2020 and 2021 Snohomish River Basin Juvenile Outmigration Monitoring

Installation of the Skykomish and Snoqualmie screw traps began on February 28th 2020 and full trapping operations commenced on February 25th. Trapping operations were initially delayed by heavy floods, making roads inaccessible for staff and trap assembly. The 2020 season ended on March 14th due to the Covid pandemic stay at home order. In April 2020 all non-essential Tribal staff were furloughed or laid off and did not return to work until the end of July. The traps had to be left in their locations between March and July because we did not have the staff or the safety protocols in place to disassemble and haul the traps. As a result the traps had to be checked every few days and during changes in river flow to ensure the traps did not get damaged or stranded with the changing river levels, this was primarily done by the project supervisor, who was an essential employee.
The traps were operated for several weeks prior to being shut down. The Snoqualmie trap was operated for approximately 159.4 hours over 12 business days within a 3-week period from Statistical Week (SW) 9 - 11. Of those 159.4 hours, 101.02 were fished at night, representing 63% of total trapping effort. On the Snoqualmie trap 1,555 salmon and trout were captured, counted and released on the Snoqualmie trap. Captured unmarked Chinook included 13 sub-yearlings and 0 yearlings. Catch per unit effort (fish/hour) of unmarked Chinook (0.08); project average CPUE is 0.61 (2001-2019). Project average catch of sub -yearling Chinook is 529. Captured unmarked Coho included 1 yearling and 9 sub-yearlings. Catch per unit effort of unmarked Coho (0.01); project average is 1.39. Project average catch of Coho yearlings is 1136 fish.
The Skykomish trap was operated for approximately 151.2 hours over 12 business days within a 3-week period from Statistical Week (SW) 9 to 11. Of those hours, 104.5 were fished at night representing 69% of total trapping effort. On the Skykomish trap a total of 9,165 salmon and trout were captured, counted, and released. Captured unmarked chinook included 38 sub-yearlings (0+) and 4 yearlings (1+). Unmarked Chinook sub-yearlings 2004-2019 average: 2,045. Captured unmarked Coho included 7 sub-yearlings and 11 yearlings. Unmarked Coho yearlings 2004-2019 average: 4,204. During the trapping and handling process a total of 10 salmonid mortalities were reported, of which 0 were unmarked Chinook
Unspent FY19 funds were carried over to fund trap operations in 2021. FY19 PCSRF funds were utilized to pay staff on the smolt traps until late April 2021.

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. More funds were rolled over than usual due to the shutdown of the smolt traps on March 14th 2020.

The project also contributed to a report developed as result data analysis (research component added September 2020) to provide some insight into yearling production over the sampled years, 2002-2019. This reports emphasis is the sub-yearling cohort. The tribe is interested in population patterns within the Skykomish and Snoqualmie rivers as well as across the Snohomish Basin, the report will include results from each river separately and provide a basin-wide assessment in the discussion.

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.