2019 and 2020 Snohomish River Basin Juvenile Outmigration Monitoring

Installation of the Skykomish and Snoqualmie screw traps began on February 27th 2019 and full trapping operations commenced on March 4th. Trapping operations were initially delayed by heavy snowpack, making roads inaccessible for staff and trap assembly. The 2019 season ended on June 13th for the Snoqualmie River trap and June 21st for the Skykomish River trap. The Skykomish trap was fished for approximately 985.7 hours over 80 days the Snoqualmie trap was fished for approximately 818 hours over 75 days.
For the Skykomish Trap the fishing effort consisted of 503.8 were fished at night representing 51% of total trapping effort. A total of 18 sampling events (both schedule cancellations, and unscheduled potential sampling days) were ultimately cancelled due to unfavorable sampling conditions. A total of 5 sampling events (both schedule cancellations, and unscheduled potential sampling days) were cancelled due to unfavorable sampling conditions. During the sampling season a total of 41,196 salmon and trout were captured, counted, and released. Captured unmarked chinook included 3,979 sub-yearlings and 162 yearlings. The number of Chinook sub-yearlings caught at the Skykomish River trap has varied from year to year, with this years’ total approximately twice as high as the project average (2004-2019 average: 2,045). Captured unmarked Coho included 951 sub-yearlings and 1,699 yearlings. The number of unmarked Coho yearlings caught in 2019 was 60% lower than the project average (2004-2019 average: 4,204).
For the Snoqualmie trap fishing effort consisted of 818 hours, 445 of those hours were fished at night representing 54% of total trapping effort. A total of 3 scheduled sampling events were ultimately cancelled due to unfavorable sampling conditions (i.e. high debris and discharge levels). During the sampling season 3,242 salmon and trout were captured, counted and released. Captured unmarked Chinook included 657 sub-yearlings and 24 yearlings. Catch per unit effort of unmarked Chinook (0.80) were significantly lower than the previous two years (2017: 1.04 / 2018: 1.35) while still remaining 33% higher than project average CPUE of 0.61. The number of unmarked sub-yearling Chinook was 19% above the project average (Project average; 530) . Captured unmarked Coho included 612 yearlings and 690 sub-yearlings. Catch per unit effort of unmarked Coho (0.75) was 46% lower than project average of 1.39. The number of unmarked Coho yearlings is significantly lower than the previous 3 years and 85% lower than project average of 1136 fish.
We has a small carryover of funds into the 2020 Trap sampling season. We utilized the remaining FY 2018 funds to fund the first portion of the operation of the screw traps in 2019 which were expended by the end of February 2020.
Overlapping PCSRF project timelines occur due to the fact that we use several funding sources to operate the screw traps. The application and award announcements for these grants operate on different schedules. When we apply for the PCSRF funds we have to assume we will not receive these additional funds since they are competitive grants.

In May of 1999, the National Marine Fisheries Service (NMFS) listed the Puget Sound Chinook salmon as threatened under the federal Endangered Species Act (ESA). This listing included Chinook salmon from the Snohomish River Basin (Skykomish and Snoqualmie populations). The recovery of these species depends upon improving the effectiveness of habitat, harvest, and hatchery management across the basin. In order to achieve such improved effectiveness, additional information is necessary to fill important data gaps within the Snohomish system and to assess impacts of restoration efforts, including information on Chinook and Coho salmon abundance, productivity, spatial structure, and diversity (Snohomish Basin Salmonid Recovery Technical Committee, 2005). Information about the trends and inter-annual variability in these population parameters is critical to inform salmon recovery efforts, provides basic information on the productivity and capacity of the system, and can lead to significant improvements in harvest management modeling and run forecasting. Additionally, the monitoring of production and survival along with other physical, chemical, and biological conditions provides a means to evaluate recovery actions, habitat conditions, and potential ecological trajectories in the basin.

A key component to provide information on Snohomish salmon populations is the operation of two rotary screw traps in the Skykomish and Snoqualmie rivers. These projects involved trapping and enumerating juvenile Chinook and Coho salmon (as well as several un-targeted species) as they emigrate from the Snohomish River Basin to the Puget Sound. The goals of these trapping efforts are to estimate Chinook and Coho salmon natural production, migration patterns, and freshwater survival. The goal of this project is to track Chinook and coho production and survival information and migration timing within the Snohomish river basin, which can be used in part to evaluate salmon recovery efforts in the various portions of the watershed, to refine preseason run size forecasting by harvest managers, and used in combination with other monitoring and research efforts to better understand and identify priority restoration areas. These goals are accomplished through the direct quantification of juvenile salmon emigrations, evaluation of trap efficiency, and assessment of influential environmental attributes.