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US Fish & Wildlife Service FieldNotes

STOCKTON FWO: 2012 Six-Year Steelhead Study

Region 8, May 1, 2012
Juvenile fall-run Chinook salmon post-surgery 
displaying sutures from tag insertion.
Juvenile fall-run Chinook salmon post-surgery displaying sutures from tag insertion. - Photo Credit: n/a
Fish being loaded into transport
tank by DJFMP crewperson Garrett Gianetta.
Fish being loaded into transport tank by DJFMP crewperson Garrett Gianetta. - Photo Credit: n/a
DJFMP crew ferrying fish holding containers
to release location.
DJFMP crew ferrying fish holding containers to release location. - Photo Credit: n/a

By Mike Marshall, Stockton Fish and Wildlife Office

The Stockton Fish and Wildlife Office’s Delta Juvenile Fish Monitoring Program (DJFMP) assisted the Bureau of Reclamation (BR) with a juvenile salmonid acoustic tagging study on the San Joaquin River. The project used both juvenile fall-run Chinook salmon and steelhead trout. Fish were anesthetized and surgically implanted with acoustic tags (Figure 1). This is the second year of a six year study to investigate migration issues that may be threatening salmonid survival through the Delta.

The study was conducted March through May. A total of 1,441 steelhead and 962 fall-run Chinook salmon were tagged from the Merced River and Mokelumne River Fish Hatcheries. The DJFMP tagged fish and transported them in large aluminum tanks to a holding location on the San Joaquin River (Figure 2). After fish were held in the river for 24 hours, DJFMP staff began releasing the fish at four-hour increments over a 24-hour period. A total of 90 releases were made during the study.

Fish were released by boat. The holding containers were attached to the gunnel and moved out into the river where a crewmember would check for mortalities before releasing the fish into the river (Figure 3). Just prior to release, the time, river temperature, and dissolved oxygen levels were measured and recorded.

After the release, fish were tracked with acoustic monitors located throughout the Sacramento-San Joaquin Delta. The data collected by these monitors will provide information about fish migration and route selection. Results from this study will be published by BR to meet their obligations under the Biological Opinion. Finally, this cooperative interagency effort will provide valuable information on the survival of juvenile salmonids in the Sacramento – San Joaquin Delta, an important first step in recommending measures to increase survival during critical early life stages.

Contact Info: Joseph Kirsch, 209-334-2968 ext. 309, joseph_kirsch@fws.gov