Climatic and economic drivers of the Bering Sea walleye pollock (Theragra chalcogramma) fishery: implications for the future

2013 ◽  
Vol 70 (6) ◽  
pp. 841-853 ◽  
Author(s):  
Alan C. Haynie ◽  
Lisa Pfeiffer
Keyword(s):  
Climate Change ◽  
Bering Sea ◽  
Climate Models ◽  
Walleye Pollock ◽  
Spatial And Temporal Variation ◽  
Theragra Chalcogramma ◽  
Climate Change Scenarios ◽  
Walleye Pollock Theragra Chalcogramma ◽  
The Impact ◽  
The Bering Sea

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.

scholarly journals Evaluating management strategies for eastern Bering Sea walleye pollock (Theragra chalcogramma) in a changing environment

2011 ◽  
Vol 68 (6) ◽  
pp. 1297-1304 ◽  
Author(s):  
James N. Ianelli ◽  
Anne B. Hollowed ◽  
Alan C. Haynie ◽  
Franz J. Mueter ◽  
Nicholas A. Bond
Keyword(s):  
Climate Change ◽  
Bering Sea ◽  
Management Strategies ◽  
Walleye Pollock ◽  
Status Quo ◽  
Theragra Chalcogramma ◽  
Recruitment Pattern ◽  
Control Rules ◽  
Eastern Bering Sea ◽  
Walleye Pollock Theragra Chalcogramma

Abstract Ianelli, J. N., Hollowed, A. B., Haynie, A. C., Mueter, F. J., and Bond, N. A. 2011. Evaluating management strategies for eastern Bering Sea walleye pollock (Theragra chalcogramma) in a changing environment. – ICES Journal of Marine Science, 68: 1297–1304. The impacts of climate change on fish and fisheries is expected to increase the demand for more accurate stock projections and harvest strategies that are robust to shifting production regimes. To address these concerns, we evaluate the performance of fishery management control rules for eastern Bering Sea walleye pollock stock under climate change. We compared the status quo policy with six alternative management strategies under two types of recruitment pattern simulations: one that follows temperature-induced trends and the other that follows a stationary recruitment pattern similar to historical observations. A subset of 82 Intergovernmental Panel on Climate Change climate models provided temperature inputs from which an additional 100 stochastic simulated recruitments were generated to obtain the same overall recruitment variability as observed for the stationary recruitment simulations. Results indicate that status quo management with static reference points and current ecosystem considerations will result in much lower average catches and an increased likelihood of fishery closures, should reduced recruitment because of warming conditions hold. Alternative reference point calculations and control rules have similar performance under stationary recruitment relative to status quo, but may offer significant gains under the changing environmental conditions.

scholarly journals Expected declines in recruitment of walleye pollock (Theragra chalcogramma) in the eastern Bering Sea under future climate change

2011 ◽  
Vol 68 (6) ◽  
pp. 1284-1296 ◽  
Author(s):  
Franz J. Mueter ◽  
Nicholas A. Bond ◽  
James N. Ianelli ◽  
Anne B. Hollowed
Keyword(s):  
Climate Change ◽  
Bering Sea ◽  
Late Summer ◽  
Walleye Pollock ◽  
Future Climate ◽  
Future Climate Change ◽  
Theragra Chalcogramma ◽  
Climate Projections ◽  
Eastern Bering Sea ◽  
Walleye Pollock Theragra Chalcogramma

Abstract Mueter, F. J., Bond, N. A., Ianelli, J. N., and Hollowed, A. B. 2011. Expected declines in recruitment of walleye pollock (Theragra chalcogramma) in the eastern Bering Sea under future climate change. – ICES Journal of Marine Science, 68: 1284–1296. A statistical model is developed to link recruitment of eastern Bering Sea walleye pollock (Theragra chalcogramma) to variability in late summer sea surface temperatures and to the biomass of major predators. The model is based on recent advances in the understanding of pollock recruitment, which suggest that warm spring conditions enhance the survival of early larvae, but high temperatures in late summer and autumn are associated with poor feeding conditions for young-of-year pollock and reduced recruitment in the following year. A statistical downscaling approach is used to generate an ensemble of late summer temperature forecasts through 2050, based on a range of IPCC climate projections. These forecasts are used to simulate future recruitment within an age-structured stock projection model that accounts for density-dependent effects (stock–recruitment relationship), the estimated effects of temperature and predation, and associated uncertainties. On average, recruitment in 2040–2050 should expectedly decline by 32–58% relative to a random recruitment scenario, depending on assumptions about the temperature relationship, the magnitude of density-dependence, and future changes in predator biomass. The approach illustrated here can be used to evaluate the performance of different management strategies and provide long-term strategic advice to managers confronted with a rapidly changing climate.

Relating trends in walleye pollock (Theragra chalcogramma) abundance in the Bering Sea to environmental factors

1995 ◽  
Vol 52 (2) ◽  
pp. 369-380 ◽  
Author(s):  
Gordon Swartzman ◽  
Emily Silverman ◽  
Neal Williamson
Keyword(s):  
Water Column ◽  
Bering Sea ◽  
Walleye Pollock ◽  
Additive Models ◽  
Theragra Chalcogramma ◽  
Thermocline Depth ◽  
Depth Range ◽  
Walleye Pollock Theragra Chalcogramma ◽  
Shelf Slope ◽  
The Bering Sea

Generalized additive models (GAM), a nonparametric regression method with less restrictive statistical assumptions than traditional regression methods, were used to model the trend in mean abundance of Bering Sea walleye pollock (Theragra chalcogramma) as a function of ocean environmental conditions including water column depth, temperature at 50 m, and depth of the thermocline. Acoustic survey data collected in the summers of 1988 and 1991 were used to test these relationships. In both surveys, mean walleye pollock abundance was highest in areas having a 70–130 m depth range and where the 50-m temperature was close to 2.5 °C. Thermocline depth, while not itself significant, had a significant effect on walleye pollock abundance through interactions with both bottom depth and temperature at 50 m. Walleye pollock in the top 50 m of the water column (mostly juveniles) were influenced differently by temperature and thermocline depth than the adult walleye pollock, which were generally deeper in the water column. The depth, temperature, and thermocline preferences of walleye pollock are hypothesized to be linked to food availability which is, in turn, related to temperature regimes or fronts along the Bering Sea shelf slope.

Mitochondrial DNA Analysis of Walleye Pollock, Theragra chalcogramma, from the Eastern Bering Sea and Shelikof Strait, Gulf of Alaska

1992 ◽  
Vol 49 (2) ◽  
pp. 319-326 ◽  
Author(s):  
Timothy J. Mulligan ◽  
Robert W. Chapman ◽  
Bonnie L. Brown
Keyword(s):  
Mitochondrial Dna ◽  
Bering Sea ◽  
Dna Analysis ◽  
Gulf Of Alaska ◽  
Fishing Effort ◽  
Walleye Pollock ◽  
Theragra Chalcogramma ◽  
Eastern Bering Sea ◽  
Walleye Pollock Theragra Chalcogramma ◽  
The Bering Sea

Increased fishing effort in the international waters of the Aleutian Basin has focused much interest on defining the stock structure of walleye pollock, Theragra chalcogramma, in the Bering Sea. Variation in mitochondrial DNA (mtDNA) was examined via restriction endonuclease digestions in 168 walleye pollock from three areas in the eastern Bering Sea and from Shelikof Strait, Gulf of Alaska. Nine endonucleases produced variant restriction patterns both within and among populations. A total of 50 restriction sites were revealed along the mtDNA molecule. Two dominant genotypes were found in 39 and 21 individuals, respectively. Fifty-one genotypes (78% of the total) were represented by a single specimen. Clustering of genetic distances suggests the existence of several walleye pollock stocks in the Bering Sea and Gulf of Alaska. Genetic divergence among stocks may be related to the prevailing current patterns found in these areas.

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