Alaska’s salmon are shrinking, and climate change may be to blame

The study confirms first-hand anecdotal accounts from Alaskans with generations of salmon tradition.

By Yereth Rosen, Reuters - August 24, 2020
One additional year in the ocean makes a big difference in the size of salmon, as seen in these two female sockeye salmon from Pick Creek, Alaska, in this undated handout photo. The top salmon spent three years at sea, the other two years. (Andrew Hendry / Handout via Reuters)

ANCHORAGE — Alaska’s highly prized salmon — a favorite of seafood lovers the world over — are getting smaller, and climate change is a suspected culprit, a new study reported, documenting a trend that may pose a risk to a valuable fishery, indigenous people and wildlife.

The study, led by University of Alaska at Fairbanks scientists, found that four of Alaska’s five wild salmon species have shrunk in average fish size over the past six decades, with stunted growth becoming more pronounced since 2010.

Hardest hit is Alaska’s official state fish, the Chinook salmon, also known as king salmon.

Chinooks on average are 8 percent smaller than they were before 1990, according to the study, published on Wednesday in the journal Nature Communications. Also shrinking are Alaska’s sockeye, coho and chum salmon, the report said. The findings are based on data from 12.5 million samples collected over six decades.

The study confirms first-hand anecdotal accounts from Alaskans with generations of salmon tradition, said co-author Peter Westley of UAF’s College of Fisheries and Ocean Sciences

“People are walking into their smokehouses and not having to duck anymore,” he said. “The fish are just smaller. ”

Warmer seas attributed to climate change and increased competition among all species of salmon are the likeliest factors behind the fish shrinkage, he said.

Salmon are maturing in the ocean at earlier ages and returning to fresh water younger and smaller than in the past, the study found.

In waterways like the Yukon River, famous for its Chinooks, the “really big whoppers” that spend seven or eight years in the ocean are no longer seen, Westley said. Instead, many returning Chinooks are only four years old, he said.

Alaska produces nearly all of the nation’s wild salmon. Last year, commercial fishermen harvested over 206 million salmon and sold them for $657.6 million, according to state officials. Salmon are also a dietary staple for some indigenous people of Alaska and Canada’s Yukon Territory.

The red-fleshed fish are also eaten by Alaska’s bears and other wildlife. Smaller fish mean fewer nutrients for those animals – and fewer salmon eggs, which can have long-term consequences for wildlife that feed on them, said UAF’s Krista Oke, the study’s lead author.

“It is impacting things that eat eggs, but it also impacts the salmon population itself,” Oke said.

The findings show the need to manage salmon not just for the size of their runs but for the size of individual fish, Westley said. “If you lose the diversity of fish and only have small fish, then you’re in troubled waters,” he said.