Home Range and Movement Behavior of Headwater Resident Bull Trout in the Southern Oregon Cascades

To increase understanding of dispersal and habitat use in a recovering population of headwater-resident Bull Trout (Salvelinus confluentus), we documented home range and movement of individually-marked trout within an 11-km reach of Sun Creek, Crater Lake National Park, Oregon.  Bull trout were individually marked with PIT-tags and relocated annually by reach-scale surveys with mobile PIT-tag antennas during 2009-2013.   The study reach was bounded downstream by a stationary antenna and upstream by a waterfall.  A smaller 500-m section was surveyed weekly during summer 2012 to characterize home range at the habitat-unit scale.  Twice we surveyed this section multiple times within 24 hours to quantify diel movement.   Preliminary analyses indicate most individuals ranged less than 200m between detections both within and among years.  Restricted movement may explain why bull trout have not colonized some recently restored habitats in the watershed.  A small proportion of tagged fish emigrated downstream from the study reach over a migration barrier designed to exclude nonnative competitors, highlighting one trade-off of managing native fish populations by isolation and suggesting that migratory behavior might be expressed if connectivity to downstream habitats is restored.  This project demonstrates the utility of mobile PIT-tag detection for evaluating behavior of small stream fishes.