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ARCATA FWO: Survival of Juvenile Coho Salmon in Northern California's Trinity River 2008
California-Nevada Offices , March 5, 2009
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FWS biologist surgically implanting a radio transmitter into a juvenile coho salmon prior to release in 2008. (photo: S. Juhnke)
FWS biologist surgically implanting a radio transmitter into a juvenile coho salmon prior to release in 2008. (photo: S. Juhnke) - Photo Credit: n/a
Automated radio telemetry receiver station on the Trinity River, California, in 2008. (photo: S. Juhnke) 
Automated radio telemetry receiver station on the Trinity River, California, in 2008. (photo: S. Juhnke)  - Photo Credit: n/a

by Gregory Stutzer, Arcata FWO

As part of a cooperative study among federal, state, and tribal groups, the survival of seaward migrating juvenile coho salmon (Oncorhynchus kisutch) in the Klamath River have been studied since 2006 (Stutzer and others 2006, Beeman and others 2008).  These studies were among the first to estimate survival of juvenile salmonids in a northern California river, and the results were difficult to interpret due to a lack of survival estimates from similar areas.  The purpose of the study in the Klamath River was to determine if there was a relation between discharge at Iron Gate Dam and survival of juvenile coho salmon downstream.  The general design was to release fish several days per week from early April until mid June to span the migration timing of wild fish in the area and cover a wide range of river discharges.

 

This study was conducted to provide estimates of survival to compare with data from the Klamath River study and to provide data on the migration timing and survival for the Trinity River Restoration Program (TRRP).  The TRRP is a federally mandated program to restore fish and wildlife populations in the Trinity River Basin to levels prior to construction of Trinity and Lewiston dams (see http://www.trrp.net).  The general design of this study was similar to that of the Klamath River study in that releases of fish were made periodically over several weeks during the spring.  This study represents a pilot effort to estimate survival and migration metrics of juvenile salmon in the Trinity River, and was comprised of collaborative efforts from staff of federal, state, and tribal agencies. The study collaborators included the USGS and, in alphabetical order, the State of California, U.S. Bureau of Reclamation, U.S. Fish and Wildlife Service, and Yurok Tribal Fisheries Department.

 

The survival of hatchery-origin juvenile coho salmon from the Trinity River Hatchery was estimated as they migrated seaward through the Trinity and Klamath rivers.  A total of 200 fish fitted with radio transmitters were released into the Trinity River near the hatchery (river kilometer 252 from the mouth of the Klamath River) biweekly from March 19 to May 28, 2008.  Fish from the earliest release groups took longer to pass the first detection site 10 km downstream from the hatchery than those from the later groups, but travel times between subsequent sites were often similar among the groups.  The travel times of individuals through the 239 km study area ranged from 15.5 to 84.6 days with a median of 43.3 days.  The data did not support differences in survival among release groups, but did support differences among river reaches.  Survival in the first 53 km was lower than in the reaches downstream, which is similar to trends in juvenile coho salmon in the Klamath River.  The lowest estimated survival in this study was in the first 10 km from release in the Trinity River (0.676 SE 0.036) and the highest was in the final 20 km reach in the Klamath River (0.987 SE 0.013). Estimated survivals of radio-tagged juvenile coho salmon from release to Klamath River kilometer 33 were 0.639 per 100 km for Trinity River fish and 0.721 per 100 km for Klamath River fish.


Contact Info: Gregory Stutzer, 707 825 5151, greg_stutzer@fws.gov



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