Chinook salmon in the Klamath River have significant economic and cultural importance to the region. These salmon are divided into two types, the spring-run and fall-run, which have multiple different characteristics but are identified by their migration patterns.
Because spring-run salmon begin their migration earlier in the year, they have more time to move further up the watershed, bringing important nutrients to the upper reaches of the rivers. Human influences, primarily through the construction of dams that blocked access to these upper rivers, have effectively removed the spring-run genetics from the Klamath River Chinook population.
There are plans to remove the dams blocking access to the upper reaches of the Klamath, restoring salmon access to hundreds of miles of potential habitat. Genetic studies have shown that one specific region of the salmon genome is strongly correlated with spring- versus fall-run migration patterns. This study intended to test whether this genomic region alone is enough to influence salmon migration timing.
This project initially aimed to restore spring-run Chinook to the Upper Klamath through genetic crossbreeding of Klamath River fall-run and Trinity River spring-run salmon. These crossbred fish were to be sampled and tagged, and their return behavior would be monitored to assess whether the identified gene region is indeed associated with spring-run behavior.
However, the combination of COVID-19, statewide drought impacts and the delay of the Klamath dam removal led to an indefinite postponement of the Chinook salmon crossbreeding project. These events caused the researchers to focus on the Russian River steelhead population — a project where the laboratory benchwork had already been completed.
The steelhead analyses found age at maturity and spawn timing are heritable life-history traits. Both traits influence steelhead ocean migrations and their heritability suggests these traits could be manipulated in the hatchery environment. Results from this project could inform a model for restoration projects of Chinook or other salmon stocks on the west coast.