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We evaluated the effects of steelhead Oncorhynchus mykiss (migratory Rainbow Trout) introduction on the population dynamics of resident Brown Trout Salmo trutta from 1995 to 2008 in a small, low-gradient trout stream. Data on Brown Trout population density, survival, and growth were collected from the treatment section in Hunt Creek, Michigan, where adult steelhead were stocked each spring during 1998–2003, as well as from two reference stream reaches. The presence of steelhead had no apparent effect on the density of age-0 Brown Trout, but the mean density of all age-1 and older (age-1+) Brown Trout year-classes that interacted with juvenile steelhead of the same age was 46% lower than the density of age-1+ year-classes that did not interact with juvenile steelhead of the same age. No differences in density of age-1+ Brown Trout were detected in reference sections between the periods of steelhead presence or absence in the treatment section. Lower annual survival rates for year-classes of age-0 B...

Excess sand bedload can significantly degrade salmonid habitat and populations. Successful use of sediment traps to restore habitat and salmonid populations on two Michigan streams in the early 1980s led to application of traps at well over 100 coldwater streams in Michigan and rivers throughout the USA within a decade. Unfortunately, little quantitative evaluation has occurred other than anecdotal observations for some traps. We conducted a broad-scale survey of 65 Michigan stream reaches with sediment traps by collecting data along transects upstream and downstream of the traps to assess downstream changes in substrate composition, channel depth, and channel stability in response to sediment traps. We found that recent applications of sediment traps (usually as stand-alone instream habitat treatments) had no significant effect on substrate, thalweg depth, or bank stability conditions in the reaches studied. Using reach-based estimates of specific stream power at the 10% annual exceedence flow, ...

We developed user-friendly fish habitat suitability tools (plots) for fishery managers in Michigan; these tools are based on driving habitat variables and fish population estimates for several hundred stream sites throughout the state. We generated contour plots to show patterns in fish biomass for over 60 common species (and for 120 species grouped at the family level) in relation to axes of catchment area and low-flow yield (90% exceedance flow divided by catchment area) and also in relation to axes of mean and weekly range of July temperatures. The plots showed distinct patterns in fish habitat suitability at each level of biological organization studied and were useful for quantitatively comparing river sites. We demonstrate how these plots can be used to support stream management, and we provide examples pertaining to resource assessment, trout stocking, angling regulations, chemical reclamation of marginal trout streams, indicator species, instream flow protection, and habitat restoration. ...

Coolwater streams, which are intermediate in character between coldwater “trout” streams and more diverse warmwater streams, occur widely in temperate regions but are poorly understood. We used modeled water temperature data and fish assemblage samples from 371 stream sites in Michigan and Wisconsin to define, describe, and map coolwater streams and their fish assemblages. We defined coolwater streams as ones having summer water temperatures suitable for both coldwater and warmwater species and used the observed distributions of the 99 fish species at our sites to identify coolwater thermal boundaries. Coolwater streams had June-through-August mean water temperatures of 17.0–20.5°C, July mean temperatures of 17.5–21.0°C, and maximum daily mean temperatures of 20.7–24.6°C. We delineated two subclasses of coolwater streams: “cold transition” (having July mean water temperatures of 17.5–19.5°C) and “warm transition” (having July mean temperatures of 19.5–21.0°C). Fish assemblages in coolwater stream...

Both site- and landscape-scale processes play important roles in the biological communities of rivers. Understanding the influences of these processes on fish abundance can help direct management and research efforts toward appropriate habitat variables and scales. We used multiple linear regression analysis of a regional fish and habitat database to determine the feasibility of using geographical information systems (GIS)–derived landscape-scale habitat variables to explain the spatial variation in the density of five sport fish species (Chinook salmon Oncorhynchus tshawytscha, steelhead O. mykiss, brown trout Salmo trutta, brook trout Salvelinus fontinalis, and white sucker Catostomus commersonii) in the rivers of Michigan's Lower Peninsula. We compared these models with those developed using site-scale variables traditionally measured in the field. Landscape-scale riverine habitat variables obtained through GIS analysis and modeling of catchment characteristics accounted for 18–69% of the vari...

We used the behavioral carrying capacity (BCC) technique to test the assumption of the instream flow incremental methodology (IFIM) that a positive linear relation exists between available fish habitat (weighted usable area, WUA) and fish biomass for populations of smallmouth bass Micropterus dolomieu at carrying capacity. The BCC experiments were performed at various streamflows, and WUA was measured at each flow. In each BCC experiment, a section of a stream was overstocked with juvenile smallmouth bass, excess fish were trapped as they emigrated, and the remaining resident fish were collected after a 10-d period. We did not find a positive relation between WUA and BCC, and we found a negative relation between stream discharge and BCC. High BCC values recorded during low-flow experiments resulted from less upstream and downstream movement by juvenile smallmouth bass. Such behavioral changes may prevent smallmouth bass populations from being limited by habitat availability during low flows. The ...