Field Notes
U.S. Fish & Wildlife Service
Field Notes Entry   
STOCKTON FWO:Fishery Biologists Conduct First PIT Tagging Experiments With Delta Smelt
California-Nevada Offices , May 1, 2007
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PIT tag and implanter used on delta smelt at the UC Davis Fish Conservation and Culture Laboratory, Byron, Calif. (CDFG Photo/Jerry Morinaka,  
PIT tag and implanter used on delta smelt at the UC Davis Fish Conservation and Culture Laboratory, Byron, Calif. (CDFG Photo/Jerry Morinaka,   - Photo Credit: n/a

Paul Cadrett, Stockton FWO

Fish biologists at the Stockton Fish and Wildlife Office are studying the use of tiny  electronic markers known as PIT (Passive Integrated Transponders) in an effort to measure the effectiveness of  salvaging techniques that could benefit the threatened delta smelt. 


The tags, about the size of a large grain of rice, enable the identification of individual fish, and have been used extensively in experiments with fish and other wildlife over the years.  Gonzalo Castillo of the Stockton Fish and Wildlife Office develop and coordinated PIT tagging tests in close collaboration with staff from the University of California, Davis Fish Conservation and Culture Laboratory (FCCL)  the California Departments of Fish and Game, and Water Resources. This first PIT tagging test on threatened delta smelt (Hypomesus transpacificus) was also supported by the Interagency Ecological Program (IEP).


Tagging was conducted in spring 2007 at the FCCL, which is adjacent to the Skinner Fish Facility at Clifton Court Forebay in the south Delta.  The Skinner Fish Facility, operated by the Department of Water Resources, is designed to salvage fish before they can enter pumps that move delta water into the California Aquaduct.  Field experiments were conducted to provide preliminary estimates of the percent of delta smelt recaptured at the Skinner Fish Facility and/or detected at the two Delta sites where salvaged fish are regularly released.


Releases of 383 delta smelt were conducted on two successive nights at the intake channel (IC) leading to the fish salvage facility and the trash rack (TR) located in front of the primary louvers in the salvage facility. About 38 percent of the fish released at the TR were accounted for, compared to 34 percent of fish released at the IC (i.e., accounted either as observed delta smelt at the salvage facility or detected PIT tags at Delta release sites). No further tags were recovered after 24 hours following each release.  Provided that survival of tagged fish improves to levels typically observed in non-tagged control fish (> 95 percent over 30 days), PIT tags could be a useful tool in future salvage efficiency studies. 


Findings of the study were considered by this team in the planning of an ongoing CALFED Science project to evaluate Skinner Fish Facility efficiency and pre-screen losses in Clifton Court Forebay. As part of this project, calcein marking is being developed to mass-mark delta smelt. Future follow up studies to track movement of individual delta smelt will be considered if smaller PIT tags or untrasonic tags are developed.  





Contact Info: Paul Cadrett, 209-334-2968 x 312, paul_cadrett@fws.gov
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