Juvenile Chinook salmon abundance in the northern Bering Sea: implications for future returns and fisheries in the Yukon River.

Juvenile Chinook salmon (Oncorhynchus tshawytscha) abundance is estimated in the northern Bering Sea and used to provide guidance to future returns and fisheries for Canadian-origin Chinook salmon in the Yukon River. Abundance estimates are based on surface trawl catch data, mixed layer depth adjustments, and genetic stock composition of juveniles in the northern Bering Sea near the end of their summer at sea (September). Estimated annual abundances range from 0.6 million to 2.55 million juveniles with an overall average of 1.44 million juvenile Chinook salmon from 2003 to 2014. Comparisons of juvenile and adult abundance provide unique insight into the survival of Chinook salmon. Although estimates of juvenile survival rates are relatively low (average of 5.2%), juvenile abundance is significantly correlated (r = 0.88, p < 0.001) with adult returns, indicating that much of the variability in survival occurs during earlier life stages (freshwater and initial marine). Survival of Chinook salmon during these early life-history stages of Chinook salmon has increased along with juvenile abundance and has important implications for future returns and fisheries in the Yukon River. The number of juveniles per spawner increased from an average of 26 (2003 to 2012) to an average of 54 in 2013 and 2014. Recent production declines in Chinook salmon have triggered closures of commercial, sport, and personal use fisheries and severe restrictions on subsistence fisheries on Chinook salmon in the Yukon River. The number of adults projected to return from juvenile abundance estimates indicate that fishing opportunities on the Canadian-origin stock group of Chinook salmon in the Yukon River could be restored as early as 2016.