Northwest Fisheries Science Center

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Document Type: Contract Report
Center: NWFSC
Document ID: 8957
Title: A study to determine the biological feasibility of a new fish tagging system, 1985-1986
Author/Editor: Earl F. Prentice, Donn L. Park, Thomas A. Flagg, Clinton Scott McCutcheon
Publication Year: 1986
Publisher: National Marine Fisheries Service
Contracting Agency: Bonneville Power Administration. Portland, Oregon

This report discusses the work completed in 1985 for an ongoing study to evaluate the technical and biological feasibility of a new identification system for salmonids.  All laboratory and field studies were conducted with tags implanted into the body cavity of 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.

Polypropylene-encapsulated tags had an unacceptable failure rate due to moisture contacting tag electronic circuitry.  Use of polypropylene-encapsulated 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, tag 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 spawning buckets.

Tag monitoting 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%.

Field studies used migrant spring and fall chinook salmon; no significant effects of 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.

Data were acquired with 90% fewer PIT tagged than branded fish being released 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.