October 30, 2020 — The following was released by NOAA Fisheries:
The annual migration of Chinook salmon up West Coast rivers from the ocean has enriched ecosystems, inspired cultures, and shaped landscapes. Yet the timing of their migration is controlled by one small section of their genome, according to research published this week in Science.
This is the first time scientists have linked a single gene region to such an influential difference in a vertebrate species. For salmon, it determines whether they return upriver from the ocean in spring or fall. This has crucial implications for other species that rely on them for food. First author Neil Thompson of the University of California Santa Cruz and NOAA Fisheries’ Southwest Fisheries Science Center said that this small genetic difference can have a major effect on a complex pattern of migration and reproduction.
Fish migrating upriver in spring may access habitat such as higher elevation tributaries. These habitats become less accessible to Chinook salmon migrating later in the year when stream flows decline. The result is that fall-run Chinook salmon remain lower in the watershed without continuing up into the tributaries.
However, the construction of dams in the West blocked spring-run Chinook salmon from much of their original spawning habitat. This contributed to the listing of several spring-migrating fish under the Endangered Species Act. Fall-run Chinook salmon on the West Coast are generally more abundant.
The scientists identified the gene region influencing migration with whole-genome sequencing. Then, they scientists examined the genetic pattern in more than 500 Chinook salmon caught by the Yurok Tribe in the Klamath River estuary. They analyzed the effects of variation in this genetic region on migration timing and other physiological traits.