Evaluation of Pit Tag Loss and Tag-induced Mortaility in Bluehead Sucker (Catostomus Discobolus)

Abstract

Native Colorado River fishes in Grand Canyon are studied extensively using Passive Integrated Transponder (PIT) tags. Since 1991 over 7,000 bluehead suckers (Catostomus discobolus) have been PIT tagged in Grand Canyon, but few of these fish are ever recaptured. The combination of low recapture rates and no previous studies on tag retention or tag induced mortality led us to evaluate tagging methods for bluehead suckers. We held 18 bluehead suckers in a net pen for 2-6 days after PIT tagging to evaluate capture and tag-induced mortality. No tag loss was observed and only one fish died during the holding period. Lack of information on the life history of this species makes interpretation of low recapture rates difficult, but current handing and PIT tagging practices for bluehead sucker in Grand Canyon do not appear to be causing delayed mortality.