North Pacific Anadromous Fish Commission Technical Report No. 15: 129–131, 2019 All correspondence should be addressed to E. Yasumiishi. email: ellen.yasumiishi@noaa.gov 129 doi:10.23849/npafctr15/129.131. Mechanisms for Shifts in the Distribution and Abundance of Juvenile Sockeye Salmon in the Eastern Bering Sea during Late Summer, 2002–2018 Ellen Yasumiishi 1 , Curry Cunningham 2 , Ed Farley 1 , Kristin Cieciel 1 , Jamal Moss 1 , Wesley Strasburger 1 , Lisa Eisner 3 , Alexander Andrews 1 , Jeanette Gann 1 , Jim Murphy 1 , Andrew Dimond 1 , and Elizabeth Siddon 1 1 NOAA Fisheries, Alaska Fisheries Science Center, Ted Stevens Marine Research Center, Auke Bay Laboratories, 17109 Point Lena Loop Road, Juneau, AK, 99801, USA 2 Alaska Pacific University, 4101 University Drive, Anchorage, AK, 99508, USA 3 NOAA Fisheries, Alaska Fisheries Science Center, 600 Sand Point Way NE, Seattle, WA, 98115, USA Keywords: Sockeye salmon, shifts, distribution, abundance, Eastern Bering Sea Objectives Climate change is altering the distribution and abundance of marine species in Arctic and sub-Arctic oceans. The eastern Bering Sea is a critical rearing habitat for juvenile sockeye salmon during summer (Farley et al. 2007). Southeast Bering Sea shelf water temperatures ranged from 4–10°C, with anomalous warm 2002–2005, cool 2006– 2013, and warm 2014–2018 periods (Fig. 1). In response to warming, significant shifts north and increases in abundance were detected for juvenile sockeye salmon and age-0 pollock in the eastern Bering Sea, 2002–2018 (Fig. 2, Fig. 3) (Yasumiishi et al. in prep.). In addition, juvenile sockeye salmon consumed more age-0 pollock during warm years and more zooplankton during cool years (Fig. 4). To get a better understanding of the mechanisms for shifts, we examined spatio-temporal covariates of the distribution and abundance of juvenile sockeye salmon. Covariates included station level sea temperature, large copepod densities (prey), juvenile pink salmon (competitors), and age-0 pollock (competitors and prey). Fig. 1. Sea surface temperature anomalies sampled in the eastern Bering Sea during the summer Alaska Fisheries Science Center bottom trawl survey, 2002–2018 (courtesy Bob Lauth). Fig. 2. Distribution and relative abundances of juvenile sockeye salmon sampled in surface waters of the eastern Bering Sea during late summer, 2002–2018. -3 -2 -1 0 1 2 3 4 2002 2004 2006 2008 2010 2012 2014 2016 2018 Sea temperature anomalies (Celsius) Year