The low chum salmon run on the Yukon River last summer was foreshadowed by the low number of juvenile chums caught three years earlier in the Northern Bering Sea Trawl survey. That 2017 catch was the lowest since the trawl survey began early this century.
But the number went up after that. In fact, the number of juvenile chums caught in the trawl survey over the last two years were the highest on record. The hope is that those numbers will mean improved runs of chums this coming summer and next when those fish return to the Yukon River as adults.
But Alaska Department of Fish and Game biologist Sabrina Garcia cautions that scientists don’t have the full picture yet. She is among a group that is just beginning to do the work needed to build more accurate predictions of adult chum numbers based on the catch of juvenile chums in the northern Bering Sea.
The relationship between the size of the juvenile catch and the return is not always consistent. For example, in 2004 a low number of chums were caught in the trawl fishery, but three years later the return of adults to the Yukon wasn’t low at all. To create models to predict the chum runs the way they estimate the king salmon runs, biologists need genetic information, along with adult return data. Garcia said that by working with scientists at the federal Alaska Fisheries Science Center in Juneau, they hope to have a preliminary model for the Yukon River in a few months.
While Kuskokwim River stocks are not usually caught in the northern Bering Sea trawl survey, the fact that low chum numbers were consistent throughout the region this season suggests that whatever happened to the Yukon stocks may be happening elsewhere.
