Northwest Fisheries Science Center

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Document Type: Contract Report
Center: NWFSC
Document ID: 7233
Title: A study to determine the biological feasibility of a new fish tagging system, 1986-1987
Author/Editor: Earl F. Prentice, Thomas A. Flagg, Clinton Scott McCutcheon
Publication Year: 1987
Publisher: National Marine Fisheries Service
Contracting Agency: Bonneville Power Administration. Portland, Oregon
Contract Number: 83-319
Date: 1987

In 1983, a multi-year project to evaluate the technical and biological feasibility of adapting a new identification system to salmonids was established.  The system is based upon a miniaturized passive integrated transponder (PIT) tag.  This report discusses the work completed in 1986 and is divided into laboratory studies, field studies, and systems development.  All studies were conducted using a glass-encapsulated tag implanted into the body cavity of test fish via a l2-gauge hypodermic needle.

Laboratory studies with juvenile Chinook salmon Oncorhynchus tshawytscha showed that retention of glass-encapsulated PIT tags was 99-100% in fish weighing 3 g or more.  No adverse tissue response to the tag was noted.  Survival of fish 5 g or larger was usually greater than 99%.  However, fish ranging in weight from 2 to 4 g, or fish undergoing a physiological change such as smoltification may have a low mortality (usually less then 5.0%) after tagging.  The mortality rate in smaller fish was dependent upon tagging skill, whereas mortality in smolting fish seemed dependent upon the level of stress.

Growth comparisons between tagged and control fish indicated PIT-tagged fish had a slightly depressed growth rate at some measurement periods.  The operational life of glass-encapsulated PIT tags implanted in fish was good, with 100% of the tags operating after 401 d.  No tags were rejected from the fish during the observation period.  Additional information on the operational life of the tag is being obtained by holding tagged fish until they mature.

Tests to determine the effect of the PIT tag on certain behavioral/physiological responses were conducted in the laboratory with one size range of juvenile steelhead Salmo gairdneri and two size groups of juvenile fall Chinook salmon.  Results showed no significant effect of the tag on opercular rate, tail beat frequency, stamina, or post fatigue survival.  Tests conducted at McNary Dam on juvenile migrant steelhead and fall and spring Chinook salmon showed similar results.

Juvenile PIT tag monitoring systems were installed and tested at Lower Granite and McNary Dam.  Tag monitoring equipment showed a high degree of reliability, efficiency, and accuracy.  During the 6-month test, tag reading efficiency exceeded 95%, with an accuracy rate of greater than 99% for all equipment. 

Field studies were conducted using spring and fall Chinook salmon and steelhead to assess performance of PIT-tagged fish in comparison to fish tagged or marked using traditional methods.  No effect of the tag on survival was noted.  Differences in survival were noted, however, between dam locations for all treatments.  A significantly higher number of PIT-tagged spring Chinook salmon were recovered at the dam than branded fish whereas no differences in recovery rates were seen between treatments for fall Chinook. 

Groups of spring chinook salmon and steelhead were tagged and branded at Dworshak National Fish Hatchery and released into the Clearwater River.  Tag recovery at Lower Granite and McNary Dam showed that significant1y higher numbers of PIT-tagged fish were recovered than branded fish.