Bering Sea | Fishes and Fish Habitats
Investigating the influence of temperature, environment, and fishing on length-at-age of Bering Sea walleye pollock Presenter: Krista Oke , kristaoke@gmail.com, NOAA Franz Mueter , fmueter@alaska.edu, UAF Mike Litzow , mike.litzow@noaa.gov, Alaska Fisheries Science Center, NOAA Fisheries Peter Westley , pwestley@alaska.edu, UAF Declines in average body size are widely reported in many harvested species, which can have important and negative ecological and socio-economic consequences. However, it is difficult to unpackage two potential interacting drivers of reduced body size: the metabolic effects of warming climate and size-selective harvest. A recent study of Southeast Bering Sea walleye pollock ( Gadus chalcogrammus ) documented age-specific impacts of temperature on body size, with warming resulting in larger juveniles but small adult body size. In the current study, we quantify the impacts of environmental factors on pollock length-at-age, with a goal of partitioning the influence of climate, ecology, and fishing in shaping pollock body size. Building on general additive mixed models developed for the study on the impacts of temperature, we account for spatial and temporal trends in length-at-age while evaluating the relative effects of temperature, fishing, and several ecosystem indicators. Our results suggest that the factors that affect length-at-age vary among ages, with density dependence, prey availability, fishing rate, and temperature all impacting length at certain ages. The previously documented effect of temperature could not be explained by any of the covariates included in the current model. By considering fishing rates on both the current and parent generation, we detect evidence for both an effect of fishing removals and potentially an evolutionary impact on length-at-age, but the specifics vary by age class. Pollock provide a rare, data-rich opportunity to study factors that influence body size in a relatively young fishery, and these results suggest that both temperature and fishing influence adult body sizes.
Alaska Marine Science Symposium 2023 216
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