Determination of the effects of fine-grained sediment and other limiting variables on trout habitat for selected streams in Wisconsin

Abstract

Two Habitat Suitability Index (HSI) models, developed by the U.S. Fish and Wildlife Service, were used to evaluate the effects of fine-grained (less than 2 millimeters) sediment on brook trout (Salvelinusfontinalis, Mitchill) and brown trout (Salmo trutta, Linnaeus) in 11 streams in west-central and southwestern Wisconsin. Our results indicated that fine-grained sediment limited brook trout habitat in 8 of 11 streams and brown trout habitat in only one stream. Lack of winter and escape cover for fry was the primary limiting variable for brown trout at 61 percent of the sites, and this factor also limited brook trout at several stations. Pool area or quality, in stream cover, streambank vegetation for erosion control, minimum flow, thalweg depth maximum, water temperature, spawning substrate, riffle dominant substrate, and dissolved oxygen also were limiting to trout in the study streams. Brook trout appeared to be more sensitive to the effects of fine-grained sediment than brown trout. The models for brook trout and brown trout appeared to be useful and objective screening tools for identifying variables limiting trout habitat in these streams. The models predicted that reduction in the amount of fine-grained sediment would improve brook trout habitat. These models may be valuable for establishing instream sediment-reduction goals; however, the decrease in sediment delivery needed to meet these goals cannot be estimated without quantitative data on land use practices and their effects on sediment delivery and retention by streams. Stream name Percent Agriculture Middle Kickapoo River watershed

Channel Morphology Response to Selective Wood Removals in a Sand‐Laden Wisconsin Trout Stream

“…Present stream conditions suggest that beaver dams and the abundant small woody debris (diameter , 0.10 m) obstructions are causing sand to be transported slowly (Bilby 1981;Harmon et al 1986;Downs and Simon 2001). Sand loading and reduced transport capacity (Lisle and Hilton 1992) have led to channel widening, filling of pool habitat, and aggradation of the streambed (Lisle 1982;Alexander and Hansen 1986;Waters 1995;Scudder et al 2000) across most Bayfield Peninsula watersheds. The Wisconsin Department of Natural Resources (WDNR) has observed sedimentation in headwater tributaries where important salmonid spawning habitat is located (W. H. Blust, WDNR, personal communication).…”