Salmon fill Auke Creek with shorter, earlier runs

Auke Creek salmon are running earlier and for fewer days than 40 years ago, according to decades of research.

University of Alaska Southeast biologist David Tallmon combed through data on sculpin, salmon and salmon relatives at the Auke Creek weir.

He says the temperature at Auke Creek has raised 1.34 degrees Celsius since 1971. Salmon are sensitive to temperature changes.

Tallmon told an Evening at Egan audience Friday that animal species will sometimes move north when their habitat warms, but Alaskans rely on steady local salmon runs.

“If you’re a commercial fisherman, or a subsistence fisherman, if salmon move up to the Beaufort Sea, that’s of little comfort. What you want to have is salmon in your local stream so you can harvest them,” Tallmon says.

Researchers have counted Auke Creek salmon runs for the last four decades.  The weir funnels the fish into a place where they are counted before continuing their migration. Tallmon says most Pacific salmon migrate earlier now than they did 40 years ago. He says in the 1970s salmon runs lasted 79 days, now they migrate for about 55 days. Sockeye are the only salmon that buck this trend.

Tallmon’s study of Auke Creek pink salmon indicate that some had a gene that told them to migrate late in the season, which kept them from breeding with salmon that migrated earlier. Now there is no late migration. Tallmon says over the years, warming temperatures may have hurt salmon with that gene, causing them to lose a little of the genetic diversity that buffers them from a changing environment.

Such changes mean that salmon predators, such as bears and humans, have to harvest the season’s return in less time. Tallmon says Auke Creek salmon are part of a community that stretches to the ocean, and all the species salmon encounter along the way are going through similar environmental changes. 

“It’s important to not think about these species in isolation, but the species that they eat and that eat them as well, and that how they’re going to respond to climate change is also going to influence the success of salmon,” Tallmon says.

But Tallmon says the Auke Creek salmon are as abundant now as 40 years ago.

“We’re also fortunate in the sense that Alaska salmon have it fairly easy. It’s not like the fish down south, there’s not huge impacts from the 4 H’s – hydropower, hatchery, habitat and harvest. I mean obviously we have harvest here, but we’ve also got our habitat largely intact and we don’t have that much influence from hydropower or hatcheries,” Tallmon says.

In the future Tallmon plans to tie the Auke Creek research to data from other weirs to see what the trends are elsewhere. He says it could be difficult to expand the study. Other weirs have data gaps, or are more influenced by hatchery fish.

Tallmon says Auke Creek could be the only weir with decades of continuous information.