Spring Chinook take on high flows because of ‘early-migration gene’

It’s a bit mind-boggling to think that a single, tiny fragment of genetic material determines whether a Chinook salmon chooses to return to its home stream in the spring or the fall.

Photo: Ingrid Taylar (CC BY-NC 2.0) https://flic.kr/p/dmbyre

I’ve been following the scientific discoveries about spring chinook since 2017, when Mike Miller’s lab at the University of California, Davis, published research findings showing the location of this “early-migration gene” on chromosome 28.

In a story published this week in the Encyclopedia of Puget Sound, I wrote about some of the latest discoveries surrounding spring Chinook. I also thought it worthwhile to describe the importance of these fish to the ecosystem and to the native people of the Puget Sound region.

Up until the past two years, I never gave much thought to spring Chinook, nor apparently have most people, including many biologists. These are the salmon that often struggle to reach the upper reaches of the rivers when the streams are swollen with spring snowmelt. Much of these upper spawning grounds have been destroyed by human activity, and more than half the spring chinook runs in Puget Sound have gone extinct.

The more I learned about spring Chinook the more fascinated I became. The southern resident killer whales used to arrive in Puget Sound in April or May to feast on spring Chinook from Canada’s Fraser River, but those salmon runs have declined along with many fall runs of chinook. The result is a major change in behavior and migration patterns by the whales.

Spring Chinook were at one time an important food for bears coming out of hibernation, for eagles who had scavenged for food through the winter, and for native people who looked forward to fresh fish after a season of dried foods.

As I researched this story, I learned about the history of spring Chinook in the Skokomish River of southern Hood Canal and how a once-plentiful fish became extinct. I was pleased to describe the success of current efforts to create a new run of spring Chinook with the help of a hatchery in the North Fork of the Skokomish, where adult spawners are showing up nearly a century after the fish disappeared.

Spring Chinook in Salmon River, California
Photo: Peter Bohler, via UC Davis

Genetics is a fascinating field, and advances are coming rapidly in the studies of many species, including humans. The idea that a single gene can completely change the migration timing of a Chinook by four months raises many scientific and legal questions — including whether spring Chinook should get their own protection under the Endangered Species Act. As things stand now, Chinook salmon in Puget Sound — both spring and fall together — are listed as threatened under the ESA. But that could change as things shake out with the ESA in Oregon and California.

Ongoing genetic studies — including those involving various salmon species — are causing biologists and legal experts to re-examine the criteria for listing populations as threatened or endangered, as they teeter on the edge of extinction. No matter what the extinction risk is judged to be, spring Chinook are now recognized as something very special.

Leave a Reply

Your email address will not be published. Required fields are marked *

Before you post, please complete the prompt below.

Please enter the word MILK here: