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We determined the dietary composition and trophic position (TP) of walleye pollock in the western East Sea (Japan Sea), based on the δ 13 C and δ 15 N values of this species, sympatric dominant fish and invertebrates, and their putative food sources in winter. A broad range of the consumer δ 13 C′ (lipid-corrected) values reflected clear distinctions between benthic and pelagic feeders, differentiating benthic vs. pelagic trophic pathways. The intermediate δ 13 C′ and δ 15 N values of pollock fell between those of benthic and pelagic feeders, indicating their trophic links through both pathways. Increases of their isotopic values with increasing body length suggest an ontogenetic change in dominant diets from pelagic to benthic prey as confirmed by stomach content analysis. Their ontogenetic pattern in resource utilization might be associated with deeper migration range with size, increasing TP during ontogeny. [ABSTRACT FROM AUTHOR]

In 2014, the Bering Sea shifted back to warmer ocean temperatures (+2 oC above average), bringing concern for the potential for a new warm stanza and broad biological and ecological cascading effects. In 2015 and 2016 dedicated surveys were executed to study the progression of ocean heating and ecosystem response. We describe ecosystem response to multiple, consecutive years of ocean warming and offer perspective on the broader impacts. Ecosystem changes observed include reduced spring phytoplankton biomass over the southeast Bering Sea shelf relative to the north, lower abundances of large-bodied crustacean zooplankton taxa, and degraded feeding and body condition of age-0 walleye pollock. This suggests poor ecosystem conditions for young pollock production and the risk of significant decline in the number of pollock available to the pollock fishery in 2–3 years. However, we also noted that high quality prey, large copepods and euphausiids, and lower temperatures in the north may have provided a refuge from poor conditions over the southern shelf, potentially buffering the impact of a sequential-year warm stanza on the Bering Sea pollock population. We offer the hypothesis that juvenile (age-0, age-1) pollock may buffer deleterious warm stanza effects by either utilizing high productivity waters associated with the strong, northerly Cold Pool, as a refuge from the warm, low production areas of the southern shelf, or by exploiting alternative prey over the southern shelf. We show that in 2015, the ocean waters influenced by spring sea ice (the Cold Pool) supported robust phytoplankton biomass (spring) comprised of centric diatom chains, a crustacean copepod community comprised of large-bodied taxa (spring, summer), and a large aggregation of midwater fishes, potentially young pollock. In this manner, the Cold Pool may have acted as a trophic refuge in that year. The few age-0 pollock occurring over the southeast shelf consumed high numbers of euphausiids which may have provided a high quality alternate prey. In 2016 a retracted Cold Pool precluded significant refuging in the north, though pollock foraging on available euphausiids over the southern shelf may have mitigated the effect of warm waters and reduced large availability of large copepods. This work presents the hypothesis that, in the short term, juvenile pollock can mitigate the drastic impacts of sustained warming. This short-term buffering, combined with recent observations (2017) of renewed sea ice presence over southeast Bering Sea shelf and a potential return to average or at least cooler ecosystem conditions, suggests that recent warm year stanza (2014–2016) effects to the pollock population and fishery may be mitigated. [ABSTRACT FROM AUTHOR]

Multi-species models can improve our understanding of the effects of fishing so that it is possible to make informed and transparent decisions regarding fishery impacts. Broad application of multi-species assessment models to support ecosystem-based fisheries management (EBFM) requires the development and testing of multi-species biological reference points (MBRPs) for use in harvest-control rules. We outline and contrast several possible MBRPs that range from those that can be readily used in current frameworks to those belonging to a broader EBFM context. We demonstrate each of the possible MBRPs using a simple two species model, motivated by walleye pollock ( Gadus chalcogrammus ) and Pacific cod ( Gadus macrocephalus ) in the eastern Bering Sea, to illustrate differences among methods. The MBRPs we outline each differ in how they approach the multiple, potentially conflicting management objectives and trade-offs of EBFM. These options for MBRPs allow multi-species models to be readily adapted for EBFM across a diversity of management mandates and approaches. [ABSTRACT FROM AUTHOR]

Age-0 juveniles may be the earliest, reliable indicators of recruitment into commercial marine fisheries, but independent fisheries assessments are usually conducted on older life stages in adult habitats. We used an 8 year juvenile gadid survey along the coast of Kodiak, Alaska to examine annual abundance, growth and mortality in age-0 Pacific cod (Gadus macrocephalus), with comparisons to saffron cod (Eleginus gracilis) and walleye pollock (Gadus chalcogrammus) where possible. Annual abundance of age-0 fish was positively correlated among all three species, suggesting Pacific gadids respond similarly to processes controlling pre-settlement survival and/or delivery to coastal nurseries. In Pacific cod, June temperature was positively correlated with size-at-settlement but post-settlement growth was density- rather than temperature-dependent. Age-0 abundance indices for Pacific and saffron cod predicted the number of age-1 fish the following year (i.e. positive "recruitment signals"), but only in the larger nursery (Anton Larsen Bay) where age-1 gadids were more likely to remain resident after their first year. Recruitment signals for Pacific cod improved with later estimates of age-0 abundance, likely because of high mortality following settlement in July. In contrast, very fewage-0 and age-1 walleye pollock were caught across the entire time-series of the survey. Collectively, these data suggest that nearshore surveys may be a tractable means of examining early life history processes and assessing year-class strength in juvenile Pacific and saffron cod, but have relatively low value in understanding the population dynamics of walleye pollock. [ABSTRACT FROM AUTHOR]

A comprehensive evaluation of the uncertainty of acoustic-trawl survey estimates is needed to appropriately include them in stock assessments. However, this evaluation is not straightforward because various data types (acoustic backscatter, length, weight, and age composition) are combined to produce estimates of abundance- and biomass-at-age. Uncertainties associated with each data type and those from functional relationships among variables need to be evaluated and combined. Uncertainty due to spatial sampling is evaluated using geostatistical conditional (co-) simulations. Multiple realizations of acoustic backscatter were produced using transformed Gaussian simulations with a Gibbs sampler to handle zeros. Multiple realizations of length frequency distributions were produced using transformed multivariate Gaussian co-simulations derived from quantiles of the empirical length distributions. Uncertainty due to errors in functional relationships was evaluated using bootstrap for the target strength-at-length and the weight-at-length relationships and for age-length keys. The contribution of each of these major sources of uncertainty was assessed for acoustic-trawl surveys of walleye pollock in the eastern Bering Sea in 2006-2010. This simulation framework allows a general computation for estimating abundance- and biomass-at-age variance-covariance matrices. Such estimates suggest that the covariance structure assumed in fitting stock assessment models differs substantially from what careful analysis of survey data actually indicate. [ABSTRACT FROM AUTHOR]

The identification of isolated populations in widely distributed marine species is often impeded by low levels of genetic differentiation. However, modern genetic approaches now allow for the efficient detection of potentially large numbers of novel genetic variations, thereby improving the power to identify biologically meaningful management units. To investigate the genetic structuring of saithe (Pollachius virens L.), we applied seascape genetic approaches to 131 single nucleotide polymorphism loci genotyped in 584 fish collected from 11 locations across the North Atlantic. Wombling analysis and the Monmonier algorithm revealed four genetic clusters (Barents Sea, Central Northeast Atlantic, Rockall, and Canada) across the species distribution range. These results imply that genetic structuring in saithe maybe influenced by abiotic factors such as geographical distance, and bathymetry as well as biotic factors such as sex-biased migration, and natal homing. The results suggest a potential mismatch between management and biological units across the Northeast Atlantic, which may have implications for sustainable exploitation of the species. [ABSTRACT FROM AUTHOR]

We examined trends in nitrogen stable isotope data as a proxy for trophic position (mean trophic level, TL) of commercial and survey catches as an ecosystem-based indicator of sustainability of four groundfish species in the Gulf of Alaska. From 2000 to 2004, walleye pollock ( Gadus chalcogrammus ), Pacific cod ( Gadus macrocephalus ), arrowtooth flounder ( Atheresthes stomias ), and Pacific halibut ( Hippoglossus stenolepis ) were collected from the waters surrounding Kodiak Island, Alaska. Several analyses of covariance (ANCOVA) models were tested to detect variations in mean TL among years with fish length as a covariate. Best-fit models were selected using the Akaiki Information Criterion to estimate trends in mean TL of commercial catch using length-frequency data from onboard fishery observers for each target species. Then, linear regression models were used to estimate mean TL of commercial catch over 1990–2009 and the mean TL of population biomass over 1984–2007 based on length-frequency data and biomass estimates from trawl surveys conducted by National Marine Fisheries Service and from historical catch data. The TL of catch for each species except walleye pollock remained stable over the time frame of the study. Walleye pollock TLs became increasingly variable after 1999. Similar trends in mean TL were observed for the survey biomass of walleye pollock. Additionally, there was an observed decrease of the occurrence of higher TL Pacific halibut over time. While the decline had no impact on overall TL estimates during 1990–2009, a continued decline may affect mean TL in the future. Overall, length seems to be the most important factor in estimating a species’ TL. Therefore, including relationships between length of catch and TL estimates could lead to an early detection of TL declines that may be associated with unsustainable fishing mortality. [ABSTRACT FROM AUTHOR]

Chinook salmon (Oncorhynchus tshawytscha) are taken as bycatch in the Bering Sea pollock (Gadus chalcogrammus) fishery, with recently revised managementmeasures in place to limit theoverall Chinook salmon catch.Historicalimpact of the bycatch onregional salmon stocks ismade difficult because, until recently, sampling for the stockcomposition of the bycatchwas patchy and diverse in approaches. In this study, extensive observer data on the biological attributes (size and age composition) of the bycatch were used to estimate the impact on specific regional stock groups (RSGs), as defined given available genetic stock identification estimates. Our model provides estimates of the impact on Chinook salmon RSGs, given seasonal and spatial variability in the bycatch, and accounts for observed in-river age compositions, uncertainty in age-specific oceanic natural mortality of Chinook salmon, and between-year variability in genetic information. The upper Yukon River stock is transboundary and subject to heightened management interest and international management agreements on escapement goals. Our study updates results from an earlier analysis used to develop the management regulations that went into place in 2011. It shows that the new data result in slight changes in previous estimates, and that the lower overall Chinook salmon bycatch since 2008 has resulted in lower impacts to the main western Alaskan RSGs. [ABSTRACT FROM AUTHOR]

The walleye pollock (Gadus chalcogrammus) fishery in the Bering Sea is one of the largest fisheries in the world. The North Pacific Fishery Management Council (NPFMC) provides management advice for this fishery, including the development of measures to minimize salmon bycatch to the extent practicable, one of the stated objectives of the US Magnuson-Stevens Fishery Conservation and Management Act National Standard Guidelines. Salmon have a unique cultural and nutritional importance in the State of Alaska and are the subject of fully allocated mixed commercial, recreational, and subsistence fisheries. Chinook salmon (Oncorhynchus tshawytscha) stocks in Alaska have been declining for the last decade, and all sources of mortality are being considered to help in rebuilding stocks. Given the extensive scientific National Marine Fisheries Service observer data collection programme, the NPFMC has developed bycatch management measures that place limits by fishery sector on the allowable catch of Chinook salmon. Part of this programme includes industry-proposed incentive programmes designed to encourage lower bycatch. Evaluating the efficacy of the new measures poses a number of challenges, particularly in light of changing ocean conditions (perhaps affecting the degree of overlap between pollock and salmon). In this study, data on pre- and post-programme implementation were evaluated to determine if the programme is meeting stated goals and objectives or if modifications are needed. These evaluations included consideration of fleet-level bycatch numbers and rates, seasonality of bycatch by sector, and individual vessel bycatch rates. Results suggest that revised management regulations appear to have resulted in reduced bycatch of salmon overall. Also, lower bycatch rates seem to reflect changing behaviour in response to new management measures. However, the extent to which the programme is effective at the vessel level remains difficult to ascertain without explicit vessel-specific benchmarks developed for evaluating programme efficacy. [ABSTRACT FROM AUTHOR]

We estimated the demands of Japan's cod and pollock markets, taking into account unknown structural changes. We used monthly wholesale price and quantity data between January 2004 and July 2013 at the Tsukiji market in Tokyo, Japan. Structural break tests detected multiple structural changes in the targeted period. A price-dependent demand model with detected structural changes successfully cleaned up the effects of the structural changes and estimated an accurate demand and elasticities. When structural changes were taken into account, the model fits improved by up to 17 points. The results indicated the one-way influence of cod on the pollock market. Also, the pollock market was sensitive to an economic recession, but household income did not affect pollock as well as cod, presumably because both goods are necessary goods for Japanese consumers. These results are helpful for policy makers in devising marketing strategies. Since fresh cod is an inelastic good, cod fisheries can reduce their cost by reducing their days at sea, which would increase the cod price due to its inelastic characteristics. As such, they can expect some profit via cost reduction and an increase in the price. [ABSTRACT FROM AUTHOR]

Many multispecies models have assumed that prey density determines per-capita predator consumption rates, following a functional response relationship. However, empirical evidence suggests that a predator's diet can also be influenced by a variety of environmental factors, including interactions with other predators. We used diet and abundance data from National Marine Fisheries Service (NMFS) bottom trawl surveys for three groundfish predators (Pacific cod ( Gadus macrocephalus), Pacific halibut ( Hippoglossus stenolepis), and sablefish ( Anoplopoma fimbria)) in the Gulf of Alaska (GOA) to determine whether temperature or other species influence the consumption of walleye pollock ( Gadus chalcogrammus). Using an information-theoretic approach, we tested for relationships between walleye pollock observed in predator stomachs and predator length, bottom temperature, prey availability (walleye pollock catch per unit effort (CPUE) scaled by observed prey lengths), and CPUE of the three predators and arrowtooth flounder ( Atheresthes stomias). Predator length was positively related to walleye pollock presence and proportion of total diet mass in all predators. Increased temperatures negatively affected consumption of walleye pollock by Pacific halibut, but not the other predators. We found evidence for a number of interpredator effects of co-occurring predators, both positive (facultative) and negative (competitive). Surprisingly, observed prey density was not statistically significant with respect to consumption for these predators, suggesting that trawls sample the environment far differently than walleye pollock predators or species interactions are more complex than those used in previous multispecies models. These factors should be considered for future models contributing to ecosystem-based management. [ABSTRACT FROM AUTHOR]

In 2003, the Alaska walleye pollock industry reported product quality issues attributed to an unspecified parasite in fish muscle. Using molecular and histological methods, we identified the parasite in Bering Sea pollock as Ichthyophonus. Infected pollock were identified throughout the study area, and prevalence was greater in adults than in juveniles. This study not only provides the first documented report of Ichthyophonus in any fish species captured in the Bering Sea, but also reveals that the parasite has been present in this region for nearly 20 years and is not a recent introduction. Sequence analysis of 18 S r DNA from Ichthyophonus in pollock revealed that consensus sequences were identical to published parasite sequences from Pacific herring and Yukon River Chinook salmon. Results from this study suggest potential for Ichthyophonus exposures from infected pollock via two trophic pathways; feeding on whole fish as prey and scavenging on industry-discharged offal. Considering the notable Ichthyophonus levels in pollock, the low host specificity of the parasite and the role of this host as a central prey item in the Bering Sea, pollock likely serve as a key Ichthyophonus reservoir for other susceptible hosts in the North Pacific. [ABSTRACT FROM AUTHOR]

An important element in the U.S. management of fisheries in the North Pacific is the existence of Community Development Quotas (CDQs) which grant community corporations the right to fish in many fisheries off the coast of Alaska. The eastern Bering Sea pollock fishery is the largest of these fisheries, with 10 % of the quota allocated to CDQs. The CDQ program evolved from a partial catch share program that existed from 1992 to 1999 within a limited-entry fishery to a full catch share program with separate spatial rights. In this paper I examine the temporal and spatial uses of CDQ rights and how these uses have changed since the implementation of catch shares throughout the fishery. I also discuss the dispersion of CDQ royalties since the program's inception and examine the prices of CDQ fishing rights from 1992 to 2005 when data on quota value were reported to the government. I compare quota prices to information about walleye pollock fishing and examine the evolving use of CDQ rights. The use of the CDQ right has changed from extending the season to enabling fishing in otherwise closed areas during the season. The number of vessels fishing with CDQ rights has declined substantially, with all pollock CDQ fishing now done by at-sea processors. [ABSTRACT FROM AUTHOR]

Climate change may affect the spatial distribution of fish populations in ways that would affect the accuracy of spatially aggregated age-structured assessment models. To evaluate such scenarios, spatially aggregated models were compared with spatially explicit models using simulations. These scenarios were based on hypothetical climate-driven distribution shifts and reductions in mean recruitment of walleye pollock ( Gadus chalcogrammus) in the eastern Bering Sea. Results indicate that biomass estimates were reasonably accurate for both types of estimation models and precision improved with the inclusion of tagging data. Bias in some aggregated model scenarios could be attributed to unaccounted-for process errors in annual fishing mortality rates and was reduced when estimating effective sample size or time-varying selectivity. Spatially explicit models that allow estimation of variability in movement and ontogenetic parameters (specified as a random walk process) were shown to be feasible, whereas models that misspecified ontogenetic movement and climate change effects resulted in biased biomass and movement parameter estimates. These results illustrate that more complex models may characterize processes better but may be less robust for management advice. [ABSTRACT FROM AUTHOR]

Hurst, T. P., Fernandez, E. R., and Mathis, J. T. 2013. Effects of ocean acidification on hatch size and larval growth of walleye pollock (Theragra chalcogramma). – ICES Journal of Marine Science, 70: 812–822.Rising atmospheric concentrations of CO2 are predicted to decrease the pH of high-latitude oceans by 0.3–0.5 units by 2100. Because of their limited capacity for ion exchange, embryos and larvae of marine fishes are predicted to be more sensitive to elevated CO2 than juveniles and adults. Eggs and larvae of walleye pollock (Theragra chalcogramma) were incubated across a broad range of CO2 levels (280–2100 µatm) to evaluate sensitivity in this critical resource species. Slightly elevated CO2 levels (∼450 µatm) resulted in earlier hatching times, but differences among egg batches were greater than those observed across CO2 treatments. Egg batches differed significantly in size-at-hatch metrics, but we observed no consistent effect of CO2 level. In three independent experiments, walleye pollock were reared at ambient and elevated CO2 levels through the early larval stage (to ∼30 days post-hatch). Across trials, there were only minor effects of CO2 level on size and growth rate, but fish in the ambient treatments tended to be slightly smaller than fish reared at elevated CO2 levels. These results suggest that growth potential of early life stages of walleye pollock is resilient with respect to the direct physiological effects of ocean acidification. [ABSTRACT FROM PUBLISHER]

This paper illustrates how climate, management, and economic drivers of a fishery interact to affect fishing. Retrospective data from the Bering Sea walleye pollock ( Theragra chalcogramma) catcher-processer fishery were used to model the impact of climate on spatial and temporal variation in catch and fishing locations and make inferences about harvester behavior in a warmer climate. Models based on Intergovernmental Panel on Climate Change scenarios predict a 40% decrease in sea ice by 2050, resulting in warmer Bering Sea temperatures. We find that differences in the value of catch result in disparate behavior between winter and summer seasons. In winter, warm temperatures and high abundances drive intensive effort early in the season to harvest earlier-maturing roe. In summer, warmer ocean temperatures were associated with lower catch rates and approximately 4% less fishing in the northern fishing grounds, contrary to expectations derived from climate-envelope-type models that suggest fisheries will follow fish poleward. Production-related spatial price differences affected the effort distribution by a similar magnitude. However, warm, low-abundance years have not been historically observed, increasing uncertainty about future fishing conditions. Overall, annual variation in ocean temperatures and economic factors has thus far been more significant than long-term climate change-related shifts in the fishery's distribution of effort. [ABSTRACT FROM AUTHOR]

Abstract: Trawls are standard tools for surveying fisheries resources, yet they are selective in what they retain, and thus provide potentially misleading information about fish populations. In order to evaluate the potential for selective retention in a midwater survey trawl used in conjunction with acoustic surveys of walleye pollock, fish behavior was examined using an integrated approach of optical, acoustic and recapture net methods. A stereo-camera system was used to provide length, position and orientation information, and a dual-frequency identification sonar was used to track fish targets in the trawl. Fish escaping the trawl were sampled using recapture, or pocket, nets mounted to the outside of the trawl. Most fish were found to be oriented along the main trawl axis, facing the forward trawl opening. Nearest distance to the trawl panel did not appear to be length-dependent, however, at night when ambient light levels were lower, fish maintained less distance to the trawl panel compared to daytime observations. Consequently, significantly more fish escapes occurred at lower light levels. Trajectories of fish escaping the trawl were highly variable compared with fish that herded into the net, or those whose retention state was unknown. Greatest escapement into pocket nets was observed from the bottom panel of the trawl at night. These findings suggest that survey trawl samples will be less biased due to selectivity when trawls are conducted during the day. [Copyright &y& Elsevier]

Abstract: Marine fish populations may exhibit a number of complexities in their reproductive dynamics, such as weight-specific relative fecundity (i.e. eggs produced per spawner weight increases with spawner size) and maternal effects (i.e. reduced larval survival with reduced spawner age), that are typically not incorporated in stock assessment models. Improved information on reproductive biology could alter estimates of stock productivity and potentially improve estimation of stock–recruitment parameters. In this study, we examined the influence of maternal effects and weight-specific relative fecundity on stock status (defined as reproductive potential and measured as eggs, larvae, or spawning stock biomass), F msy, and the statistical fit of stock–recruitment curves estimated within the Bering Sea/Aleutian Islands Pacific ocean perch (Sebastes alutus) and Gulf of Alaska walleye pollock (Theragra chalcogramma) statistical catch-at-age assessment models. In each example, estimates of recruitment strength and the variation around stock–recruitment curves were relatively insensitive to various indices of reproductive potential. However, weight-specific relative fecundity increased estimates of F msy, whereas maternal effects decreased estimates of F msy. The range of F msy estimates obtained for walleye pollock from eight indices of reproductive potential was 0.12–0.19, whereas the F msy range for Pacific ocean perch from three indices of reproductive potential was 0.079–0.084. For walleye pollock, weight-specific relative fecundity and recent increases in spawner weight-at-age resulted in an upward trend in reproductive potential relative to constant relative fecundity with spawner size. The two examples demonstrate the influence of reproductive biology upon stock productivity even in cases where residual recruitment variation is relatively unaffected, and motivate the ongoing monitoring of reproductive status and its incorporation in estimation of fishing rate reference points. [Copyright &y& Elsevier]

Pfeiffer, L., and Haynie, A. C. 2012. The effect of decreasing seasonal sea-ice cover on the winter Bering Sea pollock fishery. – ICES Journal of Marine Science, 69: .The winter fishing season for eastern Bering Sea pollock (Theragra chalcogramma) is during the period of maximum seasonal sea-ice extent, but harvesters avoid fishing in ice-covered waters. Global climate models predict a 40% reduction in winter ice cover by 2050, with potential implications for the costs incurred by vessels travelling to and around their fishing grounds and the value of their catch. Additionally, it may open entirely new areas to fishing. Using retrospective data from 1999 to 2009, a period of extensive annual climate variation, the variation in important characteristics of the fishery is analysed. When ice is present, it restricts a portion of the fishing grounds, but in general, ice-restricted areas have lower expected profits at the time of restriction than the areas left open. Some areas show a change in effort in warm years relative to cold, but the global redistribution of effort attributable to ice cover is small. This is largely because the winter fishery is driven by the pursuit of roe-bearing fish whose spawning location is stable in the southern part of the fishing grounds. [ABSTRACT FROM PUBLISHER]

Replicate acoustic surveys conducted near Kodiak Island, Alaska, USA, during summers 2001, 2004, and 2006 showed that the short-term effect of commercial fishing activities on walleye pollock ( Theragra chalcogramma) during this period was small, in most cases too small to detect. An area with commercial fishing and a nearby comparison area where commercial fishing was prohibited were surveyed before and during the fishery. Acoustic data were used to assess changes in the abundance, geographical and vertical distributions, and small-scale spatial patterns of walleye pollock, which may have occurred after the fishery commenced. A decrease in biomass after fishing began was detected only in 2004. No changes were detected in geographical or vertical distributions that could be attributed to the fishery in any year. Adults did not appear to aggregate or disperse in response to the fishery. Juvenile aggregations did differ between the prefishery and fishery surveys in 1 of the 2 years when juveniles were present. These data suggest that changes in walleye pollock abundance and distribution caused by the fishery are likely quite small compared with natural fluctuations. [ABSTRACT FROM AUTHOR]

Juvenile fish in temperate coastal oceans exhibit an annual cycle of feeding, and within this cycle, poor wintertime feeding can reduce body growth, condition, and perhaps survival, especially in food-poor areas. We examined the stomach contents of juvenile walleye pollock (Theragra chalcogramma) to explain previously observed seasonal and regional variation in juvenile body condition. Juvenile walleye pollock (1732 fish, 37-250 mm standard length) of the 2000 year class were collected from three regions in the Gulf of Alaska (Kodiak, Semidi, and Shumagin) representing an area of the continental shelf of Ca. 100,000 km2 during four seasons (August 2000 to September 2001). Mean stomach content weight (SCW, 0.72% somatic body weight) decreased with fish body length except from winter to summer 2001. Euphausiids composed 61% of SCW and were the main determinant of seasonal change in the diets of fish in the Kodiak and Semidi regions. Before and during winter, SCW and the euphausiid dietary component were highest in the Kodiak region. Bioenergetics modeling indicated a relatively high growth rate for Kodiak juveniles during winter (0.33 mm standard length/d). After winter, Shumagin juveniles had relatively high SCW and, unlike the Kodiak and Semidi juveniles, exhibited no reduction in the euphausiid dietary component. These patterns explain previous seasonal and regional differences in body condition. We hypothesize that high-quality feeding locations (and perhaps nursery areas) shift seasonally in response to the availability of euphausiids. [ABSTRACT FROM AUTHOR]

Walleye pollock (Theragra chalcogramma) is North America's most abundant and lucrative natural fishery, and is the world's largest fishery for human food. The little-known demise of the "Donut Hole" stock of pollock in the Aleutian Basin of the central Bering Sea during the 1980s is the most spectacular fishery collapse in North American history, dwarfing the famous crashes of the northern cod and Pacific sardine (Sardinops sagax). This collapse has received scant recognition and became evident only in 1993 when fishing was banned by an international moratorium; nearly 20 years later it has not recovered. The history of fishing in the North Pacific Ocean after World War II offers some insights into how the Donut Hole pollock fishery developed, and the societal and economic pressures behind it that so influenced the stock's fate. Overfishing was, without a doubt, the greatest contributor to the collapse of the Aleutian Basin pollock fishery, but a lack of knowledge about population biocomplexity added to the confusion of how to best manage the harvest. Unfortunately, the big scientific questions regarding the relationship of Donut Hole fish to other stocks are still unanswered. [ABSTRACT FROM AUTHOR]

We use a computable general equilibrium (CGE) model to investigate impacts of three exogenous shocks to Alaska fisheries: i) a 31% reduction in the walleye pollock allowable catch; ii) a 125% increase in fuel price; and iii) both shocks simultaneously. The latter scenario reflects actual industry trends between 2004 and 2008. Impacts on endogenous output, employment, factor income, and household income are assessed. We also estimate changes in a measure of household welfare and compare model results against actual change in pollock and seafood prices. Few examples of CGE studies addressing fisheries issues appear in the literature. This study is unique in that it includes more disaggregated industry sectors and examines supply-side shocks that are difficult to address using fixed-price models. This study also overcomes a serious deficiency in models that use unadjusted seafood sector data in IMPLAN (IMpact analysis for PLANning) by developing the fish harvesting and processing sectors independently from available data, supplemented by interviews with key informants to ground-truth industry cost estimates. [ABSTRACT FROM AUTHOR]

Climate variability affects marine ecosystems. The mechanisms relating low-frequency environmental fluctuations (regime shifts) and their impacts on marine populations are not well established for most species, but there is an expectation that the accuracy of scientific advice provided to fisheries management would be improved if management strategies incorporated the effects of regime shifts on stocks. Management strategy evaluation is used to examine the impact of regime shifts in average recruitment on the performance of management strategies for the fishery for walleye pollock, Theragra chalcogramma, in the Gulf of Alaska. The current and four alternative management strategies are evaluated. The alternatives include management strategies with different definitions of the average recruitment used when calculating management reference points, e.g., a 25-year sliding-window method and a “dynamic B0” method. The current management strategy, which ignores the possibility of future regime shifts, kept the spawning biomass higher relative to the target level than the other management strategies and had the lowest risk of fishing mortality exceeding the overfishing limit. The sliding-window management strategy achieved the highest catches and the lowest interannual variation in catch, although at the cost of a higher risk of the fishing mortality exceeding the overfishing limit. [ABSTRACT FROM AUTHOR]

Abstract: A pollock protein hydrolysate was used for enrichment of the live feed offered to halibut larvae from the onset of exogenous feeding and the effects of treatment on selected innate immune parameters studied. The effects of treatment on the bacterial community structure of larvae were furthermore studied using the PCR–DGGE method. C3 and lysozyme were identified in larvae already at the onset of first feeding and low concentrations of IgM detected at this stage indicate maternal origin. Endogenous production of IgM was validated in the gastrointestinal tract of larvae from 29 days post onset of first feeding, with similar concentrations found in both groups. Feeding the peptide-enriched live feed stimulated production of lysozyme and affected the distribution of C3 in larval tissue but survival and normal development of halibut larvae were not affected by the treatment. Vibrio sp. and Pseudoalteromonas sp. dominated the bacterial community of larvae from both groups and peptide enrichment of the live feed was not found to affect the bacterial community structure associated with surface sterilized larvae. [Copyright &y& Elsevier]

A’mar, Z. T., Punt, A. E., and Dorn, M. W. 2009. The evaluation of two management strategies for the Gulf of Alaska walleye pollock fishery under climate change. – ICES Journal of Marine Science, 66: 1614–1632.Management strategy evaluation (MSE) is the process of using simulation testing with feedback to examine the robustness of candidate management strategies to error and uncertainty. The structure of the management strategy can be selected to attempt to satisfy desired (but conflicting) management objectives. MSE was used to assess the performance of the current management strategy and an alternative management strategy (the “dynamic B0” strategy) for the fishery for walleye pollock (Theragra chalcogramma) in the Gulf of Alaska (GOA), when age-1 recruitment was driven by climate. The relationships between age-1 abundance and climate indices (and the uncertainties associated with these relationships) were characterized within an age-structured operating model that was fitted to the data for GOA walleye pollock. Projections into the future were based on the fitted relationships and predictions of those indices from the Intergovernmental Panel on Climate Change (IPCC) models, using the current or the alternative management strategy to determine catch limits. Management performance (the ability to leave the stock close to the management reference level and achieve high and stable catches) deteriorated when age-1 recruitment was forced by climate, although stocks were kept near the reference level on average. In addition, the ability to estimate management-related quantities, such as spawning biomass, deteriorated markedly when recruitment was forced by climate. Performance was sensitive to the choice of IPCC dataset and, in particular, estimation and management performance was poorest (outcomes most variable) for the IPCC datasets that led to the greatest variation in recruitment to the fishery. Although basing management on a “dynamic B0” management strategy led to improved management and estimation performance, the magnitude of the improvement was slight. [ABSTRACT FROM PUBLISHER]

Shen, H., Dorn, M. W., Wespestad, V., and Quinn, T. J. 2009. Schooling pattern of eastern Bering Sea walleye pollock and its effect on fishing behaviour. – ICES Journal of Marine Science, 66: 1284–1288Walleye pollock (Theragra chalcogramma) form persistent midwater and near-bottom schools in the daytime during the winter spawning season in the eastern Bering Sea (EBS). Two spawning areas in the EBS, north of Unimak Island and near the Pribilof Islands, are the main fishing grounds. To study the schooling pattern of pollock and its effect on fishing behaviour on these two fishing grounds, a principal component analysis with instrumental variables was carried out using acoustic and observer data from 2003 and 2005. Significant differences between the school descriptors distinguished the schooling patterns among areas and years. The harvester, that is to say, the fishing vessel and its crew taken together, searched for fish aggregations, which were caught in a different manner when the schooling pattern changed. School density had a greater effect than school size on fishing behaviour. Aggregations were less dense in 2003 than in 2005, and the harvester tended to fish with longer tows, at higher speeds, when it encountered less dense aggregations. [ABSTRACT FROM PUBLISHER]

The objective of this work was to evaluate the effect of adding insoluble proteins recovered from Pacific whiting surimi wash water (SWW) on the mechanical and functional properties of Alaska pollack surimi gels. Insoluble proteins from Pacific whiting SWW were added at 0 (control), 10, 30 or 50 g/kg into Alaska pollack grade FA surimi. Changes on mechanical properties, expressible water (EW ) and color attributes were evaluated in pastes and gels. Results obtained showed that texture profile analysis, puncture test and EW parameters increased significantly by increasing the amount of insoluble proteins added. Although slight changes in color attributes were detected, all surimi gels remained in the same color zone. The results obtained suggest that insoluble proteins from Pacific whiting SWW could be used to improve the mechanical properties of Alaska pollack grade FA surimi gels with a minimum effect on color. PRACTICAL APPLICATIONS Insoluble proteins recovered from surimi wash water (SWW) of Pacific whiting added at 10–50 g/kg to Alaska pollack surimi showed no adverse effects on their textural properties (hardness, fracturability, springiness and chewiness) and slight changes on color attributes. The results obtained suggest that it is feasible the use of insoluble proteins recovered from SWW of Pacific whiting in Alaska pollack surimi. Therefore, a double target is obtained: the preservation of environment and an increase in the yield of surimi processing without negative effects on texture. [ABSTRACT FROM AUTHOR]

De Robertis, A., Hjellvik, V., Williamson, N. J., and Wilson, C. D. 2008. Silent ships do not always encounter more fish: comparison of acoustic backscatter recorded by a noise-reduced and a conventional research vessel. – ICES Journal of Marine Science, 65: 623–635.The extent to which fish avoid approaching research vessels is an important source of uncertainty in fisheries surveys. Vessels radiate noise at the frequencies where fish hearing is most sensitive, and noise is thus thought to be the primary stimulus for vessel avoidance. In an effort to minimize vessel avoidance, international standards for noise emission by research vessels have been established. Although vessels meeting these criteria are now in service, the effectiveness of noise quietening on vessel avoidance remains poorly understood. The new, noise-reduced, RV “Oscar Dyson” (OD) will augment the conventionally constructed research vessel, “Miller Freeman” (MF) and serve as the primary platform in conducting acoustic surveys of walleye pollock (Theragra chalcogramma) in Alaska. To investigate whether noise-reduction measures result in differential avoidance, which would bias the pollock abundance time-series, we conducted an inter-vessel comparison of acoustic backscatter recorded by OD and MF during a survey of walleye pollock in 2006 in the eastern Bering Sea. Overall, we found no evidence for differences in vessel avoidance that would impact the echo integration results of adult pollock. Analysis of pollock depth distributions from both vessels suggests that there is a comparatively greater diving response to OD, with the reaction taking place primarily after the vessel has passed and for fish shallower than 90 m. Given that the change in vertical distribution is after the fish have been detected by the echosounder, this reaction should not influence echo-integration measurements. The results indicate that use of the OD rather than the MF is unlikely to bias the Bering Sea survey time-series through changes in vessel avoidance by adult walleye pollock. [ABSTRACT FROM PUBLISHER]

Abstract: Walleye pollock (Theragra chalcogramma) were reared from eggs to the juvenile life stage to study daily increment formation in the sagittae otoliths, which are routinely used for age and growth analyses. The apparent deposition of sub-daily growth increments becomes problematic for determining fish age from the late larval stage throughout the juvenile (young-of-the-year) development stage. Otolith marking experiments were conducted to determine interpretation criteria to differentiate between daily and sub-daily increments. Immersion of larval and transforming walleye pollock in 25mg/l of alizarin complexone (ALC) for 6h once a week produced a fluorescent mark on the day of staining. Evidence of six well defined and equally spaced increments counted between the weekly ALC marks validated the deposition of daily increments. The daily increments gradually increased in width as the fish/otolith grew. The criteria for determining the presence of sub-daily increments between the daily increments were (1) weak optical definition and (2) a sudden change in incremental distance that lasted for one or two increments and were approximately <0.5μm in width. Growth problems that occurred during the experiments were identified on otoliths as reductions in daily incremental widths and optical definition, which continued for several days. Otoliths from field-collected fish have also shown similar changes in daily increment properties during the juvenile stage, which may be an indicator of an environmental influence. The criteria for defining different increment types help to resolve our current age determination issues for late larval and early juvenile stage walleye pollock from the Gulf of Alaska. [Copyright &y& Elsevier]

The winter energy deficit and mortality of juvenile walleye pollock at extremely cold temperature were examined by field observations and laboratory experiments. In the Doto area, along the northern coast of Japan, juvenile walleye pollock resided on the continental shelf despite extremely cold temperatures (mean 0·4° C) during the latter half of winter (March to April). Measurements of the rate of energy depletion (equivalent to the routine metabolic rate) revealed that juvenile walleye pollock consumed 37% less energy at 0·5° C than at 2·0° C, suggesting an energetic benefit of residence in cold water (<1·0° C) over the shelf during winter. Prior to the starvation experiments, temperatures and ration level in the holding tanks were adjusted to create two different body condition groups of fish. Under the thermal condition of the latter half of winter (0·5° C), fish with a mean condition factor of 0·6 and 0·5 suffered 19·1 and 74·5% mortality, respectively, at the end of the experiments (after 56 days). The residual analysis of total body energy demonstrated that the cause of mortality was mainly associated with the depletion of energy reserves. When a logistic regression model for mortality derived from the experiments was applied to wild fish collected in March, the estimated overwintering mortality in 2004 and 2005 was 25·4 and <2·3%, respectively, assuming no feeding during the winter. Considering that juvenile walleye pollock feed during winter as shown in previous studies, intense overwintering mortality induced by energy depletion is improbable during the latter half of winter in the Doto area. [ABSTRACT FROM AUTHOR]

Effects of sampling errors on abundance estimates from virtual population analysis (VPA) were quantified with the bootstrap method for stock of walleye pollock in the the Sea of Japan. In the bootstrap method, individual fish measurements were resampled. A total of 1000 bootstrap samples were produced for each year from 1991 to 2001. The coefficients of variation (CV) of catch at age in 2001 ranged 6.1–33.1%. The CV of an abundance estimate in 2001 ranged 9.0–35.7%. Abundance estimates of the oldest age and the latest year, which had larger CVs than the other estimates, were sensitive to sampling errors. Effects of sampling errors became smaller when the catch at age had been accumulated over a few years. Although VPA includes various types of errors, only the sampling errors have room for improvement in reality. Quantifying the effect of sampling error on VPA estimates is essential for sound and efficient stock management, and is emphasized in this study. [ABSTRACT FROM AUTHOR]

Juvenile walleye pollock of the Japanese Pacific population were collected from the Funka Bay [spawning ground; 16–64 mm fork length (FL)] in spring and the Doto area (nursery ground; 70–146 mm FL) in summer. Hatch dates were estimated by subtracting the number of otolith daily increments from sampling dates, and their early growth was back-calculated using otolith radius–somatic length relationships. Interannual change of the hatching period was observed during 2000–02, and the peaks ranged from mid-February in 2000 to early-April in 2002. In 2000, when a strong year class occurred, early life history of the surviving juveniles could be characterized by early hatching and slower growth in the larval stage (<22 mm length). Higher growth rate in 2001 and 2002 did not always lead to good survival and recruitment success. Even though their growth was slow in 2000, the larvae hatched early in the season had larger body size on a given date than faster-growing larvae hatched in later season in 2001 and 2002. Bigger individuals at a certain moment may have advantage for survival. The delay of hatching period may result in higher size-selective mortality, and as a necessary consequence, back-calculated growth in 2001 and 2002 could shift towards higher growth rate, although abundance of such a year class would be at the lower level. Variability in spawning period, early growth and their interaction might have a strong relation to larval survival through cumulative predation pressure or ontogenetic changes in food availability. [ABSTRACT FROM AUTHOR]

Abstract: Pacific herring (Clupea pallasii) and walleye pollock (Theragra chalcogramma) are important forage species in the North Pacific Ocean, but their seasonal abundance patterns are poorly known. During three consecutive years of monthly acoustic surveys in Lynn Canal, southeastern Alaska, large schools of herring dominated during winter and were present in a 60-km long submarine gully; this gully appears to provide critical winter habitat for herring when their prey are less available and energy expenditure must be reduced. The salient change in pollock distribution is a shift from shallow waters during summer to deeper waters during winter, such that shallow (<40m) waters are nearly devoid of pollock during winter. The shift presumably occurs in response to the build-up of secondary productivity during summer and predator avoidance during winter. The seasonal changes in herring abundance drove seasonal changes in predator abundance, as Steller sea lions (Eumetopias jubatus) and humpback whales (Megaptera novaeangliae) preyed upon the winter aggregation of herring. Such seasonal links likely serve an important role in structuring trophic relationships in the North Pacific Ocean ecosystem. [Copyright &y& Elsevier]

An experiment to determine the chemical composition and protein quality of 13 fish substrates (pollock by-products, n = 5; fish protein hydrolysates, n = 5; and fish meals, n = 3) was conducted. Two of these substrates, salmon protein hydrolysate (SPH) and salmon meal with crushed bones (SMB), were used to determine their palatability as components of dog diets. Pollock by-products differed in concentrations of CP, crude fat, and total AA by 71, 79, and 71%, respectively, and GE by 4.1 kcal/g. Fish protein hydrolysates and fish meals were less variable (approximately 18, 14, and 17%, and 1.4 kcal/g, respectively). Biogenic amine concentrations were much higher in fish protein hydrolysates as compared with pollock by-products and fish meals. Pollock liver and viscera had the highest total fatty acid concentrations; however, red salmon hydrolysate and SMB had the highest total PUFA concentrations (49.63 and 48.60 mg/g, respectively). Salmon protein hydrolysate had the highest protein solubility in 0.2% KOH. Based on calculations using immobilized digestive enzyme assay values, lysine digestibility of fish meal substrates was comparable to in vivo cecectomized rooster assay values and averaged approximately 90.3%. Also, pollock milt, pollock viscera, red salmon hydrolysate, and sole hydrolysate had comparable values as assessed by immobilized digestive enzyme assay and rooster assays. A chick protein efficiency ratio (PER) assay compared SMB and SPH to a whole egg meal control and showed that SMB had high protein quality (PER = 3.5), whereas SPH had poor protein quality (PER value less than 1.5). However, using whole egg meal as the reference protein, both fish substrates were found to be good protein sources with an essential AA index of 1.0 and 0.9 for SMB and SPH, respectively. In the dog palatability experiments, a chicken-based control diet and 2 diets containing 10% of either SPH or SMB were tested. Dogs consumed more of the SPH diet compared with the control, and similar amounts of the SMB and control diets. The intake ratios for each were 0.73 and 0.52, respectively. Salmon protein hydrolysate was especially palatable to dogs. These data suggest that chemical composition and nutritional quality offish substrates differ greatly and are affected by the specific part of the fish used to prepare fish meals and fish protein hydrolysates. [ABSTRACT FROM AUTHOR]

Walleye pollock (Theragra chalcogramma) is a key species and a major commercial fishery target in the eastern Bering Sea (EBS). Recruitment of juveniles to the adult stock is largely determined by first-year survival in favourable nursery areas, and the waters around the Pribilof Islands are an important nursery area. Based on a six-year acoustic survey programme (September 1994–1999) to investigate abundance and distribution variations of age-0 pollock, we developed a set of predictive indices relating the age-0 Pribilof population to the EBS pollock stock at recruitment (age-3). EBS year-class strength at recruitment correlates with age-0 density, the spatial relationship between juveniles and euphausiids, and the degree of centricity of the age-0 distributions around the Pribilof Islands, i.e. neither too far inshore nor offshore. Seabird numbers and density ratios of predatory groundfish also influenced age-0 pollock distribution, but did not provide consistent discrimination among year classes. We hypothesize that age-0 pollock must transition from a copepod diet to a euphausiid diet by September to maximize their survival potential and to establish a strong adult cohort. [Copyright &y& Elsevier]

The current management unit for pollock on the Canadian Atlantic coast is large compared with other gadoid resources, and includes the Scotian Shelf, the Bay of Fundy, and the Canadian portion of Georges Bank. Based on an analysis of mark-recapture studies conducted in the Canadian Maritimes and off southwestern Newfoundland and a review of other published studies providing data relevant to stock identification, the stock structure of pollock in Canadian Atlantic waters was re-assessed. The analysis also includes a novel method for using the spatial distribution of standardized fishing effort to predict the distribution of tag returns. It is concluded that three stocks co-occur within the current management unit. The larger population components exist in the western Scotian Shelf (including the eastern Bay of Fundy) and on the eastern Scotian Shelf. There is a coastal population in the western Gulf of Maine that overlaps into Canadian waters, but its size is likely to be relatively small. There is a need to revise the current management unit boundaries to protect the eastern Scotian Shelf stock, which on the basis of growth rate data, appears to be the least productive component of the pollock resource in Canadian Atlantic waters. [Copyright &y& Elsevier]

Variations in trawl dimension, bottom contact, and catch with differing warp lengths during walleye pollock surveys conducted by the Fisheries Research Agency were examined. The ratio of warp length to fishing depth (scope ratio) was set at 2.5, 3.0 and 3.5 at depths of 110 m. At a 2.5 scope ratio, the net mouth shape and footgear contact fluctuated, as the trawl door did not contact the bottom. Footgear contact was complete when the scope ratio was 3.0 or more. Walleye pollock, sculpins and flatfishes were the main catch in all tows, and the catch increased with scope ratio. There was no difference in the length frequency of walleye pollock ( n = 300) captured at 2.5 and 3.0 scope ratio. However, the length frequency at 3.5 was significantly different from that of other scope ratios. These results suggest that at a scope ratio of 3.0 or more, the trawl door will not leave the bottom at any depths. To compliment echo surveys for walleye pollock, a 3.0 scope ratio would be optimal, since the catch data for a 3.5 scope ratio was dissimilar from that of scope ratios. [ABSTRACT FROM AUTHOR]

This paper investigates the relationship between sea-surface temperature (SST) and catch fluctuations in the Pacific stock of walleye pollock Theragra chalcogramma in Japan. Incorporating time lags between years of birth and harvest, the correlation coefficients between the catch and SST in two regions off the east coast of Hokkaido were calculated. The catch in year t had a high negative correlation with the SST during January–April and November–December of the years t-2 and t-3 in the spawning area. These results coincided well with the correlation observed in the northern ‘Sea of Japan’ stock. Both analyses suggested that the long-term catch fluctuations of the two stocks could be explained by the same mechanism, that is, the fluctuations would be explained by the SST in their spawning area during the spawning season using 2–3 or 3–5 years time lags, which corresponded to the dominant age of the catch within these two stocks. [ABSTRACT FROM AUTHOR]

Acoustic survey data were used to estimate the abundance and distribution of age-0 walleye pollock and zooplankton near the Pribilof Islands, Bering Sea, nursery area at two time periods in two consecutive years: the beginning of August, and mid-September, of 1996 and 1997. The 1996 pollock year class ultimately produced a large adult cohort in the eastern Bering Sea, while the 1997 year class produced a below-average adult cohort. Acoustic densities of age-0 pollock were significantly lower in August – and declined more strongly from August to September – in 1997 than in 1996, indicating that the trend to adult cohort strength was already set by August. Diet composition analyses revealed that age-0 pollock ate a much higher proportion of euphausiids in 1997 than in 1996, despite lower acoustic abundance of euphausiids in 1997. We infer that in 1996, age-0 pollock experienced greater feeding success by August, with high concentrations of copepods available for smaller fish to consume, and high concentrations of euphausiids available for larger individuals. In 1997, age-0 pollock had lower body condition in August and may have been limited by the availability of small (<2 mm) copepods. Bioenergetic modeling of prey consumption did not indicate a likelihood that age-0 pollock would begin to deplete euphausiids until late August in 1996, and not at all between August and mid-September in 1997. [ABSTRACT FROM AUTHOR]

The American Fisheries Act (AFA) of 1998 significantly altered the Bering Sea and Aleutian Islands pollock fishery by allowing the formation of harvesting and processing cooperatives and defining exclusive fishing rights. This paper uses data envelopment analysis and stochastic production frontier models to examine effects of the AFA on the fishing capacity, technical harvesting efficiency (TE), and capacity utilization (CU) of pollock catcher-processors. Results from multi-input, multi-output models indicate that fishing capacity fell by more than 30% and that harvesting TE and CU measures increased relative to past years. This work provides examples of how existing data, which is currently devoid of operator costs and provides only general indicators of earnings, may be used to analyze changes in elements of fleet and vessel performance in response to management actions. [ABSTRACT FROM AUTHOR]

In this article the authors discuss aspects of the impact of climate and ocean changes in the Bering and Barents seas on the abundance and distribution of walleye pollock (Gadus chalcogrammus) and Atlantic cod fish (G. morhua). Topics include the impact of warming ocean temperatures on the spawning stock biomass of cod in the Barents Sea and pollock in the Bering Sea, and the influence of climate forcing on trends in ocean temperature variation.

The article reviews the book "Billion-Dollar Fish: The Untold Story of Alaska Pollock" by Kevin M. Bailey.

The article focuses on a proposal to bar commercial fishing in the central Arctic Ocean. It states six of the eight Arctic nations and several other countries with major fishing industries will meet in Washington, D.C. in April 2016 to discuss the proposed ban which will last until more is learned about fish stocks in the region. It comments on the collapse of pollock fish populations in the Bering Sea in the early 1990s. It mentions plans to coordinate scientific research into Arctic fisheries.

The article examines the role of science in keeping Alaska's Bering Sea pollock fishery healthy. According to the author, the Bering Sea pollock fishery is the largest and most economically important fishery in North America. The fish is used in a variety of ways including the manufacture of fish sticks, fast-food fish fillets, and imitation crabmeat. The sustainability of the fishery is certified by the Marine Stewardship Council in London and scientists determine catch limits based on the state of the fishery which is judged through surveys and fishery models. Topics include an in-depth discussion of the 2009 data that is causing scientists concern about fish stock levels, what is being done to maintain the fishery's sustainability, and the socioeconomic effects of management decisions.

The article focuses on the decline in the king salmon harvest in Yukon River Delta in Alaska. According to Yuk'ip fisherman in the area, the decline is due to pollock boats which trawl off the Alaska's coasts which bycatches salmons. It noted that despite this problem which is being blamed to the Alaskan pollock fishery, the sector has been certified as sustainable by the Marine Stewardship Council. Measures to address the bycatch situation in the state are also cited.

A letter to the editor is presented in response to the article “Can Science Keep Alaska's Bering Sea Pollock Fishery healthy?," by V. Morell in the December 4, 2009 issue.