A Study to Determine the Biological Feasibility of a New Fish Tagging System

A multi-year cooperative project between the Bonneville Power Administration and the National Marine Fisheries Service was initiated in 1983 to evaluate the potential of the Passive Integrated Transponder (PIT) tag for marking salmonids. The second year's work had three phases. The objective of Phase I was to evaluate fish tagging with PIT tags. Phases II and III were concerned with the automatic monitoring of juvenile and adult fish injected with PIT tags. In Phase I, sham PIT tags were injected into the body cavity of juvenile salmonids. Tagged fish ranged in weight from 0.8 to 43.9 g. Observations based on six tests, ranging in time from 19 to 99 days, indicated that the best site for injecting the tag was along the mid-ventral line in the area of the pectoral or pelvic fins. Potential advantages to tagging the fish in the area of the pectoral fins were noted. As tagging techniques improved, tag retention of 99% (n = 400) and survival of 99% were achieved. Minimal tissue response to the tag was noted in both tag locations. In Phase II, a PIT tag detector system designed to detect and record the passage of juvenile salmonids was evaluated. Detection varied depending upon test conditions. By restricting the rate at which fish entered the monitoring tunnel to one fish per second, detection averaged 94.3% compared to 86.6% for multiple fish entry. Reducing the velocity fish passed through the tag monitoring channel from 10 to 8 ft/sec did not affect tag detection. In Phase III, a monitoring system designed to detect and decode adult fish tagged with a PIT tag was evaluated. The tests were conducted in winter 1984. Adult steelhead and chinook salmon measuring between 39 and 84 cm fork length were used in the test. The fish were tested with functional PIT tags injected into the body cavity. The average detection and proper decoding of these tagged fish was 94.4% for 211 fish. Improvements in the detection system are recommended.
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