Editor’s Desk: The case of the shrinking wild salmon

Back Forty will bring you periodic reviews, interviews and reporter insights about the stories they wrote. We hope you enjoy it as a companion to our main content on TheFERN.org and our Ag Insider policy news site. You can subscribe to the newsletter below.

By Elizabeth Royte

FERN has previously reported on the record salmon runs in Alaska’s Bristol Bay, while salmon in other parts of the region are disappearing. This year’s Bristol Bay run was nearly double the most recent 20-year average, reaching more than 80 million fish. But as Miranda Weiss reports in her most recent story for FERN — Trouble at Sea: When it comes to salmon, has the Pacific reached its limit? — there is a worrisome addendum to this historic season: the fish are some of the smallest on record for their age. Our story was produced in collaboration with bioGraphic, published by the California Academy of Sciences.

The shrinkage, which began in the 1960s in Bristol Bay and in the 1990s elsewhere in Alaska, has complicated fisheries management, spurred both subsistence and commercial fishermen to drop the mesh size on their nets, and forced processors to retool their production lines to fit the smaller fish and adjust their balance sheets, because larger fish bring in more money. Weiss tells us that the environment suffers as well because spawning and dying salmon deliver “torpedoes of fertilizer” — like nitrogen and phosphorus — to a range of organisms upriver, including streamside grasses, spruce trees, birds of prey, and bears.

Weiss traveled from her base in Homer, Alaska, to a research camp on Lake Nerka, in the Bristol Bay watershed, to explore the puzzle of shrinking salmon with Daniel Schindler, a biologist who’s been studying fish in the region for 26 years. According to Schindler and his colleagues, salmon are growing more slowly at sea and, in many cases, returning to spawn younger and smaller than ever before.

Warmer seas, which reflect climate change and increase fish’s caloric demands, are part of the growth slowdown. More importantly, salmon are being forced to compete with ever more hatchery-raised salmon for meals of zooplankton, small fish, and squid. Smaller salmon also produce fewer eggs than larger salmon, and those eggs develop into fish that are generally smaller than the offspring of larger fish. The size differential sets off a genetic feedback loop favoring smaller fish. The combination of factors, reports Weiss, could spell a grim future for salmon runs across the North Pacific.

This story is an important addition to FERN’s biodiversity and oceans coverage. We can only afford to pursue a story like this, which involved sending a writer and a photographer to a remote region of Alaska, with the support of our partners and contributors. So we thank you. With your donations, you can expect more ambitious stories like this ahead.