Effects Of Trout Stream Habitat Rehabilitation Projects On Nongame Fish Communities In Five Southeastern Minnesota Streams

Trout stream habitat rehabilitation projects in five streams in Winona, Olmsted, and Wabasha counties, southeastern Minnesota, were assessed for possible effects on the nongame fish community. Based on multiple-pass removal sampling in reference and rehabilitated stream sections, these rehabilitation projects had differential effects on the nongame community that appeared to be determined largely by stream gradient. In higher-gradient (>5 m/km) streams, rehabilitation project areas had nongame populations 45-58% lower then those in reference areas, but fish community diversity was higher in rehabilitated areas. In lowergradient (<5 m/km) streams, nongame populations in rehabilitated areas were 20-109% higher than those in reference areas, but fish community diversity was lower in rehabilitated areas. In higher-gradient streams, rehabilitation projects appeared to increase pool area but reduce riffle and shallow water areas, which favored trout (brown and brook) populations at the expense of the dominant nongame species such as slimy sculpin and brook stickleback. In lower-gradient streams, rehabilitation projects appeared to increase bank cover and fast-water areas, thus increasing populations of both trout and the dominant nongame species such as slimy sculpin, mottled sculpin, and white sucker.