Scientist Puzzled Over Declining King Salmon Runs

Mar 14, 2017

After a three-year study, scientists still lack answers as to why king salmon runs have declined in the Kuskokwim and other Alaskan rivers.
Credit Shane Iverson / KYUK

The statewide study of king salmon decline has not yielded any definitive conclusions. The results of the three-year study of the incidental catch of Chinooks showing up in the state's commercial salmon fisheries ended with no real information about kings headed into the Bering Sea.

Kyle Shedd is a fisheries geneticist with the Gene Conservation Laboratory at the Alaska Department of Fish and Game. He says that the genetic study of incidental catch of kings showed that most of the fish caught were not Alaska king salmon, but ones headed south to British Columbia and even further south down the west coast of the U.S.

"The vast majority of Chinook salmon incidentally harvested in commercial fisheries, and also caught in the sport fisheries, were from southern stocks, so British Columbia and the West Coast of the United States. Very few of them were Alaska."

Most of them were also young: only two and three-year-old ocean fish; not mature king salmon.

The state originally planned a three-year study of commercial and sport incidental catches in the Kodiak, Chignik, and Alaska Peninsula fisheries. But after 2014, the first year of the study, funds were cut back and only fish from the Kodiak commercial and sport salmon fishery were tested for the entire three-year period.

During the first year of the study, some Bering Sea fish showed up in the incidental catches of state commercial salmon boats fishing off of Chignik and the Southern Alaska Peninsula. But Shedd says that even in that mix, Kings headed to the Eastern Bering Sea amounted to only 20 percent of the incidental catch of Chinooks.

"Twenty percent of those fish were attributed to the Eastern Bering Sea reporting group. That reporting group includes all populations of Chinook salmon from Norton Sound all the way to Bristol Bay, so that includes both the U.S. and Canadian sides of the Yukon. The Kuskokwim and the Nushagak are the primary Chinook producers."

The genetic study was part of the Chinook Salmon Research Initiative, a program aimed at figuring out the reason for the decline of king salmon throughout the state. So far there has not been a clear smoking gun, but Shedd suspects the reason for the decline may be a change in the ocean's ecosystem.

"It is a statewide phenomena, and given that it's in so many drainages across the state that all have their own suite of issues, the likely culprit is likely ocean productivity, which is something we can't really control."

Fisheries scientist are gathering in Fairbanks next week to review the entire Chinook research program to better understand what was learned, and look at how best to proceed. 

Correction: March 15, 2017

This article, originally published on March 14, 2017, misstated the name of the agency that fisheries geneticist Kyle Shedd works for. He works for the Gene Conservation Laboratory, not the Marine Conservation Laboratory.