FY23 Stillaguamish Smolt Outmigration Monitoring

The Tribe will install and operate a rotary screw trap on the lower Mainstem of the Stillaguamish River (RM 6) with the intent of capturing emigrant hatchery and wild Chinook smolts. We will estimate the relative contribution, size, and outmigration timing of the two groups for the purposes of monitoring the Chinook Natural Stock Restoration program. Data will also be collected on other salmonid species as well. Placement of the smolt trap in the lower Mainstem allows the majority of the entire watershed is sampled for outmigrating smolts. The trap will be deployed in early February and continue to capture fish through mid-July and be crewed by a team of two technicians.

Measuring and understanding the inter-annual variation in run size of wild Chinook, listed as threatened under the ESA, is critical for managing harvest and prioritizing habitat restoration. Quantifying the number of smolts leaving the watershed is one of the few methods available that provides a direct measure of the year-to-year changes in freshwater survival and growth, free from the confounding influences of marine conditions.