Search

Forage fish form a critical trophic link in marine ecosystems, and yet, for many species, there is limited information available. As nations move from single species stock assessments to ecosystem approaches to fisheries management (EAFMs), more information on forage fish will be required. In this study, 50 years of scientific literature were systematically mapped for 11 forage fish species in Canada's Arctic, Atlantic, and Pacific oceans. The objectives were to identify (1) knowledge clusters and gaps and (2) the pressures studied in relation to forage fish outcomes. Of the 2897 articles mapped, the majority studied adults and the distribution, productivity, growth, and life history of commercially fished species. Knowledge gaps were identified for forage fish: (1) that were noncommercially exploited; (2) egg and larval life history stages of most species and juveniles of noncommercial species; (3) diets of most species; (4) migration and performance for all species and survival of noncommercial species; and (5) the effects of some pressures (e.g., large-scale climate pressures). Addressing these knowledge gaps would improve the application of EAFMs.

Estimating fish condition, the relative weight of an individual fish given its body length, is a convenient way to relate the physiological health and energetic status of fishes to their productivity. Despite evidence of density-dependence effects on condition in some species, previous research has not jointly estimated synchronous changes in condition and density operating at fine spatial scales (a few km). Therefore, we developed a spatio-temporal modeling approach that simultaneously estimates correlated variation in density (measured as numbers per area) and condition. We applied our approach to 6 eastern Bering Sea (EBS) groundfish species (4 flatfishes and 2 gadoids) for the period 1992-2016, and estimated correlations in spatial variation (unmeasured variation that is stable over time) and spatio-temporal variation (unmeasured variation that changes between years). Spatial variation in density had a strong significant negative association with spatial variation in condition for 3 flatfishes and a positive association for one gadoid. Spatio-temporal variation in density had a significant association with spatio-temporal variation in condition for one flatfish (negative) and one gadoid (positive). Moreover, for the 6 study species, bottom temperature was identified as an important predictor of both density and condition. The increasing trend in bottom temperatures between 1992 and 2016 was accompanied by an overall increase in the abundance-weighted condition of 5 species. We conclude that forecasts of changes in weight-at-age within some EBS groundfish assessments will require an understanding of both density-dependence and bottom temperature effects on fish condition to better prepare for future climate and exploitation changes.

One necessity of ecosystem based management is an understanding of the shape and functional forms of ecosystem responses to environmental and human pressures. Both nonlinear and linear relationships may provide leading indicators of ecosystem change and inform reference points for ecosystem approaches to management. The objectives of this study were to 1) determine functional forms of pressure-response relationships, 2) identify non-linear relationships, and 3) quantify potentially relevant management thresholds for the west coast of Vancouver Island marine ecosystem in British Columbia, Canada. To do this, a multi-model approach was applied to mechanistically linked indicators of pressures and responses. Both single pressure-response and multivariate relationships were examined. Results indicate that 1) nonlinear and linear relationships were not prevalent with the percentage of occurrence (6–12%) similar to other regions, 2) ecological responses (both linear and nonlinear) were more commonly associated with environmental pressures than human pressures, 3) gradient forest analysis generally produced similar results as single pressure-response models and identified additional nonlinearities, 4) dynamic factor analyses (DFA) reduced the numerous pressure and response indicator to a few trends, however, the process may have resulted in a loss of information, and 5) possibly due to this loss of information, gradient forest and single pressure-response analyses on DFA trends produced different results. Quantifying how pressures affect ecosystem components can provide advanced knowledge about changes in ecosystem productivity, structure, and function which can inform science advice and management strategies. Mechanistically linked pressure-response relationships should be explored further with multi-model ensembles to better inform ecosystem-based and climate-ready approaches to marine management.

Age-specific declines in length and weight of Pacific herring occurred in all coastal areas of British Columbia (BC) from approximately 1985 to 2010, followed by a more recent reversal in that trend. Concurrent with declining age-specific size, the number of egg layers deposited on vegetation, as estimated from diver surveys, declined but recently this trend also has reversed. In most areas egg layers declined by half, or more, of pre-decline estimates, from means of about 2–3 layers to about 0.5–1 layers. In general, as egg density declined, no corresponding reductions occurred in other metrics of herring spawning such as the mean length or width of the spawning bed. Correlation analyses indicate that the coherence of these two independently measured trends (declining size-at-age and declining egg density) is highly significant (p ≪ 0.01) in all REGIONs of the BC coast. We briefly examine two of several potential biological explanations for these temporal changes: (1) size-dependent ovary size; (2) size-dependent packing density of spawning fish. Quantitative estimates of herring spawn deposition are integral to herring spawning stock biomass assessments in BC and elsewhere so it is important to understand the factors that affect egg density. Our analyses indicate that changes in herring growth or ‘size-at-age’, which probably reflect regional warming related to climate change, can subsequently impact parameters of reproduction and spawning behaviour.

Many small pelagic fish species exhibit dramatic fluctuations in abundance accompanied by range expansions during periods of favorable environmental conditions. The location and extent of suitable habitats also shift in response to both short term variability and long term trends in climate. Near the margins of a contemporary range, trends in abundance may reflect a continuation of historical variability but may also foreshadow future changes in distribution. The Salish Sea (all inland marine waters of Washington State and southern British Columbia; made up of the Strait of Georgia, Strait of Juan de Fuca, and Puget Sound) is a highly productive estuarine system at the northern end of the distribution of Northern Anchovy (Engraulis mordax). An apparent recent (2014–2016) increase in Northern Anchovy abundance has generated interest in the dynamics of this species in the Salish Sea. We compiled recent and historical data to understand spatiotemporal patterns of distribution and fluctuations in abundance over the last century. Spatially-consistent occurrence of eggs, larvae, and juveniles, and year-round presence of multiple age classes, confirm that successful spawning and recruitment of Northern Anchovy occurs within the Salish Sea. Most periods of elevated Northern Anchovy abundance in the last century have corresponded to, or lagged, periods of elevated ocean temperatures. While a 2005 peak in abundance within the Salish Sea also corresponded to higher abundance of Northern Anchovy in adjacent regions of the coastal Pacific Ocean, it seems unlikely that Salish Sea abundance is controlled primarily by advection or migration from external populations. Persistence of elevated ocean temperatures like those observed from 2014 to 2016 could lead to consistently high abundance of Northern Anchovy within the Salish Sea, with implications for trophic relationships and ecosystem function.

To understand and manage marine ecosystems, long-term monitoring of fish biomass is needed. A challenge in estimating fish biomass using sampling nets is varying catchability with habitat, weather, or vessel traffic conditions. Underwater stereo cameras have shown promise in providing a non-lethal, efficient, and cost-effective method to observe and measure fish in areas that cannot be sampled otherwise. These methods, however, have yet to be demonstrated for mid-water pelagic or semi-pelagic fishes. We designed, built, and tested a stereo camera for its potential to augment survey assessments of pelagic fish biomass in areas where trawl net samples cannot be collected. In a pilot test, the stereo camera was used to identify fish species and to measure fish length, depth, tilt, and yaw. Five paired stereo camera deployments and pelagic midwater trawl hauls were compared during an acoustic survey in the Strait of Georgia, British Columbia. Fish sometimes moved in response to the stereo camera deployment, but acclimated quickly to its presence at depth. Pacific hake, Merluccius productus, and walleye pollock, Gadus chalcogrammus, were the two dominant species in both midwater trawl haul catches and stereo camera images, but fish sizes were significantly larger in most cases in stereo camera images compared to trawl haul catches. Fish length measurements were most accurate when yaw angles were

Determining how fish respond to variation in biotic and abiotic conditions is a crucial prerequisite to forecasting changes in productivity and spatial distribution of fish stocks and designing sustainable marine resource management strategies. In the present study, we investigated the physical and biological drivers of the spatio-temporal dynamics of Pacific Herring (Clupea pallasi), which is a marine forage fish species important for commercial fisheries and First Nations in the northeastern Pacific. We fit multivariate spatio-temporal models to fisheries-independent trawl- and acoustics-based data collected off the West Coast of Vancouver Island (WCVI), Canada, during summers over the period 2006–2014. We evaluated the effects of the main ocean environmental drivers of WCVI lower trophic level productivity, including sea surface temperature (SST), chlorophyll a, fluorescence, salinity, oxygen, transmissivity and zooplankton density on variation in Pacific Herring biomass. Models were also used to measure spatio-temporal covariation with other pelagic, semi-pelagic, and bottom-associated fish species occurring off the WCVI to address potential competitive and predation interactions. Through application of these spatio-temporal models we found: (i) Pacific Herring biomass off the WCVI increased during 2006–2014; the highest Pacific Herring biomass was repeatedly found on the continental shelf (depths 185 m), where Euphausiids, Pacific Hake, Sablefish and Arrowtooth Flounder were more abundant, which could reflect predation avoidance behaviour; (ii), the local biomass of Pacific Herring was related quadratically to the average SST in May; (iii) a positive covariation in spatio-temporal densities between Pacific Herring and its common zooplankton prey, supporting a potential bottom-up control hypothesis; (iv) a negative covariation in spatio-temporal densities between Pacific Herring and both Pacific Hake and Pacific Sardine, which could reflect predation and competitive interactions, respectively; and (v) a positive covariation in spatio-temporal densities between Pacific Herring and several groundfish species (i.e., Arrowtooth Flounder, Sablefish, Pacific Halibut, Pacific Cod), which highlights the need for an accurate assessment of the relative contribution of those species to the total summer predation pressure experienced by Pacific Herring off the WCVI. The findings of this study contribute to a better understanding of the WCVI marine ecosystem.

Human activities in coastal and marine ecosystems provide a suite of benefits for people, but can also produce a number of stressors that can act additively, synergistically, or antagonistically to change ecosystem structure, function, and dynamics in ways that differ from single stressor responses. Scientific tools that can be used to evaluate the effects of multiple stressors are needed to assist decision making. In this paper, we review indicator selection methods and general approaches to assess indicator responses to multiple stressors and compare example ecosystem assessments. Recommendations are presented for choosing and assessing suites of indicators to characterize responses. Indicators should be chosen based upon defined criteria, conceptual models linking indicators to pressures and drivers, and defined strategic goals and ecological or management objectives. Indicators should be complementary and nonredundant, and they should integrate responses to multiple stressors and reflect the status of the ecosystem. An initial core set of indicators could include those that have been tested for the effects of climate and fishing and then expanded to include other pressures and ecosystem-specific, feature-pressure interactions. Identifying indicators and evaluating multiple stressors on marine ecosystems require a variety of approaches, such as empirical analyses, expert opinion, and model-based simulation. The goal is to identify a meaningful set of indicators that can be used to assist with the management of multiple types of human interactions with marine ecosystems.

Bundy, Alida ... et al.-- 28 pages, 6 figures, 8 tables, supporting information https://dx.doi.org/10.1111/faf.12184, Fisheries have had major negative impacts on marine ecosystems, and effective fisheries management and governance are needed to achieve sustainable fisheries, biodiversity conservation goals and thus good ecosystem status. To date, the IndiSeas programme (Indicators for the Seas) has focussed on assessing the ecological impacts of fishing at the ecosystem scale using ecological indicators. Here, we explore fisheries ‘Management Effectiveness’ and ‘Governance Quality’ and relate this to ecosystem health and status. We developed a dedicated expert survey, focused at the ecosystem level, with a series of questions addressing aspects of management and governance, from an ecosystem-based perspective, using objective and evidence-based criteria. The survey was completed by ecosystem experts (managers and scientists) and results analysed using ranking and multivariate methods. Results were further examined for selected ecosystems, using expert knowledge, to explore the overall findings in greater depth. Higher scores for ‘Management Effectiveness’ and ‘Governance Quality’ were significantly and positively related to ecosystems with better ecological status. Key factors that point to success in delivering fisheries and conservation objectives were as follows: the use of reference points for management, frequent review of stock assessments, whether Illegal, Unreported and Unregulated (IUU) catches were being accounted for and addressed, and the inclusion of stakeholders. Additionally, we found that the implementation of a long-term management plan, including economic and social dimensions of fisheries in exploited ecosystems, was a key factor in successful, sustainable fisheries management. Our results support the thesis that good ecosystem-based management and governance, sustainable fisheries and healthy ecosystems go together, This is a contribution to the IndiSeas Working Group, which, by the time of the study, was cofunded by IOC-UNESCO (www.ioc-unesco.org), EuroMarine (http://www.euromarinenetwork.eu), the European FP7 MEECE research project, the European Network of Excellence Eur-Oceans and the FRB EMIBIOS project (contract n°212085)

Coll, Marta ... et al.-- 16 pages, 6 figures, 6 tables, IndiSeas (>Indicators for the Seas>) is a collaborative international working group that was established in 2005 to evaluate the status of exploited marine ecosystems using a suite of indicators in a comparative framework. An initial shortlist of seven ecological indicators was selected to quantify the effects of fishing on the broader ecosystem using several criteria (i.e., ecological meaning, sensitivity to fishing, data availability, management objectives and public awareness). The suite comprised: (i) the inverse coefficient of variation of total biomass of surveyed species, (ii) mean fish length in the surveyed community, (iii) mean maximum life span of surveyed fish species, (iv) proportion of predatory fish in the surveyed community, (v) proportion of under and moderately exploited stocks, (vi) total biomass of surveyed species, and (vii) mean trophic level of the landed catch. In line with the Nagoya Strategic Plan of the Convention on Biological Diversity (2011-2020), we extended this suite to emphasize the broader biodiversity and conservation risks in exploited marine ecosystems. We selected a subset of indicators from a list of empirically based candidate biodiversity indicators initially established based on ecological significance to complement the original IndiSeas indicators. The additional selected indicators were: (viii) mean intrinsic vulnerability index of the fish landed catch, (ix) proportion of non-declining exploited species in the surveyed community, (x) catch-based marine trophic index, and (xi) mean trophic level of the surveyed community. Despite the lack of data in some ecosystems, we also selected (xii) mean trophic level of the modelled community, and (xiii) proportion of discards in the fishery as extra indicators. These additional indicators were examined, along with the initial set of IndiSeas ecological indicators, to evaluate whether adding new biodiversity indicators provided useful additional information to refine our understanding of the status evaluation of 29 exploited marine ecosystems. We used state and trend analyses, and we performed correlation, redundancy and multivariate tests. Existing developments in ecosystem-based fisheries management have largely focused on exploited species. Our study, using mostly fisheries independent survey-based indicators, highlights that biodiversity and conservation-based indicators are complementary to ecological indicators of fishing pressure. Thus, they should be used to provide additional information to evaluate the overall impact of fishing on exploited marine ecosystems. © 2015 Elsevier Ltd. All rights reserved, We thank the Euroceans IndiSeas Working Group funded by the European Network of Excellence EUR-OCEANS (FP6, Contract N° 511106), the European collaborative project MEECE – Marine Ecosystem Evolution in a Changing Environment (FP7, Contract N° 212085) and IRD (Institute of Research for Development) and IOC/UNESCO. [...] MC was partially funded by the European Commission through the Marie Curie Career Integration Grant Fellowships – PCIG10-GA-2011-303534 – to the BIOWEB project and by the Spanish National Program Ramon y Cajal. LJS was supported through the South African Research Chair Initiative, funded through the South African Department of Science and Technology (DST) and administered by the South African National Research Foundation (NRF). LJS and YS were also funded by the European collaborative project MEECE – Marine Ecosystem Evolution in a Changing Environment – (FP7, Contract N° 212085). KMK was supported by the Northeast Fisheries Science Center and the Nature Conservancy through a grant from the Gordon and Betty Moore Foundation. MJJJ was supported by an EU Marie Curie International Outgoing Fellowship – PIOF-GA-2013-628116. MFB was supported by the Portuguese Oceanic and Atmospheric Institute and the trawl survey data collected under Biological Sampling (PNAB) Program. LJG would like to thank the Joint Research Centre of the European Commission for support. HO was financed by the Estonian Ministry of Education and Research (Grant SF0180005s10). JJH was supported by the Natural Environment Research Council and Department for Environment, Food and Rural Affairs [Grant Number NE/L003279/1, Marine Ecosystems Research Programme]. GIvdM was supported by the Institute of Marine Research, Norway. KT was partially funded by the project PERSEUS (Policy-oriented marine Environmental Research in the Southern EUropean Seas; FP7 Contract N° 287600). MAT was funded by the Spanish Institute of Oceanography (IEO) through a Predoctoral FPI fellowship. KNM was supported by a National Research Council fellowship at the Northwest Fishery Science Center. YJS and MTT were partially supported by the French project EMIBIOS (FRB, Contract No. APP-SCEN-2010-II). Chatham Rise trawl survey data were provided by the Ministry for Primary Industries. CL acknowledges DEVOTES – Development of innovative tools for understanding marine biodiversity and assessing good Environmental Status – EC project (FP7 Grant Agreement 308392)

Nursery areas for juvenile fishes are often important for determining recruitment in marine populations by providing habitats that can maximize growth and thereby minimize mortality. Pacific ocean perch (POP, Sebastes alutus) have an extended juvenile period where they inhabit rocky nursery habitats. We examined POP nursery areas to link growth potential to recruitment. Juvenile POP were captured from nursery areas in 2004 and 2008, and estimated growth rates ranged from −0.19 to 0.60 g day−1 based on differences in size between June and August. Predicted growth rates from a bioenergetics model ranged from 0.05 to 0.49 g day−1 and were not significantly different than observed. Substrate preferences and the distribution of their preferred habitats were utilized to predict the extent of juvenile POP nursery habitat in the Gulf of Alaska. Based on densities of fish observed on underwater video transects and the spatial extent of nursery areas, we predicted 278 and 290 million juvenile POP were produced in 2004 and 2008. Growth potential for juvenile POP was reconstructed using the bioenergetics model, spring zooplankton bloom timing and duration and bottom water temperature for 1982–2008. When a single outlying recruitment year in 1986 was removed, growth potential experienced by juvenile POP in nursery areas was significantly correlated to the recruitment time-series from the stock assessment, explaining ∼30% of the variability. This research highlights the potential to predict recruitment using habitat-based methods and provides a potential mechanism for explaining some of the POP recruitment variability observed for this population.

Marine ecosystems are influenced by drivers that operate and interact over multiple scales, resulting in nonlinear or abrupt responses to perturbation. Because of the inherent com- plexity of marine ecosystems, progress towards an understanding of factors that affect fisheries production will be most efficient if researchers adopt a comparative approach across ecosystems using suites of indicators. The goals of this study were to explore a suite of biomass- and catch- based ecosystem response indicators for 9 northern hemisphere ecosystems relative to indices that capture the influence of fisheries, trophodynamic and environmental drivers, and to compare the relative influence of the triad of drivers. Partial least squares regression was used to explore rela- tionships between the ecosystem response indicators and predictor drivers and to estimate the rel- ative importance of each of the triad of drivers. Across ecosystems we have identified a few com- mon observations: (1) environmental drivers, particularly temperature-related independent variables, are most likely related to total system biomass and biomass of specific biological groups (e.g. gadoid or clupeid fishes); (2) trophodynamic drivers are most relevant to the mean trophic level of community and the demersal-to-pelagic biomass ratio; and (3) fisheries drivers tend to be related to the catch-based indicators, such as fishing-in-balance and percent of primary produc- tion required to support fisheries. Overall, each of the triad of drivers was important for all eco- systems; however, the relative importance of each driver and the indicators they most affected var- ied among ecosystems, suggesting that an examination of a suite of indicators and drivers is required. A key finding is that fishing is categorically an important driver, but to explain biomass trends it is very important to consider environmental drivers as well.

The eastern Bering Sea (EBS) is a highly productive subarctic marine ecosystem that is exposed to considerable climate variability and is noted for conservative management of its fishery resources. The community size spectrum (CSS; relationship between animal abundance and size) of fish captured in EBS shelf bottom trawl surveys was examined for evidence of change over time and fishing and climate effects. The slope (indicative of fish size) and height (indicative of ecosystem productivity, or essentially fish abundance) of the CSS can change due to changes in fishing intensity and climate variability. Linear trends were not observed in EBS groundfish size or abundance during 1982–2006. The abundance of large-sized fish increased in 2001–2006 relative to 1982–2000. Observed changes in CSS height partially corroborated evidence for decreased productivity of the main fishery target species since the late 1990s, which may have been due to changes in relative species composition. In addition, abundan...

We would like to thank the IndiSeas Working Group, endorsed by IOC-UNESCO (www.ioc-unesco.org) and the European Network of Excellence Euroceans (www.eur-oceans.eu). KMK was supported by Conservation International and the Sea Around Us project, a collaboration between The University of British Columbia and The Pew Charitable Trusts. MC was partially supported by the EC Marie Curie CIG grant to BIOWEB and the Spanish Research Program Ramon y Cajal. LJS was supported through the South African Research Chair Initiative, funded through the South African Department of Science and Technology (DST) and administered by the South African National Research Foundation (NRF). YJS and MIT were supported by the French project EMIBIOS (FRB, contract no. APP-SCEN-2010-11). US and YS were also funded by the European collaborative project MEECE - Marine Ecosystem Evolution in a Changing Environment - (FP7, Contract no. 212085). CPL was supported by Defra project MF1228 (From Physics to Fisheries) and DEVOTES (DEVelopment of innovative Tools for understanding marine biodiversity and assessing good Environmental Status) funded by EU FP7 (grant Agreement no. 308392), www.devotes-project.eu. GIvdM was partially supported by the Norwegian Nature Index programme and the Institute of Marine Research, Norway. HO was funded was funded by the Estonian Ministry of Education and Research (grant SF0180005s10). MAT was funded by a predoctoral FPI fellowship from the Spanish Institute of Oceanography (IEO). MJJJ was supported by the EC Marie Curie IOF Grant, PIOF-GA-2013-628116. We acknowledge all those who conducted surveys to collect the data used in this study.; Fisheries provide critical provisioning services, especially given increasing human population. Understanding where marine communities are declining provides an indication of ecosystems of concern and highlights potential conflicts between seafood provisioning from wild fisheries and other ecosystem services. Here we use the nonparametric statistic, Kendall's tau, to assess trends in biomass of exploited marine species across a range of ecosystems. The proportion of 'Non-Declining Exploited Species' (NDES) is compared among ecosystems and to three community-level indicators that provide a gauge of the ability of a marine ecosystem to function both in provisioning and as a regulating service: survey-based mean trophic level, proportion of predatory fish, and mean life span. In some ecosystems, NDES corresponds to states and temporal trajectories of the community indicators, indicating deteriorating conditions in both the exploited community and in the overall community. However differences illustrate the necessity of using multiple ecological indicators to reflect the state of the ecosystem. For each ecosystem, we discuss patterns in NDES with respect to the community-level indicators and present results in the context of ecosystem-specific drivers. We conclude that using NDES requires context-specific supporting information in order to provide guidance within a management framework. (C) 2015 Elsevier B.V. All rights reserved.

The abundance of anadromous salmon is partially determined by size-selective mortality during the early marine life phase. Consequently, identifying the growth patterns of juvenile salmon during this life phase is important in understanding the dynamics of salmon populations. We examined patterns of early marine growth in juvenile pink salmon Oncorhynchus gorbuscha released by four hatcheries in Prince William Sound (PWS), Alaska, and explored how these patterns related to marine survival. Since larger individuals are thought to experience reduced mortality, we partitioned the data into weight-based quartiles and compared growth rates (% body weight/d) of all fish, the largest fish (top 25%), and the smallest fish (bottom 25%). Sampling occurred during summer 1997–2004 in PWS, the inshore Gulf of Alaska (GOA), and the offshore GOA. Growth rates varied significantly among years and sampling locations; however, the growth rate patterns were markedly similar among size-groups and hatcheries. Growth ...

Schweigert, J. F., Boldt, J. L., Flostrand, L., and Cleary, J. S. 2010. A review of factors limiting recovery of Pacific herring stocks in Canada. – ICES Journal of Marine Science, 67: 1903–1913. On the west coast of Canada, Pacific herring (Clupea pallasi) supported an intensive reduction fishery from the early 1930s until the collapse of all five major stocks in the late 1960s, which then recovered rapidly following a fishery closure. Despite conservative harvests, abundance has declined again recently, with little evidence of recovery. We investigated the effect of bottom-up forcing by zooplankton abundance, top-down forcing by fish and mammal predators, and the effects of sardine abundance as potential competitors on the natural mortality of the herring stock on the west coast of Vancouver Island. Herring mortality was positively related to Thysanoessa spinifera and southern chaetognaths and negatively to pteropod abundance. Estimated predation on herring decreased significantly during the years 1973–2008, with the main consumers changing from fish to mammals. However, the correlation with herring mortality was negative, whereas there was a significant positive relationship with sardine abundance. Population recovery is expected to be facilitated by a combination of factors, including adequate food supply, limited or reduced predation (including fishing), and limited competition particularly for wasp–waist systems, where different forage species may occupy similar niches.

To improve understanding of the mechanisms affecting growth and survival, we evaluated the summer diets and feeding patterns (prey composition, energy density, and stomach fullness) of hatchery and wild juvenile pink salmon Oncorhynchus gorbuscha in Prince William Sound (PWS) and the northern coastal Gulf of Alaska (CGOA). Our study (1999-2004) included 2 years of low (∼3%), mid (∼5%), and high (∼8-9%) survival of PWS hatchery pink salmon. Because variations in diet should affect growth and ultimately survival, we expected that the variations in diet, growth, and survival would be correlated. During August in the CGOA, pteropod-dominated diets and higher gut fullness corresponded to high survival (5-9%), and copepod-dominated diets and lower gut fullness corresponded to low survival (3%). Within years, no significant differences were found in diet composition or gut fullness between hatchery and wild fish or among the four PWS hatchery stocks. Diets varied by water mass (habitat) as juveniles mov...

Marine survival rate (the number of adult salmon returning divided by the number of salmon fry released) of pink salmon runs propagated by Prince William Sound, Alaska (PWS) salmon hatcheries is highly variable resulting in large year-to-year run size variation, which ranged from ∼20 to ∼50 million during 1998–2004. Marine survival rate was hypothesized to be determined during their early marine life stage, a time period corresponding to the first growing season after entering the marine environment while they are still in coastal waters. Based on the predictable relationships of 13 C/ 12 C ratios in food webs and the existence of regional 13 C/ 12 C gradients in organic carbon, 13 C/ 12 C ratios of early marine pink salmon were measured to test whether marine survival rate was related to food web processes. Year-to-year variation in marine survival rate was inversely correlated to 13 C/ 12 C ratios of early marine pink salmon, but with differences among hatcheries. The weakest relationship was for pink salmon from the hatchery without historic co-variation of marine survival rate with other PWS hatcheries or wild stocks. Year-to-year variation in 13 C/ 12 C ratio of early marine stage pink salmon in combination with regional spatial gradients of 13 C/ 12 C ratio measured in zooplankton suggested that marine survival was driven by carbon subsidies of oceanic origin (i.e., oceanic zooplankton). The 2001 pink salmon cohort had 13 C/ 12 C ratios that were very similar to those found for PWS carbon, i.e., when oceanic subsidies were inferred to be nil, and had the lowest marine survival rate (2.6%). Conversely, the 2002 cohort had the highest marine survival (9.7%) and the lowest mean 13 C/ 12 C ratio. These isotope patterns are consistent with hypotheses that oceanic zooplankton subsidies benefit salmon as food subsidies, or as alternate prey for salmon predators. Oceanic subsidies are manifestations of significant exchange of material between PWS and the Gulf of Alaska. Given that previously observed inter-decadal cycles of oceanic zooplankton abundance were climatically driven, exchange between PWS and the Gulf of Alaska may be an important process for effecting synoptic changes in marine populations of higher trophic levels, and thus an important consideration for climate-change models and scenarios.

It is believed that juvenile habitats are important to determining recruitment to adult fish populations through density dependence that occurs in nursery areas. For deepwater marine fishes, the characteristics of nursery areas are generally unknown. The objectives of this study were to examine a potential nursery area for juvenile Pacific ocean perch (POP, Sebastes alutus), determine the specific microhabitats used by juvenile POP, and compare the distribution of juvenile POP to adults. Juvenile POP habitat use was examined at three sites near Samalga Pass in the Aleutian Islands. Presence or absence and density estimates of juvenile POP were made from underwater video collected at 11 transects and from 6 bottom tows at the study sites. Juvenile POP were found predominantly in mixed sand and boulder substrata to the exclusion of most other habitat types. Juvenile POP were found within one body length of complex structure such as boulders, upright coral or sponges. There were higher densities of juvenile POP at the site south of Samalga Pass than at the other sites, while adult POP were found in highest abundance at the site north of Samalga Pass. An examination of large-scale patterns of juvenile and adult POP distribution indicates that juveniles use shallower depth zones on the continental shelf. Combined with the geographic separation we observed in this study, this suggests juvenile POP use nursery habitats that are different from adult POP. Conservation and management of this species should address the habitat requirements of juveniles to maintain the goal of healthy adult populations.

Two measures of productivity for fish stocks (recruitment and stock–recruit residuals) within two large marine ecosystems (Gulf of Alaska and eastern Bering Sea – Aleutian Islands) showed significant positive covariation within several groups of species and significant negative covariation between certain others. For example, stock–recruit residuals of gadids (Gadidae) in the Bering Sea were inversely related to those of shelf flatfishes (Pleuronectidae), suggesting that environmental forcing affects these groups in opposite ways. Salmon (Oncorhynchus spp.), Pacific herring (Clupea pallasii), and groundfish stocks each showed strong patterns of covariation within these taxonomic groups and within ecosystems, and both salmon and groundfish stocks showed positive covariation between the two ecosystems. However, we found little evidence of covariation between salmon and herring stocks or between these stocks and demersal stocks. Recruitment and stock–recruit residuals in individual stocks did not show a consistent response to known climatic regime shifts. However, combined indices of productivity across stocks showed decadal-scale variability (regime-like patterns), suggesting that both pelagic productivity (mostly salmon) and demersal productivity increased in response to the well-documented 1976–1977 climatic regime shift, whereas the 1988–1989 regime shift produced inconsistent or short-lived responses.

International audience; Understanding how external pressures impact ecosystem structure and functioning is essential for ecosystem-based approaches to fisheries management. We quantified the relative effects of fisheries exploitation and environmental conditions on ecological indicators derived from two different data sources, fisheries catch data (catch-based) and fisheries independent survey data (survey-based) for 12 marine ecosystems using a partial least squares path modeling approach (PLS-PM). We linked these ecological indicators to the total biomass of the ecosystem. Although the effects of exploitation and environmental conditions differed across the ecosystems, some general results can be drawn from the comparative approach. Interestingly, the PLS-PM analyses showed that survey-based indicators were less tightly associated with each other than the catch-based ones. The analyses also showed that the effects of environmental conditions on the ecological indicators were predominantly significant, and tended to be negative, suggesting that in the recent period, indicators accounted for changes in environmental conditions and the changes were more likely to be adverse. Total biomass was associated with fisheries exploitation and environmental conditions; however its association with the ecological indicators was weak across the ecosystems. Knowledge of the relative influence of exploitation and environmental pressures on the dynamics within exploited ecosystems will help us to move towards ecosystem-based approaches to fisheries management. PLS-PM proved to be a useful approach to quantify the relative effects of fisheries exploitation and environmental conditions and suggest it could be used more widely in fisheries oceanography.

Assessment of the historical, present, and future states of marine ecosystems and the effects that humans and climate have on the state of an ecosystem are crucial to the scientific advice required to implement an ecosystem-based fishery management system. Management of federal groundfish fisheries in Alaska considers not just the target fishery, but also the possible impact those fisheries might have on other species and the ecosystem. Management actions have ranged from providing protection of endangered species in the region to preventing new fisheries from starting on key foodweb components such as forage fish. A scientific framework for providing ecosystem-based advice that puts the ecosystem first has been evolving over the past few years. This framework provides a way of assessing ecosystem factors that influence target species, the impact the target fishery may have on associated species, and ecosystem-level impacts of fishing. An indicator approach that describes ecosystem status, and trends and measures of human and climate influence has been developed to provide advice to fishery managers. This approach is now being expanded to utilize a variety of models to predict possible future trends in various ecosystem indicators. Future implementation challenges include the refinement of these predictive models, and the inclusion of climate into the models. Identification of sensitive and meaningful ecosystem indicators is also required before a more formalized decision-making process, one that includes ecosystem considerations, can be developed. Most important, the culture of fishery management and research organizations needs to change to embrace the ecosystem-based protections already mandated by various laws.

An integral part of assessing the northern Gulf of Alaska (GOA) ecosystem is the analysis of the food habits and feeding patterns of abundant zooplanktivorous fish. Juvenile pink salmon Oncorhynchus gorbuscha are highly abundant zooplanktivores, and support valuable commercial fisheries as adults. We document variability in pink salmon distribution and size from summer to early fall, and present major trends in their food habits by summarizing interannual (August 1999–2001), seasonal (July–October 2001) and diel (August 2000, and July–September 2001) feeding patterns based on analysis of stomach contents of juvenile pink salmon collected along the Seward Line (GOA) and in Prince William Sound (PWS), Alaska. Diets of juvenile pink salmon were more diverse in 2001 compared to either 1999 or 2000. Small pteropods (Limacina helicina) composed the majority (>60%) of prey consumed in 1999 and 2000; whereas large copepods, euphausiids, and small pteropods composed the majority of prey in 2001. As juvenile pink salmon increased in size, they consumed increasingly larger prey from August to October 2001 in the GOA. The diet of GOA juvenile pink salmon was different and more diverse than the diet of fish caught in PWS. The dominant prey in PWS during July–October was hyperiid amphipods, whereas the primary prey in the GOA were larvaceans and euphausiids in July, then copepods plus small pteropods, amphipods, euphausiids, larval crabs, and shrimp in August. In September and October, diets in both PWS and GOA included high percentages of larger prey items, including fish, euphausiids, and large pteropods (Clio pyramidata). Diel comparisons of stomach contents showed pink salmon fed during daylight hours with stomach fullness increasing from dawn to a maximum fullness 8–12 h after sunrise, and declining thereafter. We hypothesize that juvenile pink salmon in the northern GOA consumed distinct and varied prey from the suite of zooplankton available during summer months, July–September. These prey were not necessarily the planktonic species with the greatest biomass or highest abundance on the shelf. Pink salmon fed on prey that were highly visible during daylight hours in the neuston and upper 10 m of the water column. Further work will integrate food habits with fish condition and growth data, zooplankton abundance, and water temperature to develop foraging and bioenergetics models. These models will enable us to assess the habitat quality and growth conditions for juvenile pink salmon and contribute to the goal of understanding how pink salmon and, therefore, tertiary production are affected by changes in ocean conditions.

Prince William Sound hatcheries release over 600 million pink salmon ( Oncorhynchus gorbuscha ) fry each year. The effect of the additional consumption demand by hatchery fish on prey biomass in Prince William Sound and the coastal Gulf of Alaska is unknown. The objectives of this study were to: (1) use bioenergetics models to compare spatial and temporal variation in the consumption demand and growth efficiency of hatchery and wild juvenile pink salmon in Prince William Sound and the coastal Gulf of Alaska between May and October 2001; and (2) compare localized population-level consumption in each region to the standing stock biomass of coexisting prey. In order to achieve observed growth, juvenile pink salmon consumed at 64–107% of their theoretical maximum consumption rate. Individual juvenile pink salmon consumed an average of 366.5 g of prey from marine entry through October of their first growing season. Growth efficiency ranged from 18.9% to 33.8% over the model simulation period. Juvenile salmon that migrated to the Gulf of Alaska grew more efficiently than those that remained in Prince William Sound until August, but after August juvenile salmon in Prince William Sound grew more efficiently than those in the Gulf of Alaska due to differences in prey quality between regions. Temperatures did not vary much between regions; thus differences in the thermal experience of juvenile pink salmon did not affect growth, consumption, and growth efficiency as much as the effects of different prey quality. Consumption demand by juvenile pink salmon exceeded the average standing stock biomass of key prey (large copepods, pteropods, hyperiid amphipods, and larvaceans) during some months. Our results are consistent with advection and production of these prey replenishing the forage base, or the reliance of individual pink salmon on high-density prey patches that occur at finer temporal scales than we were capable of sampling.

Declining wild stocks and reduced body size of pink salmon Oncorhynchus gorbuscha in Prince William Sound have led to the hypothesis that the carrying capacity of the sound, and possibly that of the Gulf of Alaska, for salmon has been reached. We compared the length, weight, and energetic content of juvenile pink salmon (1) among different stations, (2) between one hatchery group and wild pink salmon from several stations, and (3) among several hatchery release groups and wild pink salmon from two stations in the sound using analysis of variance. There were significant differences in the lengths of fish among stations but no geographic pattern. Pink salmon at two nearby stations in southwestern Prince William Sound were the smallest (71.5 mm in Whale Bay) and largest (92.4 mm in Bainbridge Passage) of the six stations sampled. There were also differences in size among the hatchery and wild groups. Wild fish were consistently larger than the most abundant hatchery group (Cannery Creek). Within cen...

Fish survival is often determined early in life and can be affected by diet and prey availability. To understand how climate changes affect food web dynamics and salmon survival, it is important to know the types of prey that salmon consume. We describe geographic and seasonal differences in the diets of juvenile pink salmon Oncorhynchus gorbuscha during 3 months of early ocean residence in Prince William Sound (PWS) and the Gulf of Alaska (GOA). Fish were sampled in PWS in July and in the GOA in July, August, and October. The diets and standard lengths of pink salmon varied significantly among stations within each sampling period. There was no discernable geographic pattern in fish length variability. Pink salmon in PWS (July) generally consumed small prey items, such as gastropods, cladocerans, small calanoid copepods, and bivalves, along with some large prey items, such as large calanoid copepods and larvaceans. In August, juvenile pink salmon sampled in the GOA consumed fewer small prey items...

Understanding the drivers of the productivity of marine ecosystems continues to be a globally important issue. A vast body of literature identifies 3 main processes that regulate the production dynamics of fisheries: biophysical, exploitative, and trophodynamic. Here, we synthe- size results from international workshops in which surplus production models were applied to 13 northern hemisphere ecosystems that support notable fisheries. The results are compared across systems, levels of species aggregation, and drivers. By applying surplus production models at sin- gle- species (SS), multi-species (MS), aggregated group, and full-system levels across ecosystems, we find that the different levels of aggregation provide distinct, but complementary, information. Further, it is clear that the triad of drivers contributes to fisheries productivity in each ecosystem, but the key drivers are system-specific. Our results also confirm that full-system yield is less than the sum of SS yields and that some MS and aggregate yields may lead to overharvest of some stocks if species groups are constructed without considering common productivity, inter-species, and en vironmental interactions. Several fundamental features emerge from this Theme Section including sigmoidal biomass accumulation curves across trophic levels, improvement of model fits by inclusion of environmental or ecological covariates, the inequality of system maximum sustain- able yield (MSY) versus aggregated sums and SS sums of MSY, a 1 to 5 t km �2 fishery yield rule of thumb, and the finding that tradeoffs among ocean use objectives may not be as harsh as origi- nally thought. These emergent features have the potential to alter our understanding of marine ecosystem dynamics and improve how we manage fisheries production.

Understanding the drivers that dictate the productivity of marine ecosystems continues to be a globally important issue. A vast literature identifies three main processes that regulate the production dynamics of such ecosystems: biophysical, exploitative and trophodynamic. Exploring the prominence among this ‘triad’ of drivers, through a synthetic analysis, is critical for understanding how marine ecosystems function and subsequently produce fisheries resources of interest to humans. To explore this topic further, an international workshop was held on 10–14 May 2010, at the National Academy of Science's Jonsson Center in Woods Hole, MA, USA. The workshop compiled the data required to develop production models at different hierarchical levels (e.g. species, guild, ecosystem) for many of the major Northern Hemisphere marine ecosystems that have supported notable fisheries. Analyses focused on comparable total system biomass production, functionally equivalent species production, or simulation studies for 11 different marine fishery ecosystems. Workshop activities also led to new analytical tools. Preliminary results suggested common patterns driving overall fisheries production in these ecosystems, but also highlighted variation in the relative importance of each among ecosystems.