Author(s): Shelby Richins

Presentation: oral

The Columbia River redband trout (Oncorhynchus mykiss gairdneri) is Idaho's least studied salmonid. In this investigation, I documented the genetics, distribution, movement, and habitat use of redband trout in Dry Creek, a tributary of the Boise River. During summer 2013, I surveyed 48 stream reaches throughout the Dry Creek watershed and PIT tagged 407 redband trout (47—250 mm TL). I analyzed the genetic integrity of 136 fish. Fish movement was monitored May 30, 2013—September 30, 2013 via two PIT Tag Antenna Systems. I gathered habitat characteristics of 20 isolated pools with and without redband trout to evaluate critical summer trout habitat. Genetic analyses confirmed a single population (FST=0.015) of non-introgressed redband trout with relatively low genetic diversity (He=0.24). Fish were distributed in Dry Creek upstream of Hidden Springs and were 94% more abundant at higher elevations (>1310-m). Movement detected by the PIT arrays was 91% (52/57) upstream (median 92-m) and 9% downstream (median 53-m). Fish persisted longest (>3 weeks) in large pools (>495-cm channel width) at mid-elevation (1042—1051-m). Redband trout were observed in pools with dissolved oxygen levels of 1.8 mg/L, indicating redband trout may have evolved physiological adaptations to hypoxia in intermittent desert streams. This project was funded by a National Fish and Wildlife Foundation-Wells Fargo Environmental Solutions for Communities Grant. It was also made possible by Trout Unlimited, Biomark, Idaho Fish and Game, and student and community volunteers.

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