ALBERT

Description: Bachiller, E., Cotano, U., Boyra, G., and Irigoien, X. 2013. Spatial distribution of the stomach weights of juvenile anchovy ( Engraulis encrasicolus L.) in the Bay of Biscay. – ICES Journal of Marine Science, 70: 362–378. Previous studies have shown that the survival of larval and juvenile anchovy off the continental shelf in the Bay of Biscay is not significantly different from that observed on the shelf, even though the food concentration is significantly higher on the shelf. In this paper we investigate the causes for the lack of relationship between food and survival for anchovy juvenile through analyses of feeding activity versus zooplankton distribution (in the transition from summer to fall from 2003 to 2010). The spatial distribution of the stomach weights of juvenile anchovy in relation to body size on and off the shelf revealed higher stomach fullness in areas off the shelf, where less zooplankton biomass was available. This result indicates that the food concentration is not always the main factor determining ingestion in fish. A situation of comparatively lesser prey abundance may provide better feeding conditions when combined with lower predation risk and lower light attenuation. In addition, the relatively heavier stomachs found in anchovies caught in years of higher recruitment indices suggest a large stomach content may be a symptom of good biological condition that may favour the winter survival of a larger fraction of the juvenile stock.

Description: Van Hoof, L. 2013. Design or pragmatic evolution: applying ITQs in EU fisheries management. – ICES Journal of Marine Science, 70: 462–470. Among the proposals for the 2012 revision of the EU Common Fisheries Policy, a strong case is made for the introduction of a system of rights-based management. The EU perceives individual fishing concessions as an important instrument for capacity management. We will use the introduction of individual tradable quotas in the management of the Dutch North Sea beam trawl fisheries as a case for exploring the effect of the introduction of such an instrument. The effect will be assessed in terms of reduction of fishing capacity in the Dutch beam trawl fleet and its economic and social impact. These Dutch experiences will be translated to the current debate on the reform of the EU Common Fisheries Policy. Especially, we will focus on the issues of "relative stability", the concentration of rights, and the effects on the small-scale fisheries sector. Some of the negative effects associated with individual tradable rights can be addressed through design. However, trying to maintain stability and counter perceived negative impacts on fishing communities will modify the effect of introducing individual fishing concessions.

Description: Spitz, J., Chouvelon, T., Cardinaud, M., Kostecki, C., and Lorance, P. 2013. Prey preferences of adult sea bass Dicentrarchus labrax in the northeastern Atlantic: implications for bycatch of common dolphin Delphinus delphis – ICES Journal of Marine Science, 70: 452–461. In the northeastern Atlantic, adult sea bass ( Dicentrarchus labrax ) is one of largest fish living on the shelf, and this species has important commercial value. However, pelagic trawl fisheries that target sea bass have negative operational interactions with common dolphins ( Delphinus delphis ). Our goal was to determine the diet of adult sea bass in the Bay of Biscay from stomach-content and stable-isotope analyses, and explore the dietary overlap between sea bass and common dolphins. We found that sea bass primarily target small pelagic fish, most notably mackerel ( Scomber scombrus ), scads ( Trachurus spp.), anchovy ( Engraulis encrasicolus ), and sardine ( Sardina pilchardus ). These four species also dominated the diets of common dolphins. This overlap in feeding preferences could increase the risk of dolphins being caught by trawl fisheries while feeding among sea bass, and may be an underlying mechanism to explain the high rate of common dolphin bycatch observed in the pelagic trawl fishery for sea bass in the Bay of Biscay. Understanding the foraging ecology and trophic interactions of predator species is an essential step for identifying and resolving management issues in the northeastern Atlantic and other marine ecosystems.

Description: Lassen, H., Pedersen, S. A., Frost, H., and Hoff. A. 2013. Fishery management advice with ecosystem considerations. – ICES Journal of Marine Science, 70: 471–479. The European Union Marine Strategy Framework Directive (MSFD) includes four descriptors of Good Environmental Status (GES) which are affected by fishing activity. These descriptors are: biodiversity, fish stocks, foodweb, and seabed integrity. This paper shows how these descriptors can be related to variables within an ecological model and how an ecological model can be used to analyse whether the fishing pressure that is estimated based on bioeconomic criteria is within general sustainable limits. The paper presents an example of such an analysis of the Eastern Baltic cod fishery using two models: a bioeconomic model and an ecological model. The models are calibrated based on historic data. The mapping between the descriptors specified by MSFD and variables available for analysis in the models is incomplete, e.g. genetics and spatial structures are not included in the models. The models can be used strategically, providing a qualitative understanding of the anticipated relative changes.

Description: Finley, C. and Oreskes, N. 2013. Maximum sustained yield: a policy disguised as science. – ICES Journal of Marine Science, 70: 245–250. Overfishing is most commonly explained as an example of the tragedy of the commons, where individuals are unable to control their activities, leading to the destruction of the resource they are dependent on. The historical record suggests otherwise. Between1949 and 1958, the US State Department used fisheries science, and especially the concept of maximum sustained yield (MSY) as a political tool to achieve its foreign policy objectives. During the Cold War, the Department thought that if countries were allowed to restrict fishing in their waters, it might lead to restrictions on passage of military vessels. While there has been much criticism of MSY and its failure to conserve fish stocks, there has been little attention paid to the political context in which MSY was adopted.

Description: The sharing of the Northeast Atlantic mackerel ( Scomber scombrus ) stock is analysed as a game between four parties: the European Union, Norway, the Faroe Islands, and Iceland. Consideration is given to how the outcome depends on the nature of the stock's migrations. Two types of migrations are considered: (i) density-dependent, where the mackerel migrates into the Icelandic economic zone only if it exceeds 3.5 million t, and (ii) stochastic migrations, where the said migrations are stochastic. It is determined that the Faroe Islands would never accept a cooperative solution wherein they can only fish with the globally optimal fishing mortality within their own zone. This is also true for Iceland when the migrations into her zone are stochastic, but not if they are density-dependent. In the latter case, the other players have incentives to retaliate to Icelandic overfishing by fishing harder, which greatly reduces the number of years when mackerel are available in the Icelandic zone. It is assumed that the objective is maximization of the catch volume over a time-horizon of 50 years.

Description: Harris, P. T., Bridge, T. C. L., Beaman, R. J., Webster, J. M., Nichol, S. L., and Brooke, B. P. 2013. Submerged banks in the Great Barrier Reef, Australia, greatly increase available coral reef habitat. – ICES Journal of Marine Science, 70: 284–293. Anthropogenic global ocean warming is predicted to cause bleaching of many near-sea-surface (NSS) coral reefs, placing increased importance on deeper reef habitats to maintain coral reef biodiversity and ecosystem function. However, the location and spatial extent of many deep reef habitats is poorly known. The question arises: how common are deep reef habitats in comparison with NSS reefs? We used a dataset from the Great Barrier Reef (GBR) to show that only about 39% of available seabed on submerged banks is capped by NSS coral reefs (16 110 km 2 ); the other 61% of bank area (25 600 km 2 ) is submerged at a mean depth of around 27 m and represents potential deep reef habitat that is spatially distributed along the GBR continental shelf in the same latitudinal distribution as NSS reefs. Out of 25 600 km 2 of submerged bank area, predictive habitat modelling indicates that more than half (around 14 000 km 2 ) is suitable habitat for coral communities.

Description: Dutertre, M., Hamon D., Chevalier C., and Ehrhold, A. 2013. The use of the relationships between environmental factors and benthic macrofaunal distribution in the establishment of a baseline for coastal management – ICES Journal of Marine Science, 70: 294–308. Relationships between benthic macrofauna and natural abiotic factors were studied along the coastal fringe of South Brittany, situated north of the Gulf of Biscay on the French Atlantic continental shelf. Within the framework of the REBENT network, sediment characteristics, depth, and macrofaunal abundance were determined for 95 stations spread over five subtidal sectors, using a combination of seabed acoustic remote sensing systems and grab sampling. The physico-chemical properties of the water column and the hydrodynamic conditions were generated by validated three-dimensional environmental models which take into account variations over shorter temporal scales. Multivariate analyses ranked 16 natural abiotic variables according to the significance of their influence on the macrofauna. Together these variables explained 51% of spatial variation in the macrofauna, with morpho-sedimentological and hydrological factors contributing 22% and 26%, respectively. The outputs from validated three-dimensional environmental models appear to be useful interpretational tools for benthic ecology studies, especially in estuarine and coastal ecosystems with high environmental variability due to regular freshwater inputs. Ten major species assemblages were identified using biological and physical characteristics. The results provide important baseline knowledge for future ecosystem and resource management.

Description: Prigge, E., Marohn, L., Oeberst R., and Hanel, R. 2013. Model prediction vs. reality—testing the predictions of a European eel ( Anguilla anguilla ) stock dynamics model against the in situ observation of silver eel escapement in compliance with the European eel regulation – ICES Journal of Marine Science, 70: 309–318. A direct monitoring of European silver eel ( Anguilla anguilla , L) escapement from rivers and estuaries has been proven to be challenging, and a Europe-wide documentation of escaping silver eel numbers therefore hardly seems realistic. To reinforce management decisions, policy-makers are thus widely reliant on the accuracy of escapement models. A 3-year programme of silver eel escapement monitoring was undertaken to compile model input data and revise an eel population model (German Eel Model II; GEM II) already used in the decision-making process of management authorities. By compiling necessary input data and analysing vital system-specific population characteristics, it was possible to compare the documented silver eel escapement with the modelled potential silver eel escapement. Resulting model predictions were close to actually monitored escapement numbers, which were distinctly lower than reference escapement values for the same freshwater system given in the implementation report of the German Eel Management Plans. Applying different commercial and recreational catch scenarios revealed the sensitivity of the model. The results show the potential of the GEM II and highlight the importance of high-quality input data to use model predictions as the basis for management measures.

Description: Sumaila, U. R. 2013. How to make progress in disciplining overfishing subsidies. ICES Journal of Marine Science, 70: 251–258. The World Trade Organization (WTO) has been working for more than seven years now to discipline overfishing subsidies, as mandated by the global community, without success. I argue that this failure is partly because WTO negotiators aim for an all-inclusive deal, i.e. negotiations are conducted as a "single undertaking", whereby results must be achieved in all areas. Negotiators are required to broker an all-inclusive deal for all maritime WTO member countries and for all fisheries, whether domestic or international; small or large scale; developing or developed country fisheries. It is argued here that this commitment to a "single undertaking" does not align the incentive to remove subsidies with national interests, and therefore needs to be changed by splitting the world's fisheries into domestic and international fisheries. In this way, the battle for eliminating overfishing subsidies for some stocks would shift to home countries, and for others this would still rest with the international community. This split, it is argued, would align the incentives and improve the chances of eliminating overfishing subsidies.

Description: Morgan, M. J., Garabana, D., Rideout, R. M., Román, E., Pérez-Rodriguez, A. and Saborido-Rey, F. 2013. Changes in distribution of Greenland halibut in a varying environment. – ICES Journal of Marine Science, 70: 352–361. Fish are expected to respond to changing oceanographic temperature by altering their distribution. Off the coast of Newfoundland, Canada, there have been major changes in oceanographic temperature over the last several decades, with both record cold and record warm years being observed. Greenland halibut is an important flatfish species in the area, and is distributed in deep waters over a very wide geographic range. Thus, it might be buffered from temperature change in the overall area by reduced temperature variation at depth, and the diverse temperature conditions over its wide range. We examined intrapopulation variation in temperature and depth distribution, and the biological changes in relation to changes in available temperature. On the Flemish Cap, variation in available temperature was limited, and changes in depth were related to changing age composition and the differential depth distribution with age/size. In other areas there was a larger decline in available temperature, and associated with this, Greenland halibut moved to deeper waters and occupied warmer temperatures than they had previously. Concurrently, growth declined and condition increased. This study shows that shifts in distribution may not result in maintenance of homogeneous environmental conditions, and that resulting biological changes will be difficult to predict.

Description: Hufnagl, M., Huebert, K. B., and Temming, A. 2013. How does seasonal variability in growth, recruitment, and mortality affect the performance of length-based mortality and asymptotic length estimates in aquatic resources? – ICES Journal of Marine Science, 70: 329–341. We tested the sensitivity of eight methods for estimating total mortality from size frequencies (modified Wetherall; Powell; Beverton and Holt; Jones and van Zalinge; Hoenig; Ssentongo and Larkin; seasonal and non-seasonal Length Converted Catch Curve) to violations of basic assumptions, such as seasonal growth, mortality, recruitment and variable asymptotic length L or growth parameter K . For each method, bias was estimated by simulating length frequency distributions with different combinations of known L , Z and K values, calculating ( Z / K ) and L estimates, and comparing the true input with the estimated output values. Input mortality was generally underestimated by all methods and in 27% of all simulations no method provided estimates within ± 1. Spring recruitment especially negatively influenced the mortality estimate. A decision tree was developed that provides general guidance in selecting appropriate methods despite violated assumptions, but species-specific case studies are recommended. An example of a species-specific study is provided for the brown shrimp, Crangon crangon. Despite inherent limitations for all methods, the results illustrate that estimates of and Z for brown shrimp can be improved substantially by selecting suitable methods and correcting for observed bias.

Description: Brunel, T., and Piet, G. J. 2013. Is age structure a relevant criterion for the health of fish stocks? – ICES Journal of Marine Science, 70: 270–283. The age and size structure of exploited fish stocks is one of the criteria for Good Environmental Status of commercial fish. However, two underlying assumptions to this criterion remain to be tested: first, that a well-balanced age structure is indeed indicative of a "healthier" stock, and second, that managers can exert a control on the age structure, independently from the regulation of stock abundance. This study investigates these questions using simulations from a population model in which recruitment is based on egg production, which is more sensitive to age structure variations than the traditionally used spawning stock biomass (SSB) and that was parameterized to represent the population dynamics of North Sea cod, plaice, and herring. Our results show that (i) the age structure is highly dependent on the selection pattern, as well as on the level of fishing mortality; (ii) the selection pattern determines the ability of fish stocks to withstand, and recover from, external perturbation; and (iii) the selection pattern determines the output of the fishery providing the management option to balance stable but relatively low yields vs strongly fluctuating high yields. Therefore, we propose to make the selection pattern, for which clear management targets can be set, a policy goal instead of the age structure that is currently in place.

Description: Bréchon, A. L., Coombs S. H., Sims D. W., and Griffiths A. M. 2013. Development of a rapid genetic technique for the identification of clupeid larvae in the Western English Channel and investigation of mislabelling in processed fish products – ICES Journal of Marine Science, 70: 399–407. A novel genetic technique, involving real-time polymerase chain reaction (PCR) and high-resolution melt (HRM) analysis was developed, which successfully identified four species of clupeid larvae from the Western English Channel and revealed the presence of herring ( Clupea harengus ). This was unexpected in a context of global warming as herring are at the southern limit of their range off southwest England, where the larvae are generally very rare. The application of the method in cases of degraded DNA, such as in processed fishery products, was also assessed, revealing a low level of misidentification or equivocal identity (8.3%). Eight-year-old formalin-preserved samples were also analysed successfully. This highlights the potentially broad applications for HRM-based approaches to species identification in marine science.

Description: Quetglas, A., Ordines, F., Hidalgo, M., Monserrat, S., Ruiz, S., Amores, Á., Moranta, J., and Massutí, E. 2013. Synchronous combined effects of fishing and climate within a demersal community. – ICES Journal of Marine Science, 70: 319–328. Accumulating evidence shows that fishing exploitation and environmental variables can synergistically affect the population dynamics of exploited populations. Here, we document an interaction between fishing impact and climate variability that triggered a synchronic response in the population fluctuations of six exploited species in the Mediterranean from 1965–2008. Throughout this period, the fishing activity experienced a sharp increase in fishing effort, which caused all stocks to shift from an early period of underexploitation to a later period of overexploitation. This change altered the population resilience of the stocks and brought about an increase in the sensitivity of its dynamics to climate variability. Landings increased exponentially when underexploited but displayed an oscillatory behaviour once overexploited. Climatic indices, related to the Mediterranean mesoscale hydrography and large-scale north Atlantic climatic variability, seemed to affect the species with broader age structure and longer lifespan, while the global-scale El Niño Southern Oscillation index (ENSO) positively influenced the population abundances of species with a narrow age structure and short lifespan. The species affected by ENSO preferentially inhabit the continental shelf, suggesting that Mediterranean shelf ecosystems are sensitive to the hydroclimatic variability linked to global climate.

Description: Papetti, C., Di Franco, A., Zane, L., Guidetti, P., De Simone, V., Spizzotin, M., Zorica, B., Cikes Kec, V. and Mazzoldi, C. 2013. Single population and common natal origin for Adriatic Scomber scombrus stocks: evidence from an integrated approach – ICES Journal of Marine Science, 70: 387–398. In order to implement proper fishery management strategies aimed at avoiding stock declines, information about connectivity among stocks and populations is critically required. In this perspective, the present study investigated population structure of the Atlantic mackerel Scomber scombrus in the northern–central Adriatic Sea by integrating multiple approaches (analysis of fisheries data, population genetics, and otolith chemistry). Monthly data of fishery landings indicate a latitudinal trend along the western Adriatic coast, with Atlantic mackerel disappearing from the northern waters in winter, corresponding to the reproductive season. Population genetic analyses by genotyping of eight microsatellites clearly point to the presence of a single panmictic population in the northern–central Adriatic Sea. Otolith cores of samples from the northern–central Adriatic were chemically homogeneous, suggesting a common spawning ground. These results strongly suggest that Atlantic mackerel perform an autumn–winter migration in the northern–central Adriatic Sea, from the northern to the central sector, to reach a single spawning ground, and that a single population is present in this area. Considering that S. scombrus has shown a marked decline in the last 40 years in the Adriatic, this study highlights a potential high vulnerability to collapse by overfishing for the Atlantic mackerel stocks in this geographic area.

Description: Uusitalo, L., Fleming-Lehtinen, V., Hällfors, H., Jaanus A., Hällfors, S., and London, L. 2013. A novel approach for estimating phytoplankton biodiversity – ICES Journal of Marine Science, 70: 408–417. Maintaining biodiversity is one of the main priorities in environmental protection. The biodiversity of phytoplankton, the key primary producers in the marine ecosystem, is, however, often very difficult to estimate, since the phytoplankton assemblage includes a vast number of taxa, many of which occur in such small quantities that they may not be recorded in routine sampling. Moreover, many taxa cannot be identified to species level by routine methods such as light microscopy of preserved samples, even by a skilled taxonomist. This means that, in general, we cannot assume to have a complete list of species in the ecosystem at any given point in time. In this paper, we present an approach for evaluating phytoplankton biodiversity in spite of this challenge. Since eutrophication, which increases phytoplankton biomass, has been identified as the most important factor causing degradation of the Baltic Sea ecosystem, the proposed approach was evaluated against total phytoplankton biomass. When phytoplankton biomass was low, both low and high biodiversity values were observed, and, as the phytoplankton biomass increased, the high biodiversity values disappeared. These results were consistent both using data based on individual samples and using yearly sampling station averages.

Description: Frie, A. K., Hammill, M. O., Hauksson, E., Lind, Y., Lockyer, C., Stenman, O., and Svetocheva, O. 2013. Error patterns in age estimation and tooth readability assignment of grey seals ( Halichoerus grypus ): results from a transatlantic, image-based, blind-reading study using known-age animals – ICES Journal of Marine Science, 70: 418–430. We analysed error patterns in a first interlaboratory grey seal ( Halichoerus grypus ) age-reading experiment. The experiment involved ten readers, who estimated age using images of cementum growth layers from teeth of 68 known-age seals (0–22 years). The percentages of correct estimates ranged from 32.4% to 60.3% among readers, and 89.3% of all errors were by ±1–2 years. Six readers showed increasing underageing with increasing seal age. An elevated risk of underestimation by 1 year occurred in teeth collected 0–5 months after breeding and was attributed to more frequent absence of a distinct growth layer for the new year and lack of information on months between the last birthday and the date of sample collection (plusmonths). For plusmonths 6–11, positive bias was predominant, suggesting that overestimation is the more common error when plusmonth information is available. Readers assigned readability scores to the tooth sections, and 79.1% of all ageing errors occurred in sections of low or intermediate readability. Excluding these sections would, however, also exclude 43.0% of all correct estimates. Neither levels of age estimation error nor predictive values of readability assignments were associated with reader experience levels. Analyses of image markings identified common errors in delineations of annual increment layers.

Description: Domínguez-Petit, R., Ouellet, P., and Lambert, Y. 2013. Reproductive strategy, egg characteristics and embryonic development of Greenland halibut ( Reinhardtius hippoglossoides ). – ICES Journal of Marine Science, 70: 342–351. Despite the commercial importance of Greenland halibut (GH), important gaps exist in our knowledge of the reproductive and early life stage biology for this species. The present study examined through laboratory experiments the spawning strategy, realized fecundity, egg characteristics, biochemical composition, and embryonic development of GH. The results confirmed the hypothesis that GH is a single-batch spawner producing large eggs, resulting in low realized fecundity. Embryonic development and hatching time are highly dependent on incubation temperature; 50% hatching occurred after 46, 30, and 24 days at 2, 4, and 6°C, respectively. Few changes in the biochemical composition of the eggs are observed during embryonic development. Newly hatched larvae are not well developed, having a large yolk sac, no pigmentation and incomplete development of the jaws. Egg specific density confirmed the mesopelagic distribution of the eggs at sea. However, important buoyancy changes occurring in the last 3–4 days before hatching indicate that larvae hatch higher in the water column. These results are important for understanding advection and dispersion processes of GH eggs and larvae and the connectivity between spawning grounds and nursery areas.

Description: Johnsen, E., and Harbitz, A. 2013. Small-scale spatial structuring of burrowed sandeels and the catching properties of the dredge – ICES Journal of Marine Science, 70: 379–386. The lesser sandeel ( Ammodytes marinus ) remains burrowed for long periods in the seabed in sandy areas, and its habitat preference is reflected in a large-scale (10 km) patchy distribution in the North Sea. The small-scale spatial structure of sandeels in the seabed is less known. In this study, it was found that sandeel catches in grabs and dredges fit gamma distributions with a common shape parameter on both a 10 m and a 100 m scale. These spatial models were used to examine the catching properties of the dredge, which, in the new ICES sandeel assessment, is used to estimate recruitment and maturity curves. Analyses of the empirical data and simulations of the dredge and grab catch rates show very low dredge catchability (~5%), but no length-dependent catchability in the dredge was found. However, analyses of the catch rates of parallel dredge hauls indicated increasing dredge catchability with sandeel density. The observed small-scale patchiness and the low and seemingly density-dependent dredge catchability result in biased abundance estimates with low precision. Therefore, we recommend a joint international effort to develop a more catch-efficient sampling dredge, where the effect of density on catchability is further examined.

Description: Rousi, H., Laine, A. O., Peltonen, H., Kangas, P., Andersin, A-B., Rissanen, J., Sandberg-Kilpi, E., and Bonsdorff, E. 2013. Long-term changes in coastal zoobenthos in the northern Baltic Sea: the role of abiotic environmental factors – ICES Journal of Marine Science, 70: 440–451. We investigated site-specific changes in a coastal zoobenthic community during 1964–2007 in the northern Baltic Sea. Multivariate analysis indicated that the community structure had changed. The amphipods Monoporeia affinis and Pontoporeia femorata decreased drastically in the late 1970s–early 1980s, and by the early 1990s P. femorata vanished and M. affinis abundance was low. The decline of M . affinis and P . femorata was followed by an increase of the bivalve Macoma balthica and the arrival of the polychaete genus Marenzelleria in the 1990s. Trend analyses showed a rising trend for near-bottom temperature from the late 1960s. There was a significant decline in salinity during the early 1980s, which stabilized during the early 1990s. A negative trend was observed for oxygen concentration during the entire study period. There were interannual variations in the phosphorus and nitrogen concentrations, and a step-like increase in phosphorus concentration at the beginning of the 21st century. The correlations of temperature, salinity, oxygen, total phosphorus and nitrogen with zoobenthic communities were examined using Constrained Correspondence Analysis. Temperature was the most highly correlated explanatory variable for the benthic species. The study highlights the importance of long-term data sets in assessing the state and ecological processes of zoobenthic systems.

Description: O'Driscoll, R. L., Oeffner, J., and Dunford, A. J. 2013. In situ target strength estimates of optically verified southern blue whiting ( Micromesistius australis ) – ICES Journal of Marine Science, 70: 431–439. Estimates of the acoustic target strength (TS) of southern blue whiting ( Micromesistius australis ) at 38 kHz were obtained using an autonomous acoustic–optical system (AOS) mounted on a demersal trawl. Data were collected from aggregations of spawning adult [mean fork length (FL) 34.4 cm] and immature (mean FL 24.6 cm) southern blue whiting south of New Zealand. Mean TS was estimated from 162 tracks containing 695 echoes from targets identified from video as southern blue whiting. The mean TS was –37.9 dB with a 95% confidence interval ( CI ) of –39.7 to –36.6 dB for 21 immature fish and –34.6 dB (95% CI –35.4 to –34.0 dB) for 141 adults. A logarithmic fit through the mean TS values produced a TS–fork length (FL) relationship from optically verified targets of TS = 22.06 log 10 FL – 68.54. This new relationship gives TS values within 1 dB of those estimated using the relationship recently adopted by ICES for blue whiting ( Micromesistius poutassou ) of TS = 20 log 10 TL – 65.2 (where TL is total length) obtained from in situ measurements, but higher values than those estimated from the previous relationship for southern blue whiting of TS = 38 log 10 FL – 97, which was based on swimbladder modelling.

Description: De Robertis, A., Wilson, C. D., Furnish, S. R., and Dahl, P. H. 2013. Underwater radiated noise measurements of a noise-reduced fisheries research vessel. – ICES Journal of Marine Science, 70: 480–484. Vessel-radiated noise is traditionally measured at naval acoustic ranges, but lower-cost options are desirable for routine monitoring of research vessels. Measurements of a noise-reduced research vessel made at a naval noise range are compared to those made using an experimental mooring equipped with commercially available instrumentation. The measurements from the mooring were precise and within 2.5 dB of those from the noise range at third-octave bands 〈500 Hz. At higher frequencies, direct comparisons were precluded by an intermittent shaft-related noise present only during the mooring measurements, but previously observed at the navy range. The agreement between the two methods suggests that simplified, field-deployable hydrophone systems can be used to accurately characterize the noise signatures of research vessels.

Description: Peck, M. A., Neuenfeldt, S., Essington, T. E., Trenkel, V. M., Takasuka, A., Gislason, H., Dickey-Collas, M., Andersen, K. H., Ravn-Jonsen, L., Vestergaard, N., Kvamsdal, S., Gårdmark, A., Link, J., and Rice, J. Forage Fish Interactions: a symposium on "Creating the tools for ecosystem-based management of marine resources". – ICES Journal of Marine Science, 71: . Forage fish (FF) have a unique position within marine foodwebs and the development of sustainable harvest strategies for FF will be a critical step in advancing and implementing the broader, ecosystem-based management of marine systems. In all, 70 scientists from 16 nations gathered for a symposium on 12–14 November 2012 that was designed to address three key questions regarding the effective management of FF and their ecosystems: (i) how do environmental factors and predator–prey interactions drive the productivity and distribution of FF stocks across ecosystems worldwide, (ii) what are the economic and ecological costs and benefits of different FF management strategies, and (iii) do commonalities exist across ecosystems in terms of the effective management of FF exploitation?

Description: Tian, Y., Uchikawa, K., Ueda, Y., and Cheng, J. Comparison of fluctuations in fish communities and trophic structures of ecosystems from three currents around Japan: synchronies and differences. – ICES Journal of Marine Science, 71: . Features of three marine ecosystems affected by the Tsushima (TWC), Kuroshio (KC), and Oyashio (OC) currents were analysed based on fishery, oceanographic, and climate datasets during 1955–2010. Principal component (PC) analysis for catches of 25 indicator species showed evident decadal variation patterns with a step change in the first principal component (PC1) in the late 1980s, indicating synchronies in the dominant variation mode across the ecosystems. Step changes were also detected in the mid-1970s in PC2 and PC3 in OC, and around 1970 in PCs in KC and TWC. These indicate that the most marked change across the ecosystems occurred in the late 1980s, corresponding to the late 1980s climate regime shift, but OC also responded strongly to the mid-1970s regime shift, indicating different responses to regime shifts. The generalized additive model showed the PCs associated largely with water temperature in each region as well as climate indices, indicating the importance of regional oceanographic conditions. Ecosystem indicators such as the mean trophic level showed similarities between TWC and KC but differences with OC, indicating that trophic structures in TWC and KC were largely dependent on the mid-trophic (small pelagic species) level, while on demersal species in OC.

Description: Litz, M. N. C., Emmett, R. L., Bentley, P. J., Claiborne, A. M., and Barceló, C. Biotic and abiotic factors influencing forage fish and pelagic nekton community in the Columbia River plume (USA) throughout the upwelling season 1999–2009. – ICES Journal of Marine Science, 71: . Large river plumes modify coastal environments and can impact production across multiple trophic levels. From 1999 to 2009, the assemblages of forage fish, predator fish, and other pelagic nekton were monitored in coastal waters associated with the Columbia River plume. Surveys were conducted at night to target vertically migrating species, and community structure evaluated to better understand ecological interactions. Distinct inshore and offshore communities were identified during spring and summer that were correlated with ocean temperature, salinity, plume volume, and upwelling intensity. Resident euryhaline forage fish species, such as smelts, anchovy, herring, market squid, juvenile salmon, and spiny dogfish, showed a high affinity for inshore habitat and the lower salinity plume during spring. Highly migratory species, such as sardine, piscivorous hake, sharks, and mackerels, were associated with warmer, saltier waters offshore, during strong upwelling periods in summer. Overall, our study of pelagic nekton revealed that temporal dynamics in abundance and community composition were associated with seasonal abiotic phenomenon, but not interannual, large-scale oceanographic processes. Forage fish assemblages differed seasonally and spatially from the assemblages of major piscivorous predators. This finding suggests a potential role of the plume as refuge for forage fish from predation by piscivorous fish in the northern California Current.

Description: Røjbek, M. C., Tomkiewicz, J., Jacobsen, C., and Støttrup, J. G. Forage fish quality: seasonal lipid dynamics of herring ( Clupea harengus L.) and sprat ( Sprattus sprattus L.) in the Baltic Sea. – ICES Journal of Marine Science, 71: . This study investigates lipid content and fatty acid composition of two important forage fish, sprat ( Sprattus sprattus ) and herring ( Clupea harengus ) in the Baltic Sea ecosystem. Seasonal variation in lipids was studied during three periods following the annual reproductive cycle considering potential differences relating to fish size, sex, and reproductive status. The isopod Saduria entomon , being at times an important prey for predatory fish, was included for comparison. In both sprat and herring, lipid content and absolute contents of essential polyunsaturated fatty acids (PUFAs) varied seasonally with high levels towards the end of the annual zooplankton production cycle, succeeded by a decline. Lipid content and fatty acid composition differed significantly between sprat and herring. Sprat lipid content was higher than herring, increasing with fish size and characterized by large proportions of monounsaturated fatty acids. Herring lipid content was related to the reproductive cycle and proportions of PUFAs were high compared with sprat. Levels of essential PUFAs were high in S. entomon compared with clupeids rendering it a valuable alternative prey species in the Baltic Sea ecosystem. The lipid dynamics of forage fish and benthos, combined with changes in availability and abundance, will affect growth and reproduction of their predators.

Description: Lassalle, G., Nelva Pasqual, J-S., Boët, P., Rochet, M-J., Trenkel, V. M., and Niquil, N. Combining quantitative and qualitative models to identify functional groups for monitoring changes in the Bay of Biscay continental shelf exploited foodweb. – ICES Journal of Marine Science, 71: . To develop and implement ecosystem-based management, it is critical to monitor foodweb components or functional groups which are robust to uncertainty in ecosystem structure and functioning yet sensitive to changes. To select such functional groups for the Bay of Biscay continental shelf, both quantitative and qualitative foodweb models were developed. First, functional groups for which predictions of directions of change following an increase in primary productivity, prey or predators, or in fishing activities were identical across alternative qualitative model structures were identified. Second, the robustness to model type was assessed by comparing qualitative predictions with quantitative Ecopath model results. The demersal fish community was identified as a sensitive and robust indicator for monitoring foodweb ecological status in the Bay of Biscay. The present study also suggested the potential antagonistic effects of alternative management measures on small pelagic fish and highlighted the need for the joint management of all pressures.

Description: Yasue, N., Doiuchi R., and Takasuka, A. 2013. Trophodynamic similarities of three sympatric clupeoid species throughout their life histories in the Kii Channel as revealed by stable isotope approach. – ICES Journal of Marine Science, 71: . Trophic similarity/difference among multispecies pelagic fish is a focal point in understanding the processes of climate impacts on their population dynamics. We tested trophic overlap of Japanese anchovy Engraulis japonicus , Japanese sardine Sardinops melanostictus , and Pacific round herring Etrumeus teres in the Kii Channel, Japan, by comparing the carbon and nitrogen stable isotope ratios among these clupeoid species from the larval to adult stages throughout the year. Space and time were both significant factors of variations of the isotopic composition values for the three species, and fish size was also significant for sardine and round herring. The isotopic composition values of the three species were homogeneous when compared with those of plankton and some other non-clupeoid species. Moreover, the isotopic composition values of the three clupeoid species collected simultaneously showed closer similarities than those in different areas and dates in all life stages. Thus, spatial and temporal differences in food availability were more apparent compared with interspecific differences in prey items specific to each species. Our analysis indicated strong trophic overlaps throughout the life histories among the three clupeoid species. Hence, they are concluded to be ecologically congeneric (directly competing) species in terms of trophic positions in the pelagic ecosystem.

Description: Essington, T. E., and Plagányi, É. E. Pitfalls and guidelines for "recycling" models for ecosystem-based fisheries management. – ICES Journal of Marine Science, 71: . Ecosystem models have been developed for many marine systems to provide guidance on fisheries management strategies that protect key ecological functions. These models are commonly "recycled", i.e. applied to new questions or policy concerns after the initial phase of model development, testing, and application. Because decisions about the model structure are typically based on the intended model use, it is important to recognize limits in the capacity of models to address questions for which they were not specifically designed. Here, we evaluate existing foodweb models in the context of their ability to identify key forage species in foodwebs and to test management strategies for fisheries that target them. We find that the depth and breadth with which predator species are represented are commonly insufficient for evaluating sensitivities of predator populations to forage fish depletion. We demonstrate that aggregating predator species into functional groups creates bias in foodweb metrics such as connectance. Models also varied considerably with respect to the extent that they have been tuned or fitted to retrospective patterns and the degree to which key sensitivities are identified. We use this case study to provide several general recommendations when "recycling" ecosystem and foodweb models. Briefly, we suggest as routine procedure careful scrutiny of structural model attributes, of scales at which ecological processes are included, and quality of fits for key functional groups.

Description: Howell, D., and Filin, A. A. Modelling the likely impacts of climate-driven changes in cod-capelin overlap in the Barents Sea. – ICES Journal of Marine Science, 71: . Recent observations have indicated that the cod distribution within the Barents Sea is expanding towards the northeast. The area into which the cod are expanding has historically been an area with large stocks of polar cod and capelin. It can be expected that the continued expansion of cod into this region would lead to greater availability of these forage fish for cod predation and have a direct impact on the forage fish stock. The distributional shift may also reduce the level of cod cannibalism. Such changes have implications for the management of both cod and capelin fisheries. In this paper, we use two different models (Gadget and STOCOBAR) to examine the effects of the changing overlap on cod and capelin. The results from the two models are compared to reduce uncertainty due to model formulation and exploit the different strengths of the two approaches. Although there are many uncertainties around the ongoing changes, the results indicate that the increased spatial overlap could contribute to modest rises by up to 20% in the average cod stock biomass, but with an increase in the impact of cannibalism, and hence an increased variability in the cod stock size.

Description: van Deurs, M., Koski, M., and Rindorf, A. Does copepod size determine food consumption of particulate feeding fish? – ICES Journal of Marine Science, 71: . The climate-induced reduction in the mean copepod size, mainly driven by a decrease in the abundance of the large Calanus finmarchicus around 1987, has been linked to the low survival of fish larvae in the North Sea. However, to what extent this sort of reduction in copepod size has any influence on adult particulate feeding fish is unknown. In the present study, we investigated the hypothesis that the availability of the large copepods determines food consumption and growth conditions of lesser sandeel ( Ammodytes marinus ) in the North Sea. Analysis of stomach content suggested that food consumption is higher for fish feeding on large copepods, and additional calculations revealed how handling time limitation may provide part of the explanation for this relationship. Comparing stomach data and zooplankton samples indicated that lesser sandeel actively target large copepods when these are available. Finally, we observed that the length of lesser sandeel began to decrease in the late 1980s, simultaneously with the C. finmarchicus decline.

Description: Engelhard, G. H., Peck, M. A., Rindorf, A., Smout, S. C., van Deurs, M., Raab, K., Andersen, K. H., Garthe, S., Lauerburg, R. A. M., Scott, F., Brunel, T., Aarts, G., van Kooten, T., and Dickey-Collas, M. Forage fish, their fisheries, and their predators: who drives whom? – ICES Journal of Marine Science, 71: . The North Sea has a diverse forage fish assemblage, including herring, targeted for human consumption; sandeel, sprat, and Norway pout, exploited by industrial fisheries; and some sardine and anchovy, supporting small-scale fisheries. All show large abundance fluctuations, impacting on fisheries and predators. We review field, laboratory, and modelling studies to investigate the drivers of this complex system of forage fish. Climate clearly influences forage fish productivity; however, any single-species considerations of the influence of climate might fail if strong interactions between forage fish exist, as in the North Sea. Sandeel appears to be the most important prey forage fish. Seabirds are most dependent on forage fish, due to specialized diet and distributional constraints (breeding colonies). Other than fisheries, key predators of forage fish are a few piscivorous fish species including saithe, whiting, mackerel, and horse-mackerel, exploited in turn by fisheries; seabirds and seals have a more modest impact. Size-based foodweb modelling suggests that reducing fishing mortality may not necessarily lead to larger stocks of piscivorous fish, especially if their early life stages compete with forage fish for zooplankton resources. In complex systems, changes in the impact of fisheries on forage fish may have potentially complex (and perhaps unanticipated) consequences on other commercially and/or ecologically important species.

Description: Smout, S., Rindorf, A., Hammond, P. S., Harwood, J., and Matthiopoulos, J. Modelling prey consumption and switching by UK grey seals. – ICES Journal of Marine Science, 71: . Grey seals ( Halichoerus grypus ) are adaptable generalist predators whose diet includes commercial fish species such as cod. Consumption by the seals may reduce the size of some fish stocks or have an adverse effect on stock recovery programmes, especially because predation may trap sparse prey populations in a "predator pit". To assess the likely impact of such effects, it is important to know how consumption and consequent predation mortality respond to the changing availability of prey. We present a model of grey seal consumption as a function of the availability of multiple prey types [a Multi-Species Functional Response (MSFR)]. We fit this MSFR to data on seal diet and prey availability (based on the overlap between the distributions of predators and prey). Bayesian methodology was employed to account for uncertainties in both dependent and independent variables, improve estimation convergence by the use of informative priors, and allow the estimation of missing data on prey availability. Both hyperbolic (Type 2) and sigmoidal (Type 3) functional response models were fitted to the data and the Type 3 model was clearly favoured during model selection, supporting the conclusion that seal–prey encounter rates change with prey abundance (sometimes referred to as "switching"). This suggests that some prey species may be vulnerable to predator pit effects. The fitted model reproduced contrasts in diet observed between different regions/years and, importantly, added information to the prior distributions of prey abundance in areas where the availability of some prey species (such as sandeels) was not known. This suggests that the diet of predators such as seals could provide information about the abundance and distribution of prey in areas that are not covered by fisheries and research surveys.

Description: Rice, J., and Duplisea, D. 2013. Management of fisheries on forage species: the test-bed for ecosystem approaches to fisheries. – ICES Journal of Marine Science, 71: . In the 1970s and 1980s, core ideas about management of fisheries on forage species emerged from work on the dynamics of foodweb models and multispecies assessments, leading to proposals for management that took some account of the role of forage species in marine ecosystems. Key developments in those years are summarized in the first part of this paper. From the 1980s to the 2000s, studies of the response of forage species to environmental variation brought into question the robustness of management strategies for forage species. As a result, additional management strategies were proposed to accommodate environmental drivers as well as dependent predators. The paper reviews these developments. This paper brings these separate lines together in a systematic framework for evaluating the performance of six different management strategies for forage species, relative to four different ecosystem considerations, as well as relative to the contribution of forage fisheries to economic prosperity and food security. The tabulated outcomes synthesize primary and secondary literature and meeting deliberations as the application of an ecosystem approach to management has evolved. No strategy is optional for all forage fisheries. As experience accumulates, the guidance in the tables comprising the framework will improve.

Description: Dickey-Collas, M., Engelhard, G. H., Rindorf, A., Raab, K., Smout, S., Aarts, G., van Deurs, M., Brunel, T., Hoff, A., Lauerburg R. A. M., Garthe, S., Haste Andersen, K., Scott, F., van Kooten, T., Beare, D., and Peck, M. A. Ecosystem-based management objectives for the North Sea: riding the forage fish rollercoaster. – ICES Journal of Marine Science, 71: . The North Sea provides a useful model for considering forage fish (FF) within ecosystem-based management as it has a complex assemblage of FF species. This paper is designed to encourage further debate and dialogue between stakeholders about management objectives. Changing the management of fisheries on FF will have economic consequences for all fleets in the North Sea. The predators that are vulnerable to the depletion of FF are Sandwich terns, great skua and common guillemots, and to a lesser extent, marine mammals. Comparative evaluations of management strategies are required to consider whether maintaining the reserves of prey biomass or a more integral approach of monitoring mortality rates across the trophic system is more robust under the ecosystem approach. In terms of trophic energy transfer, stability, and resilience of the ecosystem, FF should be considered as both a sized-based pool of biomass and as species components of the system by managers and modellers. Policy developers should not consider the knowledge base robust enough to embark on major projects of ecosystem engineering. Management plans appear able to maintain sustainable exploitation in the short term. Changes in the productivity of FF populations are inevitable so management should remain responsive and adaptive.

Description: Hammond, C. F., Conquest, L. L., and Rose, C. S. 2013. Using reflex action mortality predictors (RAMP) to evaluate if trawl gear modifications reduce the unobserved mortality of Tanner crab ( Chionoecetes bairdi ) and snow crab ( C. opilio ). – ICES Journal of Marine Science, 70: . Management of Bering Sea crab and groundfish fisheries must account for the delayed (and hence unobserved) mortality of crab that encounter bottom trawls, but are not captured. A new approach to predicting the delayed mortality of crab uses a reflex action mortality predictor (RAMP) model to establish a relationship between mortality and reflex impairments. A 2007 pilot study of 649 crab established RAMP curves for both Tanner crab ( Chionoecetes bairdi ) and snow crab ( C. opilio ). Additional data (1775 crab) collected in 2008 allowed us to update the existing RAMP curves to more fully examine the effect of injury scores on the RAMP models and to determine the best method for estimating overall mortality. Results confirmed that the additional measurements did not significantly alter the original relationship between mortality and reflex impairment score. Additionally, the RAMP curves were used to predict unobserved mortality from observed reflex impairment scores of Chionoecetes spp. captured after encounters with different parts of bottom trawl gear (footrope and sweep) and alternative types of footrope and sweep. In addition to estimating mortality rates caused by each gear part, we tested whether the alternative footrope and sweep designs reduced the unobserved mortality rates of crab. Results showed that the alternative footrope (58 cm disk footrope) reduced mortality from 11.4 to 7.2% for Tanner crab and from 9.7 to 5.0% for snow crab . The alternative (off-bottom) sweep reduced mortality from 4.1 to 1.0% for Tanner crab and from 4.9 to 0.0% for snow crab. Thus, the use of the reflex impairment score through the RAMP model is a cost effective way to estimate delayed mortality and to assess the effect of gear types on delayed mortality for management purposes.

Description: Frank, K. T., Leggett, W. C., Petrie, B., Fisher, J. A. D., Shackell, N. L., and Taggart, C. T. 2013. Pelagic fish outbreak in the Northwest Atlantic - reality or illusion? – ICES Journal of Marine Science, 70: . The collapse of Northwest Atlantic groundfish in the early 1990s yielded a "natural experiment" within which to explore responses of ecosystems to a major perturbation. The "Pelagic Outburst" hypothesis was developed to explain an up to 900% increase in the abundance of small-bodied forage fishes and macroinvertebrates following this collapse and a subsequent trophic cascade extending across four trophic levels. Recently, this theory has been challenged and an alternative "Suprabenthic Habitat Occupation" (SHO) hypothesis has been advanced; it proposes the prey outburst associated with the forage fish component was an illusion created by changes in the vertical distribution of small pelagic fishes after the cod collapse in favour of a more bottom-oriented distribution that increased their vulnerability to bottom trawls. We evaluated the SHO hypothesis as it applied to the relationship between changes in the biomass of cod and the vertical distribution of herring and sand lance, the major small pelagic species of the Scotian Shelf ecosystem off eastern Nova Scotia. Contrary to predictions of the SHO hypothesis our initial conclusion that a pelagic outburst occurred in that ecosystem was confirmed and we found no evidence of a predator effect on vertical distributions of these species. We also explored the acoustic survey design and execution that generated the data that form the cornerstone of the SHO hypothesis, and the coherence between the behaviour depicted in these data and catch rates in the surface-oriented purse-seine fishery for herring operating at the time of these surveys. In combination, the results of our re-analysis of the population dynamics and behaviour of herring on the eastern Scotian Shelf, lead us to conclude that the SHO hypothesis, at least as it relates to the post-cod collapse dynamics of the affected Northwest Atlantic ecosystems, is not supported.

Description: Wilhelm, M. R., Roux, J-P., Moloney, C. L., and Jarre, A. 2013. Data from fur seal scats reveal when Namibian Merluccius capensis are hatched and how fast they grow. – ICES Journal of Marine Science, 70: . Scat samples were collected regularly at several breeding colonies of Cape fur seals along the Namibian coast. Merluccius capensis otoliths were obtained from these samples, identified, and measured. Cohorts were easily distinguishable using otolith length measurements converted to fish total length. Growth rates of 2- to 21-month-old hake and hatch dates for each of 15 cohorts were estimated from September 1994 to October 2009 (1994–2008 cohorts) using a Schnute growth function and a non-linear mixed-effects model. The function describing growth of these young hake was length L t (cm) at age t (years) L t = 3.17 + (25.0 – 3.17) x [1 – e –0.665 x ( t – 0.140) ]/[1 – e –0.665 x (1.74–0.140) ]. Cohort-specific random effects showed a population hatch date estimate of 31 July (austral winter), varying by 94 days among cohorts, from 31 May (1996 cohort) to 1 September (2004 cohort). The mean growth rate from ages 6 to 12 months was 1.26 cm month –1 for the population, ranging between 0.97 cm month –1 (1996 cohort) and 1.38 cm month –1 (2004 cohort). As this rate is almost double the previously estimated value, which is currently used in the stock assessment models, this result may have major implications for the current stock assessment results and the management of the stock. Re-examination of growth rates needs to be extended to older fish.

Description: Teniswood, C. M. H., Roberts, D., Howard, W. R., and Bradby, J. E. 2013. A quantitative assessment of the mechanical strength of the polar pteropod Limacina helicina antarctica s hell. – ICES Journal of Marine Science, 70: . This work directly measures the mechanical properties of pteropod shells collected from the Southern Ocean on the 2007 midsummer Subantarctic Zone Sensitivity to Environmental Change (SAZ-Sense) voyage. Shells from the common Southern Ocean pteropod Limacina helicina antarctica were subjected to mechanical analyses in combination with detailed morphological studies. Average hardness and modulus of 2.30 ± 0.07 GPa and 45.27 ± 0.91 GPa, respectively were calculated from several hundred nanoindentation measurements taken from multiple positions across twelve shells of the same species collected under identical conditions. Quantitative data such as these are critical to establish a reference point for future comparative studies and to both understand and evaluate the implications of further ocean acidification on the structural integrity of these common polar calcifiers, particularly in light of their role in the Southern Ocean carbon cycle and food web.

Description: Martinez, S., and Abelson, A. 2013. Coral recruitment: the critical role of early post-settlement survival. – ICES Journal of Marine Science, 70: . Coral recruitment is a pivotal factor in coral reef stability and in recovery following substantial disturbances. Despite its immense importance, the study of coral recruitment has some major gaps, notably larval survival before and following settlement, mainly due to technical limitations, which stem from the difficulty in observing the minute larvae. To overcome the major limitation in coral recruitment studies, i.e. the in situ detection of recruits during their early stages, we designed a new detection set-up, composed of a fluorescence detection set-up, a grid-covered substrate, and a Geographic Information System tracking system. This set-up, enabling the identification of coral recruits soon after settlement, revealed that in the critical period of the first day, less than 45% of the settling corals may survive. The results also suggest that either coral larva select locations that may increase their survival chances or they experience dramatic mortality during the early hours of settlement, which induce a consistent pattern of spat distribution. Our study confirms an earlier speculation that the first 24 h post-settlement may determine the rates and spatial patterns of recruitment. The significant implications of these findings, and the implemented "detection set-up" for coral reef monitoring and management, are discussed.

Description: Murray, L. G., Hinz, H., Hold, N., and Kaiser, M. J. 2013. The effectiveness of using CPUE data derived from Vessel Monitoring Systems and fisheries logbooks to estimate scallop biomass. – ICES Journal of Marine Science, 70: . Obtaining accurate data on abundance is vital to undertaking viable stock assessments of commercially exploited species. Satellite Vessel Monitoring Systems (VMSs) combined with fisheries logbooks have the potential to provide an abundant source of data with greater spatial and temporal coverage than research surveys. However, to date it has not been demonstrated how well VMS-derived abundance or biomass indices reflect research survey results. In this study we compared biomass indices of scallops derived from (i) fishing vessel surveys, (ii) research vessel surveys, and (iii) fishery-dependent data using VMSs and logbooks. In most cases there were strong relationships between biomass indices of Pecten maximus from fishing vessels and the research vessel. There were stronger relationships between P. maximus biomass indices from fishery-dependent VMS and logbook data and research vessel data at the beginning of the fishing season, when abundance was higher, but weaker relationships at the end of the fishing season. The time and location of sampling affected biomass estimates over short periods, and without standardizing to location and vessel, biomass depletion was masked. Fishery-dependent data provides a valid means of assessing relative scallop abundance and may prove equally viable in other fisheries with appropriate standardization of Catch Per Unit Effort (CPUE) data, making real-time management of fisheries increasingly feasible.

Description: Boyra, G., Martínez, U., Cotano, U., Santos, M., Irigoien, X., and Uriarte, A. 2013. Acoustic surveys for juvenile anchovy in the Bay of Biscay: abundance estimate as an indicator of the next year's recruitment and spatial distribution patterns. – ICES Journal of Marine Science, 70: . A series of acoustic surveys (JUVENA) began in 2003 targeting juvenile anchovy ( Engraulis encrasicolus ) in the Bay of Biscay. A specific methodology was designed for mapping and estimating juvenile abundance annually, four months after the spawning season. After eight years of the survey, a consistent picture of the spatial pattern of the juvenile anchovy has emerged. Juveniles show a vertical and horizontal distribution pattern that depends on size. The younger individuals are found isolated from other species in waters closer to the surface, mainly off the shelf within the mid-southern region of the bay. The largest juveniles are usually found deeper and closer to the shore in the company of adult anchovy and other pelagic species. In these eight years, the survey has covered a wide range of juvenile abundances, and the estimates show a significant positive relationship between the juvenile biomasses and the one-year-old recruits of the following year. This demonstrates that the JUVENA index provides an early indication of the strength of next year's recruitment to the fishery and can therefore be used to improve the management advice for the fishery of this short-lived species.

Description: Beazley, L. I., Kenchington E. L., Murillo, F. J., and Sacau, M. 2013. Deep-sea sponge grounds enhance diversity and abundance of epibenthic megafauna in the Northwest Atlantic. – ICES Journal of Marine Science, 70: . The influence of structure-forming deep-water sponge grounds on the composition, diversity, and abundance of the local epibenthic megafaunal community of the Flemish Pass area, Northwest Atlantic was statistically assessed. These habitats are considered vulnerable marine ecosystems and, therefore, warrant conservation measures to protect them from bottom fishing activities. The epibenthic megafauna were quantified from four photographic transects, three of which were located on the western slope of the Flemish Cap with an overall depth range of 444–940 m, and the fourth in the southern Flemish Pass between 1328 and 1411 m. We observed a diverse megafaunal community dominated by large numbers of ophiuroids and sponges. On the slope of the Flemish Cap, sponge grounds were dominated by axinellid and polymastid sponges, while the deeper sponge ground in the southern Flemish Pass was formed mainly by geodiids and Asconema sp. The presence of structure-forming sponges was associated with a higher biodiversity and abundance of associated megafauna compared with non-sponge habitat. The composition of megafauna significantly differed between sponge grounds and non-sponge grounds and also between different sponge morphologies. Surface chlorophyll a and near-bottom salinity were important environmental determinants in generalized linear models of megafaunal species richness and abundance.

Description: Fässler, S. M. M., O'Donnell, C., and Jech, J.M. 2013. Boarfish ( Capros aper ) target strength modelled from magnetic resonance imaging (MRI) scans of its swimbladder. – ICES Journal of Marine Science, 70: . Boarfish ( Capros aper ) abundance has increased dramatically in the Northeast Atlantic from the early 1970s after successive years of good recruitment attributed to an increase in sea surface temperature. Due to increased commercial fishing over recent years, an acoustic boarfish survey funded by the Killybegs Fishermen's Organisation was initiated by the Marine Institute to establish a baseline for the future management of this stock. In the absence of any species-specific boarfish target strength ( TS ), acoustic backscatter was estimated by a Kirchhoff-ray mode model using reconstructed three-dimensional swimbladder shapes which were computed from magnetic resonance imaging scans of whole fish. The model predicted TS as a function of size, fish tilt angle, and operating frequency. Standardized directivity patterns revealed the increasing importance of changes in the inclination of the dorsal swimbladder surface at higher frequencies (120 and 200 kHz) and a less directive response at lower frequencies (18 and 38 kHz). The model predicted a TS -to-total fish length relationship of TS = 20 log 10 ( L ) – 66.2. The intercept is ~1 dB higher than in the general physoclist relationship, potentially reflecting the bulky nature of the boarfish swimbladder with its relatively large circumference.

Description: Farhadi, A., Farhamand, H., Nematollahi, M. A., Jeffs, A., and Lavery, S. D. 2013. Mitochondrial DNA population structure of the scalloped lobster Panulirus homarus (Linnaeus 1758) from the West Indian Ocean. – ICES Journal of Marine Science, 70: . The scalloped spiny lobster Panulirus homarus (Linnaeus, 1758) is a highly valuable species with a widespread global distribution, ranging from South Africa around the Persian Gulf, and across the Indo-Pacific as far as Japan and French Polynesia. Throughout its range, the species is an important fisheries species with global annual landings in the order of 3000 t. Mitochondrial control region DNA sequences (625 bp) were used to investigate the population genetic structure of this species in the West Indian Ocean (WIO), using 137 individuals collected from four sites, including two locations along the south coast of Iran, and sites along the coast of the Sultanate of Oman in the Arab Sea, as well as Tanzania in eastern Africa. High levels of haplotype diversity ( H = 0.997) were observed in all populations, although nucleotide diversity was relatively low (pi = 0.035). The hypothesis of a single stock in this region was rejected, with highly significant genetic differentiation revealed between Tanzania and the remaining locations (overall ST = 0.039, p 〈 0.00001), as well as slight genetic structure in the Arabian Sea region. Historical population expansion was inferred from Tajima's D and Fu's F tests. The results reveal at least two distinct genetic stocks in WIO and may have major implications for fisheries management.

Description: Diaz Pauli, B., and Heino, M. 2013. Ecological and evolutionary effects of harvesting: lessons from the candy-fish experiment. – ICES Journal of Marine Science, 70: . Understanding the challenges of sustainable fisheries management is not easy for non-specialists, and even many specialists fail to appreciate the potential evolutionary consequences of harvest. We propose candy-fish experiments as a savoury approach to teaching and disseminating the key principles of applied ecology and evolution to students, practitioners and the general public. We performed a simple experiment where the resource was represented by fish-shaped candy of distinct colours and flavours (strawberry and liquorice). Typically, harvesting was neither ecologically sustainable (55% of the populations were extinct by the end of the experiment) nor evolutionarily sustainable (most surviving populations had liquorice fish only). This harvest-induced evolution went apparently unnoticed. Somewhat encouragingly, the harvest was most likely ecologically sustainable when a person spontaneously took the role of a stock manager.

Description: Oliveira, M. M., Camanho, A. S., and Gaspar, M. B. 2013. The influence of catch quotas on the productivity of the Portuguese bivalve dredge fleet. – ICES Journal of Marine Science, 70: . Among the Portuguese artisanal fishing fleets, the bivalve dredge fleet is one of the most profitable. In the last decade, after the implementation of a quotas system, the management of this fishery has been largely focused on adjusting catch to the conservation status of the resources exploited. The present work aims to understand how changes in the amount of quota attributed to each vessel each year and shifts in the quota regime affected vessel productivity. Boostrapped Malmquist indices, complemented with an efficiency assessment using a directional distance function, were used to quantify productivity changes between 1999 and 2011 for the fleets operating in two areas along the Portuguese coast (northwest and southwest). The results showed that the implementation of a weekly quota, as opposed to a daily quota, led to a significant improvement in productivity. This was mainly due to the decrease in fishing days and fuel consumption. It is predicted that the implementation of weekly quotas in the south area would lead to an overall reduction of about 12% in fishing days and fuel consumption, even though the variation in fuel consumption may be affected by the status of the resources. The results achieved provide important insights for future management actions and showed the potential advantages of applying this type of management to other fisheries worldwide, mainly those using active gear.

Description: Demer, D. A., Zwolinski, J. P., Cutter, G. R. Jr, Byers, K. A., Macewicz, B. J., and Hill, K. T. Sampling selectivity in acoustic-trawl surveys of Pacific sardine ( Sardinops sagax ) biomass and length distribution. – ICES Journal of Marine Science, 70: . To annually assess the northern stock of Pacific sardine ( Sardinops sagax ) in the California Current and set harvest quotas for the US fishery, managers have used an age-structured stock synthesis model fitted with results from acoustic-trawl (ATM), daily-egg-production, and aerial-photogrammetric survey methods, fishery landing and individual-length data, and many assumed or empirically derived parameters. In these assessments, sardine landed at ports spanning from Ensenada, México to Vancouver Island, Canada were assumed to be solely from the northern stock. It was also assumed that the ATM estimates of sardine biomass were negligibly biased for the sizes of fish sampled by the survey trawls (i.e., catchability q = 1 for sardine standard length ( SL ) values greater than ~17 cm). Due to these catchability and length-selectivity assumptions, the ATM- and assessment-estimated abundances are mostly similar for larger sardine. However, the assessment estimates include large abundances of small sardine ( SL values less than ~15 cm) that are not represented in either the ATM-survey results or the fishery landings, and generally did not recruit to the migrating northern stock sampled by the ATM surveys. We considered four explanations for this disparity: (i) the ATM length-selectivity assumption is correct; (ii) the non-recruiting small fish may comprise a smaller portion of the stock than indicated by the assessments; (iii) during years of low recruitment success, those size classes may be virtually completely fished by the Ensenada and San Pedro fisheries; or (iv) they may belong to the southern sardine stock. This investigation emphasizes the previously identified importance of differentiating samples from the northern and southern stocks and surveying their entire domains.

Description: Wilson, M. T., Mier, K. L., and Jump, C. M. 2013. Effect of region on the food-related benefits to age-0 walleye pollock ( Theragra chalcogramma ) in association with midwater habitat characteristics in the Gulf of Alaska – ICES Journal of Marine Science, 70: . In the western Gulf of Alaska (GOA), we compared age-0 juvenile walleye pollock body weight, food habits, and expected growth rates between two regions during 3 years. The benefit to rearing off Kodiak Island vs. in the Semidi Islands vicinity increased among years with body length because larger fish consumed more euphausiids, and euphausiids were apparently more available in the Kodiak region. This explains previously observed regional variation in body size, condition, and growth rates within the GOA population and points to potential importance of the Kodiak region as a walleye pollock nursery. During September 2005, 2007, and 2009, Kodiak midwater was cooler and saltier than Semidi midwater, presumably due to a relatively narrow continental shelf and greater oceanic influence. Zooplankton composition differed between regions with the greater euphausiid population density off Kodiak being most relevant to walleye pollock food habits. As found historically, age-0 walleye pollock abundance was lower in the Kodiak region than in the Semidi region. However, the Kodiak fish were larger in both length and length-specific weight, and had fuller stomachs than Semidi fish, although differences were not significant in all years. Regional differences were most pronounced during the relatively warm year 2005 when fish were particularly large. Fish dietary mass was dominated by euphausiids, especially for Kodiak fish ≥55 mm standard length. Bioenergetics model output suggests that the greater euphausiid dietary proportion translates into faster growth of the Kodiak fish. The midwater habitat off Kodiak Island might therefore support above-average production of recruits to the GOA adult population due to better condition and likely survival of walleye pollock juveniles, especially when fish are large and thus able to more fully exploit euphausiids, but confirmation of above-average production of recruits depends on our ability to determine spatial structure in juvenile-adult population connectivity.

Description: Zwolinski, J. P., and Demer, D. A. 2013. Measurements of natural mortality for Pacific sardine ( Sardinops sagax ). – ICES Journal of Marine Science, 70: . The northern stock of Pacific sardine ( Sardinops sagax ) in the California Current Ecosystem is periodically assessed to provide harvest guidelines for the United States and Canadian fisheries. The assessment model incorporates the estimates of abundance from acoustic-trawl method (ATM) and other surveys and many parameters including a constant value for the instantaneous natural mortality coefficient ( M ). Here, the ATM-estimated length-structured sardine abundances for 2006–2011 are combined to directly estimate M. The stock was dominated by the 2003, 2004, and 2005 year classes (2003–2005 cohort) from 2006 to 2010 and by the 2009 and 2010 year classes in 2011. Insignificant recruitments during 2006–2010 allowed the 2003–2005 cohort to be tracked and M to be estimated. The bootstrap distributions of estimated M encompass the assessment-assumed value of 0.4 –year . The measurements suggest that M is high for a new cohort, declines during mid-life, then increases as the fish approach their longevity. The mean M for the entire period, 0.52, is 30% higher than the one currently assumed for the assessment, reflecting the steeper decline in the ATM-estimated biomass versus that in the assessment model.

Description: Williams, A. J., Leroy, B. M., Nicol, S. J., Farley, J. H., Clear, N. P., Krusic-Golub, K., and Davies, C. R. Comparison of daily- and annual-increment counts in otoliths of bigeye ( Thunnus obesus ), yellowfin ( T. albacares ), southern bluefin ( T. maccoyii ) and albacore ( T. alalunga ) tuna. – ICES Journal of Marine Science, 70: . Information on the age of individuals is often required for models assessing the status of stocks. Techniques used to estimate age of tuna have varied across species and agencies, precluding meta-analyses of age and growth. We compared age estimates obtained from commonly used ageing techniques for four important tuna species: bigeye tuna, yellowfin tuna, southern bluefin tuna, and albacore tuna. Estimates of age from counts of annual increments in transverse-sectioned otoliths were generally higher than those from counts of daily increments in transverse and longitudinal sections for all species, particularly for fish older than two years. However, annual counts produced younger estimates, on average, relative to daily counts for bigeye and yellowfin tuna younger than one year. Estimates derived from daily increments in longitudinal and transverse sections were generally similar, although longitudinal sections produced relatively older age estimates for individuals older than two years. A linear or non-linear increase in the magnitude of differences between ageing methods was the best-approximating model in all cases except when comparing daily-increment counts between transverse and longitudinal otolith sections for southern bluefin tuna. These observations are consistent with a narrowing of daily increments with increasing age, resulting in underestimates of age relative to those derived from annual increments. We conclude that (i) daily increments are unsuitable for ageing individuals over two years, especially for southern bluefin and albacore, (ii) longitudinal sections are more precise and produce older age estimates than transverse sections for daily-age estimates, (iii) there are considerable differences in these trends between species, likely dependent on longevity, and (iv) parameter estimates and/or conclusions based on meta-analyses using age data derived from different ageing methods are likely confounded with methodological biases. This result demonstrates that greater effort is required to provide consistent, validated methods for routine age determination to support the assessment and management of these valuable populations.

Description: Kuningas, S., Kvadsheim, P. H., Lam, F-P. A., and Miller, P. J. O. 2013. Killer whale presence in relation to naval sonar activity and prey abundance in northern Norway. – ICES Journal of Marine Science, 70: . In this study, retrospective data on naval sonar activity and prey abundance were correlated with killer whale sightings within a fjord basin in northern Norway. In addition, passive acoustic and visual marine mammal surveys were conducted before, during, and after a specific navy exercise in 2006. Herring abundance was the main factor affecting killer whale presence. Naval sonar, either operational navy sonar exercises (Flotex) or experimental sonar activity (CEE) alone, did not explain killer whale occurrence. However, naval sonar activity during a period of low prey availability seemed to have had a negative effect on killer whale presence. We conclude that the level of reaction to sonar can be influenced by multiple factors, including availability of prey.

Description: erter, K., Weltersbach, M. S., Strehlow, H. V., Vølstad, J. H., Alós, J., Arlinghaus, R., Armstrong, M., Dorow, M., de Graaf, M., van der Hammen, T., Hyder, K., Levrel, H., Paulrud, A., Radtke, K., Rocklin, D., Sparrevohn, C. R., and Veiga, P. 2013. Unexpectedly high catch-and-release rates in European marine recreational fisheries: implications for science and management. – ICES Journal of Marine Science, 70: . While catch-and-release (C&R) is a well-known practice in several European freshwater recreational fisheries, studies on the magnitude and impact of this practice in European marine recreational fisheries are limited. To provide an overview of the practice and magnitude of C&R among marine recreational anglers in Europe, the existing knowledge of C&R and its potential associated release mortality was collected and summarized. The present study revealed that in several European countries over half of the total recreational catch is released by marine anglers. High release proportions of 〉60% were found for Atlantic cod ( Gadus morhua ), European sea bass ( Dicentrarchus labrax ), pollack ( Pollachius pollachius ), and sea trout ( Salmo trutta ) in at least one of the studied European countries. In the case of the German recreational Baltic Sea cod fishery, release proportions varied considerably between years, presumably tracking a strong year class of undersized fish. Reasons for release varied between countries and species, and included legal restrictions (e.g. minimum landing sizes and daily bag limits) and voluntary C&R. Considering the magnitude of C&R practice among European marine recreational anglers, post-release mortalities of released fish may need to be accounted for in estimated fishing mortalities. However, as the survival rates of European marine species are mostly unknown, there is a need to conduct post-release survival studies and to identify factors affecting post-release survival. Such studies could also assist in developing species-specific, best-practice guidelines to minimize the impacts of C&R on released marine fish in Europe.

Description: de Pontual, H., Jolivet, A., Garren, F., and Bertignac, M. 2013. New insights on European hake biology and population dynamics from a sustained tagging effort in the Bay of Biscay. – ICES Journal of Marine Science, 70: . Following a pilot experiment that fundamentally challenged the knowledge of European hake life traits (growth and age at first maturity), a sustained tagging effort was carried out in the Bay of Biscay from 2004 to 2007. Out of 27 690 fish tagged between 2002 and 2007, 1199 (4.3%) have been recovered to date. These data have permitted a refinement of the growth parameters of the species, analysis of interannual variability, improved understanding of movements and migrations, and an examination of natural ( M ) and fishing mortality ( F ). Both L and K of a von Bertalanffy growth model could be estimated using a robust non-linear regression procedure. Growth varied significantly between years, which is likely related to variation in environmental factors such as temperature. Data did not reveal seasonal movements of fish perhaps because of poor tag return rates from offshore fleets. However, results clearly revealed homing behaviour and/or inshore residency. Confounding factors hindered the estimation of mortality, which resulted in high estimates of M . The outcomes of this experiment led to substantial changes in the stock assessment conducted by ICES and call into question the findings of previous studies that have used erroneous age-based data to address topics on the ecology and dynamics of this species.

Description: De Oliveira, J. A. A., Ellis, J. R., and Dobby, H. 2013. Incorporating density dependence in pup production in a stock assessment of NE Atlantic spurdog Squalus acanthias . – ICES Journal of Marine Science, 70: . An age- and sex-structured stock assessment model for Northeast Atlantic spurdog Squalus acanthias is presented that includes length-based processes, such as maturation, pup production, growth, and gear selectivity, with a length-at-age relationship to convert length to age. It relates pup production functionally to numbers of pregnant females, allowing for density-dependent effects. The model was fitted to a combined Scottish groundfish survey biomass index, to proportion-by-length category data from both trawl surveys and commercial catch sampling from target and non-target fisheries, and to fecundity data. The model was run from 1905 to better reflect virgin conditions and to allow early fecundity data to be fitted in order to estimate the extent of density dependence in pup production. The model estimated 2010 population levels to be about 23% relative to 1955 and 19% relative to 1905. Results confirm that the stock is depleted, but not to the extent estimated in a previous assessment. Current estimates of depletion would support an IUCN listing of "Endangered", but not "Critically Endangered". Model projections showed that a TAC of 1422 t (the last non-zero TAC) would allow future population growth.

Description: Zimmermann, F., and Heino, M. 2013. Is size-dependent pricing prevalent in fisheries? The case of Norwegian demersal and pelagic fisheries. – ICES Journal of Marine Science, 70: . It is commonly acknowledged that body weight of fish is a key factor in determining market value of landed catch, thus influencing optimal harvest strategies. However, in management strategy evaluations and bioeconomic modelling, body size is often an overlooked economic parameter, and there are no systematic studies on the prevalence of size-dependent pricing. Here we assess the presence and magnitude of size-dependent pricing in ex-vessel prices of fish in Norwegian fisheries. The data encompass landings of four pelagic and four demersal stocks in Norway in 2000–2010. Linear mixed models and generalized additive models were used to determine the dependence of unit price on weight class as well as on total yield and time (year). The results show a significant positive relationship between weight class and price for seven out of the eight examined fish stocks. The relative effect of body weight on price was the strongest for cod, Greenland halibut, Norwegian spring-spawning herring and mackerel, lesser for North Sea herring and saithe, and negligible for horse mackerel. These findings demonstrate that size-dependent pricing is common in Norwegian fisheries, and is therefore of high relevance for resource economics and fisheries management.

Description: Liu, Y., Saitoh, S-I., Radiarta, I. N., Isada, T., Hirawake, T., Mizuta, H., and Yasui, H. 2013. Improvement of an aquaculture site-selection model for Japanese kelp ( Saccharina japonica ) in southern Hokkaido, Japan: an application for the impacts of climate events. – ICES Journal of Marine Science, 70: . Japanese kelp ( Saccharina japonica ) is one of the most valuable cultured and harvested kelp species in Japan. In this study, we added a physical parameter, sea surface nitrate (SSN) estimated from satellite remote sensing data, to develop a suitable aquaculture site-selection model (SASSM) for hanging cultures of Japanese kelp in southern Hokkaido, Japan. The local algorithm to estimate SSN was developed using satellite measurements of sea surface temperature and chlorophyll-a. We found a high correlation between satellite- and ship-measured data ( r 2 = 0.87, RMSE = 1.39). Multi-criteria evaluation was adapted to the SASSM to rank sites on a scale of 1 (least suitable) to 8 (most suitable). We found that 64.4% of the areas were suitable (score above 7). Minamikayabe was identified as the most suitable area, and Funka Bay also contained potential aquaculture sites. In addition, we examined the impact of El Niño/La Niña–Southern Oscillation (ENSO) events on Japanese kelp aquaculture and site suitability from 2003–2010. During El Niño events, the number of suitable areas (scores 7 and 8) decreased significantly, indicating that climatic conditions should be considered for future development of marine aquaculture.

Description: Cheung, W. W. L., Pauly, D., and Sarmiento, J. L. 2013. How to make progress in projecting climate change impacts. – ICES Journal of Marine Science, 70: 1069–1074. Scientific modelling has become a crucial tool for assessing climate change impacts on marine resources. Brander et al. criticize the treatment of reliability and uncertainty of such models, with specific reference to Cheung et al. (2013 , Nature Climate Change , 3: 254–258) and their projections of a decrease in maximum body size of marine fish under climate change. Here, we use the specific criticisms of Brander et al . (2013 , ICES Journal of Marine Science ) on Cheung et al . (2013) as examples to discuss ways to make progress in scientific modelling in marine science. We address the technical criticisms by Brander et al. , then their more general comments on uncertainty. The growth of fish is controlled and limited by oxygen, as documented in a vast body of peer-reviewed literature that elaborates on a robust theory based on abundant data. The results from Cheung et al . were obtained using published, reproducible and peer-reviewed methods, and the results agree with the empirical data; the key assumptions and uncertainties of the analysis were stated. These findings can serve as a step towards improving our understanding of climate change impacts on marine ecosystems. We suggest that, as in other fields of science, it is important to develop incrementally (or radically) new approaches and analyses that extend, and ultimately improve, our understanding and projections of climate change effects on marine ecosystems.

Description: Galgani, F., Hanke, G., Werner, S., and De Vrees, L. 2013. Marine litter within the European Marine Strategy Framework Directive. – ICES Journal of Marine Science, 70: 1055–1064. There have been numerous anthropogenic-driven changes to our planet in the last half-century. One of the most evident changes is the ubiquity and abundance of litter in the marine environment. The EU Marine Strategy Framework Directive (MSFD, 2008/56/EC) establishes a framework within which EU Member States shall take action to achieve or maintain good environmental status (GES) of their marine waters by 2020. GES is based on 11 qualitative descriptors as listed in Annex I of the MSFD. Descriptor 10 (D 10) concerns marine litter. As a follow-up to the related Commission Decision on criteria and methodological standards (2010/477/EU) in which 56 indicators for the achievement of GES are proposed, the EC Directorate-General for the Environment, on the request of the European Marine Directors, established a Technical Subgroup on Marine Litter (TSG ML) under the Working Group on GES. The role of TSG ML is to support Member States through providing scientific and technical background for the implementation of MSFD requirements with regard to D 10. Started in 2011, TSG ML provides technical recommendations for the implementation of the MSFD requirements for marine litter. It summarizes the available information on monitoring approaches and considers how GES and environmental targets could be defined with the aim of preventing further inputs of litter to, and reducing its total amount in, the marine environment. It also identifies research needs, priorities and strategies in support of the implementation of D 10. The work of TSG ML also focuses on the specification of monitoring methods through the development of monitoring protocols for litter in the different marine compartments, and for microplastics and litter in biota. Further consideration is being given to monitoring strategies in general and associated costs. Other priorities include the identification of sources of marine litter and a better understanding of the harm caused by marine litter.

Description: Brander, K., Neuheimer, A., Andersen, K. H., and Hartvig, M. 2013. Overconfidence in model projections. – ICES Journal of Marine Science, 70: 1065–1068. There is considerable public and political interest in the state of marine ecosystems and fisheries, but the reliability of some recent projections has been called into question. New information about declining fish stocks, loss of biodiversity, climate impacts, and management failure is frequently reported in the major news media, based on publications in prominent scientific journals. Public and political awareness of the generally negative changes taking place in marine ecosystems is welcome, especially if it results in effective remedial action, but the scientific basis for such action must be reliable and uncertainties arising from models and data shortcomings must be presented fully and transparently. Scientific journals play an important role and should require more detailed analysis and presentation of uncertainties.

Description: Diesing, M., Stephens, D., and Aldridge, J. 2013. A proposed method for assessing the extent of the seabed significantly affected by demersal fishing in the Greater North Sea. – ICES Journal of Marine Science, 70: 1085–1096. The widespread impact of bottom towed fishing gear on benthic species and communities has long been recognized. The responses to a given intensity of fishing disturbance can be influenced by the extent to which these species and communities are preconditioned to disturbance by natural processes, in particular waves and currents. The advent of vessel monitoring system (VMS) and models of natural disturbance enable high-resolution and large-scale comparisons of fishing and natural disturbance. VMS data were employed to estimate the trawled area per 12 km by 12 km grid cell. We then quantified natural disturbance by estimating the number of days in a year the seabed was disturbed by tides and waves. As natural disturbance acts on large spatial scales, we assumed that each natural disturbance event affects whole grid cells. Frequencies could thus be translated into an area of impact, allowing us to compare fishing with natural disturbance. We show how such comparisons can be used to estimate the extent of different seabed substrate types significantly affected by demersal fishing. A measure of the probability that fishing disturbance exceeds natural disturbance provides one metric for identifying areas of significant trawling impact on seabed habitats and might be used to measure progress towards achieving good environmental status for sea-floor integrity within the context of the European Union's Marine Strategy Framework Directive. For more than half the seabed in the English sector of the Greater North Sea, the results suggest that disturbance attributable to demersal fishing exceeds natural disturbance based on data from the years 2006 to 2008. The imbalance between natural and fishing disturbance is greatest in muddy substrates and deep circalittoral habitats.

Description: Gröhsler, T., Oeberst, R., Schaber, M., Larson, N., and Kornilovs, G. 2013. Discrimination of western Baltic spring-spawning and central Baltic herring ( Clupea harengus L.) based on growth vs. natural tag information. – ICES Journal of Marine Science, 70: 1108–1117. In the Baltic Sea, several stocks of herring ( Clupea harengus L.) are surveyed and managed separately. For assessment purposes, a spatial stock separation based on ICES subdivisions is implemented. However, especially in the western Baltic, the distribution areas of two stocks, the western Baltic spring-spawning herring and the central Baltic herring, overlap. Results of regularly conducted surveys for assessment purposes indicated variable degrees of mixing of both stocks in the survey area, based on conspicuous differences in weights/lengths within certain age groups, especially in an area known for overlapping distribution of both stocks. At present, varying fractions of the central Baltic herring stock have not been taken into account during regular surveys conducted in the western Baltic, leading to possible undetected biases in assessment indices derived from these surveys. Additionally, methods otherwise applied for stock separation of Baltic herring so far are based on parameters that cannot readily be derived during regular surveys. In this paper, we present a simple and quick method to reliably allocate herring to either stock based on a separation function derived from survey-based length-at-age data, thus facilitating a more precise estimate of biomass and abundance indices from regular surveys and commercial fisheries.

Description: Legault, C. M., and Brooks, E. N. 2013. Can stock–recruitment points determine which spawning potential ratio is the best proxy for maximum sustainable yield reference points? – ICES Journal of Marine Science, 70: 1075–1080. The approach of examining scatter plots of stock–recruitment (S–R) estimates to determine appropriate spawning potential ratio (SPR)-based proxies for F MSY was investigated through simulation. As originally proposed, the approach assumed that points above a replacement line indicate year classes that produced a surplus of spawners, while points below that line failed to achieve replacement. In practice, this has been implemented by determining F med , the fishing mortality rate that produces a replacement line with 50% of the points above and 50% below the line. A new variation on this approach suggests F MSY proxies can be determined by examining the distribution of S–R points that are above or below replacement lines associated with specific SPRs. Through both analytical calculations and stochastic results, we demonstrate that this approach is fundamentally flawed and that in some cases the inference is diametrically opposed to the method's intended purpose. We reject this approach as a tool for determining F MSY proxies. We recommend that the current proxy of F 40% be maintained as appropriate for a typical groundfish life history.

Description: Sundelöf, A., Wennhage, H., and Svedäng, H. 2013. A red herring from the Öresund (ICES40G2): the apparent recovery of the Large Fish Indicator (LFI) in the North Sea hides a non-trawled area. – ICES Journal of Marine Science, 70: 1081–1084. As reported in a number of previous papers in this journal, the Large Fish Indicator (LFI) was developed for the North Sea. ICES Statistical Rectangle 40G2 was accidentally included in the North Sea calculations of LFI for 2004, 2007 and 2008. This inclusion significantly increased the LFI and was subsequently removed from the analysis. We identify and discuss three reasons to revisit rectangle 40G2 when considering LFI for the North Sea: (i) according to the Marine Strategy Framework Directive (MSFD), the area belongs to the North Sea, (ii) it is a geographically well-defined area where technical regulations have prevented the use of trawls since the 1930s, and (iii) there is evidence of a productive and rather closed cod ( Gadus morhua ) subpopulation unit in the area, which is an important species for the North Sea LFI.

Description: Zischke, M. T., Griffiths, S. P., and Tibbetts, I. R. 2013. Rapid growth of wahoo ( Acanthocybium solandri ) in the Coral Sea, based on length-at-age estimates using annual and daily increments on sagittal otoliths. – ICES Journal of Marine Science, 70: 1128–1139. The wahoo ( Acanthocybium solandri ) is an economically important species incidentally caught in oceanic fisheries targeting tuna and coastal fisheries targeting mackerels. The age and growth of wahoo was examined using whole and sectioned otoliths from 395 fish (790–1770 mm L F ) sampled from the Coral Sea. Growth increments were more reliably assigned on whole otoliths than sectioned otoliths. Edge analyses revealed that growth increments were deposited annually, primarily between October and February. Furthermore, analysis of presumed daily microincrements showed that ~90% of fish had deposited the first "annual" growth increment by the 365th day, thereby indirectly validating annual increment formation. Wahoo were aged at between 108 d and 7 years, with 76% of fish being 〈2-year old. The specialized von Bertalanffy growth function provided the best fit to length-at-age data, with parameter estimates (sexes combined) of L = 1499 mm L F , K = 1.58 year –1 , and t 0 = –0.17 years. The growth performance index for wahoo in the Coral Sea ( ' = 4.55) was one of the highest of all pelagic fish, with their growth and maximum size most similar to dolphinfish. This study suggests that wahoo are one of the fastest growing teleosts and provides growth parameter estimates that may facilitate future stock assessments and guide fisheries management.

Description: Radlinski, M. K., Sundermeyer, M. A., Bisagni, J. J., and Cadrin, S. X. 2013. Spatial and temporal distribution of Atlantic mackerel ( Scomber scombrus ) along the northeast coast of the United States, 1985–1999. – ICES Journal of Marine Science, 70: 1151–1161. The distribution of Atlantic mackerel ( Scomber scombrus ) during their spring migration along the Mid-Atlantic Bight and into the Gulf of Maine has historically been associated with spring warming along the continental shelf. Variations in mackerel distributions based on National Marine Fisheries Service spring surveys were compared with variations in sea surface temperature (SST) from satellite remote sensing for the eastern US continental shelf for the period 1985–1999. The mackerel stock was first analysed as a unit, then separated into three size classes to assess differences in distribution among years and individuals of various lengths. Results showed an across-shelf correlation between catch and March SST in the Mid-Atlantic Bight for both the entire population and each size class. Along-shelf catch variations were correlated with SST for large mackerel, but not total stock or smaller size classes. Finally, the distribution of mackerel length in the Gulf of Maine was negatively correlated with March SST in the Great South Channel. Results suggest surface temperature along the northeast continental shelf may be used to predict certain, but not all, aspects of annual migration along the shelf, and that factors in addition to temperature are also important in controlling distributions of Atlantic mackerel.

Description: Vásquez, S., Correa-Ramírez, M., Parada, C., and Sepúlveda, A. 2013. The influence of oceanographic processes on jack mackerel ( Trachurus murphyi ) larval distribution and population structure in the southeastern Pacific Ocean. – ICES Journal of Marine Science, 70: 1097–1107. The distribution of jack mackerel larvae in the main oceanic spawning area of the southeastern Pacific Ocean was investigated through three consecutive spring bio-oceanographic surveys (2003–2005). In this study, otolith microstructure analysis revealed a spatial age gradient with the smallest/youngest larvae specimens found primarily in the offshore area and the largest/oldest found in the coastal area, implying offshore-inshore larval drift. This suggests a connection between the oceanic spawning area and the historical coastal nursery ground (north of 30°S). In order to understand the oceanographic processes that drive this larval transport, we inferred circulation patterns from two data sources: mesoscale eddy trajectories identified by applying the Okubo-Weiss parameter to satellite geostrophic currents, and 20 years of satellite tracking data of drifters. Our results showed that eddy trajectories lead to net northwestward offshore transport (the opposite direction of larval connectivity). In addition, mean circulation associated with the subtropical anticyclonic gyre and recurrent energetic meandering structures seem to be the major mechanisms driving the spatial dynamics of the early jack mackerel life history, determining a net transport to nursery grounds. These mechanisms could play a key role in recruitment, which supports the continuity of the jack mackerel population.

Description: Lindegren, M., Waldo, S., Nilsson, P. A., Svedäng, H., and Persson, A. 2013. Towards sustainable fisheries of the Öresund cod ( Gadus morhua ) through sub-stock-specific assessment and management recommendations. – ICES Journal of Marine Science, 70: 1140–1150. Fisheries management traditionally relies on stock assessments assuming discrete populations within large administrational areas. However, failing to account for sub-stock structuring may result in overestimation of the stocks' true harvest potential and unsustainable exploitation of small stock elements. Atlantic cod ( Gadus morhua ) frequently occurs in spatially segregated populations, some of which exhibit fine-scaled stock structuring within current management boundaries. Here we use the locally spawning cod stock in the Sound ("Öresund") as a case study, and perform a sub-stock-specific assessment to evaluate biological and economic effects of managing the Sound cod as a separate stock. Our results indicate that reducing exploitation pressure, particularly through technical regulations i.e. increasing gill-net mesh sizes, would not only enhance the stock age distribution, but yield long-term net benefits to the local gill-net fishery. Furthermore, our study emphasizes the need for developing sub-stock-specific management recommendations in order to ensure the maintenance of fisheries resources in general, and the persistence of sub-stock structuring in particular.

Description: de Castro, C., Wright, P. J., Millar, C. P., and Holmes, S. J. 2013. Evidence for substock dynamics within whiting ( Merlangius merlangus ) management regions. – ICES Journal of Marine Science, 70: 1118–1127. Whiting in the North Sea and Eastern Channel is currently assessed as a single management unit. However, several studies suggest that this stock may be comprised of more than one subpopulation within a larger metapopulation. A key characteristic of metapopulations is asynchrony in the dynamics of component subpopulations. In this study, indices of recruitment and spawning–stock biomass (SSB) were developed to test for asynchrony across putative subpopulations in the North Sea and west of Scotland. Differences in SSB and recruitment trends were detected, consistent with expectations from metapopulation dynamics. At least three different subpopulation components (southern and northern North Sea, and west of Scotland) were indicated on the basis of differing trends. Analysis of spatial distribution suggested that the boundary between the northern and southern North Sea subpopulations was associated with the change in bathymetry that extended from the coast of Norfolk in England to the southern tip of Norway. The current management system for whiting in the North Sea assumes a unit stock, which is contrary to current sources of biological evidence and seems inappropriate. Consideration of a north–south split along the boundary detected should be beneficial for both assessment and management of the resource.

Description: Dvoretsky, A. G., and Dvoretsky, V. G. 2013. Population dynamics of the invasive lithodid crab, Paralithodes camtschaticus , in a typical bay of the Barents Sea. – ICES Journal of Marine Science, 70: 1255–1262. We investigated population dynamics of the introduced red king crab, Paralithodes camtschaticus (Tilesius, 1815), in Dalnezelenetskaya Bay, a typical coastal site of the Eastern Murman (Barents Sea) in summer over an 8-year period. In this bay, as in other coastal sites, juvenile crabs were most abundant. Among large crabs, the sex ratio was highly biased to females suggesting the important role of shallow water areas in reproduction of the red king crab. In 2002–2004, the carapace length (CL) frequency distribution of small crabs tended to be bimodal (30 and 60 mm). In 2005–2007 and 2009, crabs with a modal CL of 20 and 40 mm dominated. For small crabs, weight–length relationships were similar in males and females, while for large crabs the relationships differed significantly between sexes. Large males had a greater carapace width (CW) and merus length (ML), and higher CW/CL and ML/CL ratios, than large females due to sexual dimorphism. In 2002–2007, the total number of red king crabs was estimated to be 4100–7400 individuals; in 2008, we observed a marked decline to 350 individuals; in 2009, the total stock increased again to 3760 individuals. The observed patterns are in accordance with the stock dynamics reported for other coastal areas and could be associated with high levels of illegal fishing including recreational diving.

Description: Holt, R. E., Foggo, A., Neat, F. C., and Howell, K. L. 2013. Distribution patterns and sexual segregation in chimaeras: implications for conservation and management. – ICES Journal of Marine Science, 70: 1198–1205. Chimaeras such as Chimaera monstrosa and Hydrolagus mirabilis are commonly found in commercial bycatch of deep-sea fisheries in the Northeast Atlantic. Very little information exists on their life history, ecology or behaviour. Segregation of populations by sex and/or age classes has been demonstrated in several elasmobranchs, but whether segregation occurs in chimaeras, and if so what mechanisms are involved, remains unknown. This study investigates the distribution and sexual segregation of four species of chimaera ( C. monstrosa , H. mirabilis , C. opalescens n. sp . and Harriotta raleighana ) in relation to sex, size (maturity) class, bottom depth, and latitude. Data were obtained from annual trawl surveys undertaken by Marine Scotland, Aberdeen, from 1998–2009, at 400–2000 m in the Northeast Atlantic (55–59°N 5–11°W). A factorial General Linear Model (GLM) with planned contrasts indicated complex patterns of age- and sex-related segregation. All adult males and females were sexually segregated by depth: in all four species investigated females occurred at greater depths than males. Potential birthing grounds were identified for H. mirabilis . Latitudinal spatial segregation was not evident in relation to sex or maturity stage. The patterns of segregation reported here suggest a potential for differential exploitation of the sexes by spatially focused fisheries.

Description: Barbeaux, S. J., Horne, J. K., and Dorn, M. W. 2013. Characterizing walleye pollock ( Theragra chalcogramma ) winter distribution from opportunistic acoustic data. – ICES Journal of Marine Science, 70: 1162–1173. In 2003, acoustic data from 25 000 km of ship track lines were collected from two fishing vessels participating in the eastern Bering Sea walleye pollock ( Theragra chalcogramma ) fishery. Although these data were not calibrated or collected on a systematic grid, their broad temporal extent combined with high spatial resolution facilitated the examination of the distribution and behaviour of fished aggregations. To demonstrate their scientific applicability, these data were used to identify the spatio-temporal dynamics of pollock aggregations over scales ranging from hundreds of metres to hundreds of kilometres and from minutes to months. The spatial analysis identified three levels of pollock aggregation. The largest regions of high pollock density had an average diameter of 110 km and were comparable with distinct fishing grounds identified by fishers. The next smaller areas of high pollock density had a diameter between 2.5 and 6 km. Within these areas were clusters of pollock at even higher densities. The extent of the smallest aggregations ranged in diameter from 0.1 km in daylight to 0.6 km at night. Time-series analysis identified vertical and horizontal diel changes in pollock distribution and an overall decline in pollock density over the study period.

Description: Bucas, M., Bergström, U., Downie, A-L., Sundblad, G., Gullström, M., von Numers, M., Siaulys, A., and Lindegarth, M. 2013. Empirical modelling of benthic species distribution, abundance, and diversity in the Baltic Sea: evaluating the scope for predictive mapping using different modelling approaches. – ICES Journal of Marine Science, 70: 1233–1243. The predictive performance of distribution models of common benthic species in the Baltic Sea was compared using four non-linear methods: generalized additive models (GAMs), multivariate adaptive regression splines, random forest (RF), and maximum entropy modelling (MAXENT). The effects of data traits were also tested. In total, 292 occurrence models and 204 quantitative (abundance and diversity) models were assessed. The main conclusions are that (i) the spatial distribution, abundance, and diversity of benthic species in the Baltic Sea can be successfully predicted using several non-linear predictive modelling techniques; (ii) RF was the most accurate method for both models, closely followed by GAM and MAXENT; (iii) correlation coefficients of predictive performance among the modelling techniques were relatively low, suggesting that the performance of methods is related to specific responses; (iv) the differences in predictive performance among the modelling methods could only partly be explained by data traits; (v) the response prevalence was the most important explanatory variable for predictive accuracy of GAM and MAXENT on occurrence data; (vi) RF on the occurrence data was the only method sensitive to sampling density; (vii) a higher predictive accuracy of abundance models could be achieved by reducing variance in the response data and increasing the sample size.

Description: Pinchuk, A. I., Coyle, K. O., Farley, E. V., and Renner, H. M. 2013. Emergence of the Arctic Themisto libellula (Amphipoda: Hyperiidae) on the southeastern Bering Sea shelf as a result of the recent cooling, and its potential impact on the pelagic food web. – ICES Journal of Marine Science, 70: 1244–1254. The eastern Bering Sea shelf experienced a sequence of warm years after a regime shift in the late 1970s. Following a series of unusually warm years in the early 2000s, the climate shifted again in 2007 to a series of extremely cold years that were marked by intense ice coverage and late ice retreat. Spatial and temporal variability in zooplankton communities during the recent cold period was investigated as part of the collaborative BEST-BSIERP program. An increasing presence of the Arctic hyperiid Themisto libellula , which had not been reported from the southeastern Bering Sea since the 1970s, was observed in the Middle Shelf Domain, indicating a developing structural shift in the zooplankton community in response to continuous cold conditions. Simultaneously, T. libellula became an increasingly dominant prey in the diets of zooplanktivorous fish and seabirds, demonstrating the important role for T. libellula in the pelagic food web. Our analysis suggests that T. libellula is capable of controlling copepod populations, thus it may become a potential contributor to top-down regulation of Calanus spp. in the eastern Bering Sea.

Description: Meraz, J., Ancona, S., Rodríguez, C., and Drummond, H. 2013. Reproduction of the blue-footed booby predicts commercial fish abundance in the eastern tropical Pacific. – ICES Journal of Marine Science, 70: 1263–1272. To establish whether reproduction in a colony of the blue-footed booby in the eastern tropical Pacific predicts local abundance of prey fish several months later, 13 years of data were analysed. Eight reproductive variables assessed during the period of January–May, grouped in two factors, were related to commercial catches in the surrounding 6600 km 2 area during the following June–December. The first factor explained 33% of interannual variance in fish captures per unit effort during June–December (future FCUE), and 63% when only El Niño years were considered. Also, the proportion of large clutches present on three single-day censuses in the spring explained 51, 46 and 35% of variance in future FCUE among all years, and 78, 85 and 82% of variance among El Niño years. In contrast, sea surface temperatures in March did not explain variance in future FCUE. Proportion of large clutches is a moderately good predictor of the abundance of commercial fish during the subsequent seven months and can be satisfactorily and cheaply measured on a single day.

Description: Tam, Y-K., Ni, I-H., Yau, C., Yan, M-Y., Chan, W-S., Chan, S-M., Lu, H-J. 2013. Tracking the changes of a fish community following a megascale reclamation and ensuing mitigation measures. – ICES Journal of Marine Science, 70: 1206–1219. A fish community in Hong Kong that had experienced megascale reclamation in Chek Lap Kok International Airport, and the ensuing marine protected areas (MPAs) establishment was tracked for 12 years. Significant shifts in community structure, typified by 17 species, were revealed by multivariate analyses and community metrics. Dynamic factor analysis disclosed two underlying common trends among them and their significant correlations with changes in water quality, area of seabed disturbance, and area of MPAs. A time-lag for detectable community changes was also revealed. During reclamation, the fish density was low and community health was poor. Large species disappeared leaving a community dominated by small, fast-growing and young-to-mature species. After completion of reclamation, some large and medium species returned, but soon after the establishment of MPAs, medium-sized, fast-growing and young-to-mature species thrived on reduction of fishing pressure, and filled the guilds rapidly. Therefore, even though fish density and community health were improved, the original community structure was not restored. This study provides a good reference for impacts of reclamation at the community level and the possible outcomes of reducing fishing pressure in a depleted fish community.

Description: Peterson, M. J., Mueter, F., Hanselman, D., Lunsford, C., Matkin, C., and Fearnbach, H. 2013. Killer whale ( Orcinus orca ) depredation effects on catch rates of six groundfish species: implications for commercial longline fisheries in Alaska. – ICES Journal of Marine Science, 70: 1220–1232. Killer whale ( Orcinus orca ) depredation occurs when whales damage or remove fish caught on longline gear. This study uses National Marine Fisheries Service longline survey data from 1998–2011 to explore spatial and temporal trends in killer whale depredation and to quantify the effect of killer whale depredation on catches of six groundfish species within three management areas in Alaska: the Bering Sea, Aleutian Islands and Western Gulf of Alaska. When killer whales were present during survey gear retrieval, whales removed an estimated 54–72% of sablefish ( Anoplopoma fimbria ), 41–84% of arrowtooth flounder ( Atheresthes stomias ) and 73% (Bering Sea only) of Greenland turbot ( Reinhardtius hippoglossoides ). Effects on Pacific halibut ( Hippoglossus stenolepis ) and Pacific cod ( Gadus macrocephalus ) were significant in the Western Gulf only with 51% and 46% reductions, respectively. Overall catches (depredated and non-depredated sets) for all groundfish species significantly impacted by killer whale depredation were lower by 9–28% ( p 〈 0.05). Effects on shortspine thornyhead ( Sebastolobus alascanus ) catches were not significant in any management area ( p 〉 0.05). These results provide insight into the potential impacts of killer whale depredation on fish stock abundance indices and commercially important fisheries in Alaska and will inform future research on apex predator–fisheries interactions.

Description: Peña, H., Handegard, N. O. and Ona, E. 2013. Feeding herring schools do not react to seismic air gun surveys. – ICES Journal of Marine Science, 70: 1174–1180. The real-time behaviour of herring schools exposed to a full-scale 3D seismic survey off Vesterålen, northern Norway, was observed using an omnidirectional fisheries sonar. Throughout the study period, the herring swam slowly against the predominant northeast current, with a net displacement along with the current. The mean swimming speed after subtracting the drift velocities was 0.35 m s – 1 , and the mean response speed in the direction away from the air gun array was 0.22 m s – 1 . No changes were observed in swimming speed, swimming direction, or school size that could be attributed to the transmitting seismic vessel as it approached from a distance of 27 to 2 km, over a 6 h period. The unexpected lack of a response to the seismic survey was interpreted as a combination of a strong motivation for feeding, a lack of suddenness of the air gun stimulus, and an increased level of tolerance to the seismic shooting.

Description: Wigand, L. A., Klinger, T., and Logsdon, M. G. 2013. Patterns in groundfish abundance along the Eastern Bering Sea outer continental margin. – ICES Journal of Marine Science, 70: 1181–1197. Place-based management approaches require understanding the spatial arrangement and interaction of elements. To address this need, we explored the utility of spatial-pattern analysis to understand the distribution of groundfish in the Eastern Bering Sea outer continental margin. We divided this region into discrete geomorphological units to explore spatial pattern on a range of scales. We used groundfish catch per unit effort (cpue) trawl survey data collected in four years to quantify spatial autocorrelation. Global statistics indicated that groundfish cpue was dominated by clusters of low values in all years. Local statistics showed that clusters of low values in groundfish cpue were confined to the southern portion of the study area, while clusters of high values varied across the study area. Outliers were most commonly found in close proximity to the shelf–slope break. Our results reveal the existence of spatial dependency in groundfish abundance and demonstrate that spatial analysis can be used to better understand spatial arrangements of these and other living marine resources, and to quantify and validate the local ecological knowledge of resource users. Our results indicate the feasibility of using spatially explicit tools to improve integration and visualization of marine environmental data for purposes of management and conservation.

Description: Williams, R., Vikingsson, G. A., Gislason, A., Lockyer, C., New, L., Thomas, L., and Hammond, P. S. 2013. Evidence for density-dependent changes in body condition and pregnancy rate of North Atlantic fin whales over four decades of varying environmental conditions. – ICES Journal of Marine Science, 70: 1273–1280. A central theme in ecology is the search for pattern in the response of a species to changing environmental conditions. Natural resource management and endangered species conservation require an understanding of density-dependent and density-independent factors that regulate populations. Marine mammal populations are expected to express density dependence in the same way as terrestrial mammals, but logistical difficulties in data acquisition for many large whale species have hindered attempts to identify population-regulation mechanisms. We explored relationships between body condition (inferred from patterns in blubber thickness) and per capita prey abundance, and between pregnancy rate and body condition in North Atlantic fin whales as environmental conditions and population size varied between 1967 and 2010. Blubber thickness in both males and females declined at low per capita prey availability, and in breeding-age females, pregnancy rate declined at low blubber thickness, demonstrating a density-dependent response of pregnancy to prey limitation mediated through body condition. To the best of our knowledge, this is the first time a quantitative relationship among per capita prey abundance, body condition, and pregnancy rate has been documented for whales. As long-lived predators, marine mammals can act as indicators of the state of marine ecosystems. Improving our understanding of the relationships that link prey, body condition, and population parameters such as pregnancy rate and survival will become increasingly useful as these systems are affected by natural and anthropogenic change. Quantifying linkages among prey, fitness and vital rates will improve our ability to predict population consequences of subtle, sublethal impacts of ocean noise and other anthropogenic stressors.

Description: Heino, M., Baulier, L., Boukal, D. S., Ernande, B., Johnston, F. D., Mollet, F. M., Pardoe, H., Therkildsen, N. O., Uusi-Heikkilä, S., Vainikka, A., Arlinghaus, R., Dankel, D. J., Dunlop, E. S., Eikeset, A. M., Enberg, K., Engelhard G. H., Jørgensen, C., Laugen, A. T., Matsumura, S., Nusslé, S., Urbach, D., Whitlock, R., Rijnsdorp, A. D., and Dieckmann, U. 2013. Can fisheries-induced evolution shift reference points for fisheries management? – ICES Journal of Marine Science, 70: 707–721. Biological reference points are important tools for fisheries management. Reference points are not static, but may change when a population's environment or the population itself changes. Fisheries-induced evolution is one mechanism that can alter population characteristics, leading to "shifting" reference points by modifying the underlying biological processes or by changing the perception of a fishery system. The former causes changes in "true" reference points, whereas the latter is caused by changes in the yardsticks used to quantify a system's status. Unaccounted shifts of either kind imply that reference points gradually lose their intended meaning. This can lead to increased precaution, which is safe, but potentially costly. Shifts can also occur in more perilous directions, such that actual risks are greater than anticipated. Our qualitative analysis suggests that all commonly used reference points are susceptible to shifting through fisheries-induced evolution, including the limit and "precautionary" reference points for spawning-stock biomass, B lim and B pa , and the target reference point for fishing mortality, F 0.1 . Our findings call for increased awareness of fisheries-induced changes and highlight the value of always basing reference points on adequately updated information, to capture all changes in the biological processes that drive fish population dynamics.

Description: Jennings, S. 2013. When can "principles" support advice on fisheries and environmental management? – ICES Journal of Marine Science, 70: 726–733. Demands for advice on fisheries and environmental management often outstrip scientists' capacity to supply it. The imbalance would be smaller if some of the advice could be based on principles rather than tailored case-by-case analyses, where I define principles as "evidence-based rules that underpin scientific advice on management options and reduce uncertainty about decisions and outcomes with fewer resources than tailored case-by-case analyses". I consider the role, development, existing and potential uses, strengths and weaknesses of principles in underpinning advice, and how principles might complement methodological innovations and risk assessment. The extent to which principles might replace case-by-case analyses is expected to depend on structures and processes in the management system, particularly the treatment of uncertainty and risk. If advice based on principles is seen as less salient, credible, and legitimate than advice developed from case-by-case analyses then this could lead to political push-back or non-compliance with management measures, transferring costs from the advisory process to other parts of the management system. In general, I propose that principles provide the greatest benefits in a management system when they address complex advisory issues that lead to advice on management measures with relatively small social and economic consequences or when they simplify parts of an advisory process leading to management measures with a range of consequences. Notwithstanding limits on their application, further development and uptake of principles could reduce demands for case-by-case advice on fisheries and environmental management. A formalized challenge, testing, and updating process for principles, supported by an audit trail, would encourage and increase their use. The development of principles would provide a new focus for the targeting, review, and uptake of research. Spatial planning initiatives, the emergence of marine protected area networks, and other changes in management measures can be treated as experiments to inform development and testing of principles.

Description: Skagen, D. W., Skern-Mauritzen, M., Dankel, D., Enberg, K., Kjesbu, O. S., and Nash, R. D. M. 2013. A simulation framework for evaluating fisheries management decisions using environmental information. – ICES Journal of Marine Science, 70: 743–754. The population dynamics of marine fish stocks are influenced by both physical and biological conditions. Yet, such environmental impacts on stock dynamics, and hence stock production, are rarely included in applied fisheries management. To test the utility of taking ecosystem information into account in management decisions requires efficient tools. We propose a simulation framework for evaluating fisheries management schemes that use environmental information as part of the decision basis. A key feature is to link environmental signals to parameters in functions that define the population dynamics. This allows a direct incorporation of environmental drivers into models of population dynamic processes and emphasizes the need for a quantitative understanding of the influence of environmental drivers on such processes. The utility of the simulation framework is demonstrated through a worked example with different management scenarios, where decisions to increase or decrease the exploitation rely on environmental indicators only, or also on information on stock abundance. In this example, a management that was based on indicators only, without updated measures of the state of the stock itself, failed to respond adequately to changes in stock productivity.

Description: Misund, O. A., and Olsen, E. 2013. .Lofoten–Vesterålen: for cod and cod fisheries, but not for oil? – ICES Journal of Marine Science, 70: 722–725. Over the last decade, the most controversial issue regarding the management of Norwegian marine waters has been about opening the Lofoten–Vesterålen areas for offshore oil and gas exploration. This paper outlines the political and management processes and reviews the arguments for and against. Our conclusion is that these valuable areas should not be opened for such activity because of their high biological significance as the main spawning grounds for northeast Arctic cod ( Gadus morhua ) and other important fish stocks in the northeast Arctic waters.

Description: Large, S. I., Fay, G., Friedland, K. D., and Link, J. S. 2013. Defining trends and thresholds in responses of ecological indicators to fishing and environmental pressures. – ICES Journal of Marine Science, 70: 755–767. Both fishing and environmental forces can influence the structure of marine ecosystems. To further understand marine ecosystems and to implement ecosystem-based fisheries management (EBFM), an evaluation of ecosystem indicators is warranted. In this context, it is particularly important to identify thresholds where fishing and environmental pressures significantly influence ecological indicators. We empirically determined numerical values of environmental forces and fishing pressure that significantly altered the response of ecological indicators for the Northeast Shelf Large Marine Ecosystem. Generalized additive models predicted a non-linear relationship for each pressure–response pairing. With this smoother, 95% confidence intervals (CI) for estimated first and second derivatives for each relationship were determined via parametric bootstrap. A significant trend or threshold was noted when the CI for the first or second derivative was greater or less than zero, delineating the level at which pressure variables influence the rate and direction of ecosystem indicator responses. We identify reference levels where environmental forces and fishing pressure result in ecosystem change by collectively examining the responses of multiple ecological indicators. Individual indicators showed unique responses to pressures, however, similar values for the pressures were associated with significant changes for multiple indicators. These reference levels establish a foundation for implementation of EBFM.

Description: Le Bris, A., Fréchet, A., Galbraith, P. S., and Wroblewski, J. S. 2013. Evidence for alternative migratory behaviours in the northern Gulf of St Lawrence population of Atlantic cod ( Gadus morhua L.). – ICES Journal of Marine Science, 70: 793–804. Inter-individual variation in migration propensity affects population dynamics and connectivity. The diversity of migratory behaviours of Atlantic cod (fork length 〉40 cm) in the northern Gulf of St Lawrence was studied using data-storage tags that record depth and temperature. Movement patterns of Atlantic cod equipped with data-storage tags were reconstructed using a geolocation model based on daily maximum depth and bottom temperature. Reconstructed migration routes revealed the previously undocumented coexistence of resident and migratory individuals in the population. Migratory cod overwintered in relatively deep (300–500 m) and warm (5°C) waters, while residents displayed a prolonged period of immobility in shallow (〈100 m) and near-freezing (–1.5°C) coastal waters of western Newfoundland. In the spring, migratory cod displayed extensive diel vertical migration suggestive of spawning behaviour. The presence of alternative migratory behaviours should be considered in the spatiotemporal management of the collapsed population.

Description: Marchal, P., and Vermard, Y. 2013. Evaluating deepwater fisheries management strategies using a mixed-fisheries and spatially explicit modelling framework. – ICES Journal of Marine Science, 70: 768–781. We have used in this study a spatially explicit bioeconomic modelling framework to evaluate management strategies, building in both data-rich and data-limited harvest control rules (HCRs), for a mix of deepwater fleets and species, on which information is variable. The main focus was on blue ling ( Molva dypterygia ). For that species, both data-rich and data-limited HCRs were tested, while catch per unit effort (CPUE) was used either to tune stock assessments, or to directly trigger management action. There were only limited differences between the performances of both HCRs when blue ling biomass was initialized at the current level, but blue ling recovered more quickly with the data-rich HCR when its initial biomass was severely depleted. Both types of HCR lead, on average, to a long-term recovery of both blue ling and saithe ( Pollachius virens ) stocks, and some increase in overall profit. However, that improvement is not sufficient to guarantee sustainable exploitation with a high probability. Blue ling CPUE did not always adequately reflect trends in biomass, which mainly resulted from fleet dynamics, possibly in combination with density-dependence. The stock dynamics of roundnose grenadier ( Coryphaenoides rupestris ), black scabbardfish ( Aphanopus carbo ) and deepwater sharks ( Centrophorus squamosus and Centroscymnus coelolepis ) were little affected by the type of HCR chosen to manage blue ling.

Description: Rice, J., Daan, N., Gislason, H., and Pope, J. Does functional redundancy stabilize fish communities? – ICES Journal of Marine Science, 70: 734–742. Functional redundancy of species sharing a feeding strategy and/or maximum size has been hypothesized to contribute to increased resilience of marine fish communities (the "portfolio effect"). A consistent time-series of survey data of fish in the North Sea was used to examine if trophic functional groups or maximum length of species (L max) groups with larger numbers of species had lower coefficients of variation in abundance and biomass over time than did groupings with fewer species. Results supported this hypothesis. However, the stabilizing effect of numbers of species in a group on variation in abundance or biomass could be accounted for by the Law of Large Numbers, providing no evidence that specific ecological processes or co-adaptations are necessary to produce this effect. This implies that successful conservation policies to maintain the resilience of a marine fish community could be based on strategies to maintain the number of species in functional groups, without having to know the detailed ecological interactions between the species.

Description: Homrum, E. í, Hansen, B., Jónsson, S. Þ., Michalsen, K., Burgos, J., Righton, D., Steingrund, P., Jakobsen, T., Mouritsen, R., Hátún, H., Armannsson, H., and Joensen, J. S. 2013. Migration of saithe ( Pollachius virens ) in the Northeast Atlantic. – ICES Journal of Marine Science, 70: 782–792. Saithe ( Pollachius virens ) stocks in the Northeast Atlantic intermingle as a result of migration among stock areas. The extent of migration has been poorly quantified. Here, we estimate measures of the migration based on existing tagging data from Icelandic, Faroese and Continental (Scotland, North Sea and Norway) waters. Saithe tagged in Icelandic waters were seldom caught outside Icelandic waters (〈1% of tag returns), whereas 42% of adult saithe tagged in Faroese waters were recaptured outside Faroese waters. Of adult saithe tagged in Norwegian waters 6.6% were recaptured outside Continental waters. In broad terms, there was a net migration of saithe towards Icelandic waters. The distance between tagging and recapture increased with increasing size and age, with saithe tagged in Norwegian waters moving the longest distances. The results demonstrate significant, but variable, migration rates of adult saithe in the Northeast Atlantic. More detailed studies are needed to clarify the mechanisms behind the migration and what causes the differences among the areas.

Description: Busch, D. S., Harvey, C. J., and McElhany, P. 2013. Potential impacts of ocean acidification on the Puget Sound food web. – ICES Journal of Marine Science, 70: 823–833. Ecosystem impacts of ocean acidification (OA) were explored by imposing scenarios designed to mimic OA on a food web model of Puget Sound, a large estuary in northwestern USA. The productivity of functional groups containing mostly calcifiers was decreased while still allowing other species groups to respond to the scenarios in a dynamic way through indirect effects. Results focus on changes in ecosystem services and structure. Sometimes the direct and indirect effects of OA countered each other due to interactions between predators and prey within the food web, leading to little change in the food web. In other cases, direct and indirect effects caused greater change in the food web than anticipated from direct effects alone. Results were strongly affected by the group on which OA was directly imposed, with changes in copepod productivity being the most influential. While there is much uncertainty in our predictions, focusing on the complex interactions among species, and between species and their environment, will yield better understanding of how ecosystems may respond to OA.

Description: Bernard, K. S., and Steinberg, D. K. 2013. Krill biomass and aggregation structure in relation to tidal cycle in a penguin foraging region off the Western Antarctic Peninsula. – ICES Journal of Marine Science, 70: 834–849 Antarctic krill are a key component of the diet of Adélie penguins inhabiting the Western Antarctic Peninsula (WAP), yet our understanding of the variability of krill distribution patterns within nearshore penguin feeding grounds is limited. A recent study of the foraging patterns of penguins breeding in the northern WAP suggests that tidal phase plays a role in foraging distance. We used acoustics to examine biomass and aggregation structure of krill in the penguin foraging grounds off Palmer Station during diurnal and semi-diurnal tides. Nearshore, integrated krill biomass during diurnal tides was significantly higher than during semi-diurnal tides. Krill aggregations were also shallower, closer together, and larger in dimension during diurnal tides. Conversely, krill aggregations had higher volumetric biomass and abundance during semi-diurnal tides. Further offshore, at the head of the Palmer Deep canyon, krill aggregations were similar to those observed nearshore during diurnal tides (i.e. shallow, close together, and large in dimension). Since krill aggregation structure strongly influences availability as a potential prey source, we suggest that foraging behavior of Adélie penguins in this region is strongly linked to the variability in nearshore krill aggregation structure as well as biomass.

Description: Bacheler, N. M., Schobernd, Z. H., Berrane, D. J., Schobernd, C. M., Mitchell, W. A., and Geraldi, N. R. 2013. When a trap is not a trap: converging entry and exit rates and their effect on trap saturation of black sea bass ( Centropristis striata ) – ICES Journal of Marine Science, 70: 873–882. Catch rates are often used to index the abundance of marine organisms, but catch saturation (i.e. declining catch rate as fishing time increases) can decouple catch and abundance. Researchers have struggled to account for saturation when using trap catch to infer population dynamics. We used the underwater video to document entries and exits of black sea bass ( Centropristis striata ) from chevron traps ( n = 26) to quantify catch saturation. Black sea bass catch varied between 3 and 188 individuals for soak times of ~90 min. Overall, 3564 black sea bass entered the traps and 1826 exited; therefore, over half (51%) of black sea bass entering traps exited before traps were retrieved. Black sea bass catch rates were non-linear and asymptotic for most (81%) trap samples, despite short soak times. Moreover, catch saturation occurred at 50 min, when the entry rate declined and the exit rate increased to a point where their confidence intervals overlapped. Several lines of evidence suggest that the level of black sea bass catch once saturation occurred may be positively related to true abundance, but additional research is needed to more fully test this hypothesis.

Description: Pansch, C., Schlegel, P., and Havenhand, J. 2013. Larval development of the barnacle Amphibalanus improvisus responds variably but robustly to near-future ocean acidification. – ICES Journal of Marine Science, 70: 805–811. Increasing atmospheric CO 2 decreases seawater pH in a phenomenon known as ocean acidification. In two separate experiments we found that larval development of the barnacle Amphibalanus (Balanus) improvisus was not significantly affected by the level of reduced pH that has been projected for the next 150 years. After 3 and 6 days of incubation, we found no consistent effects of reduced pH on developmental speed or larval size at pH 7.8 compared with the control pH of 8.1. After 10 days of incubation, there were no net changes in survival or overall development of larvae raised at pH 7.8 or 7.6 compared with the control pH of 8.0. In all cases, however, there was significant variation in responses between replicate batches (parental genotypes) of larvae, with some batches responding positively to reduced pH. Our results suggest that the non-calcifying larval stages of A. improvisus are generally tolerant to near-future levels of ocean acidification. This result is in line with findings for other barnacle species and suggests that barnacles do not show the greater sensitivity to ocean acidification in early life history reported for other invertebrate species. Substantial genetic variability in response to low pH may confer adaptive benefits under future ocean acidification.

Description: Hurst, T. P., Fernandez, E. R., and Mathis, J. T. 2013. Effects of ocean acidification on hatch size and larval growth of walleye pollock ( Theragra chalcogramma ). – ICES Journal of Marine Science, 70: 812–822. Rising atmospheric concentrations of CO 2 are predicted to decrease the pH of high-latitude oceans by 0.3–0.5 units by 2100. Because of their limited capacity for ion exchange, embryos and larvae of marine fishes are predicted to be more sensitive to elevated CO 2 than juveniles and adults. Eggs and larvae of walleye pollock ( Theragra chalcogramma ) were incubated across a broad range of CO 2 levels (280–2100 µatm) to evaluate sensitivity in this critical resource species. Slightly elevated CO 2 levels (~450 µatm) resulted in earlier hatching times, but differences among egg batches were greater than those observed across CO 2 treatments. Egg batches differed significantly in size-at-hatch metrics, but we observed no consistent effect of CO 2 level. In three independent experiments, walleye pollock were reared at ambient and elevated CO 2 levels through the early larval stage (to ~30 days post-hatch). Across trials, there were only minor effects of CO 2 level on size and growth rate, but fish in the ambient treatments tended to be slightly smaller than fish reared at elevated CO 2 levels. These results suggest that growth potential of early life stages of walleye pollock is resilient with respect to the direct physiological effects of ocean acidification.

Description: O'Neill, F. G., Simmons, S. M., Parsons, D. R., Best, J. L., Copland, P. J., Armstrong, F., Breen, M., and Summerbell, K. 2013. Monitoring the generation and evolution of the sediment plume behind towed fishing gears using a multibeam echosounder. – ICES Journal of Marine Science, 70: 892–903. We compare optical and acoustic-based measurements of sediment concentration in plumes behind the otter door of a demersal trawl and behind the roller clump of a demersal twin trawl. Measurements were made using a LISST 100X and a RESON 7125 multibeam echosounder (MBES), and we demonstrate how the MBES can be used to reliably monitor and quantify the evolution of sediment plumes in the wake of towed demersal fishing gears. The MBES data detail the spatial and temporal decay of the plume size and the concentration behind the gear and also reveal significant differences in the behaviour of plumes in the wake of different fishing gear components. The results highlight the importance of being able to measure and understand the processes at work at the level of the individual gear components and also detail the range of conditions over which an acoustic-based MBES technique can be applied to monitor such dynamics and to assess the impact of fishing on the seabed and on the marine environment.

Description: Herrmann, B., Mieske, B., Stepputtis, D., Krag, L. A., Madsen, N., and Noack, T. 2013. Modelling towing and haul-back escape patterns during the fishing process: a case study for cod, plaice, and flounder in the demersal Baltic Sea cod fishery. – ICES Journal of Marine Science, 70: 850–863. The survival likelihood of fish escaping through trawl codends may depend on when they escape. It is therefore relevant to investigate when during the fishing process fish actually attempt to escape and do escape from trawl codends. This subject is addressed by modelling data collected during a specially designed experiment. Results demonstrate that the escape process during towing cannot be described sufficiently by a traditional logistic model or something similar. Instead, a model is required that explicitly considers that not all fish necessarily contact the codend netting to attempt escape during the towing phase. A model that accounts for such behaviour is applied and it is demonstrated that this model can adequately describe the size selection process during towing. The overall escape process, which consists of the attempt probability, partial escape during towing, and partial escape during the haul-back phase, is also modelled. This proposed model sufficiently described the observed escape pattern for cod ( Gadus morhua ), plaice ( Pleuronectes platessa ), and flounder ( Platichtys flesus ). For all three species, a significant percentage of the individuals entering the codends during fishing first attempt to escape during the haul-back operation.

Description: Weltersbach, M. S., and Strehlow, H. V. 2013. Dead or alive—estimating post-release mortality of Atlantic cod in the recreational fishery. – ICES Journal of Marine Science, 70: 864–872. Atlantic cod ( Gadus morhua ) is one of the most important commercial and recreational target species in European marine waters. Recent recreational fisheries surveys revealed that recreational cod catches and release rates are substantial compared to the commercial fishery, particularly in the western Baltic Sea. Despite high release rates, no literature exists exploring the post-release mortality of cod and potential sublethal effects after catch-and-release in recreational fisheries. This study investigates (i) the post-release mortality of undersized cod, (ii) potential factors affecting mortality, and (iii) consequences of the catch-and-release process on cod. During four experimental trials, western Baltic Sea cod were angled from a charter vessel and thereafter observed together with control fish in netpens for 10 d at holding temperatures between 6.2 and 19.8°C. Adjusted mortality rates for angled cod ranged from 0.0–27.3% (overall mean 11.2%). A logistic regression analysis revealed that bleeding and holding-water temperature were the only significant predictors of mortality. Slow hook injury healing (〉10 d) and bacterial wound infections were observed in some surviving cod. The results will help to increase the accuracy of recreational cod removal estimates and thereby improve the management of western Baltic cod stock.

Description: Polak, O., and Shashar, N. 2013. Economic value of biological attributes of artificial coral reefs – ICES Journal of Marine Science, 70: 904–912. Visitor appreciation of natural scenes such as coral reefs is well documented. However, what part the value of the biological component in these scenes plays in fostering people's enjoyment is unclear. Using the contingent valuation method (CVM), we examined divers' willingness to pay for changes in the fish and coral attributes over an artificial reef. Using image manipulations, different levels of community descriptors, such as richness, abundance, and biodiversity of corals and fish, were isolated, and the willingness to pay for proposed factors was examined. The results showed that divers were willing to contribute towards all increases in reef community attributes, and were partially able to discriminate between them. Biodiversity was the most valued index, while fish abundance was the least favoured. These results, which demonstrate that visitors understand the fundamentals that constitute a coral reef community and value its diversity, may help direct conservation efforts undertaken in the design of marine reserves and pre-planned artificial reefs.