ALBERT

Description: Rice, J. 2014. Evolution of international commitments for fisheries sustainability. – ICES Journal of Marine Science, 71: 157–165. The basic standards for the sustainability of fisheries were set by international policy in the UN Fish Stocks Agreement (FSA). However, each year since the FSA was ratified, the United Nations General Assembly has negotiated and agreed to resolutions on Ocean Law of the Sea and on Sustainable Fisheries. This paper reviews chronologically how the interpretation of "sustainability" has evolved in those resolutions, as well as been addressed in the decadal world summits on sustainable development. Although the basic biological benchmarks for sustainability have not been altered by these resolutions, commitments for the standards to be met by all ecosystem components impacted by fishing have become increasingly strong. The annual resolutions have increasingly stressed that environmental sustainability is critically important, but is not more important than social well-being aspects of sustainability, with fisheries having a vital role in sustainable development in many parts of the world. In addition, agreements on biodiversity conservation made largely in Oceans and Law of the Sea resolutions are increasingly influencing the nature and pace of evolution of how "sustainability" is interpreted in fisheries.

Description: Lassen, H., Kelly, C., and Sissenwine, M. 2014. ICES advisory framework 1977–2012: from F max to precautionary approach and beyond. – ICES Journal of Marine Science, 71: 166–172. The International Council for the Exploration of the Sea (ICES) provides fishery advice in the context of international agreements and addressing the policy and legal needs of ICES Member Countries. This advice is often formulated for an annual total allowable catch based on decisions made by the North East Atlantic Fisheries Commission (NEAFC) during the first half of the 1970s. Although this early advice was initially focused on the best usage of the growth potential of the fish stocks, the collapse of important pelagic stocks in the late 1960s and the early 1970s suggested that the biological advice should include serious considerations of the spawning–stock biomass (SSB). ICES responded with a new advisory framework in 1976. Over the next 30 years, the advisory framework evolved, with increasing emphasis placed on ensuring SSB to avoid impairing recruitment. The Plan of Implementation of the 2002 UN World Summit on Sustainable Development (WSSD) calls for the restoration and maintenance of fish stocks to levels than can produce the fisheries that provide maximum sustainable yield (MSY). In 2009, ICES revised its advisory framework now formulated as a harvest control rule aimed at achieving MSY.

Description: Agnew, D. J., Gutiérrez, N. L., Stern-Pirlot, A., and Hoggarth, D. D. 2014. The MSC experience: developing an operational certification standard and a market incentive to improve fishery sustainability. – ICES Journal of Marine Science, 71: 216–225. The Marine Stewardship Council (MSC) standard for sustainable fisheries is represented by three high-level principles and a set of 31 indicators and scoring guidelines, known as the "default assessment tree". Over the 14 years, since it was developed in 1999, the MSC has faced the challenge of maintaining its standard at the level of global best practice, keeping up with developments in the science and management of fisheries, and making sure that certified fisheries maintain their performance at that standard, or raise it where they fall below it. The MSC has had to regularly and widely engage with multiple stakeholders to ensure that its policy development is consistent with stakeholder expectations. Although many fisheries have made significant improvements to their performance, sometimes performance has declined, leading to further requirements for improvement. The MSC needed to design a program that balances credibility, accessibility, and improvement to move the world's fisheries towards sustainability.

Description: Record, N. R., Pershing, A. J., and Maps, F. 2014. The paradox of the "paradox of the plankton". – ICES Journal of Marine Science, 71: 236–240. One of the central orienting questions in biodiversity theory and ecology is the "paradox of the plankton", which asks how it is possible for many species to coexist on limited resources given the tendency for competition to exclude species. Over the past five decades, ecologists have offered dozens of solutions to the paradox, invoking game theory, chaos, stochastics, and many other concepts. Despite the plentitude of solutions to the paradox, ecologists continue to offer up novel solutions. Ocean modellers are now faced with the opposite paradox: given the overabundance and the diversity of solutions to the paradox, what is the appropriate way to build coexistence into ecosystem models? Ocean ecosystem models have a very standardized form—nutrient–phytoplankton–zooplankton (NPZ)-type systems of differential equations—where competitive exclusion is a common model behaviour. We suggest approaching the problem from the perspective of community-level patterns. We offer a prototype for building coexistence into NPZ models. The model allows for diverse assemblages of phytoplankton or zooplankton groups to persist and produces accurate community-level patterns. The approach is simple, adding only one additional parameter, and allows us to test the effects of trait distributions and environmental variables on diversity.

Description: Daewel, U., Hjøllo, S. S., Huret, M., Ji, R., Maar, M., Niiranen, S., Travers-Trolet, M., Peck, M. A., van de Wolfshaar, K. E. 2014. Predation control of zooplankton dynamics: a review of observations and models. – ICES Journal of Marine Science, 71: 254–271. We performed a literature review to examine to what degree the zooplankton dynamics in different regional marine ecosystems across the Atlantic Ocean is driven by predation mortality and how the latter is addressed in available modelling approaches. In general, we found that predation on zooplankton plays an important role in all the six considered ecosystems, but the impacts are differently strong and occur at different spatial and temporal scales. In ecosystems with extreme environmental conditions (e.g. low temperature, ice cover, large seasonal amplitudes) and low species diversity, the overall impact of top-down processes on zooplankton dynamics is stronger than for ecosystems having moderate environmental conditions and high species diversity. In those ecosystems, predation mortality was found to structure the zooplankton mainly on local spatial and seasonal time scales. Modelling methods used to parameterize zooplankton mortality range from simplified approaches with fixed mortality rates to complex coupled multispecies models. The applicability of a specific method depends on both the observed state of the ecosystem and the spatial and temporal scales considered. Modelling constraints such as parameter uncertainties and computational costs need to be balanced with the ecosystem-specific demand for a consistent, spatial-temporal dynamic implementation of predation mortality on the zooplankton compartment.

Description: Plourde, S., McQuinn, I. H., Maps, F., St-Pierre, J-F., Lavoie, D., and Joly, P. 2014. Daytime depth and thermal habitat of two sympatric krill species in response to surface salinity variability in the Gulf of St Lawrence, eastern Canada. – ICES Journal of Marine Science, 71: 272–281. We describe the response of acoustically determined weighted mean depth (WMD) of two sympatric species of krill, Thysanoessa raschii and Meganyctiphanes norvegica , to variations in surface salinity during summer in the Gulf of St Lawrence. In this coastal system, non-living particulates and CDOM carried by the freshwater run-off of the St Lawrence River and several large rivers have a strong impact on turbidity and light attenuance in the surface layer. The WMD of T. raschii and M. norvegica were significantly and positively related to surface salinity. However, M. norvegica was found deeper and in warmer water than T. raschii , and the latter had a steeper response to surface salinity. The species-specific relationships between daytime WMD and surface salinity enabled us to estimate both species regional and interannual variations in summertime temperature habitat during a 21-year period (1991–2011). The variability in daytime WMD resulted in significant inter- and intraspecific differences in the temperature experienced by adult krill that may impact development, growth, and reproduction. Our study illustrated the importance of considering species-specific responses to environmental forcing in coupled biophysical models that aim to explore the impacts of environmental variations on krill dynamics.

Description: Gullestad, P., Aglen, A., Bjordal, Å., Blom, G., Johansen, S., Krog, J., Misund, O. A., and Røttingen, I. 2014. Changing attitudes 1970–2012: evolution of the Norwegian management framework to prevent overfishing and to secure long-term sustainability. – ICES Journal of Marine Science, 71: 173–182. Fisheries have been important for livelihood in Norwegian coastal communities for centuries. The development of new fishing technology and increasing fishing capacity posed challenges for the sustainability of the fisheries. The Norwegian spring spawning herring was depleted in the1960s—with dire consequences. This event, and the subsequent efforts to rebuild the stock, was paramount to the gradual development of a coherent Norwegian policy to prevent overfishing and secure long-term sustainability. Nevertheless, overfishing continued during the ensuing transitional decades when a range of new management tools were developed and made effective. Internationally, the extension of the economic zones to 200 nautical miles, and agreement on sharing and management of joint stocks were important elements. At the national level, the development of measures to curb overcapacity, improvement of exploitation patterns through technical regulations, ban on discard and the evolution of procedures for rational decision-making for setting total allowable catches (TACs) on the basis of harvest control rules, were all decisive elements. Another crucial factor was the creation of a whole new profession of fishery inspection. We describe a system of close collaboration between specialists—scientists, fishery managers, and stakeholders—each with a distinct role in building a solid framework to prevent overfishing and secure long-term sustainability.

Description: Viñas, J., Sanz, N., Peñarrubia, L., Araguas, R-M., García-Marín, J-L., Roldán, M-I., and Pla, C. 2014. Genetic population structure of European anchovy in the Mediterranean Sea and the Northeast Atlantic Ocean using sequence analysis of the mitochondrial DNA control region. – ICES Journal of Marine Science, 71: 391–397. The European anchovy ( Engraulis encrasicolus ) exhibits a complex population structure in the Mediterranean Sea and Northeast Atlantic Ocean. To resolve the population genetic structure of this species, we surveyed sequence variability in the mitochondrial (mtDNA) control region in samples ( n = 563) from 13 locations in the Northeast Atlantic, the Bay of Biscay, and the Mediterranean Sea. Based on pairwise ST s, SAMOVA, and multidimensional scaling, a complicated population structure composed of multiple populations emerged. Combining these results with those from previous population studies based on mitochondrial and nuclear markers, we identified nine genetically differentiated European anchovy populations: (i) Canary Islands; (ii) Cádiz; (iii) Alborán Sea; (iv) Garona; (v) Arcachon and Donostia; (vi) a large population in the northwestern Mediterranean, including Cadaqués, Gulf of Lyon, Elba, and Sicily; (vii) southern Adriatic; (viii) northern Adriatic; and (ix) Aegean Sea. We suggest that independent management strategies should be implemented for each genetically differentiated population, and, in cases where several fisheries stocks are recognized within an area of genetic homogeneity, each stock should be managed separately.

Description: Jansen, T. 2014. Pseudocollapse and rebuilding of North Sea mackerel ( Scomber scombrus ). – ICES Journal of Marine Science, 71: 299–307. The largest observed change in mackerel ( Scomber scombrus ) abundance in the North Atlantic happened when the so-called "North Sea mackerel" collapsed due to overfishing. Despite protection, it has remained in a depleted state. Central to this interpretation was that the "North Sea mackerel" was considered to be a distinct spawning component. However, a recent study has shown that this is not likely. In the light of this study, a review of the history of mackerel spawning in the North Sea found that the traditional explanation of the collapse did not account for a range of unfavourable environmental changes: high fishing pressure was followed by decreasing temperatures that reduced the spawning migration into the North Sea. This was further supplemented by unfavourable changes in food and wind-induced turbulence. On the population level, this was, therefore, not a local stock collapse, but a southwest shift in spawning distribution combined with a reduction in that portion of the population cline with an affinity for spawning in the northeastern part of the spawning area, including the North Sea. No indication of irreversible genetic or behavioural losses caused by the events was found. The previously unexplained lack of rebuilding of spawning in the North Sea consequently seems related to two environmental factors that have remained unfavourable: (i) zooplankton concentration, and (ii) wind-induced turbulence. Furthermore, the large commercial autumn–winter fishery in the North Sea continues to land unknown quantities of mackerel that have an affinity for spawning in the northeastern part of the spawning area, including the North Sea.

Description: Hjelset, A. M. 2014. Fishery-induced changes in Norwegian red king crab ( Paralithodes camtschaticus ) reproductive potential. – ICES Journal of Marine Science, 71: 365–373. The introduced red king crab ( Paralithodes camtschaticus ) in the Barents Sea supports a valuable fishery in northern Norway. In this paper, I examine the effect of the increased harvest rate and the recently added female quota on the potential egg production of the stock. The size ranges of males and females in the period 1995–2011 were recorded, and estimated stock abundance of ovigerous females and established individual fecundity parameters from 2000–2007 were used to assess the reproductive potential of the stock from 1995–2011. The upper size ranges of males and females decreased throughout the period studied, presumably mainly due to fishing. The change in size composition among ovigerous females and functional mature males, and the reduced mean individual fecundity in the stock seem to have had a negative effect on the potential egg production of the stock.

Description: Sammarco, P. W., Lirette, A., Tung, Y. F., Boland, G. S., Genazzio, M., and Sinclair, J. 2014. Coral communities on artificial reefs in the Gulf of Mexico: standing vs. toppled oil platforms. – ICES Journal of Marine Science, 71: 417–426. Thousands of oil platforms in the northern Gulf of Mexico have provided hard substrate for settlement of Caribbean corals and have facilitated their range expansion. The US Department of the Interior, Bureau of Ocean Energy Management now allows platforms to be purposely toppled to the bottom and used as artificial reefs to promote fisheries development. We compared the coral communities on standing offshore oil/gas production platforms with those on "Rigs-to-Reef" structures through Remotely Operated Vehicle reconnaissance (max. depth ~110 m) to assess comparative population sizes of several coral species. Corals found were the zooxanthellate Madracis decactis and azooxanthellate Tubastraea coccinea , Oculina diffusa , and Phyllangia americana . There was no significant difference in total coral density between standing and toppled platforms, due to varying species-specific abundances. Madracis decactis and T. coccinea densities were significantly higher on toppled structures than on standing ones, P. americana was more abundant on standing platforms, and O. diffusa densities were not significantly different between the two sets of platforms. Corals were distributed more deeply on standing platforms than on toppled ones (particularly O. diffusa and P. americana ). Madracis decactis (requiring light) and T. coccinea were concentrated at shallower depths (≤50 m). Rigs-to-Reefs structures serve as substrate for coral settlement. The probability of continued coral growth in these early stages of succession varies between species, when considering standing vs. toppled structures. We did not see overall evidence that toppling enhanced hermatypic coral populations, increased coral abundances in general, or created 3D reef-like fish habitat.

Description: Reilly, T., Fraser, H. M., Fryer, R. J., Clarke, J., and Greenstreet, S. P. R. 2014. Interpreting variation in fish-based food web indicators: the importance of "bottom-up limitation" and "top-down control" processes. – ICES Journal of Marine Science, 71: 406–416. Proposed indicators for the Marine Strategy Framework Directive (MSFD) food webs Descriptor focus on structural elements of food webs, and in particular on the abundance and productivity of top predators. However, the inferences that can be drawn from such indicators depend on whether or not the predators are "bottom-up limited" by the availability of their prey. Many seabird populations appear to be "bottom-up limited" so that variation in their reproductive success and/or abundance reflects changes in lower trophic levels. Here we find that gadoid fish predators off the Firth of Forth, southeast Scotland, do not appear to be "bottom-up limited" by the biomass of their main prey, 0-group sandeels; gadoid biomass and feeding performance was independent of sandeel biomass. Variability in food web indicators based on these gadoid predators seems to impart little insight into underlying processes occurring at lower trophic levels in the local food web. The implications of this in terms of how the currently proposed MSFD food web indicators should be used and interpreted are considered, and the ramifications in terms of setting targets representing good environmental status for both fish and seabird communities are discussed.

Description: Torniainen, J., Vuorinen, P. J., Jones, R. I., Keinänen, M., Palm, S., Vuori, K. A. M., and Kiljunen, M. 2014. Migratory connectivity of two Baltic Sea salmon populations: retrospective analysis using stable isotopes of scales. – ICES Journal of Marine Science, 71: 336–344. Migratory connectivity refers to the extent to which individuals of a migratory population behave in unison, and has significant consequences for the ecology, evolution and conservation of migratory animals. We made a retrospective assessment of the migratory connectivity of River Simojoki and River Kymijoki populations of Atlantic salmon Salmo salar L. by using stable isotope analysis of archived scales to identify the final feeding areas used before ascending rivers for spawning. We also tested differences in migratory connectivity between wild and hatchery-reared salmon and compared Carlin-tag recoveries with salmon scale stable isotope analysis as methods for studying salmon migrations. Stable isotope ( 13 C, 15 N) values from the last growth region of scales from salmon caught ascending their natal rivers were compared via discriminant analysis with those from scales of salmon caught in different Baltic Sea areas during 1989–2011. Most River Simojoki salmon had likely fed in the Baltic Proper (mean ± SD for ascending fish probability 0.59 ± 0.32) with secondary likely feeding areas in the Bothnian Sea (0.21 ± 0.26) and the Gulf of Finland (0.20 ± 0.27). Most River Kymijoki salmon had likely fed in the Gulf of Finland (0.71 ± 0.42) with the Baltic Proper (0.29 ± 0.41) a secondary feeding area. The results did not indicate the Bothnian Sea to be an important feeding area. The two salmon populations showed weak migratory connectivity and rather fixed areal preference throughout the record irrespective of wild or stocked origin. Although the results from the scale stable isotope analyses were broadly consistent with previously reported Carlin-tag recoveries, we argue that the stable isotope approach offers several important advantages in the study of salmon migratory behaviour.

Description: Demer, D. A., and Zwolinski, J. P. 2014. Corroboration and refinement of a method for differentiating landings from two stocks of Pacific sardine ( Sardinops sagax ) in the California Current. – ICES Journal of Marine Science, 71: 328–335. Efforts to survey, assess and manage Pacific sardine ( Sardinops sagax ) in the California Current may depend on accurate differentiation of the purported two migrating stocks. The southern stock spans seasonally from southern Baja California, México to Point Conception, California; the northern stock spans seasonally from Punta Eugenia, México northwards to southern Alaska. Their seasonal north–south migrations are approximately synchronous within their respective domains, resulting in segregated spawning and different identities. A decade ago, a practical method was proposed for differentiating landings from the two stocks using concomitant measurements of sea-surface temperature ( SST ). Here, we corroborate and refine the method using regional indices of optimal and good potential habitat for the northern stock, and SST -based indices associated with the 99.9 and 100% confidence intervals of the potential habitat. For months when the index is 〈0.5, (i.e. when the minority of a fishing region probably includes potential northern stock habitat), the landings are attributed to the southern stock, and vice versa. We applied this method to regional monthly landings data from 2006–2011 and the results indicated that an average of 63–72 and 32–36% of the summertime landings at Ensenada, México and San Pedro, southern California were probably from the southern stock, respectively, depending on the index used. Allocation error could be reduced if the landings were evaluated on finer spatio-temporal scales, particularly during habitat-transition periods. Our method may be used to improve estimates of northern stock biomass, spatial and length distributions, recruitment, and mortality.

Description: Sissenwine, M. M., Mace P. M., and Lassen, H. J. 2014. Preventing Overfishing: Evolving Approaches and Emerging Challenges. – ICES Journal of Marine Science, 71: 153–156. The evolution of fishery management frameworks to prevent overfishing is the theme of the eight papers that follow in this issue of the ICES Journal of Marine Science . The current paper describes common elements of the frameworks. All the frameworks are based on the maximum sustainable yield concept. Frameworks to prevent overfishing have evolved to be increasingly prescriptive. This evolution probably reflects past abuse of flexibility which led to overfishing. The outcome has been a decline in the proportion of stocks suffering from overfishing. However, loss of flexibility may result in large foregone yields from multispecies fisheries, create a mis-match between the expectations for scientific information and the realities of scientific uncertainty, and fail to recognize ecosystem dynamics.

Description: Rothschild, B. J., Keiley, E. F., and Jiao, Y. 2014. Failure to eliminate overfishing and attain optimum yield in the New England groundfish fishery. – ICES Journal of Marine Science, 71: 226–233. Under US law, fishery management is required to eliminate overfishing and attain optimum yield (OY). In New England, many groundfish stocks continue to be overfished, and the fishery continues to harvest less than OY. The reasons for the shortfalls are rooted in the socio-economic structure of the management regime, and technical and scientific issues that constrain the management system. The most recent change in the management regime (days-at-sea to catch shares) and performance relative to OY and the prevention of overfishing are analyzed along with metrics used to gauge performance. The commonly used age-based production model gives a problematic perception of stock abundance. Structural issues that seem to impair achieving OY are the adherence to the single-species interpretation of multiple-species yield and the use of the F x % proxy. Simpler approaches to stock assessment are discussed. A management system that creates feasible goals and uses improved and simpler metrics to measure performance is needed to facilitate attainment of management goals.

Description: Mace, P. M., Sullivan, K. J., and Cryer, M. 2014. The evolution of New Zealand's fisheries science and management systems under ITQs. – ICES Journal of Marine Science, 71: 204–215. New Zealand implemented a comprehensive management system using individual transferable quotas in 1986 that has been instrumental in guiding the roles, responsibilities, and accountabilities of fisheries science, fisheries management, and the fishing industry ever since. However, at the time of the initial design, a number of issues were not adequately considered. These relate mainly to the dynamic nature of fish stocks, multispecies considerations, and environmental and other externalities. Subsequent efforts to address these issues have been challenging and many are not yet fully resolved. The outcomes for fisheries science, stock status, multispecies management, ecosystem effects, and fishing industry accountability have been mixed, although mostly positive. Fisheries science, fisheries management, and the fishing industry have all become much more professionalized and their activities have been increasingly streamlined. New initiatives to further improve the system continue to be researched and implemented. Overall, we believe that the positives considerably outweigh the negatives. The initial design has proved to be a system that can be built upon. Comparing New Zealand with most of the rest of the world, key positive outcomes for preventing overfishing are the current lack of significant overcapacity in most fisheries, the development of biological reference points and a harvest strategy standard, the favourable stock status for the majority of stocks with known status, and the development and implementation of comprehensive risk assessments and management plans to protect seabirds and marine mammals.

Description: Chust, G., Castellani, C., Licandro, P., Ibaibarriaga, L., Sagarminaga, Y., and Irigoien, X. 2014. Are Calanus spp. shifting poleward in the North Atlantic? A habitat modelling approach. – ICES Journal of Marine Science, 71: 241–253. In the last decade, the analysis based on Continuous Plankton Recorder survey in the eastern North Atlantic Ocean detected one of the most striking examples of marine poleward migration related to sea warming. The main objective of this study is to verify the poleward shift of zooplankton species ( Calanus finmarchicus , C. glacialis , C. helgolandicus , C. hyperboreus ) for which distributional changes have been recorded in the North Atlantic Ocean and to assess how much of this shift was triggered by sea warming, using Generalized Additive Models. To this end, the population gravity centre of observed data was compared with that of a series of simulation experiments: (i) a model using only climate factors (i.e. niche-based model) to simulate species habitat suitability, (ii) a model using only temporal and spatial terms to reconstruct the population distribution, and (iii) a model using both factors combined, using a subset of observations as independent dataset for validation. Our findings show that only C. finmarchicus had a consistent poleward shift, triggered by sea warming, estimated in 8.1 km per decade in the North Atlantic (16.5 per decade for the northeast), which is substantially lower than previous works at the assemblage level and restricted to the Northeast Atlantic. On the contrary, C. helgolandicus is expanding in all directions, although its northern distribution limit in the North Sea has shifted northward. Calanus glacialis and C. hyperboreus , which have the geographic centres of populations mainly in the NW Atlantic, showed a slight southward shift, probably responding to cool water penetrating southward in the Labrador Current. Our approach, supported by high model accuracy, shows its power in detecting species latitudinal shifts and identifying its causes, since the trend of occurrence observed data is influenced by the sampling frequency, which has progressively concentrated to lower latitudes with time.

Description: Methot, R. D., Tromble, G. R., Lambert, D. M., and Greene, K. E. 2014. Implementing a science-based system for preventing overfishing and guiding sustainable fisheries in the United States. – ICES Journal of Marine Science, 71: 183–194. Fisheries management in the United States is primarily governed by the Magnuson–Stevens Fishery Conservation and Management Act, first enacted in 1976. Overarching principles are that fishing mortality rates should not jeopardize the capacity of a stock to produce maximum sustainable yield (MSY) and that overfished stocks (i.e. biomass is too low) should be rebuilt to the level that will support MSY. The science-based system for achieving sustainable fisheries is implemented, in part, through setting annual catch limits (ACLs) that cannot exceed the acceptable biological catch that is recommended by Scientific and Statistical Committees using methods that account for scientific uncertainty. Accountability measures (AMs) are management measures to prevent ACLs from being exceeded or correct any overages that occur. Implementation in 2012 of ACLs and AMs in all Federal fisheries was a historical achievement in the United States; one that will help rebuild stocks and ensure sustainable fisheries into the future. Some remaining challenges include: determining appropriate catch levels and management approaches for stocks with incomplete data; assessing more stocks, more frequently; addressing differences between managing stocks as a complex vs. managing individual stocks in a multistock fishery; and incorporating social and economic factors in determining the appropriate response to uncertainty.

Description: Plourde, S., and Browman, H. I. 2014. Parameterizing and operationalizing zooplankton population dynamic and trophic interaction models. – ICES Journal of Marine Science, 71: 234–235. This themed set (TS) of articles was motivated by the need for modellers and biologists–ecologists to work more closely together to produce more realistic simulation models of zooplankton population dynamics and trophic interactions. The TS was intended to cover a broad range of subjects and potential approaches, including identifying crucial gaps in our knowledge and parameterization of biological/physiological processes, experimental/fieldwork aimed at quantifying the response of key physiological and behavioural processes to variations in the environment, identifying novel modelling approaches that would enable the development of simulation models that would minimize the need for species-specific (and stage-specific) model parameterization, etc. Five articles were accepted for inclusion in the TS. They cover the majority of these themes. TSs are intended to be instrumental in focusing attention, triggering opinions, and stimulating ideas, discussion and activity in specific research fields. We hope that this TS has achieved that.

Description: Smith, A. D. M., Smith D. C., Haddon, M., Knuckey, I., Sainsbury, K. J., and Sloan, S. 2014. Implementing harvest strategies in Australia: 5 years on. – ICES Journal of Marine Science, 71: 195–203. Australian Commonwealth fisheries are managed using a formal harvest strategy policy (HSP) introduced by the federal government in 2007. At the State level, a number of commercial fisheries are also managed under formal harvest strategies, but no overarching policy currently exists to guide their consistent implementation across jurisdictions. There have been 5 years of experience with implementation of the Commonwealth policy across the highly diverse array of commercial fisheries found in Australia. The HSP has an explicit target of maximum economic yield, and an explicit limit set at half the biomass that would support maximum sustainable yield. The policy also specifies an acceptable level of risk associated with falling below the limit reference point. We discuss the experience gained from implementing the HSP in Australia, including a number of challenges faced, and attempt to summarize the benefits and costs of implementing harvest strategies. Our view is that, overall, the benefits clearly outweigh the costs.

Description: Cropp, R., and Norbury, J. 2014. Comment on "The paradox of the ‘paradox of the plankton’" by Record et al. – ICES Journal of Marine Science, 71: 293–295. The biodiversity of plankton ecosystems is no longer a paradox. The mathematical mechanisms that determine the coexistence of competitors in a general class of models, which includes almost all theoretical and applied mass conserving ecosystem models in present use, are clear. Knowledge of these mechanisms simplifies the identification and construction of models with the structural property that all species coexist for all time, irrespective of environmental forcings, spatial interactions, and further model complexities. Here, we discuss the "paradox of the ‘paradox of the plankton’" proposed by Record et al . (ICES Journal of Marine Science, 71: 235–239) and explain the mechanisms that underpin the solution.

Description: Maps, F., Plourde, S., Lavoie, D., McQuinn, I., and Chassé, J. 2014. Modelling the influence of daytime distribution on the transport of two sympatric krill species ( Thysanoessa raschii and Meganyctiphanes norvegica ) in the Gulf of St Lawrence, eastern Canada. – ICES Journal of Marine Science, 71: 282–292. The Gulf of St Lawrence (GSL) provides several species of North Atlantic baleen whale with an abundant supply of krill, dominated by Thysanoessa raschii and Meganyctiphanes norvegica . We aimed to quantify the differences in upstream advection resulting from the interaction between the circulation and the specific diel vertical migration of T. raschii and M. norvegica at the scale of the northwest GSL. We coupled a regional circulation model with Lagrangian models where the daytime depth followed specific functions of surface salinity. Our results help to explain the spatio-temporal variability in both T. raschii and M. norvegica distributions. We identified in particular spatio-temporal patterns in krill upstream transport. During summer and autumn, the upstream transport of krill is steady across Jacques Cartier Strait, limited across Honguedo Strait, and more sporadic across the Estuary mouth. We estimated that the upstream advection of krill particles across the Estuary mouth would be higher by 16–17% for the T. raschii than for the M. norvegica daytime behaviour. Our results also suggest that the advective processes operating on the adults during the productive season are not the only cause for the observed magnitude of the interannual and interspecific variability in krill abundance.

Description: Smith, S. J., and Hubley, B. 2014. Impact of survey design changes on stock assessment advice: sea scallops. – ICES Journal of Marine Science, 71: 320–327. Annual surveys of marine resources are used to monitor changes in population composition and abundance. Improvements in the performance and coverage of these surveys can readily be evaluated for the surveys themselves but should also be considered in the context of the stock assessment models that use the estimates from these surveys. For those surveys based on a probability design, improvements in the probability design are usually evaluated with respect to the resultant increase in precision of the survey estimates. Survey precision estimates can be included in many stock assessment models as observation error, as long as the process error component of the model is also identified. Advice on catch levels for sea scallop populations ( Placopecten magellanicus ) around Nova Scotia is developed using a Bayesian state space assessment model in which both observation and process error terms have been defined. Information on survey estimates of precision are included in the observation error component of the assessment model and the impacts of changes in survey precision on the provision of advice can be evaluated in terms of reference points and management advice. The sensitivity of stock assessment advice to changes in the level of precision of survey estimates was evaluated for three scallop fisheries around Nova Scotia. The results indicated that the impact of the changes depended upon the degree of concurrence between the annual changes in biomass as observed from the survey and those predicted by the model.

Description: Record, N. R., Pershing, A. J. and Maps, F. 2014. Plankton post-paradox. – ICES Journal of Marine Science, 71: 296–298. Classical theoretical ecology has largely focused on the coexistence of populations at the species level, particularly since the coining of the "paradox of the plankton". The known mechanisms for coexistence, both mathematically and in nature, are myriad and diverse. Building on a dialogue in this journal (Cropp, R., and Norbury, J. 2014. Comment on "The paradox of the ‘paradox of the plankton’" by Record et al . ICES Journal of Marine Science; Record, N. R., Pershing, A. J., and Maps, F. 2014. The paradox of ‘the paradox of the plankton’. ICES Journal of Marine Science, 71: 235–239.), we outline a perspective whereby approaching the problem from a different organizational level—namely the community level—can offer valuable simplifications and insights. We expand on a prototype model that demonstrates the potential of this approach.

Description: Isaac C. Kaplan, Daniel S. Holland, and Elizabeth A. Fulton. 2014. Finding the accelerator and brake in an individual quota fishery: linking ecology, economics, and fleet dynamics of US West Coast trawl fisheries. – ICES Journal of Marine Science, 71: 308–319. In 2011, the Pacific Fisheries Management Council implemented an individual transferrable quota (ITQ) system for the US West Coast groundfish trawl fleet. Under the ITQ system, each vessel now receives transferrable annual allocations of quota for 29 groundfish species, including target and bycatch species. Here we develop an ecosystem and fleet dynamics model to identify which components of an ITQ system are likely to drive responses in effort, target species catch, bycatch, and overall profitability. In the absence of penalties for discarding over-quota fish, ITQs lead to large increases in fishing effort and bycatch. The penalties fishermen expect for exceeding quota have the largest effect on fleet behaviour, capping effort and total bycatch. Quota prices for target or bycatch species have lesser impacts on fishing dynamics, even up to bycatch quota prices of $50 kg –1 . Ports that overlap less with bycatch species can increase effort under individual quotas, while other ports decrease effort. Relative to a prior management system, ITQs with penalties for exceeding quotas lead to increased target species landings and lower bycatch, but with strong variation among species. The model illustrates how alternative fishery management policies affect profitability, sustainability and the ecosystem.

Description: Shephard, S., Minto, C., Zölck, M., Jennings, S., Brophy, D., and Reid, D. 2014. Scavenging on trawled seabeds can modify trophic size structure of bottom-dwelling fish. – ICES Journal of Marine Science, 71: 398–405. Disturbance by towed bottom-fishing gears often kills larger sensitive benthos, leading to changes in the abundance, size, and species composition of benthic communities. Short-term availability of trawl-damaged prey, and longer-term shifts in benthic prey community composition, both have the potential to affect feeding opportunities and realized dietary preferences of bottom-feeding (benthivorous) fish. To investigate these effects of bottom-fishing activity (by otter trawls, beam trawls, and dredges) on the feeding of benthivorous fish, we compared the trophic level at body size and diets of four species in areas of the Celtic Sea subject to low, intermediate, and high fishing activity. Trophic level was estimated using nitrogen stable isotope analysis, and fishing activity was quantified with vessel monitoring system (VMS) data. For whiting ( Merlangius merlangus ) of all sizes, trophic level was slightly lower in areas of higher fishing activity. After accounting for the results of the diet analysis, we concluded that this reflected increased scavenging of benthic invertebrates in more intensively fished areas. For megrim ( Lepidorhombus whiffiagonis ), the rate of increase in trophic level with size was lower with increasing fishing activity, implying that megrim may also substitute fish with lower-trophic invertebrates that can be scavenged in more intensively fished areas. For plaice ( Pleuronectes platessa ) and lemon sole ( Microstomus kitt ), no significant effects of fishing activity on trophic level were detected. We conclude that differences in the intensity of fishing activity with towed bottom gears had small but variable effects of the trophic size structure of the four species, and that this primarily reflected scavenging rather than diet changes following longer-term shifts in composition of the prey community.

Description: Pacariz, S., Björk, G., Jonsson, P., Börjesson, P., and Svedäng, H. 2014. A model study of the large-scale transport of fish eggs in the Kattegat in relation to egg density. – ICES Journal of Marine Science, 71: 345–355. A process-oriented model, with high vertical resolution, has been used to investigate variation in the transport of fish eggs and early larvae in relation to egg density. The main focus is on gadoid eggs from the spawning grounds in the southern Kattegat. Additionally, transport from the neighbouring areas, the central Kattegat and Öresund, is presented. The model results clearly indicate that transport is dependent on the egg density; lighter eggs are transported northwards whereas heavier eggs are to a larger extent retained or transported southwards. This study suggests that optimum densities in order to promote retention in the southern Kattegat are in the range of 1023–1026 kg m –3 . Observations from 2005 and 2006 of the vertical distribution of gadoid eggs combined with hydrographical data indicated high concentrations of eggs at the upper part of the pycnocline at densities of 1017–1022 kg m –3 . Combining the observations and modelling results on amount of dispersal and retention, suggests that gadoid eggs are mainly retained in the southern Kattegat (although shifted from maximum retention density) and simultaneously dispersed northwards. Even though the results of the study are described in the context of gadoid eggs, the results are applicable for other marine species with pelagic stages and buoyant particles within the tested density range.

Description: Kajajian, A., Schaffler, J. J., and Jones, C. M. 2014. Lack of equivalence in the elemental and stable isotope chemistry within the sagittal otolith pair of the summer flounder, Paralichthys dentatus . – ICES Journal of Marine Science, 71: 356–364. In fish that are not bilaterally symmetrical, the left and right sagittae are often not symmetrical, exhibiting divergent growth patterns and mass, and may have differences in chemical composition. We investigated this in the asymmetrical summer flounder Paralichthys dentatus , collected from different nursery habitats along the US east coast. Significant differences were detected in otolith mass, 13 C, 18 O, Li:Ca, Mg:Ca, and Sr:Ca, and overall chemical signatures. These results refute the hypothesis of left–right equivalence that is prevalent for bilaterally symmetrical fishes. We tested whether a specific side was better suited for classification. The best models differed between sagittae and resulted in different classification accuracies. The left otolith produced better classification accuracies. Simulated samples of randomized sets of left or right otoliths produced mean accuracies intermediate to classification and were often highly variable. We recommend that future otolith chemistry studies involving bilaterally asymmetrical species test the hypothesis of equivalence within the sagittae before randomly choosing an otolith for chemical analyses.

Description: Niklitschek, E. J., Secor, D., Toledo, P., Valenzuela, X., Cubillos, L., and Zuleta, A. 2014. Nursery systems for Patagonian grenadier off Western Patagonia: large inner sea or narrow continental shelf? – ICES Journal of Marine Science, 71: 374–390. Adjacent to Chile's long and narrow continental shelf, the Patagonian Inner Sea (PES) is among the largest and most complex estuarine systems in the world. The PES harbours high concentrations of juveniles and adults of important groundfishes, which spawn within or in near proximity to it. A dominant view is that recruitment primarily originates here rather than in adjacent coastal regions. We used otolith stable isotopes to evaluate the relative contribution of several PES and continental shelf regions to recruitment of Patagonian grenadier, one of the most abundant groundfishes in the area. Seawater chemistry confirmed that 13 C and 18 O differentiated these nursery and feeding regions. Estimated recruitments from PES nurseries to adult feeding regions were important (10–35%), but lower than dominant contributions from shelf nurseries (64–85%). Stable isotope differences within otoliths indicated, however, that most adults had previously used PES habitats as subadults. Adults exhibited stronger homing to feeding habitats in the PES than to shelf regions, suggestive of seasonal site fidelity or partial migration behaviours. The proximity of principal spawning areas to the bifurcation of the West Wind Drift Current may cause large interannual and decadal variations in larvae transport and the relative contribution of different shelf and PES nurseries to recruitment.

Description: The value of big old fat fecund female fish (BOFFFFs) in fostering stock productivity and stability has long been underappreciated by conventional fisheries science and management, although Hjort (1914) indirectly alluded to the importance of maternal effects. Compared with smaller mature females, BOFFFFs in a broad variety of marine and freshwater teleosts produce far more and often larger eggs that may develop into larvae that grow faster and withstand starvation better. As (if not more) importantly, BOFFFFs in batch-spawning species tend to have earlier and longer spawning seasons and may spawn in different locations than smaller females. Such features indicate that BOFFFFs are major agents of bet-hedging strategies that help to ensure individual reproductive success in environments that vary tremendously in time and space. Even if all else were equal, BOFFFFs can outlive periods that are unfavourable for successful reproduction and be ready to spawn profusely and enhance recruitment when favourable conditions return (the storage effect). Fishing differentially removes BOFFFFs, typically resulting in severe truncation of the size and age structure of the population. In the worst cases, fishing mortality acts as a powerful selective agent that inhibits reversal of size and age truncation, even if fishing intensity is later reduced. Age truncation is now known to destabilize fished populations, increasing their susceptibility to collapse. Although some fisheries models are beginning to incorporate maternal and other old-growth effects, most continue to treat all spawning-stock biomass as identical: many small young females are assumed to contribute the same to stock productivity as an equivalent mass of BOFFFFs. A growing body of knowledge dictates that fisheries productivity and stability would be enhanced if management conserved old-growth age structure in fished stocks, be it by limiting exploitation rates, by implementing slot limits, or by establishing marine reserves, which are now known to seed surrounding fished areas via larval dispersal. Networks of marine reserves are likely to be the most effective means of ensuring that pockets of old-growth age structure survive throughout the geographic range of demersal species.

Description: The ability of management strategies to achieve the fishery management goals are impacted by environmental variation and, therefore, also by global climate change. Management strategies can be modified to use environmental data using the "dynamic B 0 " concept, and changing the set of years used to define biomass reference points. Two approaches have been developed to apply management strategy evaluation to evaluate the impact of environmental variation on the performance of management strategies. The "mechanistic approach" estimates the relationship between the environment and elements of the population dynamics of the fished species and makes predictions for population trends using the outputs from global climate models. In contrast, the "empirical approach" examines possible broad scenarios without explicitly identifying mechanisms. Many reviewed studies have found that modifying management strategies to include environmental factors does not improve the ability to achieve management goals much, if at all, and only if the manner in which these factors drive the system is well known. As such, until the skill of stock projection models improves, it seems more appropriate to consider the implications of plausible broad forecasts related to how biological parameters may change in the future as a way to assess the robustness of management strategies, rather than attempting specific predictions per se .

Description: Dynamic factor analysis was used to explore monthly landings per unit effort (LPUE) series of Octopus vulgaris and environmental variables recorded in the southwest Iberian Peninsula, south Portugal. Despite the large fluctuations in the octopus abundance series, results showed a strong aggregation pattern for the last 3 months of the year, possibly related to the input of new recruits to the fishery. The calculated common trend for the 12 months time-series presented significant correlations with autumn rainfall of the previous year (lag – 1), particularly for the October, November, and December series. Other important correlations were found for the Western Mediterranean Oscillation index (lag – 1), Ekman transport, summer river run-off (lag – 1), horizontal and vertical component of windstress, among others. The main trend describes a moderate steady increase in LPUE during the last 10 years, suggesting that octopus abundance has increased from 1990 to 2010. The strong correlations of the monthly octopus LPUE series, together with the annual life cycle, suggest that after environmentally controlled recruitment, population dynamics is largely fishery driven, resulting in strong seasonality in the landings.

Description: Locusts and some noctuid moths exhibit polyphenism whereby they can change their " phase " from a solitary ("solitarious") condition to a gregarious one. Gregarious phase insects are often migratory travelling from recession areas into larger invasion zones and, among locusts, occur in swarms. Difference equation models of the population dynamics of insects that take account of such changes between solitarious or gregarious phases in relation to predation, both with and without time delays, are described. Solutions of the models are non-linear. Chaotic solutions are obtainable under some circumstances even with very low values for the intrinsic rate of increase in the prey population, in contrast to previous conclusions from models without predation. Comparisons with the results obtained for single species with those obtained in this paper show that predation can reduce (i) the average density of the prey, (ii) durations of periods when the populations stay in the gregarious phase , and (iii) the frequency of their shifts from the solitarious state to the gregarious form. Similar results are obtained if a time delay is introduced to mimic a transient phase . With a wide range of parameter values, models including predation with or without random perturbation reveal several stable attractors for phase diagrams of the populations, which are biologically meaningful compared with empirical datasets and which were unobtainable without predation, suggesting that inclusion of predation and time delays improved the realism of the models. However, comparisons between autocorrelation analyses of locust time-series, but of swarms only, with those of model outputs suggest that inclusion of the time delay leads to less, not more, realism. The prediction of non-linearity in the dynamics of migrant insects with phase changes and its significance for forecasting to aid control is briefly discussed in relation to published data on the desert locust Schistocerca gregaria .

Description: In his seminal work, Hjort (in Fluctuations in the great fisheries of Northern Europe. Conseil Parmanent International Pour L'Exploration De La Mar. Rapports et Proces-Verbaux, 20: 1–228, 1914) observed that fish population levels fluctuated widely, year-class strength was set early in life, and egg production by adults could not alone explain variability in year-class strength. These observations laid the foundation for hypotheses on mechanisms driving recruitment variability in marine systems. More recently, researchers have sought to explain year-class strength of important fish in the Laurentian Great Lakes and some of the hypotheses developed for marine fisheries have been transferred to Great Lakes fish. We conducted a literature review to determine the applicability of marine recruitment hypotheses to Great Lakes fish. We found that temperature, interspecific interactions, and spawner effects (abundance, age, and condition of adults) were the most important factors in explaining recruitment variability in Great Lakes fish, whereas relatively fewer studies identified bottom-up trophodynamic factors or hydrodynamic factors as important. Next, we compared recruitment between Great Lakes and Baltic Sea fish populations and found no statistical difference in factors driving recruitment between the two systems, indicating that recruitment hypotheses may often be transferable between Great Lakes and marine systems. Many recruitment hypotheses developed for marine fish have yet to be applied to Great Lakes fish. We suggest that future research on recruitment in the Great Lakes should focus on forecasting the effects of climate change and invasive species. Further, because the Great Lakes are smaller and more enclosed than marine systems, and have abundant fishery-independent data, they are excellent candidates for future hypothesis testing on recruitment in fish.

Description: For most of the past 100 years, research into recruitment processes—as pioneered by Johan Hjort—has been a consistent focus of research in fisheries science. This was reflected not only in the literature but in the organizational structures and research strategies of national and international fisheries research and management institutions. Over the past decade or so, we perceived that recruitment research is fading, if not into obscurity then at least into a more marginal place in fisheries and marine research. In this paper, we assess if our perception is real by quantifying trends in scientific publications and in the work activities within ICES during specific periods extending back to the 1920s. Our analysis documents a decline in research on recruitment processes. We put forward three possible hypotheses to explain this decline: 1. All the key research questions about recruitment have been answered ; 2. The volume of research on recruitment processes has declined because the answers are no longer relevant ; 3. Recruitment research has been co-opted by more trendy, possibly ephemeral, and research topics . There is little evidence to support the first two of these hypotheses and we consider the third to be the most plausible. Finally, we conclude that this new terminology/repackaging of recruitment research does not bring with it new and fresh thinking and, therefore, comes at a cost that should be carefully considered.

Description: The use of modelling approaches in marine science, and in particular fisheries science, is explored. We highlight that the choice of model used for an analysis should account for the question being posed or the context of the management problem. We examine a model-classification scheme based on Richard Levins' 1966 work suggesting that models can only achieve two of three desirable model attributes: realism, precision, and generality. Model creation, therefore, requires trading-off of one of these attributes in favour of the other two: however, this is often in conflict with the desires of end-users (i.e. mangers or policy developers). The combination of attributes leads to models that are considered to have empirical, mechanistic, or analytical characteristics, but not a combination of them. In fisheries science, many examples can be found of models with these characteristics. However, we suggest that models or techniques are often employed without consideration of their limitations, such as projecting into unknown space without generalism, or fitting empirical models and inferring causality. We suggest that the idea of trade-offs and limitations in modelling be considered as an essential first step in assessing the utility of a model in the context of knowledge for decision-making in management.

Description: This paper presents a brief review of the present state of knowledge in stock–recruitment forecasting, including process and current methodological challenges to predicting stock–recruitment. The discussion covers the apparent inability of models to accurately forecast recruitment even when environmental covariates are included as explanatory variables. The review shows that despite the incremental success in the past hundred years, substantial challenges remain if the process of modelling and forecasting stock–recruitment is to become relevant to fisheries science and management in the next 100 years.

Description: Hjort's insights on marine fish recruitment and larval fish advection are presumed not applicable to freshwater lakes because most freshwater lakes are small. The Laurentian Great Lakes (LGL), however, are large enough for certain oceanic-type hydrodynamics, such as strong currents and upwelling, to affect the distribution and survival of larval fish and thus fall under Hjort's purview. However, there are evolutionary constraints because LGL species underwent an evolutionary bottleneck during glaciation, ~10 000 years BP. We consider three narratives pertinent to both the spatial scale and the evolutionary time-scale of the LGL. The first reviews recent evidence of offshore advection and subsequent cross-lake dispersal of larval and juvenile yellow perch, a coastal demersal species in Lake Michigan. The second narrative suggests that biotic interactions, rather than spatial scale itself, could account for the transition in the critical period of Lake Michigan yellow perch period from a juvenile to a larval critical period. In the third narrative, we consider whether the deep LGL lack a significant native pelagic larval fish predator. We propose that the LGL, in combination with the older World's Great Lakes, present an opportunity to explore evolution and adaptation of fish to oceanic type physical conditions.

Description: Hjort (1914. Fluctuations in the great fisheries of northern Europe. Rapport et Procès-Verbaux des Réunions du Conseil Permanent International pour l'exploration de la Mer, XX: 1–228) identified two important aspects of the early life of fish as being important determinants of fluctuations in year-class strength: changes in nutrition and transport. He dismissed a third possible influence, changes in the abundance of the reproductive stock. Here, we describe how a recently discovered characteristic behaviour of age-structured populations termed cohort resonance, which does involve changes in adult abundance, can have a substantial effect on fluctuations in fished populations. Cohort resonance involves selectively greater sensitivity of age-structured populations to generational frequencies and to very low frequencies in the environmental signal influencing a population. This frequency-dependent selectivity has been shown to increase with fishing, as do the total amounts of variability in recruitment, egg production, and catch. Cohort resonance differs from other recent model mechanisms proposed to explain the observed increase in variability with fishing in that it does not require over-compensatory density-dependence. It stems from the compensatory ascending limb of the egg–recruit relationship, and is a characteristic of a stable population driven by a random environment. We demonstrate the differences in frequency selectivity and increases in variability with fishing among three different Pacific coast species with different longevity: coho salmon ( Oncorhynchus kisutch ; ~3 years), Pacific hake ( Merluccius productus ; ~25 years), and Pacific Ocean perch ( Sebastes alutus ; ~90 years). The shortest lived, coho salmon is the most sensitive to environmental variability, but variability in egg production and catch both increase more rapidly with fishing in the longer-lived species. Understanding cohort resonance will aid in anticipation of predicted potential changes in the frequency content of the physical environment with changing climate (e.g. more frequent El Niños), and it provides a warning regarding the possible confounding of increasing sensitivity to slow change due to fishing with actual slow change of population parameters due to climate change. Our understanding of the role of cohort resonance in population variability will be enhanced by further identification of empirical examples. We describe some of the challenges in this effort.

Description: Sustainable management of fisheries resources requires quantitative knowledge and understanding of species distribution, abundance, and productivity-determining processes. Conventional sampling by physical capture is inconsistent with the spatial and temporal scales on which many of these processes occur. In contrast, acoustic observations can be obtained on spatial scales from centimetres to ocean basins, and temporal scales from seconds to seasons. The concept of marine ecosystem acoustics (MEA) is founded on the basic capability of acoustics to detect, classify, and quantify organisms and biological and physical heterogeneities in the water column. Acoustics observations integrate operational technologies, platforms, and models and can generate information by taxon at the relevant scales. The gaps between single-species assessment and ecosystem-based management, as well as between fisheries oceanography and ecology, are thereby bridged. The MEA concept combines state-of-the-art acoustic technology with advanced operational capabilities and tailored modelling integrated into a flexible tool for ecosystem research and monitoring. Case studies are presented to illustrate application of the MEA concept in quantification of biophysical coupling, patchiness of organisms, predator–prey interactions, and fish stock recruitment processes. Widespread implementation of MEA will have a large impact on marine monitoring and assessment practices and it is to be hoped that they also promote and facilitate interaction among disciplines within the marine sciences.

Description: Fisheries oceanography is largely an applied discipline with a major goal of improving fisheries management and marine conservation. Johan Hjort's critical period hypothesis, and its decedents, remain a dominant theme and focuses on year-class success as mediated by prey availability and feeding. Bottom-up forcing, a related hypothesis, focuses on the sequential transfer of energy through the pelagic foodweb from primary productivity to fishery productivity. Another approach assumes that trophic interactions of adults determine abundance. Fisheries assessment and management, however, is based on the hypothesis that fishery abundance is determined by time-varying fishing and year-class success related to spawning-stock biomass. These approaches, their basic hypotheses, and underlying processes and mechanisms suggest very different dynamics for fishery populations. Other hypotheses challenge these traditional views: predation of early life stages, parental condition, shifting migration pathways, and physiological limits. Support for these other hypotheses is reviewed and the research needs are described to apply these hypotheses to fisheries assessment and management. Some of these hypotheses were identified by Hjort (e.g. parental condition hypothesis) and others are relative new (e.g. early life stage predation hypothesis). Moving into the future, we should focus on Hjort's approach: multi-hypothesis, integrative, and interdisciplinary. A range of hypotheses should be pursued with an emphasis on comparing and linking multiple hypotheses. The results then must be incorporated into fishery assessments and management decisions to support the long-term sustainability of exploited species and the conservation of threatened and endangered species.

Description: Risk assessment methods are used worldwide to evaluate threats posed by fisheries and other impacts on living marine resources, and to prioritize management of these threats. We derive a simplified risk analysis for aggregate fish communities as a preliminary tool to identify priorities for further detailed assessment. Because some of the largest observed rates of sea surface temperature increase are on the northeast US continental shelf, we focused on climate change-driven risks to marine communities in this region. We evaluated climate vulnerability for six communities across two ecosystems: both commercial and non-commercial demersal fish, pelagic fish, and benthic invertebrates in the Gulf of Maine (GOM) and Mid-Atlantic bight (MAB). We first evaluated the probability that anticipated climate changes (e.g. warming water, decreased salinity, increased acidity, altered boundary currents) would occur in these regions, and rated the potential severity of change over the next 10 years. Then, we evaluated the sensitivity of each biological community in each region using 12 attributes (e.g. habitat and prey specificity, temperature and acidity sensitivity, larval dispersal, adult mobility, population productivity, etc.). Exposure to the key climate risks was related to community sensitivity in each region for an overall assessment of climate vulnerability. Climate risks from increased surface water temperature, sea level rise, and earlier spring were rated moderate to high in both regions, with additional moderate to high risks in the GOM from increased bottom temperature, stratification, and river inputs. Benthic invertebrates were rated most sensitive, with demersals intermediate and pelagics lowest. Two MAB communities were rated more sensitive than corresponding GOM communities, but greater short-term climate risks in the GOM indicated increased exposure for GOM communities. Overall, this simple analysis may help prioritize short-term regional climate risk management action, thus addressing key conditions related to fishery fluctuations beyond fishing itself.

Description: The divergence between most stock assessments and studies in marine ecology is characterized by the low priority usually given to assessing the holding capacity of marine habitats. Habitats of high structural complexity are relatively uncommon in shelf waters, are contagiously distributed, and are damaged incidentally by bottom-towed gear. Structurally complex habitats are used by many demersal fish and crustaceans for predation abatement and as a site for feeding forays. Successive life-history stages typically migrate through several structurally complex habitats which recent studies show often to have fractal properties. One consequence of fractal structures as cover is a rapid reduction of protection from predators with growth in size: migration is the only response possible when further growth of the recruiting age class renders individuals in that habitat vulnerable to predation. A common feature of structurally complex habitats with high vulnerability at size is the occurrence of population bottlenecks. It is suggested that identifying and rectifying shortages of structured habitat, and eliminating habitat bottlenecks, will be effective in stock enhancement. This will require placing strict spatial constraints on the operation of bottom gear. This paper reviews new methods of estimating juvenile predation mortality, including mortality-at-age and mortality-at-life-history stage, which depend on the fractal characteristics of structurally complex habitats.

Description: Knowledge of settlement timing and duration, which has been identified as an important milestone for demersal fish, is critical to understanding population connectivity, relevant to the development of spatially—and temporally—resolved conservation measures, and recruitment variability, as important density-dependent dynamics may take place at this stage. To study the settlement ecology of cod haddock, and whiting, sampling was conducted over spring and summer 2004–2006 at the northern North Sea nursery area. Over 4000 0-group juveniles were collected. Settlement was associated with clear and progressive changes in the prey composition of these juveniles. The size of fish that could be considered settled was estimated as 49 (±3) mm for cod, 78 (±4) mm for haddock, and 85 (±6) mm for whiting. Clear differences in temporal settlement patterns were also apparent. Cod settled in a single pulse lasting about a month (mid-May to mid-June) and initially occupied shallower, inshore waters, whereas haddock settled in one pulse, lasting ~2 weeks (second half of May), favouring deeper, farther offshore locations. Whiting settled much later in the season and over a more protracted period (early June to early August), and their depth preferences also changed over time and with increasing length.

Description: Recruitment of the 2002–2012 year classes to the North Sea herring stock has been below expectations given the spawning biomass, due to exceptionally low overwinter survival of larvae. Here, we investigate whether changes in survival of larvae in the northwestern North Sea could be attributed to changes in parasite prevalence or feeding conditions. We used a method that combined particle tracking models and survey data to estimate survival, and microscopic examination of gut contents of archived samples of larvae collected in February each year between 1995 and 2007 to investigate parasite prevalence and feeding. We deduced that we can use the incidence of tetraphyllidean parasites as an index of the cumulative feeding history of the larval population. We found that the prevalence of larvae of a tetraphyllidean cestode in the gut contents varied significantly between years and was positively correlated with feeding success. High feeding success, indicated by high prevalence of tetraphyllideans, influenced survival by offsetting the effect of a second parasite type, a digenean trematode. We suggest that variability in cumulative food intake over the lifespan up to February is a significant determinant of variability in survival.

Description: Previous meta-analysis of spawner–recruit relationships suggested that depensatory behaviour is uncommon, and stocks pushed to low abundance are unlikely to suffer decreases in recruitment more severe than would be expected based on the decline in spawning stock. Using an updated database that has over 100 stocks that were depleted to less than 20% of their maximum observed stock size, we tested for depensatory behaviour in both total surplus production and recruitment and we also examined the probability of stock increase as a function of stock size and fishing pressure. The number of stocks that showed a significant improvement with depensatory models was less than that expected by chance. Hierarchical meta-analysis showed that the majority of the evidence was for no depensatory behaviour but could not rule out depensation at very low stock sizes. Stocks that are depleted to low abundance are expected to rebuild when fishing pressure is reduced if the environment has not changed but there is considerable evidence that the majority of fish stocks are impacted by changes in productivity regimes. Nevertheless, if stocks are very heavily depleted and fishing pressure is not reduced to quite low levels, the expected recovery time is both uncertain and long. Very low abundance should clearly be avoided for many reasons and the range of abundance where depensation cannot be ruled out is well below commonly adopted limit reference points.

Description: Despite 100 years of research testing the link between prey availability during the larval stage and year-class strength, field-based evidence for Hjort's "critical period" hypothesis remains equivocal. Here, we argue that a minority of past studies have relied on sufficient taxonomical knowledge of larval fish prey preference to reveal the potential effects of variability in zooplankton prey production on larval vital rates and year-class strength. In contrast to the juvenile and adult stages, larval fish diet and prey field are often poorly resolved, resulting in the inclusion of zooplankton taxa that do not actually contribute to the diet as part of the prey field considered by fisheries scientists. Recent studies have demonstrated that when accounting for prey selectivity, the expected positive relationships between preferred prey availability and larval feeding success, growth and survival are revealed. We strongly recommend that laboratories conducting research on larval fish trophodynamics take prey selectivity into account and acquire the necessary taxonomic expertise for providing valid assessments of the influence of prey availability on larval vital rates. We make the prediction that the proportion of studies supporting the existence of a "critical period" will increase proportionally to the progress of knowledge on prey preference during the early larval stage.

Description: Hidden within the seminal 1914 publication by Johan Hjort, we find what is probably one of the first comprehensive teleost time-series ever published. The series is liver size and fat content of northeast Arctic (NEA) cod measured during the traditional winter fishery in Lofoten, Northern Norway, in 1880–1912 and 1883–1913, respectively. The data were collected well before the advent of the great industrialized fisheries in the 1930s. The raw data used by Hjort originate from annual reports of the Lofoten fishery, initiated by Member of Parliament and pioneer fishery inspector of Northern Norway, Ketil Motzfeldt, in 1859. Based on these reports and following various calibration exercises, we present robust estimates of the hepatosomatic index (HSI) from 1859 to 2012 (except 1863), i.e. over 153 years—extending Hjort's analysis both backwards (1859–1879) and forwards (1913–present). This series of bulk HSI contained five major periods: 1859–1880, 1881–1919, 1920–1974, 1975–2003, and 2004–2012; the highest HSI was recorded 1920–1974, whereas the lowest was from the most recent period. Despite variability, total length was a significant predictor of HSI, 1932–2012. A weak but significant relationship existed with both total-stock biomass and ocean temperature, as well as with the North Atlantic Oscillation winter index under a 1-year lag. The present exceptionally long HSI series will give an excellent opportunity for further research on the "quality of the cod" in a historic perspective.

Description: The Barents Sea stock of Atlantic cod ( Gadus morhua ) is currently the world's largest cod stock. It is also a stock for which long time-series are available and much research has been carried out. With this review, we wish to present an overview and evaluation of the knowledge on Barents Sea cod early life dynamics. The focus is on the effects of the biotic and abiotic drivers, which jointly determine the strength of a year class. A stage-by-stage approach is employed. We summarize and assess the significance of the different processes described in the literature to be at play during each specific life stage, from spawning stock, through eggs, larvae, and pelagic juvenile, to demersal juvenile and recruitment at age 3. Also Russian work is included, some of which until now has not been available to non-Russian readers. Physical drivers examined include sea temperature, advection and dispersal, wind-induced turbulence, and light. Biotic mechanisms studied range from maternal effects and skipped spawning in the adult stock through egg quantity and quality, to prey availability for the larvae and effects of cannibalism on the juveniles. Finally, we evaluate the main hypotheses put forth by Johan Hjort a hundred years ago in the light of our synthesis of present knowledge. A main conclusion is that it is unlikely that there is any one single life stage during which recruitment with any generality is determined.

Description: Recent temporal variability in abundance, size and age structure, distribution, and recruitment of the Skagerrak population of the commercially exploited long-lived deep-water demersal macrourid roundnose grenadier ( Coryphaenoides rupestris ) appeared strongly influenced by a combined effect of a single pronounced recruitment incident in the early 1990s and a subsequent pulse in targeted exploitation a decade later. Fishery-independent annual survey data showed that probably only one strong year class occurred across an almost three-decade period, 1985–present. Recruitment studies in deep-water fish remain few, yet rarity of successful recruitment events may have to be added to life-history characteristics already recognized as limiting the potential for sustainable harvesting of deep-water demersal fish, i.e. extended lifespan, slow growth, high age at first maturity, and low fecundity.

Description: The southern-most stock of winter flounder ( Pseudopleuronectes americanus ), a cold temperate species of the Northwest Atlantic, has not recovered from overfishing despite continued restrictive measures, and appears to be contracting northward. We regressed larval and settled juvenile abundance (after accounting for adult and larval contribution to variation, respectively) on temperature over several decades from collections in New Jersey, the United States, at the southern edge of their range to determine if increasing temperatures during the first year of life were responsible for this contraction. A significant stock–recruitment relationship at both stages was moderate, explaining 27.5% of the variance for larvae on adults and 20.6% for juveniles on larvae. There was no significant effect of average monthly temperature in explaining variance of the residuals for larvae, or of degree day on explaining the abundance of residuals for juveniles over a months-long settlement period. However, in both cases, residuals were widely distributed at cold temperatures, while they were always low at warm temperatures. Thus, years in which spring temperatures were warm (5–7 o C for February, 7–9 for March, and 11–20 for May) always experienced poor recruitment. This threshold effect may result from an intersection with predators in response to temperature, and this may play a more important role than heat stress in determining recruitment success.

Description: Recruitment success in marine species is mostly driven by the high and variable mortality of first life stages, and the relationships between stock and recruitment are then largely dominated by residual variability. We show that analysing the residual variability may provide insights on the density-dependence process occurring during the recruitment. Following the seminal formulation of Minto et al . (Survival variability and population density in fish populations. Nature, 2008), we show that when recruitment is considered as a sequence of a pelagic stage with stochastic density-independent mortality followed by a second stage with stochastic density-dependent mortality, then the variability of the recruitment rate per spawning biomass (RPSB) should be a decreasing function of the spawning biomass. Using stock–recruit data of 148 stocks from the RAM legacy database, we provide a test of this hypothesis by showing that the variability of RPSB is lower for fish species with the higher concentration during juvenile stages. Second, a hierarchical Bayesian model (HBM) is built to derive a meta-analysis of stock–recruit data for 39 flatfish stocks, characterized by a high concentration of juveniles in coastal nursery habitats. Results of the HBM show that the variance of the RPSB decreases with the spawning biomass for almost all stocks, thus providing strong evidence of density-dependence during the recruitment process. Finally, we attempt to relate patterns in recruitment variance to relevant life-history traits of flatfish species.

Description: The population dynamics of marine fish at low abundance has long been of interest. One century ago, Johan Hjort drew attention to the importance of understanding "the laws which govern the renewal of the animal population". Integral to the current work on the recovery of collapsed fish stocks is the association between abundance and per capita population growth rate ( r ), a negative correlation being representative of compensation and a positive correlation indicative of an Allee effect, also termed depensation. Allee effects are predicted to slow the rate, and increase the uncertainty, of recovery. Based on studies having sufficient data at low abundance, the magnitude of depletion experienced by some fish populations appears to have been sufficient to have generated either an Allee effect or a transition from strong to weak (or absent) compensatory dynamics. To a first approximation, empirically based Allee-effect reference points are consistent with suggested thresholds for overfishing and stock collapse. When evaluating Allee effects in marine fish, it is important not to conflate causal mechanism(s) with the pattern between r and abundance; the latter is of greater practical import. An additional caveat is that the longer a population remains at low abundance, the more likely it is that the environment around it will change in ways that are unfavourable to recovery. It might be this "temporal tyranny" of small population size that is most likely to produce an emergent Allee effect and depensatory dynamics in some collapsed marine fish populations.

Description: We confirm that sardine recruitment in the California Current, during the last three decades, mimics aspects of the environment in the North Pacific indicated by the Pacific Decadal Oscillation (PDO) index. The periods of stock increase and decrease followed consecutive years with positive and negative PDO values, respectively. During the "warm" periods, the average number of recruits per biomass was more than threefold higher than that during the "cold" periods. In addition to the environmental conditions experienced by the sardine larvae, we show that the variability in sardine recruitment is partially explained by the environmental conditions many months before the spawning season and the adult condition factor. We hypothesize that sardine have a metabolic deficit during spawning, so prior good feeding opportunities are necessary to increase both total fecundity and offspring robustness, to enhance both reproduction and survival, respectively. Our findings augment a century-old theory that the reproductive success of small pelagic fish is governed by the survival of the early life stages. The condition of each parent also matters. To predict sardine recruitment, we propose a "dual-phase" model based on seasonal PDO-based indices and a condition factor. The model identifies summer feeding seasons conducive to a good adult condition factor followed by spring-spawning seasons supportive of good larval retention and growth.

Description: As it becomes ever clearer that on longer time scales marine ecosystems function as non-linear "complex adaptive systems", potential consequences of global change become obscured within a maze of multiple possibilities. This essay attempts to route one pathway to a potentially more robust conceptual synthesis, employing the globally important example of anchovies and sardines as a model. Expressly, the anchovy emerges as an efficient specialist of neritic origin. In contrast, the sardine's oceanic-based adaptations equip it to deal with intermittent episodes of poorly productive conditions and to take advantage of associated reduction in predation pressure on early life stages of their offspring. Based on the overall synthesis, the nimble, wide-ranging, actively opportunistic sardine appears notably well equipped to deal with climate-related disruptions and dislocations and even to profit from their adverse effects on predators and competitors. Global-scale multispecies population synchronies in the 1970s to the mid-1980s suggest that a variety of different species types might be flagged for investigation as perhaps embodying similar "active opportunist" attributes. If so, events and anecdotes might, as global changes proceed, be viewed within a developing universal framework that could support increasingly effective transfers of experience and predictive foresight across different species groups and regional ecosystems.

Description: Food-dependent growth and size-dependent interactions form cornerstones in the dynamics of fish populations. Using two freshwater examples, we illustrate the importance of considering both these cornerstones for understanding system dynamics. Moreover, a proper understanding of the dynamics requires mechanistic linkages between individual-, population-, and community-level processes based on mass conservation principles. In one example, we further find that quantitative predictions of individual-level energy flows are essential for understanding the community dynamics. This mechanistic approach to understanding system dynamics is generally not reflected in fisheries models as an overview shows that only half of them incorporate food-dependent growth, and none fully observe the principles of mass conservation. As a marine example we examine patterns in the Baltic Sea system and show that no relationship between cod growth and sprat biomass is present related to the low size resolution in prey fish. Linking individual cod performance to its resource base is complicated by the many prey types cod uses over its life cycle. We conclude that an ecological perspective including size- and food-dependent processes is vital for ecosystem-based fisheries management making necessary a proper description of the interactive trophic structure as a result of mechanistic linkages between individual, population, and community processes.

Description: That recruitment of juveniles to the stocks of fish is subject to natural variations is considered a scientific truth, if not a truism, in marine science. However, in 1914, when the zoologist Johan Hjort (1869–1948) published the notion, it meant a basic change in the understanding of the biology of the sea fish. A century later, his insight is a topic still at the centre of interest in fish biology. Hjort based his concept largely on investigations of herring ( Clupea harengus ) and cod ( Gadus morhua ) in the North Atlantic. He was the mastermind, but worked with a small group at the Directorate of Fisheries in Bergen, Norway, and in cooperation with the International Council for the Exploration of the Sea (ICES). The theory of natural fluctuations prompted an important step from migration thinking to population thinking, and gave the emerging fish biology and multidisciplinary marine science a theoretical basis. The article aims to explore the set of important facts and reasoned ideas intended to explain the causes for variations in year classes, and in this the fluctuations in the recruitment to the stocks. It argues that in addition to scientific factors, economic and political circumstances had an important say in the shaping of the understanding of stock fluctuations. The mere existence of a theory does not alone account for a breakthrough, and the article draws attention to the acceptance of scientific results.

Description: We analyse how Johan Hjort's publication, "Fluctuations in the great fisheries of northern Europe, viewed in the light of biological research" (Hjort, 1914), has been cited in the subsequent scientific literature. In the context of this special issue commemorating the 100th anniversary of Hjort's seminal publication, our objective is to provide insights into how his work has penetrated the literature and influenced the development of fishery science. We also tracked Hjort's related article, "Fluctuations in the year classes of important food fishes" (Hjort, 1926). We present the citation life cycles of these articles and analyse various characteristics of the publications that cite them. The importance of Hjort (1914) is reflected in the large number of citations that it has accrued (908), and by the 40–50 citations that it continues to receive every year. This is exceptional for a 100-year-old scientific article, in any field. Hjort (1926) initially received as many cites as Hjort (1914), but the latter subsequently became the paradigmatic article. Hjort (1914) has been cited in 162 different journals and by scientists in 53 countries—Hjort's work has had a broad and global impact on fisheries research. The contextual analysis demonstrated that Hjort (1914) is considered a seminal, novel, and paradigm setting study—the core research questions addressed by Hjort (1914) remain unsolved and several of his hypotheses continue to drive fisheries science to this day.

Description: This historical essay describes the theory behind, and implications of, models of optimum yield from an exploited animal population (in particular for whaling) formulated by Johan Hjort and his colleagues, Per Ottestad and Gunnar Jahn, in the 1930s. The essay places the evolution of fishery science during the 1930s–1940s into context.

Description: The haddock ( Melanogrammus aeglefinus ) stock on Georges Bank in the Northwest Atlantic is characterized by extremely large recruitment events relative to spawning-stock biomass. Recent work has indicated that the dynamics of the preceding autumn bloom may have explanatory power to describe these events. In this paper, we examine the hypothesis that autumn phytoplankton dynamics affect the recruitment of haddock, examine the temporal and spatial characteristics of the autumn phytoplankton bloom on Georges Bank, and correlate individual sex-specific condition measurements of haddock made in spring to recruitment patterns. Autumn bloom characteristics vary considerably across Georges Bank with earlier-occurring and larger-integral blooms occurring on the northern flank. On average, autumn blooms start on day 273 (29 September) and persist ~50 days. There was a significant negative correlation detected between bloom start date and recruitment and a significant positive correlation of bloom integral and recruitment. The survivor ratio log e ( R /SSB) was positively and significantly correlated with individual condition of females in spring. The analysis of autumn bloom on Georges Bank provides a predictive index for recruitment strength of haddock and has utility for the assessment of this stock.

Description: By leading the Canadian Fisheries Expedition of 1914–1915 Johan Hjort took the opportunity to do far more than just survey herring, other fish stocks, and the hydrography of Canadian Atlantic waters. He also attempted to improve the backward fish-processing technologies used in the local fisheries, an agenda blocked by the Canadian government. Hjort did succeed markedly, however, in introducing Canadian scientists to the International Council for the Exploration of the Sea's new scientific methods for fisheries research. He and his colleagues offered training in the new dynamic oceanography as well as population demographic studies and biometrics for studying fish populations, races, and other units. His extroverted leadership-initiated lasting linkages between Canadian and Scandinavian scientists, and created an international network of fisheries biologists.

Description: The year 2014 marks the 100th anniversary of Johan Hjort's seminal treatise, Fluctuations in the great fisheries of northern Europe, viewed in the light of biological research . This special issue of the ICES Journal of Marine Science commemorates this anniversary. The thirty-two articles that appear herein demonstrate the deep influence that Johan Hjort's work has had, and continues to have, on fisheries and marine science.

Description: The potential ecosystem effects of fishing for Antarctic toothfish ( Dissostichus mawsoni ) in the Ross Sea region were investigated. Mixed trophic impact analysis was applied to a model of the Ross Sea foodweb and used to calculate the relative trophic importances of species and trophic groups in the system. The trophic impact of toothfish on medium-sized demersal fish was identified as the strongest top-down interaction in the system based on multiple-step analysis. This suggests a potential for a strong predation-release effect on some piscine prey of toothfish (especially grenadiers and ice-fish on the Ross Sea slope). However, Antarctic toothfish had moderate trophic importance in the Ross Sea foodweb as a whole, and the analysis did not support the hypothesis that changes to toothfish will cascade through the ecosystem by simple trophic effects. Because of limitations of this kind of analysis, cascading effects on the Ross Sea ecosystem due to changes in the abundance of toothfish cannot be ruled out, but for such changes to occur a mechanism other than simple trophic interactions is likely to be involved. Trophic importances were highest in the middle of the foodweb where silverfish and krill are known to have a key role in ecosystem structure and function. The six groups with the highest indices of trophic importance were (in decreasing order): phytoplankton, mesozooplankton, Antarctic silverfish, small demersal fish, Antarctic krill and cephalopods. Crystal krill and small pelagic fish also had high trophic importance in some analyses. Strengths and limitations of this kind of analysis are presented. In particular, it is noted that the analysis only considers trophic interactions at the spatial, temporal and ecological scale of the whole Ross Sea shelf and slope area, averaged over a typical year and in 35 trophic groups. Interference and density-dependent effects were not included in this analysis. Effects at smaller spatial and temporal scales, and effects concerning only parts of populations, were not resolved by the analysis, and this is likely to underestimate the potential risks of fishing to Weddell seals and type-C killer whales.

Description: Elasmobranch populations are declining worldwide, calling for urgent assessment of fishery exploitation and application of effective conservation strategies. Here, we applied a novel approach, integrating long-term time-series of landings (1945–2012) and extensive surveys at the fish market of Chioggia, Italy, home of the major fishing fleet of the northern Adriatic Sea, to evaluate the status of elasmobranch populations and fisheries in the one of the most fished Mediterranean basins. The time-series highlight a dramatic decline in elasmobranch landings, particularly for skates and catsharks ( Scyliorhinus spp.), whose current catch rates are 2.4 and 10.6% of the average 1940s levels, respectively. These data likely reflect similar large reductions in abundance, as indicated by the analysis of catch-per unit-effort time-series. The biomass of landed skates and catsharks showed regular fluctuations that disappeared after the collapse of the landings. Elasmobranch market composition, assessed through the sampling of 11 900 specimens from 2006 to 2013, included 14 species, but was dominated by just two: Mustelus mustelus and M. punctulatus , which represented more than 60% of the catch. The proportion of sexually immature individuals was generally very high, up to 83% of landed females and 71% of landed males, depending on the species. Although some correlations were detected between landings and local hydrography or climatic indices, the analyses of landings and surveys at the fish market identified fishery exploitation as the main driver of the striking, long-term elasmobranch decline in the northern Adriatic Sea, calling for urgent management actions to improve the conservation status of these fish.

Description: Natural mortality ( M ) rates are difficult to measure empirically and are often specified in stock assessments based on life history characteristics. More recently, these specifications have included M as a function of the size or age of a fish. However, natural mortality is a dynamic parameter that will change with the suite of predators and, thus, indirectly with cohort size and age. As an alternative, a density-dependent M rate function is derived and compared with the commonly used Lorenzen model, where M at age forms an allometric relationship with weight-at-age. The density-dependent model expresses M as a function of two parameters: one density dependent and one density independent. Properties of the two models (size-based vs. density-dependent) were explored to indicate conditions where the results are and are not similar. Associated catch equations, equilibrium analyses, and non-linear replacement lines in stock–recruitment theory are examined. Just as with density-independent values of M , most assessment data are not sufficient to provide precise estimates of density-dependent M parameters. However, the density-dependent model provides a basis for incorporating ecological variability into single-species assessments, noting the differing dynamics between short- and long-lived species. The incorporation of dynamic natural mortality has implications when estimating abundance trends and stock status, and ultimately setting management reference points.

Description: Vertebrates have a universal requirement for essential fatty acids (FAs), but in the ocean these FAs are synthesized only by phytoplankton. All other marine organisms must source their essential FA directly from phytoplankton or indirectly through the food web. Thus, the growth and abundance of all organisms in the marine ecosystem is constrained not just by the rate of carbon fixation in photosynthesis but also by the rate of synthesis of essential FAs. Despite the significance of this controlling step, we have had until now only very limited knowledge of the amount, distribution and rate of synthesis of essential FAs in the sea. Here, we report results on the quantity of a specific essential omega-3 FA, eicosapentaenoic acid (EPA) in the ocean, obtained with a novel application of ocean-colour data collected by remote sensing. Using in situ samples collected in the Northwest Atlantic, we developed a simple model to describe the relationship between total FAs and total chlorophyll- a . We refined these by examining the relationships of FAs produced predominantly by diatoms with the fraction of total chlorophyll- a derived from diatoms. These models were then applied to satellite data to map the distribution of EPA relative to diatom carbon in the Northwest Atlantic. With extrapolation to the global oceans, we were able to provide a first estimate of annual production of EPA, which demonstrated that the supply was barely sufficient to meet the nutritional demand of the world population in the present day; as the world population increases, this resource may become inadequate to meet those demands. This approach will allow us to begin to address issues such as the budget of essential FAs in the ocean and the maximum sustainable rate at which these FAs could be harvested from the ocean without compromising the integrity of the marine ecosystem.

Description: Reduced economic circumstances have moved management goals towards higher profit, rather than maximum sustainable yields in several Australian fisheries. The eastern king prawn is one such fishery, for which we have developed new methodology for stock dynamics, calculation of model-based and data-based reference points and management strategy evaluation. The fishery is notable for the northward movement of prawns in eastern Australian waters, from the State jurisdiction of New South Wales to that of Queensland, as they grow to spawning size, so that vessels fishing in the northern deeper waters harvest more large prawns. Bioeconomic fishing data were standardized for calibrating a length-structured spatial operating model. Model simulations identified that reduced boat numbers and fishing effort could improve profitability while retaining viable fishing in each jurisdiction. Simulations also identified catch rate levels that were effective for monitoring in simple within-year effort-control rules. However, favourable performance of catch rate indicators was achieved only when a meaningful upper limit was placed on total allowed fishing effort. The methods and findings will allow improved measures for monitoring fisheries and inform decision makers on the uncertainty and assumptions affecting economic indicators.

Description: Acoustic backscattering measurements were made of individual sandeel ( Ammodytes marinus L. ) at frequencies from 100 to 280 kHz in a laboratory tank. Measurements were made versus incidence angle, –30° to 30° relative to both dorsal and lateral aspect directions, for dead whole sandeel and for excised backbones. Backscatter spectra from whole fish have deep minima at frequencies that vary with fish length and shift to lower frequencies at higher incidence angles. The backscatter spectra from dorsal and lateral aspects differ both in amplitude and in positions of the minima. The backscatter from the excised backbone increases almost linearly with frequency and, below about 150 kHz, contributes only a minor amount to the total sandeel backscatter. A finite element model of sandeel backscatter, developed and compared with the measurements, indicates that shear waves in the backbone contribute little to the overall backscatter from sandeel.

Description: There has been a growing interest in the potential of Google Earth for scientific inquiries, and our previous paper (Al-Abdulrazzak and Pauly, 2014. Managing fisheries from space: Google Earth improves estimates of distant fish catches. ICES Journal of Marine Science, 71: 450–454) on weirs and their catch in the Persian Gulf is a case in point. Garibaldi et al . (2014. Comment on: "Managing fisheries from space: Google Earth improves estimates of distant fish catchs" by Al-Abdulrazzak and Pauly. ICES Journal of Marine Science), while agreeing in principle with using Google Earth for fisheries-related purposes, criticized the assumptions, data, methodology, and results of this paper. Here, we refute their criticisms, notably by showing that the "derelict weirs" that they thought they had "ground-truthed" are not weirs at all, but another type of fishing gear in one case, and debris from a boat anchoring system in the other. We develop the theme that ground-truthing requires local knowledge, and provide recommendations for using Google Earth images in fisheries management.

Description: This Comment was prompted by the substantial difference in weir catch estimates in the Gulf between (i) those reported by Al-Abdulrazzak and Pauly (2014. Managing fisheries from space: Google Earth improves estimates of distant fish catches. ICES Journal of Marine Science, 71(3), 450–454), who used Google Earth to count weir numbers, and (ii) those available from official national statistics provided by two major weir fishing countries (Bahrain and Iran). Satellite imageries, including Google Earth, are powerful tools for collecting data on visible structures when verified with adequate ground validation. However, an extension of their contribution to improving overall catch estimates is rather limited without having solid information on daily catch, which will substantially differ according to time and area, and fishing season lengths. It was noted that Al-Abdulrazzak and Pauly (2013) introduced positive biases through their interpretation of Google Earth images and data treatment. They included several assumptions, such as removing the impact of poor visibility, correcting grids of low resolutions, estimating number of unseen weirs, and applying daily catch rates higher than referenced observed values. The overall extent of such potential positive bias could be more than six times that which we considered reasonable. This Comment also corrects misconceptions about "FAO catch data", discusses other available national data, and introduces the existence of the Regional Commission for Fisheries (RECOFI), a mechanism for fisheries management in the Gulf region, and its recent activities to collect more complete catch and effort data separated by gear.

Description: The boreal Pacific sand lance ( Ammodytes hexapterus ) was recently detected in southeastern Beaufort Sea (Canadian Arctic), numbering as the second most abundant ichthyoplankton species after the polar cod ( Boreogadus saida ) in 2011. We contrast the hatching periods, growth, prey selectivity, and feeding success of the planktonic stages of the two species. Polar cod hatched from January to mid-July and sand lance from mid-July to early September, precluding any competition among the larval stages. By weight, sand lance larvae grew 3.7 times faster than polar cod larvae. The co-occurring juveniles of both species fed primarily on copepods and to a lesser extent on bivalve larvae, shifting to larger prey with growth. The feeding success of both species appeared limited by the availability of their preferred prey. A significant diet overlap in juveniles 〉25 mm suggested potential competition for Pseudocalanus spp., Calanus spp., and bivalve larvae. However, sand lance strongly selected for nauplii while the more diversified diet of polar cod comprised mainly the copepodites of these species. Interspecific competition for food is unlikely at this time but is predicted to amplify with a climate-related reduction in the size of zooplankton prey and an increase in the abundance of sand lance.

Description: Fish stock fluctuations are affected by two potentially confounding forces: the removal of individuals by fisheries and climatic variations affecting the productivity of fish populations. Disentangling the relative importance of these forces has thus been a question of primary importance for fisheries management and conservation. Through the analysis of long-term time-series for 27 fish stocks from the Northeast Atlantic, the present study shows that the sign and intensity of the effect of temperature on biomass are dependent on the geographical location: the stocks located at the southernmost and northernmost latitudes of our study displayed stronger associations with temperature than the stocks located in the middle range of latitudes. As a consequence, the investigation of the combined effects of exploitation and the environment revealed that the stocks at the northern/southern boundaries of the spatial extent of the species were more prone to combined effects. The interplay between geographic location, climate and exploitation thus plays a significant role in fish stock productivity, which is generally ignored during assessment, thus affecting management procedures.

Description: There is growing interest in bioeconomic models as tools for understanding pathways of fishery behaviour in order to assess the impact of alternative policies on natural resources. A model system is presented that combines stochastic age-structured population dynamics with complex fisheries economics. Explicitly, the economic response of fleet segments to changes in stock development is analysed by applying observed values and stochastic recruitment. The optimization of net profits determines the fishing effort and the investment and disinvestment behaviour of fleet segments, which, in turn, affect the level of catch rates and discards. This tool was applied to the North Sea saithe fishery, where ICES re-evaluated the existing EU–Norway management plan, focusing on biological reference points only. Two scenarios were tested with alternative harvest control rules and then contrasted with one unregulated scenario with no quotas and driven by optimizing the net profit of the whole fleet. The model showed the success of both harvest control rules in rebuilding the stock and the associated costs to the fleets in terms of maximal 21% reduction in net profits, 21% reduction in crew wages and 11% reduction in fleet size in the midterm (2007–2015). In the long term (2022), successful stock recovery coincided with net profits almost equalling that of the unrestricted fishery. The model is highly sensitive to the parameter values but can be used strategically, providing a qualitative understanding of the anticipated relative changes.

Description: Experiments were conducted to evaluate a fishing captain's ability to predict species composition, sizes, and quantities of tunas associated with drifting fish-aggregating devices (FADs), before encirclement with a purse-seine net. Operating in the equatorial eastern Pacific Ocean, during 11 May–23 July 2011, Captain Ricardo Diaz detected small quantities of bigeye ( Thunnus obesus ) and yellowfin ( Thunnus albacares ) tunas within large FAD-associated aggregations dominated by skipjack tuna ( Katsuwonus pelamis ). The captain's predictions were significantly related to the actual total catch and catch by species, but not to size categories by species. His predictions of species composition were most accurate when estimates of bigeye and yellowfin tuna were combined. If purse-seine captains are able to make accurate predictions of the proportion of bigeye and yellowfin tunas present in mixed-species aggregations associated with FADs, managers may wish to consider incentives to fishers to reduce the fishing mortality on those species.

Description: Fish aggregating devices (FADs) are deployed to aggregate fish over a limited area to improve fish catch. Fish enhancing devices (FEDs), which are FADs deployed in no-fishing areas, are fast gaining popularity as a fisheries management tool in the western Pacific. Yet, the impacts of utilizing FADs and FEDs are not yet well understood. In this work, we used a mean-field model to assess the effects of utilizing FADs and FEDs on stock biomass and catch. Our results indicate that using FADs enhances catch per boat when total fishing pressure is low, but can exacerbate fishery collapse when fishing effort is high. On the other hand, a FED-based system can increase the resistance of the fishery to collapse. A FED-based fishery may thus serve as pelagic marine protected areas and/or refugia. In a quota-based system, where fishing time is tied to catch quota, a phase transition occurs: both catch and biomass abruptly shift to low levels without warning. Deploying FADs to act as FEDs in a high quota fishery can prevent this phase transition resulting to a stabilizing effect.

Description: Collecting spatial information on fisheries catch and effort is essential to understanding the spatial processes of exploited population dynamics and to manage heterogeneously distributed resources and uses. The use of fishers' knowledge through geographical information systems (GISs) is increasingly considered as a promising source of local information on small-scale coastal fisheries. In this paper we describe the first framework for mapping entire small-scale coastal fisheries using fishers' knowledge on catch size and fishing effort. Four mangrove and coral reef fisheries targeting invertebrates or finfish in New Caledonia (southwest Pacific) were mapped following a five-step framework: (i) stratified random sampling of regular fishers; (ii) collection of fishers' knowledge of fishing areas, fishing effort, and catch size through map-based interviews; (iii) data integration into a spatial geodatabase; (iv) statistical extrapolation of fisher data to the fishery scale; and (v) mapping of catch, effort, and catch per unit effort (CPUE) for each fishery using a GIS overlay procedure. We found evidence that fishers' knowledge supplied precise and accurate quantitative and spatial information on catch size, fishing effort and CPUE for entire fisheries. Fisheries maps captured the fine-scale spatial distribution of fishing activities in a variety of ways according to target taxa, gear type, and home ports. Applications include area-based marine conservation planning and fishery monitoring, management, and governance. This integrated framework can be generalized to a large range of data-poor coastal and inland small-scale fisheries.

Description: Fisheries management agencies and fishing industry representatives depend on reliable estimates of fish biomass and mortality for the determination of sustainable catch levels. Lack of data or misreporting may be reasons for unreliable stock assessment, which, in turn, may result in advice that does not reflect the availability of fisheries resources. It has been suggested that the mixed pelagic trawl fisheries in the Baltic represent a case of biased estimates of fish biomass and mortality resulting from misreporting. Here, we estimate the degree of misreporting in the Swedish pelagic fishery (1996–2009) and propose an approach for reconstructing historical catches based on commercial effort data. The analysis suggests that total catches have been underestimated during part of our study period and that systematic misreporting of species composition has taken place over the whole study period. The analysis also suggests that there is overcapacity in the fishery and that such economic incentive could explain the general patterns of misreporting. Applying our method for fisheries with suspected misreporting could significantly improve assessment accuracy, reduce uncertainty and thereby allow for a better link between catches and resource levels.

Description: Fisheries management decisions have the potential to influence the safety of fishers by affecting how and when they fish. This implies a responsibility of government agencies to consider how fishers may behave under different policies and regulations in order to reduce the incidence of undesirable operational health and safety outcomes. In the Tasmanian southern rock lobster fishery, Australia, the expansion of the quota lease market under individual transferable quota (ITQ) management coincided with a rise in the number of commercial fishing fatalities, with five between 2008 and 2012. A discrete choice model of daily participation was fitted to compare whether physical risk tolerance varied between fishers who owned the majority of their quota units (quota owners) and those who mainly leased (lease quota fishers). In general, fishers were averse to physical risk (wave height), however this was offset by increases in expected revenue. Lease quota fishers were more responsive to changes in expected revenue than quota owners, which contributed to risk tolerance levels that were significantly higher than those of quota owners in some areas. This pattern in behaviour appeared to be related to the cost of leasing quota. Although ITQs have often been considered to reduce the incentive for fishers to operate in hazardous weather conditions, this assumes fishing by quota owners. This analysis indicated that this doesn't hold true for lease quota fishers in an ITQ system, where in some instances there remains an economic incentive to fish in conditions with high levels of physical risk.

Description: Due to unregulated blast fishing and episodic bleaching events, the back-reef zone near Barangay Lucero in Bolinao, Pangasinan, Philippines, was reduced to a barren area of unconsolidated sand and coral rubble. Anecdotal accounts from local inhabitants, scientific reports, and examination of rubble on the substratum revealed that the area had been dominated by staghorn Acropora corals prior to degradation. With no significant signs of natural recovery, a low-tech restoration method that is both transferable to the community and cost-effective was devised and implemented. Through the help of local inhabitants, 450 fragments of two staghorn coral species ( Acropora intermedia and A. pulchra ) were transplanted, without using SCUBA equipment, in a total of six 4 x 4 m plots. There were two transplant density treatments: low and high, receiving 25 and 50 fragments of each coral species, respectively. Survivorship and growth of transplants, as well as the assemblage of fishes and macroinvertebrates inside the transplantation and control plots, were monitored periodically for up to 19 months. Transplant survivorship was generally high (68–89%) at the end of the study. There was also an average of a 15-fold increase in ecological volume of the transplants (from 1784.25 ± 162.75 to 26 540.765 ± 4547.25 cm 3 ). Consequently, a significantly higher number of fish and of macroinvertebrates was recorded inside the transplantation plots than in the control plots, indicating signs of restoration success with the reintroduction of the two coral species. Exhibiting significant differences in coral cover, fish biomass and abundance, high-density is more cost-effective than low-density treatment, attaining optimal effects on key reef recovery parameters. The total cost of restoring a thicket of Acropora in a sandy-rubble field using this low-tech rehabilitation method with community participation was estimated to be US$9198.40 ha –1 (US$0.90 m –2 ), and thus ~60% cheaper than without community involvement. Community involvement not only reduced the cost of the restoration activity but also provided the community with a sense of ownership and responsibility for their resources, thus ensuring the long-term success of the intervention.

Description: Arctic and Antarctic marine systems have in common high latitudes, large seasonal changes in light levels, cold air and sea temperatures, and sea ice. In other ways, however, they are strikingly different, including their: age, extent, geological structure, ice stability, and foodweb structure. Both regions contain very rapidly warming areas and climate impacts have been reported, as have dramatic future projections. However, the combined effects of a changing climate on oceanographic processes and foodweb dynamics are likely to influence their future fisheries in very different ways. Differences in the life-history strategies of the key zooplankton species (Antarctic krill in the Southern Ocean and Calanus copepods in the Arctic) will likely affect future productivity of fishery species and fisheries. To explore future scenarios for each region, this paper: (i) considers differing characteristics (including geographic, physical, and biological) that define polar marine ecosystems and reviews known and projected impacts of climate change on key zooplankton species that may impact fished species; (ii) summarizes existing fishery resources; (iii) synthesizes this information to generate future scenarios for fisheries; and (iv) considers the implications for future fisheries management. Published studies suggest that if an increase in open water during summer in Arctic and Subarctic seas results in increased primary and secondary production, biomass may increase for some important commercial fish stocks and new mixes of species may become targeted. In contrast, published studies suggest that in the Southern Ocean the potential for existing species to adapt is mixed and that the potential for the invasion of large and highly productive pelagic finfish species appears low. Thus, future Southern Ocean fisheries may largely be dependent on existing species. It is clear from this review that new management approaches will be needed that account for the changing dynamics in these regions under climate change.

Description: The aim of this study was to explore the effect of sex, size, region, and density on dispersal rate of the introduced red king crab ( Paralithodes camtschaticus ) in Norwegian waters. We examined the effect of these factors using logistic regression analysis. Tag-recapture data corrected for fishing effort enabled us to estimate dispersal rates from four main regions along the Norwegian coast: Varangerfjorden, Tanafjorden, Laksefjorden, and Porsangerfjorden. The probability of dispersal was independent of sex and size, but both the logistic regression and the evaluation of corrected tag-recapture data revealed differences in dispersal between region and with increasing duration. The recapture data indicated a relationship between population density and dispersal within research regions but not between population density and dispersal between research regions. Our main conclusion is that there are large individual differences in dispersal ability and the range expansion of red king crab is a result of (i) the presence of long-distance dispersers and (ii) time-dependent slow migration by short distance dispersers. We also conclude that there appears less dispersal in Norwegian waters than in native waters, which might be caused by differences in geographical complexity.

Description: This paper highlights the value for marine spatial planning (MSP) of engaging with terrestrial planning theory and practice. It argues that the traditions of reflection, critique, and debate that are a feature of land-based planning can inform the development of richer theoretical underpinnings of MSP as well as MSP practice. The case is illustrated by tempering the view that MSP can be a rational planning process that can follow universal principles and steps by presenting an alternative perspective that sees MSP as a social and political process that is highly differentiated and place-specific. This perspective is discussed with reference to four examples. First, the paper considers why history, culture, and administrative context lead to significant differences in how planning systems are organized. Second, it highlights that planning systems and processes tend to be in constant flux as they respond to changing social and political viewpoints. Third, it discusses why the integration ambitions which are central to "spatial" planning require detailed engagement with locally specific social and political circumstances. Fourth, it focuses on the political and social nature of plan implementation and how different implementation contexts need to inform the design of planning processes and the style of plans produced.

Description: Understanding the trophic interactions and the position of species within a foodweb is crucial if we want to understand the dynamics of marine communities and the impact individual components of the community have on trophic network compartments. Recent studies have indicated sharks and rays are important elements within foodwebs. In this study, we evaluated the ecological importance of sharks and rays in a subtropical ecosystem off the coast of southern Brazil by using topological analyses. We tested the hypotheses that some elasmobranchs can be considered key elements within the foodweb, and that large predators have topological importance (act as keystones), so that, when large predators are excluded, mesopredator elasmobranchs occupy higher topological positions. Our results indicate that Galeocerdo cuvier, Carcharhinus obscurus, Carcharias taurus, Sphyrna lewini and S. zygaena are species with large ecological function values and may exert a powerful influence over lower levels. These issues need to be considered by conservation and fishery management groups since it appears that ecosystem integrity may be compromised by reductions in the populations of large predators. Carcharhinus obscurus, S. zygaena and Zapteryx brevirostris were found to be the elasmobranchs with largest values of centrality, and can, therefore, be considered key elements in the topological structure.

Description: Pelagic fish are key elements in marine foodwebs and thus comprise an important part of overall ecosystem health. We develop a suite of ecological indicators that track pelagic fish community state and evaluate state of specific objectives against Good Environmental Status (GES) criteria. Indicator time-series are calculated for the EU Marine Strategy Framework Directive "Celtic Seas" (CS) and "Greater North Sea" subregions. Precautionary reference points are proposed for each indicator and a simple decision process is then used to aggregate indicators into a GES assessment for each subregion. The pelagic fish communities of both subregions currently appear to be close to GES, but each remains vulnerable. In the CS subregion, fishing mortality is close to the precautionary reference point, although the unknown dynamics of sandeel, sprat, and sardine in the subregion may reduce the robustness of this evaluation. In the North Sea, sandeel stocks have been in poor state until very recently. Pelagic fish community biomass is slightly below the precautionary reference point in both subregions.

Description: Most demographic models are single sex, and assume both sexes have the same vital rates. However, many species, including the shortfin mako shark, are sexually dimorphic in vital rates, which suggests the need for two-sex models. In this study, a two-sex stage-structured matrix model was constructed to estimate shortfin mako shark demography and population dynamics. Monte Carlo simulations were used to evaluate the impact of uncertainties on the estimate of population growth rate. The number of shortfin mako sharks is found to be dropping under current conditions, but will stabilize if size-limit management is implemented. The simulations indicated that population growth rate estimates are mainly influenced by the uncertainty related to survival rate and fecundity. The effects of uncertainty regarding the age at maturity and longevity were found to be relatively minor. Future research should focus on obtaining estimates of natural mortality and reproductive traits for this species to improve the accuracy of demographic estimates.

Description: Knowledge of the spatial and temporal extent of covariation in survival during the critical ocean entry stage will improve our understanding of how changing ocean conditions influence salmon productivity and management. We used data from the Pacific coastwide coded-wire tagging program to investigate local and regional patterns of ocean survival of Chinook salmon ( Oncorhynchus tshawytscha ) from the Central Valley of California to southeastern Alaska from 1980–2006. Ocean survival of fish migrating as subyearlings covaried strongly from Vancouver Island to California. Short-term correlations between adjacent regions indicated this covariability increased, beginning in the early 1990s. Chinook salmon survivals exhibited a larger spatial scale of variability (50% correlation scale: 706 km) than those reported for other northeast Pacific Ocean salmon. This scale is similar to that of environmental variables related to ecosystem productivity, such as summer upwelling (50% correlation scale: 746 km) and sea surface temperature (50% correlation scale: 500–600 km). Chinook salmon ocean survival rates from southeastern Alaska and south of Vancouver Island were not inversely correlated, in contrast to earlier observations based on catch data, but note that our data differ in temporal and spatial coverage from those studies. The increased covariability in Chinook salmon ocean survival suggests that the marine phase contributes little to the reduction in risk across populations attributable to the portfolio effect. In addition, survival of fish migrating as yearlings from the Columbia River covaried with Chinook salmon survival from the northernmost regions, consistent with our understanding of their migration patterns.

Description: The relationship between larval fish assemblages and coastal oceanography is the basis for much of our understanding of connectivity and productivity of fish populations. Larval fish assemblages were sampled from the upper mixed layer (〈50 m depth) at three prominent circulation features [separation of the East Australian Current (EAC), anticyclonic eddy, and cyclonic eddy] off the southeast Australian coast across three bathymetric zones (shelf, slope and ocean) for each feature. The separation of the EAC from the coast at ~32°S was characterized by warmer, less saline water compared with the cyclonic and anticyclonic eddies further to the south (~34 and ~35°S, respectively), which were both characterized by cooler Tasman Sea water and greater fluorescence. The anticyclonic eddy had separated from the EAC three months prior to sampling, which facilitated the movement of a cyclonic eddy from the Tasman Sea westwards to the shelf at ~34°S. The larval assemblage in the EAC had high numbers of fish of the families Labridae and Stomiidae. The cyclonic eddy was characterized by larval clupeids, carangids, scombrids and bothids, indicating recent entrainment of shelf waters and proximity to major spawning regions. In contrast, the anticyclonic eddy had fewer larval fish, with little evidence for entrainment of shelf assemblages into the near-surface waters. Myctophids were found in high abundance across all oceanographic features and bathymetric zones. The evidence of selective entrainment of coastal larval fish into the near-surface waters of a cyclonic eddy compared with a similar anticyclonic eddy indicates a potential offshore nursery ground.

Description: This study investigated the spatial distribution of juvenile North Pacific albacore ( Thunnus alalunga ) in relation to local environmental variability [i.e. sea surface temperature (SST)], and two large-scale indices of climate variability, [the Pacific Decadal Oscillation (PDO) and the Multivariate El Niño/Southern Oscillation Index (MEI)]. Changes in local and climate variables were correlated with 48 years of albacore troll catch per unit effort (CPUE) in 1° latitude/longitude cells, using threshold Generalized Additive Mixed Models (tGAMMs). Model terms were included to account for non-stationary and spatially variable effects of the intervening covariates on albacore CPUE. Results indicate that SST had a positive and spatially variable effect on albacore CPUE, with increasingly positive effects to the North, while PDO had an overall negative effect. Although albacore CPUE increased with SST both before and after a threshold year of 1986, such effect geographically shifted north after 1986. This is the first study to demonstrate the non-stationary spatial dynamics of albacore tuna, linked with a major shift of the North Pacific. Results imply that if ocean temperatures continue to increase, US west coast fisher communities reliant on commercial albacore fisheries are likely to be negatively affected in the southern areas but positively affected in the northern areas, where current albacore landings are highest.

Description: Many coral reef fish species form predictable, transient spawning aggregations. Many aggregations are overfished, making them a target for spatial management. Here, we develop a per-recruit model to evaluate the performance of no-take marine reserves protecting transient spawning aggregations. The model consists of only 14 demographic and exploitation-related parameters. We applied the model to a protogynous grouper and a gonochoristic rabbitfish from Seychelles and tested six scenarios regarding the extent of protected areas, the level of fish spawning-site fidelity, and fishing effort redistribution post reserve implementation. Spawning aggregation reserves improve spawning-stock biomass-per-recruit and reduce the sex ratio bias in protogynous populations for all scenarios examined. However, these benefits are often small and vary among the different scenarios and as a function of sexual ontogeny. In all scenarios, increases in yield-per-recruit do not occur or are negligible. The long-term yield increases due to spawning aggregation reserves may still occur, but only if spawning-stock biomass recovery results in a recruitment subsidy. Given these limited benefits, the value of no-take reserves must be weighed against those of other management options, such as fishing effort reduction and seasonal fishery closures. The latter is particularly appropriate when spawning and non-spawning areas overlap in space.

Description: The strong international market for shark fins, but the often relatively low value of shark meat and the practical constraints for preserving it on board, have led to the practice whereby fins are removed from any shark caught by a fishing vessel and retained on board while the remainder of the shark is discarded at sea. This practice, known as "shark finning", has raised increasing concerns, at both the international and European levels, due to the killing of large quantities of sharks, with devastating and unsustainable effects on shark populations. Despite the importance of shark fisheries for EC fleets, to date shark fisheries are not subject to a comprehensive management framework at the European level. A number of measures aiming directly or indirectly at the conservation and management of sharks have been adopted over time. Considering that, the range of existing measures must be strengthened to ensure the rebuilding of many depleted stocks fished by the EU fleet both in and outside EU waters. At the EC level a new regulation has recently been implemented. This paper carries out an overview of the legal framework for the finning bans in the EU to improve current knowledge about this topic and to aid in focusing future research.

Description: The Atlantic dipole phosphate utilization (ADPU) index, derived through statistical conversion of 20th century Atlantic basin subpolar sea surface temperatures, is used as a fingerprint of Atlantic meridional overturning circulation (AMOC) variability and as an indicator of global Meridional Overturing Circulation (MOC) variability. ADPU index correlations with differences in sea level anomalies (SLAs) between Canada and the UK and across the Isthmus of Panama demonstrate intrabasin and interbasin associations with MOC variability. Cross-correlation analyses of ADPU index, SLAs, and sardine (S) and anchovy (A) catch differences [S –A] (normalized sardine catch minus normalized anchovy catch) confirm strong correlations between ADPU and [S –A] off Japan, California, Peru and Southwest Africa (Benguela). Statistically significant cross correlations also exist between the ADPU index and SLAs for Japan, California, Peru and Benguela, and for SLAs and [S – A] for Japan, California and Peru, but the short time-series lengths compared with the length of the multidecadal cycle limit the interpretation of the observed lead-lags. Though correlation is not causality, the correlation analyses developed here are useful in support of hypothesis generation. The proposed hypothesis to explain the observed small pelagic fishery synchronies asserts: (i) ocean bathymetry and continental distributions interact with multidecadal variations in MOC strength that occur along the conceptual global conveyor belt to generate changes in global oceanic planetary waves and mesoscale eddies that propagate through the world ocean; (ii) each small pelagic fishery region has a unique spatial relationship with pertinent oceanic planetary wave and mesoscale eddy source regions that affect the timing and strength of the waves and eddies that influence the nearby boundary current; (iii) synchronous changes or phasing among global fisheries depend on how and when MOC variability mediated by oceanic planetary waves and mesoscale eddies reaches each fishery region; (iv) oceanic planetary waves and/or mesoscale eddies influence the strength or meandering of the boundary current adjacent to a small pelagic fishery region to change local SLAs and environmental conditions to favour sardine or anchovy populations at different times.

Description: The recruitment success of some herring stocks fluctuates strongly, and apparently, success is often already determined during the early life stages, i.e. before metamorphosis. In studying the survival of early life stages and its affecting factors, particularly those during the egg stage, it is crucial to examine the processes at the spawning sites, which often cannot be explored directly. A recent decline in the recruitment of Western Baltic spring-spawning herring (WBSSH) increases the urgency of filling the knowledge gap for this stock, especially because one bottleneck in the recruitment seems to occur before hatching. We examined the successful 2003–2009 spawning sites of WBSSH in the main spawning ground, the Greifswalder Bodden lagoon. Instead of using common techniques such as diving or underwater videography, which are usually unsuitable for mapping large areas, we applied a model approach. We tracked herring larvae at length 6–10 mm, recorded by larval surveys during March–June of the respective years, back to their hatching sites using a Lagrangian particle backtracking model. We compared the spawning areas identified by the model with the results of earlier field studies; however, we also analysed variations between years, larval length groups, and different applied growth models, which are needed to define hatch-dates. Although spawning sites could not be identified with high precision because of the strong diffusion in the area studied, results indicate that larvae up to 10 mm length are caught near their hatching sites. However, the location of successful spawning sites varied largely between years, with the main hatching sites situated in the Strelasund and the eastern entrance of the lagoon. This may reflect variations in spawning-site selection or quality. A better knowledge of the locations and relative importance of, and the processes occurring on, the different spawning sites will provide an important contribution to the sustainable management of this commercially valuable herring stock.

Description: Galicia (NW Spain) is an important fishing region with a high potential for cetacean–fishery interactions. Cetacean depredation on catch and damage to fishing gear can potentially lead to substantial economic loss for fishers, while cetacean bycatch raises conservation concerns. With the aim of gathering information on the types and scale of interactions and of suggesting possible management strategies, we conducted face-to-face interviews with fishers in local fishing harbours, in particular to identify specific problematic interactions and to quantify the level of economic loss and bycatch rates associated with these interactions. We found that cetacean–fishery interactions are frequent, although damage to catch and fishing gear by cetaceans was mostly reported as small. Nevertheless, substantial economic loss can result from common bottlenose dolphins ( Tursiops truncatus ) damaging coastal gillnets and from short-beaked common dolphins ( Delphinus delphis ) scattering fish in purse-seine fisheries. Cetacean bycatch mortality was reported to be highest for trawls and set gillnets, and probably exceeds sustainable levels for local common and bottlenose dolphin populations. Although interview data may be biased due to the perceptions of interviewees, and therefore should be interpreted with care, the methodology allowed us to cover multiple sites and fisheries within a reasonable time frame. Minimizing cetacean–fishery interactions requires the implementation of case-specific management strategies with the active participation of fishers. For set gillnet and purse-seine fisheries, the use of acoustic deterrent devices (pingers) may prevent cetaceans from approaching and getting trapped in the nets. For trawl fisheries, where bycatch appears to be particularly high at night in water depths of 100–300 m, possible solutions include the implementation of time/area closures and the relocation of some fishing effort to deeper waters.

Description: The objectives for many commercial fisheries include maximizing either yield or profit. Clearly specified management targets are a key element of effective fisheries management. Biomass targets are often specified for major commercial fisheries that are managed using quantitative stock assessments where biomass is calculated and tracked over time. B MSY , the biomass corresponding to Maximum Sustainable Yield, is often used as a target when maximizing yield is important, while B MEY is the biomass target to maximize profit. There are difficulties in estimating both quantities accurately, and this paper explores default proxies for each target biomass, expressed as biomass levels relative to carrying capacity, which are more easily estimated. Integration across a range of uncertainties about stock dynamics and the costs of fishing suggests that a proxy for B MSY in the range of 35–40% of carrying capacity minimizes the potential loss in yield compared with that which would arise if B MSY was known exactly, while a proxy for B MEY of 50–60% of carrying capacity minimizes the corresponding potential loss in profit. These estimates can be refined given stock-specific information regarding productivity (particularly the parameter which defines the resilience of recruitment to changes in spawning stock size) and costs and prices. It is more difficult to find a biomass level that achieves a high expected profit than a biomass level that achieves a high expected catch, because the former is sensitive to uncertainties related to costs and prices, as well as parameters which determine productivity.

Description: The removal of large predatory sharks from the world's oceans poses profound threats to marine community structure and species conservation. Effective management of exploited shark stocks requires a sound understanding of the life histories of target species. Here we provide the first assessment of age and growth for Carcharhinus brevipinna in Australian waters, and for C. obscurus and C. plumbeus in eastern Australian waters, based on interpretations of vertebral growth bands. In doing so, we provide arguably among the most robust growth parameters to date for the abovementioned taxa on the bases of genetic validation and sample size and distribution, but acknowledge equally a range of limitations—most notably those associated with vertebral ageing and our lack of age validation. Comparatively, the three species displayed both contrasts and consistencies in their growth characteristics off Australia's southeast coast. For all three sharks, rates of growth were greatest in the years immediately after birth, males grew more rapidly than females in the juvenile phase, and females were observed to grow larger, live longer and were generally larger at any given age. Longevity and all modelled growth parameters ( L , k and L 0 ), however, differed among the three species, and appeared to challenge the findings for conspecific populations in other parts of the world. The validity of these latter comparisons is, however, compromised by a range of confounding factors. Nevertheless, we provide the least conservative k estimates for C. obscurus and C. plumbeus of those previously reported, and extend maximum age estimates for C. brevipinna . In this way, our results have important implications for the assessment of natural mortality, productivity, and hence resilience to stock depletion, in these species in southeastern Australian waters.

Description: Egg production methods have been used successfully in the provision of advice for fisheries management. These methods need accurate and unbiased estimates of fecundity. We explore the reproductive strategy of horse mackerel and estimation of fecundity. Fecundity and fecundity regulation in relation to condition was investigated over a number of years. Fulton's K , lipid content, and hepatosomatic index increased after the start of spawning, though decreased again at the end of spawning. The increase in the gonadosomatic index, fecundity, and body condition after the onset of spawning suggests that horse mackerel utilizes food resources during the spawning season and might be an income breeder. However, the decline in K and lipid before the spawning season suggests that the first batch of oocytes is developed on stored energy. Fecundity varied between years and within a spawning season. Over latitude, variations in fecundity were small. K and lipid content are not reliable indices as proxy for fecundity. Batch fecundity appears to be heterogeneous across the spawning season but homogeneous across latitude. The homogeneity of batch fecundity over latitude could indicate that the daily egg production method is an appropriate approach for estimating the abundance of a wide ranging species, as horse mackerel.

Description: Stable isotope analysis has become a common tool for mapping trophic relationships, describing foodweb changes, and assessing ecosystem health. Clear interpretation of stable isotopes is facilitated by understanding how environmental factors can affect isotopic values; in estuarine systems, these factors may include salinity, land use, and shoreline habitat. To evaluate these factors, fish were collected from shallow-water habitats next to hardened (bulkhead and riprap) and unhardened (beach and marsh) shorelines within five subestuaries of the Chesapeake Bay that differed in predominant land use and salinity. This study focused on three common mid-Atlantic fish species: mummichog, Fundulus heteroclitus , Atlantic silverside, Menidia menidia , and white perch, Morone americana . Multiple regression analyses pointed to standard length, salinity, % of watershed as developed or crop land, and shoreline habitat type as important predictors for 15 N in all three species and for 13 C in mummichog and white perch. Further analysis controlling for the effects of salinity, land use, and fish size demonstrated that 13 C and 15 N were lower in tissues of fish collected next to marsh compared with hardened or beach habitat. Habitat effects were strongest for mummichog. This study focused on overarching patterns driving stable isotope signatures in fish; however, it also indicated potentially important interactions between nearshore habitat type and land use or salinity that deserve further analysis. Results have implications for the scale of isotope inquiry and give justification for more detailed follow-up studies of foodweb structure along modified and natural shorelines.