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US Fish & Wildlife Service FieldNotes

LOSI FWO: South Delta survival studies in 2017

Region 8, June 8, 2017
Tagging crew at the Tracy Fish Collection Facility in April of 2017
Tagging crew at the Tracy Fish Collection Facility in April of 2017 - Photo Credit: n/a

Pat Brandes


During the spring of 2017, the Lodi Fish and Wildlife Office participated in a juvenile salmon survival study. The study will estimate juvenile Chinook Salmon survival through the lower San Joaquin River and Delta of California. The studies will identify route distribution, route specific survival and total through-Delta survival through the use of acoustic telemetry. The objectives of the studies are to help identify the causes of mortality in the Delta due to flows, exports and other factors on smolts out-migrating from the San Joaquin Basin. The juvenile Chinook salmon study was funded by Central Valley Project Improvement Act Restoration Funds and the California Department of Water Resources (CDWR) to assess survival through the lower San Joaquin River and Delta under the extremely high flows we experienced during the spring of 2017.

Two groups of juvenile Chinook Salmon originating from the Merced River Hatchery and tagged at the U.S. Bureau of Reclamation (USBR)’s Tracy Fish Collection Facility in Byron, were released in April. Each salmon group consisted of 648 tagged salmon, tagged over a 4 day period, for the second and fourth weeks of the month. Half of the tagged salmon each week were transported to a release site about 12 miles upstream of Mossdale (Durham Ferry) and held in holding containers for approximately 24 hours prior to release to allow for acclimation. Fish were then released every 4 to 6 hours over a 24-hour period, after being held for 24 hours. The other half of the tagged salmon were held for 24 hours in a marina near Stockton and released near there in the mainstem San Joaquin River on the slack tide before the ebb or during the ebb tide. The Stockton release was made to provide better estimates of survival downstream of Stockton, as was also done in 2016. In many years, survival has been so poor through the Delta that estimates of survival in downstream reaches were uncertain due to low numbers arriving there. Having a supplemental release at Stockton was a way to increase precision of the downstream survival estimates.

The Lodi Fish and Wildlife Office’s Salmonid Survival Studies Program was responsible for designing and implementing the project. Temporary and term staff contributed to the tagging and release components of the study but individuals from other agencies and offices also participated. The Service’s CA/NV Fish Health Center conducted the fish health analyses on a subset of the fish after they had been held at the upstream release site for 48 hours. One individual from the USBR Denver Technical Service Center and one individual from the Service’s Coleman National Fish Hatchery contributed to the project by driving fish transport tanks from the tagging location in Bryon to the fish holding and release sites in the San Joaquin River at Durham Ferry and Stockton. The CDWR supported the project by funding staff from the U.S Geological Survey in Cook Washington, to help with the tagging training, tagging and tagging oversight and coordination. CDWR also supported the project by contributing a surgeon who contributed to the tagging.

The California Department of Fish and Wildlife (CDFW) also supported the project by providing fish and UC Davis was responsible for deploying and maintaining the receiver array in the Delta. Some receivers were delayed in their deployment due to a back-order of batteries to the receiver manufacturer. 2017 was the first year we have used Juvenile Salmon Acoustic Telemetry System (JSATS) tags and receivers. The tags only weighed 0.3 grams and could be used on smaller fish than in previous studies. Although it still involved a learning curve to switch to a new technology, the JSATS tags and mobile receiver worked well. We are appreciative of those in the acoustic telemetry community who loaned us equipment (FWS-Red Bluff, Army Corp of Engineers, U.C. Davis and NOAA Fisheries) and helped to teach us how to activate tags and detect tags with the mobile receiver.

It will be a couple of months before all the data is downloaded from the receivers and several more months before the data is completely analyzed, but the tagging and the release components of the projects have been completed for this year. With the high flows, low temperatures, fish of the right size and in good condition made the tagging and release processes go well this year. Having USGS support for our new biologist, Kristen Towne, and the return of experienced surgeons also helped to assure the tagging operation went smoothly. Having to switch our planned tagging location from Merced River Fish Hatchery to the Tracy Fish Collection Facility due to flooding and other problems at the hatchery, did create some challenges but thanks to the staff at the Tracy Fish Collection Facility for accommodating our needs, this ended up working out well. Challenges were also encountered with the deployment of the receivers in time for the fish releases. The Jersey Point receivers were not put in until almost a week after the first fish release due to manufacturer delays in shipping equipment. It was through the hard work, dedication and cooperation of our diverse team and support from our partners that helped us succeed.

Contact Info: Yvette Sky, (209) 334-2968 x301, yvette_sky@fws.gov