USFWS employee Jerrica Lewis tags a Chinook salmon smolt. (photo: USFWS)

by Paul Cadrett, Stockton FWO
In 2008, the Service's Stockton Fish and Wildlife Office collaborated with California Department of Fish and Game, U.S. Geological Survey, Hansen Environmental Services, and FishBio for the second year of acoustic tagging of juvenile Chinook salmon as part of the Vernalis Adaptive Management Plan (VAMP).

 The objective of the VAMP study is to estimate Chinook salmon survival and route distribution throughout the San Joaquin River and Delta.  The VAMP has been transitioning from coded wire tagged (CWT) fall-run Chinook salmon to acoustically-tagged salmon due to lack of production fish from the Merced River Fish Hatchery (MRFH) and the reduction in sampling at Chipps Island for the recovery of CWTs because of concern for delta smelt. 

Staff involved in the study were trained over a two-week period using standard protocols for surgical acoustic tagging of juvenile Chinook salmon. Mokelumne River Fish Facility  served as the training location and provided all fish used in the training session.  Surgeons were required to tag, necropsy, and photograph a minimum of 220 fish for competency prior to tagging fish for VAMP.  After training, 950 fall-run Chinook salmon were acoustically tagged at the MRFH.  Fish were held for 24 hours at the hatchery prior to transport to release sites. 

In addition to the 950 acoustic-tagged fish, 80 fish were dummy tagged.  Twenty of the dummy-tagged fish were taken to Coleman National Fish Hatchery for fish-health assessment associated with acoustic tagging to help determine if there were any negative health affects as a result of the tagging procedure.  Twenty additional fish were held at two release sites for 48 hours for fish-condition assessment. 

Prior to release, fish were acclimated in tanks on shore for one hour and then held for one hour in river to allow the fish time to become used to the river environment.  Fish were detected and identified as they passed receivers set up through out the river and delta.  Data will be analyzed in a release-recapture model to estimate abundance and route distribution.