Evan Crews, Evaluation Of Sampling Methodologies For Assessing Fish Species Richness In Ridge And Valley Streams In Chattanooga, Tennessee
Faculty Chair: Dr. Mark Schorr
I evaluated the adequacy of different electrofishing approaches for estimating species richness in small Ridge and Valley streams. My study objectives were to determine the effects of the sampling season, reach length, habitat sequences surveyed, and sampling intensity on estimates offish species richness. Fish assemblages were sampled at 18 sites across five streams in the Chattanooga, Tennessee area, May-June (spring) and July-August (summer) 1998. Reach lengths ranged from 103 to 278 m (30 to 61 times the mean stream width [MSW]). At each site, fish were collected using one or two backpack electrofishers within habitat-specific enclosures (riffle-run or pool). Two-and three-pass sampling was conducted at selected sites. Species richness averaged slightly higher (P < 0.1) in the spring than summer; these estimates were positively correlated (r = 0.829; P < 0.0001). Regression analysis revealed a positive asymptotic relationship between species richness and the reach length sampled (r2 > 0.87; P < 0.0001). Sampling a reach of 41 times the mean stream width (MSW) yielded 90% of the estimated maximum species richness. Species richness averaged higher (P < 0.1) in samples from two habitat sequences versus one habitat sequence, sampling more than two habitat sequences did not yield significantly greater numbers of species (P > 0.1). Estimates of species richness from single- and multiple-pass (two and three collections) electrofishing were statistically similar (P > 0.1). This study demonstrated that sampling reach lengths equal to at least 41 times the MSW with one electrofishing pass was sufficient to collect 90% of the species present in small streams in the Ridge and Valley ecoregion. Additionally, at least two habitat sequences should be included within this sampling reach.