Habitat Use, Availability, and Preference for Johnny Darter, White Sucker, Northern Hog Sucker, Common Shiner, and Creek Chub in Streams in Central Wisconsin
Moody, Robert C.
University of Wisconsin-Stevens Point, College of Natural Resources
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I determined habitat use, availability, and preference for johnny darters (Etheostoma nigrum), white suckers (Catostomus commersoni), hog suckers (HyPentelium nigricans), common shiners (Notropis cornutus), and creek chubs (Semotilus atromaculatus) that I observed using above and under-water techniques, and collected by electroshocking in eight first to third order streams in central Wisconsin. Data were stratified into six life history stages--egg incubation, fry, young-of-the-year, juvenile, adult, and spawning adult--for each species and into day and night records, when samples were sufficient for each species-life stage. Physical habitat use was quantified by measurement of total depth, fish depth, mean column velocity (MCV), fish nose velocity (FNV), substrate composition, and kind of cover. Habitat availability was estimated along with habitat use by measurement of the same variables (exclusive of fish depth and FNV) along randomly selected stream channel cross sections. Preference was calculated by dividing the relative frequency of use by the relative frequency of availability within an interval of a habitat variable. Habitat use, availability, and preference distributional patterns were presented as histograms. I constructed habitat suitability index curves for data sets having SO or more observations of habitat use. Utilization, availability, preference, and conditional preference (i.e., day v. night data) curves were derived from nonparametric tolerance limits. I collected habitat suitability criteria for 32 species-life stages, of which 16 species-life stages had sufficient data for suitability index (SI) curve development. I developed a substrate composition index compatible with the Instream Flow Incremental Methodology that provided numerical representation for non-adjacent particle size groups (e.g., a rubble-sand mixture). I quantified bias associated with each method of aquisition of habitat use data; above water observations yielded the least biased data relative to underwater observation and electrofishing. For each species-life stage having sufficient data, I identified an optimal range (SI= 1.0) within a preferred range within a used range for each habitat variable except cover. Within a species, mean values for total depth, MCV, FNV, and substrate coarseness increased as fish body length increased from fry to adult. Habitat used by fry was uniform for several species. FNV utilization curves were similar for all species-life stages, exclusive of spawning adults, and tended towards zero suitability in velocities exceeding 21 cm/sec. FNV measurements also remained more consistent, among several habitat use data aquistion methods, relative to other habitat variables. Habitat use differed for most species-life stages between day and night. Habitat use varied, to some extent, among streams for most species-life stages, but habitat preference did not vary significantly among streams.