South Delta Survival Studies in 2015

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San Joaquin River

Written by Pat Brandes, supervisory fish biologist in the Lodi Fish and Wildlife Office, Lodi, Calif.

During the spring of 2015, the Lodi Fish and Wildlife Office participated in two salmonid survival studies. The studies estimated juvenile salmon and steelhead survival through the lower San Joaquin River and Delta. The studies will identify route distribution, route specific survival and total through-Delta survival through the use of acoustic telemetry.

San Joaquin River

The San Joaquin River is shown at low flow in late March 2015. In the foreground, a series of containers used to hold juvenile steelhead. – Photo Credit: Pat Brandes USFWS

The objective of the studies are to identify the causes of mortality in the Delta due to flows, exports and other non-project effects on smolts out-migrating from the San Joaquin basin. The juvenile steelhead study is the fifth year of a six year study funded by U.S. Bureau of Reclamation as a reasonable and prudent alternative( Action IV.2.2, NMFS, 2009, page 645), for the National Marine Fisheries Service’s, Biological Opinion and Conference Opinion on the Long-term Operations of the Central Valley Project and State Water Project. The juvenile Chinook salmon study was funded by Central Valley Project Improvement Act (CVPIA) and others to assess survival through the lower San Joaquin River and Delta with a head of Old River barrier installed.

Three groups of juvenile steelhead and two groups of juvenile salmon from the Mokelumne River Hatchery were released between early March and early May. Each steelhead group consisted of 480 tagged fish, tagged over a three day period. Each salmon group consisted of 648 tagged salmon, tagged over a four day period. For all of the steelhead and for about half of the salmon, once the tagging was completed, the fish were transported to the Durham Ferry release site and held there in containers for a minimum of 24 hours prior to release to evaluate pre-release mortality and allow for acclimation.

Fish were then released every four to six hours over a 24 hour period, after being held for 24 hours. The other half of the tagged salmon were released between April 30 and May 2. They were held at the hatchery for 24 hours after tagging and then transported to a release site near Medford Island and released on the late afternoon/evening ebb tide. Medford Island is much further downstream within the Sacramento-San Joaquin Delta than the Durham Ferry release site. This change in release location was due to the high (likely lethal) water temperatures (77 degrees Fahrenheit) observed at Durham Ferry on April 28th. Water temperatures were higher than usual and river flows were extremely low this spring in the lower San Joaquin River due to the fourth year of a drought. Results of the fish health component of the studies will be forthcoming in future months.

Crew moving fish

A crew preparing to move juvenile salmon in containers to release site downstream. – Photo Credit: Pat Brandes USFWS

The Salmonid Survival Studies program within the Lodi office was responsible for the tagging and release components of the studies but these projects had labor contributions from multiple groups both within the Service as well as those from the U.S. Bureau of Reclamation and California Department of Water Resources. The studies also included staff participation from other programs within the Lodi Fish and Wildlife Office, as well as staff from two other Service offices and two other federal agencies to get the job done. Participants from within the Lodi Fish and Wildlife office included one staff person from the Aquatic Invasive Species Program, and twelve staff from the Delta Juvenile Fish Monitoring Program, supplementing the field efforts of ten, temporary staff hired for the studies.

Administration staff at the Lodi office also contributed to the project by ordering services and purchasing supplies. In addition, two individuals from the Service’s Bay-Delta Office helped with field work at the release site. 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 release site or hatchery for 48 hours. Two individuals from two separate U.S. Bureau of Reclamation offices’ (the Sacramento Bay-Delta office and the Denver Technical Service Center) also contributed to the project by driving fish transport tanks. One staff member from the California Department of Water Resources helped with the tagging.

A crew works at the release site near a series of juvenile salmon holding containers in the San Joaquin River in mid April 2015. - Photo Credit: Pat Brandes USFWS

A crew works at the release site near a series of juvenile salmon holding containers in the San Joaquin River in mid April 2015. – Photo Credit: Pat Brandes USFWS

Other partners also supported the project by purchasing tags, providing fish and tagging space and deploying and maintaining the wide-spread VEMCO 180 Khz receiver array in the Delta. For instance, the California Department of Water Resources purchased a portion of the acoustic tags used in the Chinook salmon study to facilitate their evaluation of predator control efforts downstream of the release location. In addition, the Chinook salmon and steelhead were provided by, and tagging was done at, the Mokelumne River Hatchery, an East Bay Municipal District (EBMUD) hatchery operated by the California Department of Fish and Wildlife. Lastly, the receiver array was funded by the U.S. Bureau of Reclamation as part of the six year steelhead study, and was deployed and maintained by the U.S. Geological Survey.

It will be a couple of months before the data is downloaded from all the receivers in the river and Delta 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. Several challenges were encountered and overcome this year. It was through the hard work, dedication and cooperation of our diverse team and support from our partners that helped us succeed.

The Lodi Fish and Wildlife Service office has been conducting these survival studies for several years, with the 2012 study report almost completed.

Article written by By Pat Brandes, supervisory fish biologist in the Lodi Fish and Wildlife Office, Lodi, Calif.; Sourced from U.S. Fish and Wildlife Field Notes

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