Bering Sea | Fishes and Fish Habitats
More than meets the eye: isotopic analysis of eye lens layers in adult Bering Sea walleye pollock show differences in regional fidelity and trophic behavior Presenter: Todd Miller , todd.miller@noaa.gov, Ted Stevens Marine Research Institute (TSMRI), NOAA Alaska Fisheries Science Center Wil Licht , wil.licht@noaa.gov, Ted Stevens Marine Research Institute (TSMRI), Azura Consulting, Azura Consulting Calvin Mordy , calvin.w.mordy@noaa.gov, CICOES, University of Washington, Seattle, WA, United States Mariela Brooks , mariela.brooks@noaa.gov, Ted Stevens Marine Research Institute (TSMRI), NOAA Alaska Fisheries Science Center Matthew Rogers , matthew.rogers@noaa.gov, NOAA Fisheries Recent warming of the Bering Sea has allowed for the expansion of southern boreal species of fish into the benthopelagic waters of the northern Bering Sea. This shift in boreal species has the potential to drastically alter the subarctic-Arctic shallow water food web and energy flow. Walleye pollock (pollock, Gadus chalcogrammus ) are a species of notable concern given their ecological significance as predators and prey, and commercial importance as one of the largest fisheries in the world.. Here, we applied stable isotope analysis of eye lense layers in adult pollock to assess isotopic values that are indicative of movement and trophic level feeding over the life of a fish. We compared pollock collected from the northeastern (NBS) and southeastern (SEBS) Bering Sea, to test for differences in regional fidelity and relative trophic position. Our results showed strong trophic and spatial shifts early in life for all pollock samples. However, NBS individuals showed strong oscillations in δ15N that matched highly elevated δ15N baseline values within a persistent denitrification zone between 61° and 63°N latitude. In contrast, SEBS pollock showed lower overall δ15N and δ13C values and reduced oscillations, indicating movement between the shelf and slope waters. To expand our interpretation of isotopic patterns to specific life history stages, we are in the process of measuring the relationship of lens diameter to body length from young of year to adult (age 3+) pollock. This relationship can then be used to retrospectively connect body size to a specific lens layer isotope value.
Alaska Marine Science Symposium 2023 213
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