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Monday, January 29 • 4:20pm - 4:40pm
SALMONIDS: Brown Trout Movement in Response to Large Scale Population Reduction

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AUTHORS. Travis R. Rehm, South Dakota State University; Steve R. Chipps, U.S Geological Survey; Kelsen L. Young, Jacob L. Davis, Greg Simpson - South Dakota Department of Game Fish and Parks

ABSTRACT. Density-dependent growth in stream-dwelling Brown Trout (Salmo trutta) has been well documented (Jenkins et al. 1999; Vollestad et al. 2002; Lobon-Cervia 2007). In Spearfish Creek, South Dakota, mean size of Brown Trout is inversely related to trout density. Due to high abundance, slow growth rate, and low angler harvest, management options for increasing the size structure of the trout population may be limited. Experimental manipulation of Brown Trout abundance shows promise as an approach for increasing growth rate.  While studies have shown that Brown Trout generally exhibit small home range sizes and strong site fidelity (Burrell et al. 2000; James et al. 2007), the effect of localized density reductions on movement patterns in Brown Trout is poorly understood.  For reduced populations to have desired effects on fish growth, it is important that immigration from high to low density areas is negligible. We implanted a total of 38 Brown Trout with radio transmitters in Spearfish Creek, South Dakota and tracked them throughout the life of the tags.  Seven experimental sections (425 m/section) were randomly selected to reduce Brown Trout densities by 50% and seven sections (425 m/section) served as control reaches. Mean gross fish movement was similar between experimental (17.4 m, n=9, SE 3.5) and control (15 m, n=7, SE=1.2) sections (t = -0.84; P = 0.403). Net movement was similar between treatments at 15.2 m (SE=19.42) or -25.1 m (SE=45.1) for experimental and control sections, respectively. Home range also did not show any significant differences between experimental 122.5 m (SE=49.3) or control 108.3 m (SE=22.3) sections. We found that large scale reductions in Brown trout density did not lead to increased fish movement or home range size compared to sites with natural densities. This suggests that immigration of Brown Trout into experimental sections would be negligible.

Monday January 29, 2018 4:20pm - 4:40pm CST