A Study to Determine the Biological Feasibility of a New Fish Tagging System, 1985-1986




active, adult, Atlantic salmon, Bonneville Dam, chinook, denil, fatigue, field tests, fish ladder, fish tagging, identification, juvenile, laboratory study, marking, McNary Dam, monitoring, PIT tag, salmon, salmonids, spawning, stamina, steelhead, survival, swimming, tagging, transponder


An ongoing cooperative project between the Bonneville Power Administration and the National Marine Fisheries Service was initiated in 1983 to evaluate the technical and biological feasibility of adapting a new identification system to salmonids. The system is based upon the passive integrated transponder (PIT) tag. This report discusses the work completed in 1985 and is divided into laboratory and field studies. All studies were conducted with the tag implanted into the body cavity of the test fish via a 12-gauge hypodermic needle. Laboratory studies with juvenile chinook salmon and steelhead showed no adverse effect of the tag on growth or survival. Once the tag was established in the body cavity, its location was found to be consistent over time. Behavioral tests showed no significant effect of the tag on opercular rate, tail beat frequency, stamina, or post fatigue survival on juvenile steelhead. Active swimming did not affect tag retention in steelhead. Tests revealed a minimum size threshold for tag retention in juvenile steelhead at 8.5 g before acceptable tag retention levels were achieved. No effect on growth or survival was observed for juvenile chinook salmon or steelhead. The polypropylene encapsulated tags had an unacceptable failure rate due to moisture contacting the tag's electronic circuitry. The use of polypropylene encapsulated PIT tags was not recommended. The tag manufacturer now produces the tag encapsulated in glass - which should provide significant improvements in tag longevity and tag retention. No evidence of infection due to tagging procedures was observed in tagged fish. Nevertheless, it was demonstrated that the PIT tag and tagging apparatus could be disinfected against Aeromonas salmonicida by exposure to a 50% or stronger solution of ethanol for a minimum of 1 minute. Maturing Atlantic salmon were PIT tagged. In males, retention was 100% prior to and after spawning. Females had 100% tag retention prior to spawning and 83% retention after multiple hand strippings. Lost tags accompanied the egg mass during strippings and were easily detected in the spawning bucket. All field tests using juvenile salmonids were conducted at McNary Dam, whereas tests using adult fish were conducted at Bonneville Dam. The Pit tags monitoring equipment is described and discussed. The tag monitoring equipment showed a high degree of reliability, efficiency, and accuracy. During the 6-month testing period, tag reading efficiency exceeded 90%, and tag reading accuracy for juvenile chinook salmon was 100%. Only two minor equipment failures occurred during the testing period. Field studies used migrant spring and fall chinook salmon; no significant effects on the tag on survival could be determined when compared to traditional tagging and marking methods. No significant difference was observed in the recovery rate between branded and PIT tagged juvenile fall chinook salmon released into McNary reservoir and recovered at the dam. The PIT tag data were acquired with 90% fewer PIT tagged fish being released than branded fish and a 33-fold reduction in the number of tagged fish being physically handled to recover the data. Adult steelhead were successfully PIT tagged and automatically interrogated as they passed through a PIT tag monitor installed on a Denil fish ladder. It was concluded that a PIT tag monitor for adults can be installed at any location that can accommodate a coded wire tag monitor. Future work related to PIT tag systems development is described and discussed.

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