It won't be a revelation to locals, but researchers have determined that Alaska salmon are shrinking. For example, Chinook salmon are 8% smaller today than they were before 1990, say researchers in Nature Communications. Sockeye, coho, and chum salmon have also shrunk, though to a lesser extent, reports Reuters. So what's going on? Scientists think they have part of the answer: The fish aren't staying in the ocean as long as they once did before returning to spawn, reports CNN. While they can remain in the ocean 7 years or so, it seems today's fish are returning younger—and thus smaller—after maybe 4 years. “People are walking into their smokehouses and not having to duck anymore,” says study co-author Peter Westley of the University of Alaska at Fairbanks. “The fish are just smaller."
As for the question of why the fish are returning earlier, that gets a little more complicated. "We didn’t find any single smoking gun," says lead author Krista Oke, per the Juneau Empire. "It really seems to be a cumulative effect of smaller impacts across lots of different factors." However, researchers point to two top suspects in a news release—climate change and growing numbers of wild and hatchery salmon in the ocean. Both factors might be making it harder for the Alaska salmon to find food, forcing them home sooner. "We know that climate drives changes in ocean productivity, and we see a consistent signal of climate factors associated with decreasing salmon size," says co-author Eric Palkovacs. He adds: “It seems that the ocean is becoming a riskier place to be.” (Read more salmon stories.)