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MEPS prepress abstract   -  DOI:

Juvenile western Alaska chum salmon and critical periods during their marine life history in a changing climate

Edward V. Farley Jr. *, Ellen M. Yasumiishi, James M. Murphy, Wesley Strasburger, Fletcher Sewall, Kathrine Howard, Sabrina Garcia, Jamal H. Moss

*Corresponding author:

ABSTRACT: Recent precipitous declines in western Alaska chum salmon (Oncorhynchus keta) returns followed unprecedented warming in the northern Bering Sea ecosystem. To better understand the role of anomalous events on juvenile chum salmon early marine ecology in the northern Bering Sea, we utilized time-series observations over a 17 yr period (2003–2019) of juvenile chum salmon size (length and weight), diet, energy density, relative abundance, and of the sea surface temperature (SST). Particular attention was paid to more recent (2014 to 2019) years that had unprecedented loss of sea ice in the northern Being Sea in comparison to previous warm (2003 to 2005) and cold (2006 to 2013) periods. Our findings indicate significant correlations between SST and juvenile chum salmon relative biomass (positive) and energy density (negative). We found that juvenile chum salmon were larger during warm periods than during cold periods; however, there was no significant difference in their length and weight between the warm periods. Juvenile chum salmon fed on lower quality prey during warm periods when compared to during cold periods, with an increase in the proportion of lower quality prey during the recent warm period. Consequently, energy density of juvenile chum salmon was also lower during warm periods than during cold periods, with the lowest values occurring during the recent warm period (2014 to 2019). These results identify a shift in energy allocation and/or prey quality of juvenile Chum salmon with temperature and illustrate how marine ecosystems have altered the nutritional condition of juvenile Chum salmon prior to winter when energy reserves are considered critical to survival.