (2012)
    Oxford University Press
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    Publication Date: 2012-08-22
    Description: González-Irusta, J. M., Punzón, A., and Serrano, A. 2012. Environmental and fisheries effects on Gracilechinus acutus (Echinodermata: Echinoidea) distribution: is it a suitable bioindicator of trawling disturbance? – ICES Journal of Marine Science, 69: . Habitat preferences of Gracilechinus acutus in the southern Bay of Biscay were studied using data from autumn bottom-trawl surveys. Wet weight and number of specimens of G. acutus were obtained and related to environmental variables (depth, sediment type, and organic matter percentage) at each haul and to trawl fishing effort. With this information and the otter trawl effort data, the environmental requirements and the impact of the trawl fishery on G. acutus populations were analysed. Although the species was present in all depth strata and all sediment types studied, it had clear habitat preferences, as greater abundances and mean weight values were found at depths ranging from 71 to 200 m and in bottom sediments dominated by coarse and medium sands. The effect of disturbance by trawling on this echinoid was significant and clearly negative. Seabeds exposed to higher trawling disturbance showed lower values of urchin abundance and smaller urchins than areas with lower disturbance. Results of the present study confirm the initial hypothesis of the suitability of using this urchin as a bioindicator of trawling impact but only in areas with appropriate environmental conditions, highlighting the importance of attaining a wider knowledge on the essential habitat of the species.
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    Does predation by grey seals (Halichoerus grypus) affect Bothnian Sea herring stock estimates? (2012)
    Oxford University Press
    Details
    Publication Date: 2012-08-22
    Description: Gårdmark, A., Östman, Ö., Nielsen, A., Lundström K., Karlsson O., Pönni, J., and Aho, T. 2012. Does predation by grey seals ( Halichoerus grypus ) affect Bothnian Sea herring stock estimates? – ICES Journal of Marine Science, 69: . Mortality of small pelagic fish due to marine mammals is generally considered to be low compared with other sources of mortality. With recent recoveries of marine mammal predators worldwide, this may no longer hold. The grey seal ( Halichoerus grypus ) population in the Bothnian Sea has increased fivefold since 1985. Its main prey, herring ( Clupea harrengus ), is a key species for fisheries in the region. Yet, current stock assessments assume constant natural mortality, leading to a risk of biased stock estimates with increasing predation and misleading analyses of herring population dynamics. We estimated grey seal predation from diet data and reanalysed herring spawning stock biomass (SSB) during 1973–2009. Accounting for predation increased the herring SSB 16% (maximum 19%), but this was within the confidence intervals when ignoring predation. Although mortality in older individuals was inflated when accounting for seal predation, this did not change the conclusions about drivers of herring dynamics. Accounting for grey seal predation is important for abundance estimates of old herring, but currently not for SSB estimates, given the great uncertainties in the standard assessment. The grey seal impact on Bothnian Sea herring will need to be reassessed if stock age composition, grey seal feeding preferences, or total stock development change.
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    The response of herring to high crowding densities in purse-seines: survival and stress reaction (2012)
    Oxford University Press
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    Publication Date: 2012-08-22
    Description: Tenningen, M., Vold, A., and Olsen, R. E. 2012. The response of herring to high crowding densities in purse-seines: survival and stress reaction. – ICES Journal of Marine Science, 69: . To study the effects of crowding in purse-seines on the survival and stress response of herring ( Clupea harengus ), large-scale field experiments were conducted in the North Sea during 2008 and 2009. The mortality was 28% at a crowding density of 221 kg m –3 and increased further with increasing density. Crowding densities 〈150 kg m –3 did not result in any additional mortality compared with the control group (0.9–2.0%). Smaller herring and herring with a lower condition factor were more vulnerable to the effects of crowding. Blood analyses showed a significant increase in cortisol, lactate, and blood ions in the crowded fish. Lactate returned to control levels 2 d post-stress, whereas cortisol and blood ion levels continued to increase during the 4- to 5-d monitoring period. Furthermore, plasma glucose appeared to be substantially reduced at the end of the trial, indicating that the herring were incapable of restoring homeostasis and were approaching energy exhaustion. These results provide important information about the crowding densities that can be tolerated in the purse-seine fisheries for herring and will benefit future development of guidelines for purse-seine slipping operations.
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    Assessing global marine fishery status with a revised dynamic catch-based method and stock-assessment reference points (2012)
    Oxford University Press
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    Publication Date: 2012-08-22
    Description: Anderson, S. C., Branch, T. A., Ricard, D., and Lotze, H. K. 2012. Assessing global marine fishery status with a revised dynamic catch-based method and stock-assessment reference points. – ICES Journal of Marine Science, 69: . The assessment of fishery status is essential for management, yet fishery-independent estimates of abundance are lacking for most fisheries. Methods exist to infer fishery status from catches, but the most commonly used method is biased towards classifying fisheries as overexploited or collapsed through time and does not account for still-developing fisheries. We introduce a revised method that overcomes these deficiencies by smoothing catch series iteratively, declaring fisheries developing within three years of peak catch, and calibrating thresholds to biological reference points. Compared with status obtained from stock-assessment reference points for 210 stocks, our approach provides a more realistic assessment than the original method, but cannot be perfect because catches are influenced by factors other than biomass. Applied to FAO catches, our method suggests in 2006 32% of global fisheries were developing, 27% fully exploited, 25% overexploited, and 16% collapsed or closed. Although less dire than previous assessments, this still indicates substantial numbers of overexploited stocks. Probably because median exploitation rate decreased since 1992, our catch-based results do not reflect recent stabilization of assessed-stock biomass. Whether this outlook also applies to unassessed stocks can only be revealed with increased or more representative collection of biomass- and exploitation-rate trends.
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    Changes in life-history traits in relation to climate change: bluefish (Pomatomus saltatrix) in the northwestern Mediterranean (2012)
    Oxford University Press
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    Publication Date: 2012-06-14
    Description: Sabatés, A., Martín, P., and Raya, V. 2012. Changes in life-history traits in relation to climate change: bluefish ( Pomatomus saltatrix ) in the northwestern Mediterranean. – ICES Journal of Marine Science, 69: 1000–1009. This study shows the strong relationship between the increasing surface temperature in the NW Mediterranean and the expansion northwards of the bluefish distribution range with the species reproducing in the new distribution areas. Two shifts in temperature were detected: the first one in the early 1980s and the second around 1997. This last shift, explained by warmer springs (April–June), when the species migrates for spawning, led to the observed changes in bluefish. In the western Mediterranean basin, a significant increase in bluefish landings was observed by the mid nineties, whereas in the Catalan coast, the northern edge of the species distribution, a northward expansion was observed from 2000. At present, spawning takes place all along the Catalan coast (June to September), including the new distribution areas, being 21°C the threshold for the presence of larvae in the plankton. This temperature was not attained in June two decades ago. The highest concentrations of larvae were located near the mouth of the Ebro River and their distribution to the north did not extend beyond the thermal front. Bluefish has taken the advantage of the changing environmental conditions and is established in new northernmost distribution areas.
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    Escapement of eel (Anguilla anguilla) in coastal areas in Sweden over a 50-year period (2012)
    Oxford University Press
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    Publication Date: 2012-06-14
    Description: Andersson, J., Florin, A.-B., and Petersson, E. 2012. Escapement of eel ( Anguilla anguilla ) in coastal areas in Sweden over a 50-year period – ICES Journal of Marine Science, 69: 991–999. The escapement of eel from coastal areas in Sweden during the last 50 years was assessed using data from voluntary fishery journals and fishery-independent coastal fish monitoring programmes. It was evident that the level of escapement, determined as catch per unit of effort in numbers, from the Baltic Sea decreased over time, with the most rapid decline occurring in the 1960s and early 1970s, but also in recent years. There were, however, differences in the temporal variability in escapement between areas. Escapement from the northernmost studied site did not change significantly during the last 50 years, while there was a rapid decline in the southern areas. Escapement remained relatively stable between the late 1970s and 2000 however, and escapement at the Swedish west coast, inferred from yellow eel catch per unit of effort, generally increased during the same time. The loss in numbers has to some extent been compensated by an increase in mean weight of silver eel. Possible explanations for the retained level of escapement during the last decades despite the continued reduction in recruitment are discussed. Favourable environmental conditions in combination with a lower fishing effort are suggested as the most probable reasons why the escapement decline has not been more dramatic, but stocking and density-dependent effects cannot be ruled out.
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    An ecosystem approach for the assessment of fisheries impacts on marine top predators: the Bay of Biscay case study (2012)
    Oxford University Press
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    Publication Date: 2012-06-14
    Description: Lassalle, G., Gascuel, D., Le Loc'h, F., Lobry, J., Pierce, G. J., Ridoux, V., Santos, M. B., Spitz, J., and Niquil, N. 2012. An ecosystem approach for the assessment of fisheries impacts on marine top predators: the Bay of Biscay case study. – ICES Journal of Marine Science, 69: 925–938. A number of marine mammal populations is currently threatened by their interactions with fisheries. The present study aimed to provide insights into the severity of potential impacts of operational and biological interactions between top predators and fisheries, in the Bay of Biscay region. Our approach was to modify an Ecopath with Ecosim (EwE) model describing the overall structure and function of the ecosystem by including landings and discards of exploited stocks and estimations of the bycatch of non-target compartments. Second, a set of ecological indices and a trophic level ( TL )-based model (EcoTroph, ET) were derived from the EwE model. ET was used to simulate the effects of increasing fishing pressure on the ecosystem and, more particularly, on top predators. The Bay of Biscay was demonstrated to be not far from overexploitation at the current fishing rate, this phenomenon being particularly noticeable for the highest TL s. Within the toothed cetacean community, bottlenose dolphins appeared the most sensitive to resource depletion, whereas common dolphins and harbour porpoises were most impacted by their incidental captures in fishing gears. This study provides a methodological framework to assess the impacts of fisheries on ecosystems for which EwE, or other ecosystem models, already exist.
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    A prey-related shift in the abundance of small pelagic fish in eastern Tasmania? (2012)
    Oxford University Press
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    Publication Date: 2012-06-14
    Description: McLeod, D. J., Hobday, A. J., Lyle, J. M., and Welsford, D. C. 2012. A prey-related shift in abundance of small pelagic fish in eastern Tasmania? – ICES Journal of Marine Science, 69: 953–960. Shifts in the relative abundance of small pelagic fish species have signalled a change in the ocean environment in a number of locations. Here we show that the replacement of jack mackerel, Trachurus declivis , with redbait, Emmelichthys nitidus , as the dominant small pelagic species from eastern Tasmania, following a period of high fishing pressure on jack mackerel, is consistent with altered zooplankton communities and long-term climate change. Stomach contents analysis and morphology measurements were conducted on both species to determine if they were functionally equivalent with regard to zooplankton prey. Diet varied between species and with fish size. Krill ( Nyctiphanes australis ) was consumed by both species, with redbait feeding more heavily on small copepods. The diet overlap and morphometric characteristics indicated that these species are not equivalent with regard to prey and therefore changes in prey availability may have contributed to the observed shifts in relative abundance. The continued poleward extension of the East Australian Current is expected to favour small warm-water copepods; thus, redbait may have an advantage over jack mackerel due to prey preferences. An increase in relative abundance of redbait has decreased effort in surface fisheries and may impact on surface-feeding higher predators in this region.
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    Abiotic drivers of coastal fish community change during four decades in the Baltic Sea (2012)
    Oxford University Press
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    Publication Date: 2012-06-14
    Description: Olsson, J., Bergström, L., and Gårdmark, A. 2012. Abiotic drivers of coastal fish community change during four decades in the Baltic Sea – ICES Journal of Marine Science, 69: 961–970. Evidence for long-term change of marine ecosystems is increasing worldwide. Coastal areas harbour the socio-economically and ecologically most vital aquatic ecosystems, but are under increasing anthropogenic pressure. Little is known, however, about how environmental perturbations affect the development of coastal systems. In this paper, datasets of coastal fish communities covering almost four decades (early/mid 1970s to 2008) in three different basins of the Baltic Sea were analysed. There were clear changes in species composition over time in all but one dataset and coherence among basins in the timing of change. Changes were mainly associated with variables related to climate (water temperature, salinity, and North Atlantic Oscillation index), but less so with those reflecting nutrient status (nutrient concentrations and loading). Despite the importance of local water temperature, regional climatic variables were more important for the temporal development of communities. The results indicate that Baltic coastal fish communities have undergone large structural changes governed by processes acting on both local and regional scales. The findings suggest that ecological targets should be set accounting for long-term changes in community structure and that a common management of coastal and offshore ecosystems would be beneficial.
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    Trends of fish and elasmobranch landings in Italy: associated management implications (2012)
    Oxford University Press
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    Publication Date: 2012-06-14
    Description: Dell'Apa, A., Kimmel, D. G., and Clò, S. 2012. Trends of fish and elasmobranch landings in Italy: associated management implications. – ICES Journal of Marine Science, 69: 1045–1052. Elasmobranchs are extremely vulnerable to overexploitation, owing to their specific biology and life-history characteristics. However, European-managed shark fisheries have historically received less attention than fisheries targeting more commercially important fish species. We analysed and compared the national data of elasmobranch and fish landings in Italy between 1959 and 2004 to examine changes in fishery interest and the exploitation of elasmobranchs over time. Rays ( Raja spp.) and smooth-hounds ( Mustelus spp.) are the only elasmobranch categories present in the data, but also other similar species could have been mistakenly counted within these groups. Elasmobranch landings were steady until the beginning of the 1970s, peaked in the 1990s, then sharply declined. The mean annual landing for elasmobranchs between 1997 and 2004 decreased 77% compared with the previous years (1959–1982). This decrease may be attributed to overharvesting that occurred during the 1980s and 1990s in Italian seas. This was likely a direct consequence of the 41/82-law, which was developed to manage fish and not elasmobranchs. A direct effect of the 41/82-law was the establishment of an unreported and unregulated elasmobranch fishery since 1983 that lasted almost 10 years. We suggest that the conservation status of elasmobranch species in the Mediterranean and Black Seas be reconsidered.
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    Atlantic salmon post-smolt migration routes in the Gulf of St. Lawrence (2012)
    Oxford University Press
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    Publication Date: 2012-06-14
    Description: Lefèvre, M. A., Stokesbury, M. J. W., Whoriskey, F. G., and Dadswell, M. J. 2012. Atlantic salmon post-smolt migration routes in the Gulf of St. Lawrence – ICES Journal of Marine Science, 69: 981–990. The migration of Atlantic salmon ( Salmo salar ) post-smolts from the Rivière Saint-Jean on the north shore of the Gulf of St. Lawrence (Canada) was studied during 2009 and 2010. Salmon from rivers in this region spend ≥2 years at sea before returning to spawn, and are believed to migrate to ocean feeding areas off Greenland. To determine residency time in the nearshore environment, and to define the migration routes of post-smolts, tagged post-smolts were tracked passively in Jacques Cartier Strait and at the two exits of the Gulf of St. Lawrence to the Atlantic Ocean (Cabot Strait and the Strait of Belle Isle). Post-smolts moved rapidly south in the nearshore area; two of them were detected 45 km south of the estuary exit, suggesting that they were moving towards the centre of the Gulf of St. Lawrence. One tagged post-smolt was detected exiting the Gulf of St. Lawrence via the Strait of Belle Isle after 44 d and exhibited a minimum swimming speed of 14.4 km d –1 . There was no apparent linkage between the detection patterns of post-smolts and surface water temperatures or surface water currents close to shore. Post-smolts, however, appeared to orient to higher salinity.
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    Coastal migrations, temporary use of neighbouring rivers, and growth of sea trout (Salmo trutta) from nine northern Baltic Sea rivers (2012)
    Oxford University Press
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    Publication Date: 2012-06-14
    Description: Degerman, E., Leonardsson, K., and Lundqvist, H. 2012. Coastal migrations, temporary use of neighbouring rivers, and growth of Sea trout ( Salmo trutta ) from nine northern Baltic Sea rivers – ICES Journal of Marine Science, 69: 971–980. The wild migratory trout ( Salmo trutta ) stocks in the northern Baltic Sea are threatened, and the fishery is thought to play a significant role in the population decline. Therefore, knowledge about the migration patterns of these stocks is needed to develop appropriate management plans. For this reason, we analysed the movement pattern from recaptures of mandatory releases of tagged hatchery-reared trout smolt from nine rivers in the region (1998–2007). The median time from release until recapture was 366 days, and the median migration distance at recapture was 27 km, with a dominating southward direction for northern stocks. Most of the recaptured fish were immature (65%), and recaptures in rivers (55%) dominated over recaptures along the coast (44%). Riverine recaptures were most frequent during autumn–spring. A total of 16% of all recaptures in rivers occurred in non-natal rivers. Straying was about twice as frequent among fish from small rivers as from large rivers. The results from the river Gideälven indicate that using broodstock from other rivers in stocking programmes may lead to a high proportion of strayers. In addition, temporary use of neighbouring rivers was more frequent in large rivers during winter. Growth, in terms of length increment, was high, especially in fish from southern parts of the Baltic, and higher than in neighbouring warmer and more saline sea areas.
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    Brazilian sardine (Sardinella brasiliensis Steindachner, 1879) spawning and nursery habitats: spatial-scale partitioning and multiscale relationships with thermohaline descriptors (2012)
    Oxford University Press
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    Publication Date: 2012-06-14
    Description: de Souza Moraes, L. E., Marcolino Gherardi, D. F., Katsuragawa, M., and Tavares Paes, E. 2012. Brazilian sardine ( Sardinella brasiliensis Steindachner, 1879) spawning and nursery habitats: spatial-scale partitioning and multiscale relationships with thermohaline descriptors. – ICES Journal of Marine Science, 69: 939–952. We provide a detailed account of the spatial structure of the Brazilian sardine ( Sardinella brasiliensis ) spawning and nursery habitats, using ichthyoplankton data from nine surveys (1976–1993) covering the Southeastern Brazilian Bight (SBB). The spatial variability of sardine eggs and larvae was partitioned into predefined spatial-scale classes (broad scale, 200–500 km; medium scale, 50–100 km; and local scale, 〈50 km). The relationship between density distributions at both developmental stages and environmental descriptors (temperature and salinity) was also explored within these spatial scales. Spatial distributions of sardine eggs were mostly structured on medium and local scales, while larvae were characterized by broad- and medium-scale distributions. Broad- and medium-scale surface temperatures were positively correlated with sardine densities, for both developmental stages. Correlations with salinity were predominantly negative and concentrated on a medium scale. Broad-scale structuring might be explained by mesoscale processes, such as pulsing upwelling events and Brazil Current meandering at the northern portion of the SBB, while medium-scale relationships may be associated with local estuarine outflows. The results indicate that processes favouring vertical stability might regulate the spatial extensions of suitable spawning and nursery habitats for the Brazilian sardine.
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    Sprat feeding behaviour, selective predation, and impact on plaice egg mortality (2012)
    Oxford University Press
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    Publication Date: 2012-06-14
    Description: Plirú, A., van der Kooij, J., Engelhard, G. H., Fox, C. J., Milligan, S. P., and Hunter, E. 2012. Sprat feeding behaviour, selective predation, and impact on plaice egg mortality. – ICES Journal of Marine Science, 69: 1019–1029. Although the causes of fish egg and larval mortality are poorly understood, predation is thought to be a major contributing factor. The feeding behaviour of sprat at a plaice spawning ground in the Irish Sea during February 2009 is described and their contribution to plaice egg mortality investigated. Acoustic observations and analysis of stomach contents revealed diel behaviour, with dense schools associated with feeding formed during daylight dispersing into thinly spread aggregations at dusk. Of 338 stomachs analysed, 95% contained identifiable prey items. Feeding activity peaked between 10:00 and 18:00, for all food groups. Numerically, gadoid eggs were the most frequently consumed prey (64%), followed by copepods (25%) and plaice eggs (7%). Plaice eggs were present in 91% of the stomachs analysed. Converting stomach content data to daily consumption suggested that sprat may consume 73% of all plaice eggs spawned in the area. Predation by sprat appears to account for a large proportion of plaice egg mortality, so the abundance and distribution of this pelagic predator may have important consequences for the recruitment dynamics of other fish species. Moreover, fish eggs may be an important energy source for sprat during late winter, when alternative prey is scarce.
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    Reconstructing the population dynamics of sprat (Sprattus sprattus balticus) in the Baltic Sea in the 20th century (2012)
    Oxford University Press
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    Publication Date: 2012-06-14
    Description: Eero, M. 2012. Reconstructing the population dynamics of sprat ( Sprattus sprattus balticus ) in the Baltic Sea in the 20th century. – ICES Journal of Marine Science, 69: 1010–1018 . Long time-series of population dynamics are increasingly needed in order to understand human impacts on marine ecosystems and support their sustainable management. In this study, the estimates of sprat ( Sprattus sprattus balticus ) biomass in the Baltic Sea were extended back from the beginning of ICES stock assessments in 1974 to the early 1900s. The analyses identified peaks in sprat spawner biomass in the beginning of the 1930s, 1960s, and 1970s at ~900 kt. Only a half of that biomass was estimated for the late 1930s, for the period from the late 1940s to the mid-1950s, and for the mid-1960s. For the 1900s, fisheries landings suggest a relatively high biomass, similar to the early 1930s. The exploitation rate of sprat was low until the development of pelagic fisheries in the 1960s. Spatially resolved analyses from the 1960s onwards demonstrate changes in the distribution of sprat biomass over time. The average body weight of sprat by age in the 1950s to 1970s was higher than at present, but lower than during the 1980s to 1990s. The results of this study facilitate new analyses of the effects of climate, predation, and anthropogenic drivers on sprat, and contribute to setting long-term management strategies for the Baltic Sea.
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    Beam trawlermen take feet off gas in response to oil price hikes (2012)
    Oxford University Press
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    Publication Date: 2012-06-14
    Description: Beare, D., and Machiels, M. 2012. Beam trawlermen take feet off gas in response to oil price hikes. – ICES Journal of Marine Science, 69: 1064–1068. Average towing speed by Dutch beam trawlermen has fallen substantially between 2002 and 2009. Changes in towing speed are related to changes in oil price. The price of their valuable main target species (sole, Solea vulgaris ) did not influence towing speed.
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    Genetic characterization of the endangered and endemic anchialine squat lobster Munidopsis polymorpha from Lanzarote (Canary Islands): management implications (2012)
    Oxford University Press
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    Publication Date: 2012-06-14
    Description: Cabezas, P., Alda, F., Macpherson, E., and Machordom, A. 2012. Genetic characterization of the endangered and endemic anchialine squat lobster Munidopsis polymorpha from Lanzarote (Canary Islands): management implications. – ICES Journal of Marine Science, 69: 1030–1037. Anchialine species show restricted geographic ranges, high habitat specificity, and small population sizes. These factors make them particularly vulnerable to human activities, yet little is known about their ecology and evolutionary history. Munidopsis polymorpha is a decapod endemic to an anchialine cave system of the Corona lava tube in Lanzarote (Canary Islands). The present study, the first genetic survey conducted on this largely unknown species, was designed to characterize its genetic diversity, population structure and recent demographic history, using sequence data for the cytochrome oxidase I gene and eight microsatellites. A single haplotype was identified in the mitochondrial dataset. Nuclear genetic diversity was also low (average = 4.375 ± 1.685). No significant genetic structure was detected between sampling sites and years, either by analysis of molecular variance ( F ST = 0.006, p = 0.110) or Bayesian clustering analysis ( K = 1), indicating this species should be treated as a single management unit. Neither did we find evidence for a recent bottleneck event, and estimates of effective population size were extremely low (~50). The lack of population structure, low genetic diversity and extremely low effective population size reinforce the high degree of isolation and endemicity of this species, and, consequently, the need to implement appropriate management actions.
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    Regional-scale benthic monitoring for ecosystem-based fisheries management (EBFM) using an autonomous underwater vehicle (AUV) (2012)
    Oxford University Press
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    Publication Date: 2012-06-14
    Description: Smale, D. A., Kendrick, G. A., Harvey, E. S., Langlois, T. J., Hovey, R. K., Van Niel, K. P., Waddington, K. I., Bellchambers, L. M., Pember, M. B., Babcock, R. C., Vanderklift, M. A., Thomson, D. P., Jakuba, M. V., Pizarro, O., and Williams, S. B. 2012. Regional-scale benthic monitoring for ecosystem-based fisheries management (EBFM) using an autonomous underwater vehicle (AUV). – ICES Journal of Marine Science, 69: 1108–1118. Monitoring marine habitats and biodiversity is critical for understanding ecological processes, conserving natural resources, and achieving ecosystem-based fisheries management (EBFM). Here, we describe the application of autonomous underwater vehicle (AUV) technology to conduct ongoing monitoring of benthic habitats at two key locations in Western Australia. Benthic assemblages on rocky reefs were sampled with an AUV, which captured 〉200 000 geo-referenced images. Surveys were designed to obtain 100% coverage of 25 x 25 m patches of benthic habitat. In 2010, multiple patches were surveyed at 15–40-m depths at three reference sites at the Houtman Abrolhos Islands and at six reference sites at Rottnest Island. The following year, repeat surveys of the same geo-referenced patches were conducted. Benthic assemblages at the Houtman Abrolhos Islands were varied in that one reference site was dominated by hard corals, whereas the other two were macroalgae dominated. Conversely, assemblages at Rottnest Island were dominated by the kelp Ecklonia radiata . The AUV resurveyed each patch with high precision and demonstrated adequate power to detect change. Repeated observations at the reference sites will track natural variability in benthic habitat structure, which in turn will facilitate the detection of ecological change and ultimately feed back into EBFM processes.
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    Target strength and tilt-angle distribution of the lesser sandeel (Ammodytes marinus) (2012)
    Oxford University Press
    Details
    Publication Date: 2012-06-14
    Description: Kubilius, R., and Ona, E. 2012. Target strength and tilt-angle distribution of lesser sandeel ( Ammodytes marinus ) – ICES Journal of Marine Science, 69: 1099–1107. North Sea stocks of lesser sandeel have recently become depleted, and improved methods for abundance estimation are sought. This paper focuses on the acoustic target strength (TS) and orientation of sandeel, measured simultaneously in several field experiments. A specially designed cubic cage, fitted with an echosounder and a video camera, was lowered onto the sea bottom, trapping wild sandeel inside. Methods for manually selecting valid echotraces from individual sandeel are described. Scattered mean TS values from several experiments are reported. These are, in spite of the observed variability, summarized in a TS–fish length (cm) relationship as TS = 20logL – 93.1 (dB) at 200 kHz. We believe that the accuracy of the relationship may still be debated; incorporating larger uncertainty in the overall mean TS will increase the total uncertainty of the stock biomass estimate from sandeel acoustic surveys. This uncertainty is now, using standard narrow-beam echosounders, dominated by the fish patchiness relative to the survey coverage. Results from pilot investigations of the sandeel swimming orientation using video cameras are also presented, showing that sandeel usually has an anguilliform swimming pattern with substantial positive (head-up) tilt. The spread of the tilt-angle distribution is also larger than for more neutrally buoyant fishes.
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    Assessing fishery footprints and the trade-offs between landings value, habitat sensitivity, and fishing impacts to inform marine spatial planning and an ecosystem approach (2012)
    Oxford University Press
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    Publication Date: 2012-06-14
    Description: Jennings, S., Lee, J., and Hiddink, J. G. 2012. Assessing fishery footprints and the trade-offs between landings value, habitat sensitivity, and fishing impacts to inform marine spatial planning and an ecosystem approach. – ICES Journal of Marine Science, 69: 1053–1063. European and national policy commitments require further integration of fisheries and environmental management. We measured fishery footprints and assessed trade-offs between landings value, habitat sensitivity, and beam trawling impacts in UK territorial waters in the southern and central North Sea where marine spatial planning is underway and a network of Marine Protected Areas has been proposed. For fleets (UK and non-UK) and years (2006–2010) considered, total trawled area included extensive ‘margins’ that always accounted for a smaller proportion of total fishing effort and value (proportions investigated were ≤10, 20, or 30%) than their proportional contribution to total habitat sensitivity and trawling impact. Interannual and fleet-related differences in the distribution and intensity of trawling activity, driven by location choice and fisheries regulations, had more influence on overall trawling impacts than the exclusion of beam trawlers from a proposed network of Marine Protected Areas. If reducing habitat impacts is adopted as an objective of fisheries or environmental management, then the direct management of fishing footprints, e.g. by defining fishing grounds that exclude existing margins, can disproportionately reduce trawling impacts per unit effort or value.
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    Managing harvest risk with catch-pooling cooperatives (2012)
    Oxford University Press
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    Publication Date: 2012-06-14
    Description: Sethi, S. A., Dalton, M., and Hilborn, R. 2012. Managing harvest risk with catch-pooling cooperatives – ICES Journal of Marine Science, 69: 1038–1044. Catch-pooling cooperatives are a strategy for fishers to manage variability which can be organized independently of a central management agency. We examined the statistical properties of equal-share catch-pooling cooperatives, and tested their potential to mitigate risk using data from two Bering Sea crab fisheries prior to rationalization. The results suggest that small cooperatives of crabbers could have reduced vessel-level catch risk by as much as 40% in the red king crab fishery, but would have been ineffective in the snow crab fishery. Analytical examination of catch variances under cooperatives explains the discrepancy between the two fisheries and demonstrates that variability reduction depends on the degree of correlation amongst participants' catches. In the best-case scenario, catch-pooling cooperatives can diversify away all season to season variation resulting from individuals' luck and skill, leaving only variation in fishery-wide harvest.
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  • 93
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    What is behind fleet evolution: a framework for flow analysis and application to the French Atlantic fleet (2012)
    Oxford University Press
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    Publication Date: 2012-06-14
    Description: Quillérou, E. and Guyader, O. 2012. What is behind fleet evolution: a framework for flow analysis and application to the French Atlantic fleet – ICES Journal of Marine Science, 69: 1069–1077. The study of fishery dynamics considers national-level fleet evolution. It has, however, failed to consider the flows behind fleet evolution as well as the impact of the dynamics of owners of invested capital on fleet evolution. This paper establishes a general conceptual framework which identifies different vessel and owner flows behind fleet evolution and some relationships between these flows. This descriptive conceptual framework aims to change the current focus on drivers of fleet evolution to drivers of the flows behind fleet evolution. We identify a direct impact of vessel flows on the fleet size and nature, and an indirect impact of the movements of capital owners on the fleet evolution (size and nature). This conceptual framework is illustrated using French Atlantic fleet data over a 15-year period (1994–2008). It is shown that the identified flows vary in size and nature and therefore impact differently on the fleet evolution. This description also shows some dependence of vessel flows on owner dynamics. This relationship should be better taken into account for more effective capacity management.
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    Impact of naval sonar signals on Atlantic herring (Clupea harengus) during summer feeding (2012)
    Oxford University Press
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    Publication Date: 2012-06-14
    Description: Sivle, L. D., Kvadsheim, P. H., Ainslie, M. A., Solow, A., Handegard, N. O. Nordlund, N., and Lam, F-P. A. 2012. Impact of naval sonar signals on Atlantic herring ( Clupea harengus ) during summer feeding. – ICES Journal of Marine Science, 69: 1078–1085. Naval anti-submarine sonars produce intense sounds within the hearing range of Atlantic herring ( Clupea harengus ). In this study, schools of Atlantic herring were exposed to sonar signals of 1–2 kHz (low-frequency active sonar, LFAS) and 6–7 kHz (mid-frequency active sonar, MFAS) and playbacks of killer whale feeding sounds during their summer feeding migration in the Norwegian Sea. The fish schools neither significantly dived nor changed their packing density in response to the LFAS and MFAS transmissions received by the fish at estimated sound pressure levels ( SPL s; RMS) up to 176 and 157 dB re 1 μPa and estimated cumulative sound exposure levels up to 181 and 162 dB re 1 μPa² s, respectively. In contrast, killer whale feeding sounds induced diving responses at received SPL s at ~150 dB re 1 μPa. Herring behaviour was studied by using a 116-kHz hull mounted fishery sonar. This seems a promising method for studying the behaviour of free-ranging fish in situations in which other methods are difficult to use, such as migrating schools and fish close to the surface.
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  • 95
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    Utility of 18-kHz acoustic data for abundance estimation of Atlantic herring (Clupea harengus) (2012)
    Oxford University Press
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    Publication Date: 2012-06-14
    Description: Saunders, R. A., O'Donnell, C., Korneliussen, R. J., Fässler, S. M. M., Clarke, M. W., Egan, A, and Reid, D. 2012. Utility of 18-kHz acoustic data for abundance estimation of Atlantic herring ( Clupea harengus ) – ICES Journal of Marine Science, 69: 1086–1098. Current acoustic survey protocols for Atlantic herring ( Clupea harengus ) abundance estimation are principally dependent upon 38-kHz backscatter data. This can constitute a substantial problem for robust stock assessment when 38-kHz data are compromised. Research vessels now typically collect multifrequency data during acoustic surveys, which could be used to remediate such situations. Here, we investigate the utility of using 18- and 120-kHz data for herring abundance estimation when the standard 38-kHz approach is not possible. Estimates of herring abundance/biomass in the Celtic Sea (2007–2010) were calculated at 18, 38, and 120 kHz using the standard 38-kHz target-strength (TS) model and geometrically equivalent TS models at 18 and 120 kHz. These estimates were compared to assess the level of coherence between the three frequencies, and 18-kHz-derived estimates were subsequently input into standard 38-kHz-based population models to evaluate the impact on the assessment. Results showed that estimates of herring abundance/biomass from 18 and 38 kHz acoustic integration varied by only 0.3–5.4%, and acoustically derived numbers-at-age estimates were not significantly ( p 〉 0.05) different from 1:1. Estimates at 120 kHz were also robust. Furthermore, 18-kHz-derived estimates did not significantly change the assessment model output, indicating that 18-kHz data can be used for herring stock assessment purposes.
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    Good ethics or political and cultural censoring in science? (2012)
    Oxford University Press
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    Publication Date: 2012-04-10
    Description: Torrissen, O., Glover, K. A., Haug, T., Misund, O. A., Skaug, H. J., and Kaiser, M. 2012. Good ethics or political and cultural censoring in science? – ICES Journal of Marine Science, 69: 493–497. Peer-reviewed journals are the cornerstones to communicating scientific results. They play a crucial role in quality assurance through the review process, but they also create opportunities for discussions in the scientific community on the implications of the results or validation of methods and data. This requires that journals adhere to commonly accepted scientific standards and are open about their editorial policy. Norwegian scientists experience problems in getting research on minke whales accepted for publication where the data have been collected in association with commercial whaling. The journal Biology Letters refuses to publish papers based on data from the Norwegian whale register while publically claiming a sole focus on scientific quality. Although there are good arguments for claiming that clearly unethical research should not be rewarded with scientific publications, one also has to realize that some fields of research are beset with unresolved ethical and cultural debates. In these cases, it is to the benefit of the progress of science, and indeed society, to be open about the issues and support arguments through scientific studies. Political or cultural censoring of scientific information will in any case jeopardize the role of journals in quality assurance of scientific research and undermine the credibility of science as a supplier of objective and reliable knowledge.
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  • 97
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    Seasonal dynamics of growth and mortality suggest contrasting population structure and ecology for cod, pollack, and saithe in a Norwegian fjord (2012)
    Oxford University Press
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    Publication Date: 2012-04-10
    Description: Heino, M., Svåsand, T., Nordeide, J. T., Otterå, H. 2012. Seasonal dynamics of growth and mortality suggest contrasting population structure and ecology for cod, pollack, and saithe in a Norwegian fjord. – ICES Journal of Marine Science, 69: 537–546. We study the dynamics of Atlantic cod ( Gadus morhua L.), pollack ( Pollachius pollachius L.), and saithe ( Pollachius virens L.) in Masfjorden, a small fjord in western Norway. Annually, cohorts of pollack and cod grow in size and decline in abundance, as expected of closed populations, whereas saithe virtually disappear before maturity. Seasonally, in contrast, the dynamics of cod and pollack differ. Pollack shows a regular growth pattern, with most of the growth taking place in summer. Its abundance-at-age shows strong seasonal variations, with a marked increase from spring to summer followed by a decline through autumn and winter. These patterns relate partly to seasonal changes in depth distribution and catchability. Combined with the observation that spawning-stage pollack are abundant in spring, we interpret these patterns to suggest that pollack in Masfjorden represent a dynamically independent unit. Seasonal changes in abundance are less marked for cod, and seasonal changes in depth distribution seem insignificant. However, cod shows an unusual pattern in length at age, with no apparent growth in summer and fast growth in autumn. These patterns suggest that the population structure of cod may be more open than that of pollack and may involve mixing of more than one population component.
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  • 98
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    Historical variations in the year-class strength of beaked redfish (Sebastes mentella) in the Barents Sea (2012)
    Oxford University Press
    Details
    Publication Date: 2012-04-10
    Description: Planque, B., Johannesen, E., Drevetnyak, K. V., and Nedreaas, K. H. 2012. Historical variations in the year-class strength of beaked redfish ( Sebastes mentella ) in the Barents Sea. – ICES Journal of Marine Science, 69: 547–552. The present work provides the first quantitative estimate of the historical fluctuations in the year-class strength of beaked redfish in the Barents Sea. The year-class strength index is based on scientific survey data collected by Norway and Russia during the past three decades. It is defined as the effective number of 0-group fish that will eventually enter the fishery. Uncertainties in the year-class strength indices are estimated using a statistical modelling approach, which accounts for observation errors. The reconstructed series indicate clear periods of high recruitment (late 1980s–early 1990s) and 8 years of near complete recruitment failure (1996–2003). The apparent recovery in recent years is highly uncertain and needs to be confirmed by future observations. The modelling approach developed here can be applied to other fish stocks for which catch-at-age data are available from several surveys.
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  • 99
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    Fishing intensity metrics for use in overfishing determination (2012)
    Oxford University Press
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    Publication Date: 2012-04-10
    Description: Cordue, P. L. 2012. Fishing intensity metrics for use in overfishing determination. – ICES Journal of Marine Science, 69: 615–623. The issue of constructing a technically correct fishing intensity metric from the output of a stock assessment model is considered. Four metrics of annual overall "fishing intensity" are defined. The metrics are applicable to age- or length-structured stock assessment models, which may, or may not, include complex spatial and temporal structure in the population and the fisheries. Two of the metrics are termed "direct" as they are calculated from the model output in the given year. Equivalent annual U is a number-based exploitation rate, and equivalent annual F is an average fishing mortality rate. The other two metrics, equilibrium stock depletion ( ESD ) and spawning potential ratio ( SPR ), measure fishing intensity in terms of the potential long-term effect on the stock (via 1– ESD and 1– SPR ). The use of the metrics for overfishing determination is illustrated with a simple, spatial, two-fishery model. Summary statistics, which are sometimes used as a measure of fishing intensity, such as total catch over a reference biomass, or a number-weighted F are shown to be technically invalid for overfishing determination. The common approach, for virtual population analysis assessments, of using an average F over a specified age range is also discussed.
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  • 100
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    Responses to changes in sprat abundance of common tern breeding numbers at 12 colonies in the Firth of Forth, east Scotland (2012)
    Oxford University Press
    Details
    Publication Date: 2012-04-10
    Description: Jennings, G., McGlashan, D. J. and Furness, R. W. 2012. Responses to changes in sprat abundance of common tern breeding numbers at 12 colonies in the Firth of Forth, east Scotland. – ICES Journal of Marine Science, 69: 572–577. Breeding numbers collected in 12 common tern Sterna hirundo colonies in the Firth of Forth, Scotland, along with sprat landings data for the area, were used to investigate how the dynamics of a shared prey resource may affect different colonies in a region. Between 1969 and 2010, breeding numbers fluctuated much more at individual colonies than across the region as a whole, with the largest colonies showing opposite trends, suggesting relocation by birds. This indicates that data from individual colonies may be less useful than regional numbers when using seabirds as indicators. Tern breeding numbers in the region were reduced when the sprat stock ( Sprattus sprattus ) collapsed in the early 1980s after targeted fishing, but recovered during recent decades when the stock was unfished. This should be considered for reopening the Firth of Forth sprat fishery, as well as in the management of other shared prey stocks.
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