Fall home-range size and movement patterns of Columbia River redband trout (Oncorhynchus mykiss gairdneri) in a sagebrush desert stream

The Columbia River redband trout (Oncorhynchus mykiss gairdneri) is the only trout native to sagebrush desert basins of southwestern Idaho.  The redband trout occupies 64% of its historic range (inland drainages of the Pacific Northwest) and is listed as a species of special concern in Idaho, Oregon, and Montana. The objective of this study is to determine redband trout fall home-range size and movement patterns; and to examine if individual fish exhibit a high degree of year-to-year stream reach fidelity.  In September 2005, radio telemetry tags were surgically implanted into 15 adult (>150-g) trout.  Fish were collected from a 7-km reach of Jordan Creek, a 4th order tributary of the Owyhee River basin in southwestern Idaho.  Trout were tracked weekly for 55-d.  Fish locations were incorporated into an ArcGIS database for analyses. Mean home-range size of redband trout was 397-m (SD=365-m; range=13-1041-m).  Total distance moved by all fish during the study ranged from 29-m to 1197-m (mean= 460-m; SD=374-m).  Median weekly distance traveled by fish during late September (median=6-m) was not significantly different from distances traveled during late October (median=28-m) (p=0.24, U_A=89). The majority of fish (79%) moved downstream and the movement appeared to be associated with the availability of complex pools for over-wintering. To examine long-term fidelity of trout for the 7-km study reach, we PIT tagged 202 adult fish over a 4-y period.  Annual summer and fall surveys resulted in a 2.5% recapture rate, indicating the likelihood of extensive year-to-year movement of redband trout in this system.  Redband trout in Jordan Creek occupy a much larger fall home-range size and exhibit more extensive movements than other redband trout populations. Our results lend strong support for the development of population-specific Columbia River redband trout conservation plans.