Michael A. Bozek

Cumulative Effects of Incremental Shoreline Habitat Modification on Fish Assemblages in North Temperate Lakes

Abstract To evaluate effects of habitat modification at different spatial scales, we assessed species richness and tolerance of fish assemblages in littoral zones of 17 Wisconsin lakes with extensive residential and recreational development, and compared fish associations among site-specific and lakewide conditions. Samples consisted of combined DC electrofishing and seining. Stations were randomly selected within strata defined by type of shoreline erosion control structure, including retaining walls, rock riprap, and no structure. Habitat characteristics differed among the site types. Species richness at the site level was greatest in complex habitat (riprap) regardless of fish assemblage structure. However, more effort was required to achieve complete sampling of fish species present in sites without erosion control structures. This result may be related to homogeneity of habitat among sites altered by manmade structures. We used an analysis of covariance (ANCOVA) to compare site level habitat effects ...

Assessing Habitat Requirements of Young Colorado River Cutthroat Trout by Use of Macrohabitat and Microhabitat Analyses

Abstract We used both microhabitat and macrohabitat analyses to better assess habitat requirements of young Colorado River cutthroat trout Oncorhynchus clarki pleuriticus. Microhabitat analyses revealed that among a range of stream types, young cutthroat trout consistently preferred slow water (<0.06 m/s) and depths over 3 cm. Suitable habitat of this type was provided by different types of pool habitat within the geomorphically diverse study streams. Macrohabitat analysis indicated that the density of young cutthroat trout was positively correlated with the abundance of spawning gravel and negatively correlated with stream depth (adjusted R 2 = 0.67). This relationship helped explain the absence of young cutthroat trout from some stream reaches that had suitable microhabitat but that often lacked suitable spawning habitat. The two types of habitat analysis provided complementary information concerning the habitat requirements of young Colorado River cutthroat trout in the study streams.

Seasonal Variation in Fish Assemblage Structure and Habitat Structure in the Nearshore Littoral Zone of Wisconsin Lakes

Abstract To evaluate whether fish abundance, fish habitat, and fish–habitat associations vary across seasons in nearshore littoral zones of five northern Wisconsin lakes, we assessed fish abundances and quantified habitat characteristics in littoral zones across three seasons (spring, summer, and fall) during 1996. Seasonal responses of the fish community in the nearshore littoral zone were taxa specific and guild specific. In the nearshore littoral zone, species richness and the abundance of pumpkinseeds Lepomis gibbosus, rock bass Ambloplites rupestris, yellow perch Perca flavescens, and centrarchids differed significantly across seasons. Some habitat characteristics, including mean water depth, maximum water depth, percent floating vegetation, and percent submersed vegetation, also differed significantly among seasons. Analysis of covariance indicated that changes in fish abundance for the three species coincided with variation in habitat characteristics in the nearshore littoral zone. Significant inte...

Comparison of Streamside Visual Counts to Electrofishing Estimates of Colorado River Cutthroat Trout Fry and Adults

Abstract Streamside visual counts and depletion-removal electrofishing were compared for estimating fry and adult abundances of Colorado River cutthroat trout Oncorhynchus clarki pleuriticus. Visual counts of fry were significantly correlated (R = 0.92) with three-pass depletion-removal electrofishing estimates of abundance. Streamside visual counts were generally lower than electrofishing estimates, except in streams having turbulent water, where electrofishing was difficult. Disturbance of fry by observers reduced estimates obtained with the visual counts; however, visual counts can be a useful method for estimating the abundance of cutthroat trout fry in small streams with shallow water. For adults, correlations between streamside visual counts and electrofishing population estimates were low, and therefore visual counts were not considered a viable method for older fish.