Factors Affecting Winter Survival of Chinook Salmon in the Bering Sea
The goal of this project, which is funded by the North Pacific Research Board, is to identify physical and physiological factors that affect winter survival of Chinook salmon (Oncorhynchus tshawytscha) in the Bering Sea. Low returns of Chinook salmon to western Alaska and bycatch in trawl fisheries have led to management restrictions on commercial and subsistence fishing. The decline in run sizes is larger than the reported bycatch. Other factors have likely contributed to the decline. Beamish and Mahnken (2001) hypothesized that overwinter survival of juvenile salmon is related to summer growth and severity of winter, as fish rely on stored lipids during periods of low prey quantity or quality (the critical size/critical period hypothesis). Mortality after the first winter at sea can be from 20% to 95% (Farley at al. 2007). Winter conditions in the Bering Sea are severe. Most salmon species leave the Bering Sea in winter, migrating southward to the North Pacific Ocean. Western Alaska Chinook salmon are a well-known exception, and some northern populations spend their entire ocean life in the Bering Sea. Northern populations of Chinook salmon (e.g., Yukon River) are also renowned for their high fat (lipid) content, making them a potentially valuable food resource for marine mammals, birds, fish, and humans in the Bering Sea ecosystem. High lipid storage may enhance the ability of Chinook salmon to survive prolonged periods of poor ocean conditions. Interannual variation in salmon survival is associated with the synoptic type of winter (cold or warm). We hypothesize that survival of Chinook salmon in the Bering Sea is linked to their energetics (food, metabolism, growth) in winter, their diets and growth during peak summer feeding periods, and their nutritional (lipid) status in fall. Our specific objectives are to compare seasonal trophic, nutritional, and energetic status of Chinook salmon in the Bering Sea, and to use models to explore potential effects of seasonal and interannual environmental change on Chinook salmon energetics. The use of NPRB funds for this project will contribute to long-term research needs identified by the United States in a plan developed in 2009 by the North Pacific Anadromous Fish Commission and supported in part by NPRB.
This research extends a previous study of Bering Sea Chinook and climate effects (Myers et al. 2010). In this project, we are examining the condition of young fish as they overwinter as an indication of mortality risk. We present preliminary results from our first fall (2010) field sampling of Chinook salmon bycatch from southeastern Bering Sea trawl fisheries.
Study Area – Fall 2010
Pre-winter sampling was conducted at an onshore processing plant in the eastern Aleutian Islands in September 2010.
Fish processing plant in the Aleutian Islands (photo by R.V. Walker)
Data and samples were collected from smaller, more smaller, more vulnerable fish (ocean age .0 and .1, primarily under 45 cm) and from larger fish (primarily ocean age .2) for reference. Younger fish are less common in the bycatch.
Young (39 cm fork length) Bering Sea Chinook salmon
Bering Sea Chinook salmon: fork lengths 37, 51, and 58 cm
In addition to basic biological data, scales, stomach contents, dorsal muscle for isotope analysis, and whole body homogenate for calorimetric and lipid analyses were collected. Sampling and methods of obtaining homogenates follow methods of Fournier (2011).
Salmon sampling, fatmeter is at lower left
Lipids were measured with a lipid (fat) meter which estimates water content of the fish based on the attenuation of microwave signals (lipid is estimated from an inverse relationship with water content). Fatmeter measurements are a rapid method of obtaining lipid content (Crossin and Hinch 2005, Kaga et al. 2009). Whole fish homogenates were dried, and moisture content was determined.
Lipid and moisture content
Figure 1. Relationship between fatmeter lipid measures and body weight
Figure 2. Relationship between % water in whole body homogenate and
We reported sampling for the first six months of a two-year study. Our schedule is:
The support provided by the North Pacific Research Board, Project 1009, is gratefully acknowledged.
We thank Jerry Berger, Martin Loefflad, Paul Wilkins, and groundfish observers of the Fisheries Monitoring and Analysis Division of the Alaska Fisheries Science Center (AFSC), NOAA Fisheries, for assistance in arranging sampling. A special thanks to Dave Abbasian, Tai Cho, and many others at Trident Seafoods Akutan plant for a rewarding and informative sampling experience. We express our appreciation to Wyatt Fournier, University of Washington for advice and his earlier work.
Beamish, R.J., and C. Mahnken. 2001. A critical size and period hypothesis to explain natural regulation of salmon abundance and the linkage to climate and climate change. Prog. Oceanogr. 49: 423-437.
Crossin, G.T., and S.G. Hinch. 2005. A non lethal, rapid method for assessing the somatic energy content of migrating adult Pacific Salmon. Trans. Amer. Fish. Soc. 134:184-191.
Farley, E.V., J.H. Moss, and R.J. Beamish. 2007. A review of the critical size, critical period hypothesis for juvenile Pacific salmon. N. Pac. Anadr. Fish Comm. Bull. 4: 311–317. (Available at http://www.npafc.org)
Fournier, W. 2011. Seasonal and Interannual Variation in Food Habits and Growth of Chinook Salmon (Oncorhynchus tshawytscha) in the Bering Sea. Master of Science. University of Washington. 57 p.
Kaga, T., S. Sato, T. Nagasawa, M. Fukuwaka, T. Nomura, S. Urawa. 2009. Rapid estimation of lipid content of immature chum and pink salmon in the ocean with a hand held microwave meter. NPAFC Doc. 1208. 8 pp. (Available at http://www.npafc.org)
Myers, K.W., R.V. Walker, N.D. Davis, J.A. Armstrong, W.J. Fournier, N. J. Mantua, and J. Raymond-Yakoubian. 2010. Climate-ocean effects on Chinook salmon. Arctic Yukon Kuskokwim Sustainable Salmon Initiative, Project Final Product. SAFS-UW-1003, School of Aquatic and Fishery Sciences, University of Washington, Seattle. 249 p. (available at https://digital.lib.washington.edu/researchworks/handle/1773/16308)
Other Recent Research Topics
The current goal of our international cooperative high seas salmon research is to advance scientific understanding of the effects of climate and ocean conditions on marine survival of Pacific salmon and steelhead. In 2005, we participated in the development of a new 5-year (2006-2010) NPAFC Science Plan. Two overarching hypotheses emerged from the results of scientific research under previous NPAFC science plans, as well as from research by other organizations and independent scientists: (1) salmon play an important role in North Pacific marine ecosystems, and (2) there is a close relation between climate and climate change and subsequent changes in marine productivity and survival of salmon in the ocean.
Two broad scientific questions relevant to the program goals of NPAFC were identified:
Over the past decade, significant annual variation in the marine production of Asian and North American salmon appears to be linked to climate change. There is a strong need for new international cooperative research that provides better scientific information on the status and trends in marine production of salmon, identifies the roles of salmon in North Pacific marine ecosystems, and examines the extent to which salmon, since they return to coastal regions, can be used as indicators of conditions in North Pacific marine ecosystems.
Variation in the time, frequency, and amplitude of climate events that affect the ocean production of marine fish seems to be increasing. This has led many experts to conclude that precision monitoring of abundance and biomass in the ocean may be the only reliable method for predicting changes in production of salmon. That each species of salmon follows a life history strategy in the ocean is probable. Cooperative research that identifies the common mechanisms will improve regional forecasting. In addition, the conceptual framework for the management of fish populations has expanded from relatively simple assessments of abundance and productivity to broader needs for information on population structure (spatial and temporal) and diversity.
International Cooperative research under the 2006-2010 NPAFC Science Plan is focused on one research theme:
Status and Trends of Production of Anadromous Stocks in Ocean Ecosystems
The influence of regional and local environmental stressors on the status of different salmon species and stocks at initial and subsequent life history stages is varied. These stressors may affect the quantity and biomass of juvenile salmon migrating to the sea, immature and maturing salmon migrating in the open ocean, and adult salmon returning to coastal and freshwater fisheries. Obtaining reliable abundance estimates is essential to understanding survival at each marine life history stage. For sustainable conservation of salmon, better scientific information is needed on the effects of climate and climate change on salmon, ecologically related species, and their North Pacific marine ecosystems.
Cooperative research activities will attempt to clarify the present status and trends in production of salmon, to determine important stressors and stressor regimes that affect population structure and diversity, to evaluate subsequent effects of these mechanisms on the viability and performance of salmon at critical marine life-history stages, and to evaluate effects of climate and climate changes on marine production of salmon.
Cooperative high-seas salmon research under the broad theme of “Status and Trends of Production of Anadromous Stocks in Ocean Ecosystems” is focused on three components:
In at least some species of anadromous stocks (e.g. pink and chum salmon), variation in adult returns may depend more on marine survival than on reproductive efficiency during the freshwater period. A common hypothesis is that the initial period of after migration to sea is the most critical phase with respect to ocean survival of salmon. Recent cooperative and national research on juvenile salmon suggests considerable interannual variation in abundance, growth, and survival rates of juvenile salmon in the ocean. These variations may be related to climate-induced changes in habitat environments that operate at regional and local scales. To a greater or lesser extent, these processes are monitored annually in marine survey areas along the coasts of Asia and North America. A better understanding of these processes is needed for sustainable conservation and management of salmon.
The centerpiece of NPAFC’s coordinated program of marine ecosystem research to date is the Bering-Aleutian Salmon International Survey (BASIS). In 2001-2002, we assisted in the development and implementation of BASIS. Under the 2001-2005 Science Plan, BASIS research progressed and evolved to more complex research issues, and has become an integral part of ecosystem research planned by other international, national, and regional conservation, management, and research organizations, e.g., the North Pacific Marine Sciences Organization (PICES), the U.S. National Marine Fisheries Service (Alaska Fisheries Science Center, Auke Bay Laboratories, which redefined "BASIS" as "Bering Arctic Subarctic Integrated Surveys"), and the Arctic-Yukon-Kuskokwim Sustainable Salmon Initiative).
In the face of global climate change, the Bering Sea may become the most important marine ecosystem for production of Asian and North American salmon. The results of cooperative BASIS ecosystem monitoring research in 2002-2004 indicated a very high density of Asian and North American salmon in the Bering Sea from summer to late fall. BASIS process studies have demonstrated the important influences that various physical and biological stressors and stressor regimes may have on production of anadromous stocks and ecologically related species in the Bering Sea ecosystem. While this recent research confirms the high productivity of the Bering Sea, carrying capacity, growth, and production of salmon has shown a high degree of variation. These results confirm the necessity of continuing cooperative research in the Bering Sea to clarify the mechanisms of biological response of salmon to climate and climate change.
Salmon play a very important role in the Western Subarctic Gyre and Gulf of Alaska ecosystems. Immature and maturing salmon originating from Asia and North America intermingle in both of these ecosystems. Recent research vessel surveys by Canada, Japan, Russia, and the USA have collected a considerable amount of new data on anadromous stocks, ecologically related species, and environmental conditions in the Western Subarctic Gyre and Gulf of Alaska ecosystems. In particular, three species pink, chum, and sockeye salmon occur in high abundance in Western Subarctic Gyre and Gulf of Alaska ecosystems during all seasons. Salmon consume a substantial quantity and biomass of prey organisms in these ecosystems, and play an important role as a higher trophic level predator. Changes marine tropic relations in these ecosystems influence the productivity of salmon populations returning to different reproduction regions in Asia and North America.
Both ecosystems provide the major wintering habitats for various salmon stocks. While previous research has identified this as a critical period that defines the biological characteristics and biomass of salmon, open ocean field research and monitoring programs have typically been carried out only during the late spring to early fall period. Better information on the status and trends in production and condition of Pacific salmon during the late fall to early spring period is needed for sustainable conservation and management of salmon resources.
Knowledge of variation in the characteristics of marine production in the Western Subarctic Gyre and Gulf of Alaska ecosystems is needed for sustainable conservation of Pacific salmon and steelhead resources in Asia and North America. In addition, more accurate forecasts of adult salmon returns will benefit salmon industries around the Pacific Rim.
U.S. GLOBEC (GLOBal ocean ECosystems dynamics) is a research program organized by oceanographers and fisheries scientists to address the question of how global climate change may affect the abundance and production of animals in the sea.
Our current U.S. GLOBEC research (Principal Investigators: D. Beauchamp, K. Myers) is part of the Northeast Pacific (NEP) program. The goal of this program is to understand the effects of climate variability and climate change on the distribution, abundance and production of marine animals (including commercially important living marine resources) in the eastern North Pacific. To embody this understanding in diagnostic and prognostic ecosystem models, capable of capturing the ecosystem response to major climatic fluctuations. The NEP research is focused on two oceanic regions: the California Current System and the Coastal Gulf of Alaska (CGOA).
Our research addresses Goal #4 of the GLOBEC CGOA Program: “to determine the extent to which high and variable mortality of juvenile pink salmon in the coastal region of the Northern Gulf of Alaska is responsible for large interannual variation in adult salmon populations.” We are exploring Core Hypothesis #3 in the GLOBEC NEP Implementation Plan: “ocean survival of salmon is primarily determined by survival of the juveniles in coastal regions, and is affected by interannual and interdecadal changes in physical forcing and by changes in ecosystem food web dynamics” (U.S. GLOBEC 1996).
U.S.-GLOBEC NEP III-b CGOA: Modeling the Effects of Spatial-Temporal Environmental
Inter-annual differences in stage-specific survival and growth of pink salmon will be examined in relation to monthly differences in spatial distribution and spatial-temporal patterns in environmental conditions, food availability, diet, size, and growth. Physical and biological data will be combined in bioenergetics models to estimate consumption and growth efficiency of juvenile pink salmon among regions, months and years, and bioenergetic growth potential will be mapped among sampling sites, water masses and regions through time to mechanistically examine the growth and survival consequences of different spatial-temporal distribution patterns and how interannual differences in the biophysical environment contribute to differences in survival and production of pink salmon in CGOA.
Armstrong, J.L., K.W. Myers, N.D. Davis, R.V. Walker, D.A. Beauchamp, J.L. Boldt, J. Piccolo and L.J. Haldorson. 2008. Interannual and Spatial Feeding Patterns of juvenile pink salmon in the Gulf of Alaska in years of low and high survival. Transactions of the American Fisheries Society 137:1299-1316.
Armstrong, J.L., J.L. Boldt, A.D. Cross, J.H. Moss, N.D. Davis, K.W. Myers, R.V. Walker, D.A. Beauchamp and L.J. Haldorson. 2005. Distribution, Size and Interannual, Seasonal and Diel Food Habits of the Northern Gulf of Alaska Juvenile Pink Salmon, Oncorhynchus gorbuscha. Deep-Sea Research II 52(1-2):247-265. (US GLOBEC Contribution 421).
Beauchamp, D.A., A.D. Cross, J. Armstrong, K.W. Myers, J.H. Moss, J.L. Boldt, and L.J. Haldorson. 2007. Bioenergetic Responses by Pacific Salmon to Climate and Ecosystem Variation. North Pacific Anadromous Fish Commission Bulletin 4:257-268.
Cross, AD, DA Beauchamp, JH Moss, KW Myers. 2009. Interannual variability in early marine growth, size-selective mortality, and marine survival for Prince William Sound pink salmon. Marine and Coastal Fisheries: Dynamics, Management and Ecosystem Science 1:57-70.
Cross, A.D., D.A. Beauchamp, K.W. Myers, and J.H. Moss. 2008. Early Marine growth of pink salmon in Prince William Sound and the coastal Gulf of Alaska during years of low and high survival. Trans. Am. Fish. Soc. 137:927-939.
Cross, A.D., D.A. Beauchamp, J.L. Armstrong, M. Blikshteyn, J.L. Boldt, N.D. Davis, L.J. Haldorson, J.H. Moss, K.W. Myers and R.V. Walker. 2005. Consumption demand of juvenile pink salmon in Prince William Sound and the coastal Gulf of Alaska in relation to prey biomass. Deep Sea Res. II 52(1-2):347-370. (US GLOBEC Contribution no. 475).
Moss, J.H., D.A. Beauchamp, A.D. Cross, E.V. Farley, J.M. Murphy, J.H. Helle, R.V. Walker, and K.W. Myers. 2009. Bioenergetic model estimates of interannual and spatial patterns in consumption demand and growth potential of juvenile pink salmon (Oncorhynchus gorbuscha) in the Gulf of Alaska. Deep-Sea Research II:2553-2559.
Moss, J. H., D. A. Beauchamp, A. D. Cross, K. W. Myers, E. V. Farley, Jr., J.M. Murphy, and J.H. Helle. 2005. Evidence that faster growth is associated with higher marine survival for pink salmon (Onchorhynchus gorbuscha). Transactions of the American Fisheries Society 134:1313-1322. (U.S. GLOBEC Contribution no. 252).
Project Summary: Climate-Oean Effects on Chinook Salmon
A high priority issue of the AYK SSI is to determine whether the ocean environment is a more important cause of variation in the abundance of salmon populations than marine fishing. New analyses and syntheses of historical data, as well as the collection and analysis of new field and laboratory data, are needed to address this issue. The goal of this project is to identify and evaluate life history patterns of use of marine resources (habitat and food) by Chinook salmon, and to explore how these patterns are affected by climate-ocean conditions in the Bering Sea and North Pacific Ocean. Specific objectives include: (1) develop a comprehensive high seas Chinook salmon database (1955-present) for AYK SSI, (2) map ocean distribution and migration routes of Chinook Salmon, (3) reconstruct histories of ocean age, growth, and size-selective mortality of Chinook salmon, (4) map climate and oceanographic conditions in regions where AYK salmon migrate, (5) collect new seasonal (summer, winter) food habits data, and evaluate variation in marine diets of Chinook salmon, (6) estimate consumption and growth efficiencies modeled under different climate scenarios; (7) map spatial and temporal variability in ocean growth potential; (8) simulate climate effects on age and growth, and (9) synthesize information on the ocean life history and climate-ocean effects on Chinook salmon. Results will benefit salmon, salmon fishers, and salmon fisheries of the AYK region by providing products and information that can be used to improve fishery management. The project, led by the High Seas Salmon Research Program, University of Washington, includes an international team of cooperating investigators. Methods include retrospective, graphical, and statistical analyses of existing data, fieldwork aboard Japanese research vessels in summer, labwork (diet, scale age and growth), computer mapping and spatial analyses, computer simulations of climate-ocean effects, local capacity building, and public outreach.
Relevant Peer-Reviewed Publications
Bugaev, A.V., and K.W. Myers. 2009. Stock-specific distribution and abundance of immature Chinook salmon in the western Bering Sea in summer and fall 2002-2004. N. Pac. Anadr. Fish Comm. Bull. 5:87-97 (Available at http://www.npafc.org).
Davis, N.D., K.W. Myers, and W.J. Fournier. 2009. Winter food habits of Chinook salmon in the eastern Bering Sea. N. Pac. Anadr. Fish Comm. Bull. 5. (Available at http://www.npafc.org).
Davis, N.D., A.V. Volkov, A. Ya. Efimkin, N.A. Kuznetsova, J.L. Armstrong, and O. Sakai. 2009. Review of BASIS salmon food habits studies. N. Pac. Anadr. Fish Comm. Bull. 5. (Available at http://www.npafc.org)..
Myers, K.W., R.V. Walker, N.D. Davis, J.L. Armstrong, and M. Kaeriyama. 2009. High seas distribution, biology, and ecology of Arctic-Yukon-Kuskokwim salmon: direct information from high seas tagging experiments, 1954-2006. Pages 201-239 in Pacific salmon: ecology and management of western Alaska’s populations. Edited by C.C. Krueger and C.E. Zimmerman. Am. Fish. Soc. Symp. 70, Bethesda, MD.
Walker, R.V., and K.W. Myers. 2009. Behavior of Yukon River Chinook salmon
Project Summary: Climate-change effects on steelhead in North Pacific marine ecosystems
The overarching goal of the proposed research is to increase scientific understanding of the biophysical mechanisms that affect survival of steelhead (Oncorhynchus mykiss) in North Pacific marine ecosystems. Dramatic fluctuations in the abundance of adult steelhead returning to rivers in the Pacific Northwest in 2000-2006 appear to be linked to climate effects on their ocean survival. We hypothesize that climate induced changes in ocean environmental conditions and food webs in offshore waters of the North Pacific Ocean are affecting ocean growth and survival of Pacific Northwest steelhead. Our proposal addresses National Sea Grant priorities for understanding ocean ecosystems, habitats, and the effects of natural and human-induced climate change, as well as regional priorities for conserving living marine resources and ensuring sustainable fisheries and healthy populations.
Over the past 55 years, the High Seas Salmon Research Program has accumulated a large number of sets of data. Our data come from US salmon tagging and research cruises in the North Pacific Ocean and Bering Sea, cooperative tagging and research cruises with Canadian, Japanese, and Russian fishery agencies, measurements of salmon scales for stock identification and growth studies, examination of salmon stomach contents carried out aboard Japanese research vessels, and salmon research cruises of the former Bureau of Commercial Fisheries, predecessor to the US National Marine Fisheries Service. We also update and maintain salmon and steelhead tag release and recovery databases from high seas tagging experiments. We hope to provide some of our data sets through this page in the future.
NPAFC High Seas Tagging Database
A Canadian scientist created the original International North Pacific Fisheries Commission (INPFC) high seas salmon tag recovery database, and these data, containing recoveries reported in INPFC documents through 1979, were provided to the University of Washington (UW) in 1980. A UW scientist created the original INPFC tag release database. Under previous funding from NOAA, the High Seas Salmon Research Program added tag release and recovery data reported in INPFC documents through 1992 and in NPAFC documents from 1993 through 2005. The Fisheries Agency of Japan assisted us in corrections to the 1956-1985 INPFC tag recovery database. Currently, NOAA Fisheries (Auke Bay Laboratory, Juneau) has assumed the task of reporting tag returns to NPAFC. We continue to use data reported to NPAFC to correct and update our historical high seas salmon and steelhead tag databases.
High Seas Coded-wire Tag Database
In 1980 a US scientist aboard a Japanese research vessel noted steelhead with missing adipose fins in the catch. Coded-wire tags (CWTs) were recovered from the snouts of these fish, and the Auke Bay Laboratory (ABL) became responsible for analyzing snout samples potentially carrying CWTs from salmonids caught by high seas research vessels or in the U.S. groundfish fishery. ABL also maintained a database of these tag recoveries and reported them to INPFC and later to NPAFC. From 1998-2005 the SAFS’s High Seas Salmon Research Program was contracted by ABL to maintain and update the database, and report new high seas recoveries of CWT salmon to NPAFC. Currently, ABL has resumed this activity, and periodically transmits new high seas CWT recovery data to the Pacific States Marine Fisheries Commission for inclusion in their online database (http://www.rmpc.org). The High Seas Salmon Research Program continues to use information reported to NPAFC and RMIS to correct and update our historical high seas salmon and steelhead CWT databases.
High Seas Scale Collections
Historical collections of scales and acetate impressions of scales that are archived in our laboratory at the School of Aquatic and Fishery Sciences (SAFS), University of Washington, include samples from US, Canadian, and Japanese INPFC-related high seas research and observer programs (1955-1992), from cooperative US-USSR high seas salmon research (1983-1991), from recent cooperative NPAFC-related research (1992-present), and from various NMFS observer programs (1976-present). SAFS's high seas scale collections from historical tagging studies comprise over 240,000 scales from 1956 to 1991. The SAFS is also the repository of scales collected during high seas salmon research by the former Bureau of Commercial Fisheries (BCF, now NMFS) from 1955 to 1973, and from various NMFS observer programs (Japanese mothership and squid driftnet fisheries, and some salmon bycatch samples from Bering Sea and Gulf of Alaska groundfish fisheries). The SAFS also has an extensive collection of acetate impressions of scales and biological data from Canadian high seas salmon research in the Gulf of Alaska (1962-1969), and from Oshoro maru (1980-present) and Wakatake maru (1991-present) cruises in the central North Pacific, Bering Sea, and Gulf of Alaska. These historical collections and associated databases are useful for retrospective analyses of age, growth, and stock composition of salmon in the North Pacific Ocean and Bering Sea. Currently, we are developing a plan to integrate our historical high seas scale collections with the University of Washington Fish Collection.