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Bioenergetic responses by Pacific salmon to climate and ecosystem variation
Bulletin No, 2007
Salmon growth can respond to changes in temperature, food availability, food quality, and activity. Climatic variability can affect one or more of these factors, because different climate regimes are associated with different temporal-spatial patterns of temperature, salinity, and other oceanographic features that can alter ocean distribution patterns of salmon and cause shifts in assemblages of other organisms. Consequently, climate variability can simultaneously change the availability or productivity of exploitable prey, and the intensity of competition or predation experienced by salmon at various stages of ocean life. Variability across multiple factors can potentially confound the understanding and prediction of salmon growth or survival. Bioenergetics models can account for changing thermal and food conditions explicitly, and are valuable analytical tools for isolating and evaluating the relative contribution of different factors (e.g., temperature, feeding rate, food availability, food quality) to the consumption and growth of salmon during different life stages. Model simulations, coupled with data on growth trajectories, diet composition, and thermal experience, provide estimates of: 1) consumption rates on each prey (measures of both the importance of various prey to the energy budget of salmon, and the predation impact of salmon on prey species); 2) feeding rate as a proportion of the theoretical maximum consumption rate, a measure of relative food availability; and 3) growth efficiency, a measure of how much food was required to achieve the observed growth rate. We applied bioenergetics models to juvenile pink salmon in the Gulf of Alaska during years of low (2001) versus high (2002) ocean survival to examine feeding and growth performance between years while explicitly accounting for significant variability in stage-specific distribution, diet, growth, and consumption. From these simulations, we determined that higher feeding rates on pteropods, primarily during July-August 2002, explained the higher growth rates and larger body mass of juveniles that were associated with higher stage-specific marine survival for juveniles in 2002. Current bioenergetics models for salmonids provide valuable diagnostic and analytical tools. However, as modeling applications become more predictive and demanding, modifications and improvements will be required to address important topics like behavior, variable activity costs, seasonal and ontogenetic energy allocation, and foraging models.
Predicting climate change effects on subarctic–Arctic populations of Atlantic salmon ( Salmo salar )
Canadian Journal of Fisheries and Aquatic Sciences, 2013
We predict an increase in parr recruitment and smolt production of Atlantic salmon (Salmo salar) populations along a climate gradient from the subarctic to the Arctic in western and northern Norway in response to future climate change. Firstly, we predicted local stream temperature and discharge from downscaled data obtained from Global Climate Models. Then, we developed a spatially explicit individual-based model (IBM) parameterized for the freshwater stage, with combinations of three different postsmolt survival probabilities reflecting different marine survival regimes. The IBM was run for three locations: southern Norway (ϳ59°N), western Norway (ϳ62°N), and northern Norway (ϳ70°N). Increased temperatures under the future climate regimes resulted in faster parr growth, earlier smolting, and elevated smolt production in the western and northern locations, in turn leading to increased egg deposition and elevated recruitment into parr. In the southern location, densitydependent mortality of parr resulting from low summer wetted-areas reduced predicted future smolt production in comparison to the other locations. It can be inferred, therefore, that climate change may have both positive and negative effects on anadromous fish abundance within the subarctic-Arctic according to geographical region.
on marine growth and survival of Fraser River sockeye salmon
2015
Simulation results from the Canadian Climate Centre's atmospheric general circulation model (CCC GCM) coupled to a simplified mixed-layer ocean model predict that doubled atmospheric C8, concentrations would increase northeast Pacific Ocean sea surface temperatures and weaken existing north-south air pressure gradients. On the basis of predicted changes to air pressure and an empirical relationship between wind-driven upwelling and zooplankton biomass, we calculate that production of food for sockeye salmon (Bncorhynckus nerkca) may decrease by 5-9%. We developed empirical relationships between sea surface temperature, zooplankton biomass, adult recruitment, and terminal ocean weight for the early Stuart stock of Fraser River sockeye salmon. Our analyses show that warmer sea surface temperatures, larger adult recruitment, and lower zooplankton biomass are correlated with smaller adult sockeye. Bioenergetics modeling suggests that higher metabolic costs in warmer water coupled with lower food availability could cause the observed reductions in size. Warmer sea surface temperatures during coastal migration by juveniles were correlated with lower recruitment 2 yr later. Warmer sea surface temperatures may be a surrogate for increased levels of predation or decreased food during the juvenile stage. We speculate that Hraser sockeye will be less abundant and smaller if the climate changes as suggested by the Canadian Climate Centre's general circulation model. RCsnmC : Les resultats obtenus par des simulations faites avec le modkle de circulation atmosphkrique general du Centre climatologique canadien, et combines ?i ceux d'un modkle simplifik ?i couche ockanique mixte, nous amknent ?i prkvoir que le doublement de la concentration atmospherique du CO, conduirait A une hausse de la temperature en surface de l'eau dans le nord-est du Pacifique ainsi qu'h un affaiblissement des gradients de pression atmosphkrique nord-sud. En nous appuyant sur Ies changements prevus de la pression atmospherique et sur un rapport einpirique entre les remontees des eaux sous l'effet du vent et la biomasse zooplanctonique, nous pouvons caleuler que la production des ressources alimentaires exploitkes par le saumon rouge (Oncorhynchus nerka) pourrait &re rkduite de 5 8 9%. Nous avons dktermink des rapports empiriques entre la tempkrature en surface de l'eau, la biomasse zooplanctonique, le recrutement chez les adultes et le poids au retour de la migration en mer des sujets qui constituent le stock hitif de saumon rouge de la Stuart dans le Fraser. Nos analyses montrent que 1'Clkvation de la temperature en surface de l'eau, le recrutement plus important chez les adultes et la baisse de la biomasse zooplanctonique sont en corrklation avec une taille infkrieure des adultes du saumon rouge. Les modkles de bioenergktique paraissent montrer que le coQt metabolique accru de la vie en eaux plus chaudes, lorsqu'il est combink B une baisse des ressources alimentaires, pourrait expliquer la rCduction observee de la taille. Une hausse de la temperature en surface de l'eau pourrait avoir le m@me effet que la prkdation accrue ou qu'une
Proceedings of the National Academy of Sciences, 2014
Climate change in the last century was associated with spectacular growth of many wild Pacific salmon stocks in the North Pacific Ocean and Bering Sea, apparently through bottom-up forcing linking meteorology to ocean physics, water temperature, and plankton production. One species in particular, pink salmon, became so numerous by the 1990s that they began to dominate other species of salmon for prey resources and to exert top-down control in the open ocean ecosystem. Information from long-term monitoring of seabirds in the Aleutian Islands and Bering Sea reveals that the sphere of influence of pink salmon is much larger than previously known. Seabirds, pink salmon, other species of salmon, and by extension other higher-order predators, are tightly linked ecologically and must be included in international management and conservation policies for sustaining all species that compete for common, finite resource pools. These data further emphasize that the unique 2-y cycle in abundance of pink salmon drives interannual shifts between two alternate states of a complex marine ecosystem.
Climate impacts on Pacific salmon : bibliography
2010
The long-term outlook for salmon returns to Alaska. Alaska Fish. Res. Bull. 10(2): 83-94. With the exception of some western Alaska stocks, Alaska's salmon populations are numerically healthy. However, even fisheries on abundant stocks are suffering economically due to sharp declines in the value of the catch. The abundance of Alaskan salmon stocks has fluctuated greatly, both in modern times and prehistorically. These fluctuations are thought to be caused by multi-decadal changes in environmental conditions over large areas that affect many other species as well as salmon. Forecasts of salmon returns are not very reliable, and the potential for significant improvement in their accuracy is low in the short term. A viable fishing industry must be able to adapt to dramatic, persistent, and unanticipated changes in harvest levels. Nonetheless, Alaska's salmon stocks should continue to produce healthy harvests for the foreseeable future, barring significant damage to their habitat either via local activities or global warming. Adkison, M.D., R.M. Peterman, et al. 1996. Alternative models of climatic effects on sockeye salmon (Oncorhynchus nerka) productivity in Bristol Bay, Alaska, and the Fraser River, British Columbia. Fish. Oceanogr. 5(3/4): 137-152. We compare alternative models of sockeye salmon, Oncorhynchus nerka, productivity (returns per spawner) using more than 30 years of catch and escapement data for Bristol Bay, Alaska, and the Fraser River, British Columbia. The models examined include several alternative forms of models that incorporate climatic influences as well as models not based on climate. For most stocks, a stationary stock-recruitment relationship explains very little of the interannual variation in productivity. In Bristol Bay, productivity covaries among stocks and appears to be strongly related to fluctuations in climate. The best model for Bristol Bay sockeye involved a change in the 1970s in the parameters of the Ricker stock-recruitment curve; the stocks generally became more productive. In contrast, none of the models of Fraser River stocks that we examined explained much of the variability in their productivity. Anderson, D.M., S.A. Shankle, et al. 1993. Valuing effects of climate change and fishery enhancement on Chinook salmon. Contemporary Policy Issues 2: 82-94. This paper represents a continuing multidisciplinary analysis of species preservation and global change. It explores the economic cost of a potential regional warming's effect on the spring Chinook salmon (Oncorhynchus tshcawytscha). Climate change and planned habitat improvements impact the production and economic value of spring Chinook salmon in the Yakima River tributary of the Columbia River in eastern Washington. A Chinook salmon's total economic value includes the summation of the existence, commercial, recreational, andcapital values. The analysis here applies currently available data on these four components of value to estimated changes in Chinook salmon population resulting from regional warming. Results show that the estimated change in economic value per fish associated with reducing one fish run is significant. Anderson, J. 1998. Decadal climate cycles and declining Columbia River salmon. Sustainable Fisheries Conference Proceedings. 22 pp. (Available at http://www.cbr.washington.edu/papers/jim/victoria.pdf). This paper explores the effects of the interaction of anthropogenic trends and climate cycles on salmon declines in the Columbia and Snake river basins. A basic population model, including anthropogenic and environmental factors, is discussed and literature relating decadal scale climate patterns and the response of the North Pacific ecosystem is reviewed. From this background a ratchet-like decline in Columbia and Snake river salmon production resulted from the interactions of human activities and climatic regime shifts. These interactions are illustrated using hundred year patterns in spring Chinook salmon (Oncorhynchus tshawytscha) catch, the Columbia River hydroelectric generating capacity, and a climate index characterizing the shifts between a cool/wet regime favorable to West Coast salmon and a warm/dry regime unfavorable to West Coast salmon. A half century correlation of the climate index and Chinook catch suggest that a favorable climate regime counteracted detrimental impacts of hydrosystem development between 1945 and 1977, while an unfavorable climate regime negated beneficial effects of salmon mitigation efforts after 1977. This hypothesis is elaborated by a comparison of changes in the climate index relative to changes in Snake River salmon survival indicators.
ICES Journal of Marine Science, 2011
Hunt, G. L., Coyle, K. O., Eisner, L. B., Farley, E. V., Heintz, R. A., Mueter, F., Napp, J. M., Overland, J. E., Ressler, P. H., Salo, S., and Stabeno, P. J. 2011. Climate impacts on eastern Bering Sea foodwebs: a synthesis of new data and an assessment of the Oscillating Control Hypothesis. – ICES Journal of Marine Science, 68: 1230–1243. Walleye pollock (Theragra chalcogramma) is an important component of the eastern Bering Sea ecosystem and subject to major fisheries. The Oscillating Control Hypothesis (OCH) predicted that recruitment of pollock year classes should be greatest in years with early ice retreat and late blooms in warm water, because more energy would flow into the pelagic (vs. benthic) community. The OCH further predicted that, with pollock population growth, there should be a shift from bottom-up to top-down regulation. New data support the predictions that in those years with early ice retreat, more primary production accrues to the pelagic compartment and that l...
Canadian Journal of Fisheries and Aquatic Sciences, 2009
Recent climate changes have had marked effects on the ice-free season and thermal conditions in many highlatitude lakes, but their ecological effects combine with density-dependent processes to affect fish growth and life history. To better understand the relative roles of climate and intraspecific density, we applied Gaussian state-space models to long-term data on growth of juvenile sockeye salmon (Oncorhynchus nerka) in Iliamna Lake, Alaska, USA. Both temperature and density influenced fry size at the end of their first growing season, but the positive effect of temperature exceeded the negative effects of density. Fry growth was affected by the magnitude of their own cohort more strongly than by the previous brood (i.e., yearlings). In contrast, density was more important than temperature in Lake Aleknagik, also in Bristol Bay, over the same period of record, probably because Iliamna Lake is cooler and has generally lower densities of juvenile sockeye salmon than Lake Aleknagik. In both lakes, the size of the fish at the end of the first growing season affects smolt size and age at seaward migration, hence survival at sea and age at maturity, so the relative effects of climate and density depend on the ecological context.
Variable effects of climate and density on the juvenile ecology of two salmonids in an Alaskan lake
Canadian Journal of Fisheries and Aquatic Sciences, 2014
Despite concerns over rapidly warming temperatures, an empirical understanding of climatic impacts on wild salmonid populations is limited. We tested how temperature and density affected juvenile coho (Oncorhynchus kisutch) and sockeye salmon (Oncorhynchus nerka) using a 31 year census from an Alaskan lake. There were positive effects of temperature on overall salmon biomass, sockeye biomass, and the length of age 2 sockeye smolts. There was, however, little evidence for relationships between temperature or length of growing season and coho biomass, coho length, smolts per spawner (both species), and age structure (both species). In some cases there were temporal changes contrary to what is generally expected in a warming Alaskan lake with longer growing seasons (e.g., increasing proportions of age 2 smolts). Intraspecific density was negatively related to sockeye length at out-migration, but there was no evidence for relationships between density and other response variables. Overall, patterns observed here and in other studies emphasize that responses to climatic variation can vary substantially across locations, between similar species occupying the same habitats, and among alternative life history strategies within populations.