Reconstruction of Ocean Entry Timing and Growth Rates of Juvenile Chum Salmon in Alaskan Waters of the Chukchi and Northern Bering Seas

Recent climate change is most pronounced in the Arctic, with implications for shifts in juvenile salmon distributions and life-history patterns. Chum Salmon are the most widely distributed Pacific salmon; however, few studies have examined their early marine life history. The objectives of this study were to determine ocean entry timing of Chum Salmon in the Chukchi and northern Bering seas and increase our understanding of their early life history characteristics. Otolith microchemistry analysis and daily growth increments were used to estimate entry dates and growth rates of Chum Salmon from summers 2007 (a year of minimal seas ice), 2012, and 2013. Similar growth was observed between regions in 2007, but significant differences were detected in 2012, with northern Bering Sea juveniles having greater lengths-at-age than Chukchi Sea fish. No differences in growth were observed between years within regions. Both regions exhibited similar characteristics with respect to entry timing. Chukchi Sea fish in 2012 had an earlier entry date than northern Bering Sea individuals the same year and in both regions in 2007. By understanding the early life history and growth of Chum Salmon, informed predictions can be made on the effects of climate change on these stocks.