Gulf of Alaska | Fishes and Fish Habitats
Mapping the thermal habitat across Yukon chum salmon early life history stages Presenter: Emily Lemagie , emily.lemagie@noaa.gov, NOAA Pacific Marine Environmental Laboratory Shaun Bell , shaun.bell@noaa.gov, NOAA Pacific Marine Environmental Laboratory Ed Farley , ed.farley@noaa.gov, National Marine Fisheries Service, Alaska Fisheries Science Center Joe Langan , jalangan@alaska.edu Calvin Mordy , calvin.w.mordy@noaa.gov, CICOES, University of Washington Phyllis Stabeno , phyllis.stabeno@noaa.gov, NOAA Pacific Marine Environmental Laboratory It is evident that warming temperatures in the North Pacific Ocean are impacting salmon fitness and survival. Record- low Yukon River chum salmon run sizes were recorded during 2020 and 2021, a shared concern among Alaskan communities. Salmon are particularly sensitive to environmental impacts in their first year at sea. Here we analyze ocean temperatures along the hypothesized seasonal migration path of Yukon chum salmon in order to characterize their thermal habitat during their early life history stages across the North Pacific relative to historic conditions and modeled salmon temperature preferences. For Yukon chum salmon, juveniles are thought to spend their first year on the northern Eastern Bering Sea (EBS) shelf, migrate to the Gulf of Alaska (GOA) during late fall, and overwinter in the central GOA before returning to the Bering Sea slope/basin for their second summer. They repeat this migration between the GOA and EBS slope/basin until they mature (two to three winters) and migrate back to the Yukon River. Here we track satellite sea surface temperature (SST) anomalies and variability along the seasonal migration path. Particular focus is on the International Year of the Salmon period from summer 2018 through early 2022 in order to compare SST with chum salmon catches from summer surveys in the central Bering Sea and distribution maps of immature chum salmon caught in winter in the central GOA. In the summers of 2018-2021 SST in the EBS were warmer than the historical climatology. The evolution and variability of summer temperatures in the Bering Sea is compared across these warm years. While surface temperatures are an important indicator for salmon habitat, subsurface temperatures and stratification from moorings will also be used to examine the full temperature range that may be accessible to salmon during this phase of their migration. Winter SST in the GOA were above average in 2019, close to the historical mean in 2020 and 2021, and cooler than average in 2022. The surface mixed layer is deeper in winter, and for winter we map the spatial extent of suitable thermal habitat based on SST, subsurface variability from ARGO floats, and profiles collected during winter surveys. These results will help us answer key questions about the impact of warming temperatures, marine heatwaves, and loss of seasonal sea ice on Yukon chum salmon.
Alaska Marine Science Symposium 2023 197
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