Friday September 2, 2022
San Francisco Estuary Magazine —
The technique, spearheaded by geneticist Melinda Baerwald from the California Department of Water Resources, allows researchers to accurately distinguish young spring-run salmon from other runs by targeting DNA sequences specific to these fish.
In a paper published in San Francisco Estuary and Watershed Science, lead authors Baerwald and Peter A. Nelson explain some of the challenges of developing this estimate, called the spring-run juvenile production estimate. A key hurdle is differentiating spring-run fish from salmon that migrate during other seasons. Unlike juvenile salmon from the winter run, spring-run juveniles are hard to identify using the conventional length-at-date approach, which determines age and spawning migration season based on size.
“There’s nothing visually about a spring-run salmon that distinguishes it from a winter-run, fall-run, or late-fall-run salmon,” says Nelson. The spring-run Chinook population is at a historic low, and “the more we know about how this run is doing from one year to the next and across the different tributaries [where they spawn], the better we’ll be able to manage and hopefully bring this particular run back.”