Date of Award
Master of Science (MS) in Biology
Seasonal and directional movements, and distributions of Bull Trout and Lake Trout between Priest Lake and Upper Priest Lake, Idaho, were studied from May 2015 to April 2017. Lake Trout (n=220) and Bull Trout (n=40) movements were monitored using Lotek JSATS transmitters and hydrophones both passively, using gate formations at either end of the Thorofare, and actively in both lakes. No significant difference was found between directional or seasonal movements of either species (P>0.05) and all movements were observed when water surface temperatures were below 15oC. Poisson regression analysis indicated that there were significantly more detections by the Upper Priest Lake array than the Priest Lake array (P0.05). Lake Trout distributions in Priest Lake varied insignificantly from their original capture and release points (P>0.05). These results indicate that Lake Trout have use the southern portion of Priest Lake at high rates and movement to Upper Priest Lake is random.
The effects and impacts introduced species have on native species is well known in some cases and less well for others. The introduction and success of Lake Trout in the Priest Lake system, in Idaho, poses a threat to native fish populations. In an effort to further understand the potential competition and predation on native species in Upper Priest Lake, 283 stomachs were collected from Lake Trout in 2015 and 2016. Small Lake Trout (<500 mm total length (TL)) fed at a significantly higher rate on Mysis shrimp (Mysis diluviana) than larger Lake Trout (>500 mm TL; P<0.001). Larger Lake Trout (>500 mm TL) fed at a significantly higher rate on fish than small Lake Trout (P<0.001). Additionally, large Lake Trout had a significantly higher proportion of empty stomachs suggesting that large Lake Trout do not supplement their diet with Mysis shrimp (P<0.001). Based on the diet items of Lake Trout at different lengths suggest that competition between Lake Trout and Bull Trout in UPL is possible and predation was not seen
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Entz, Derek C., "INTERACTIONS BETWEEN LAKE TROUT AND BULL TROUT IN THE PRIEST LAKE SYSTEM, IDAHO" (2017). EWU Masters Thesis Collection. 457.