Electrofishing effort and fish species richness and relative abundance in Ozark Highland streams of Arkansas

摘要

We sampled 15 stream sites in the Ozark Highlands ecoregion of Arkansas and examined the effect of increased backpack electrofishing effort on the richness and relative abundance estimates of fish species. Each site was 75 mean stream widths (MSWs) long and was divided into 15 consecutive segments that were each 5 MSWs long. For each site the percent of empirical and theoretical species richness and the percent of relative abundance similarity to the entire fish assemblage were calculated by adding consecutive segments using an approach that resulted in 15 accumulation curves per assemblage character for each stream site. On average, a distance of 53.8 MSWs (SD = 7.4) was needed to sample 95% of empirical species richness at a stream site, which was equal to an area of 2,722.0 m(2) (SD = 1,967.0). For sampling 95% of theoretical species richness, an average of 101.8 MSWs (SD = 34.5), or 5,055.7 m(2) (SD = 3,667.4), was needed. Obtaining 95% relative abundance similarity required an average sampling effort equivalent to 24.0 MSWs (SD = 8.9), or 1,269.7 m(2) (SD = 932.1). Mean stream width explained more variance in the reach lengths and areas needed for estimates of species richness and relative abundance than did riffle-pool sequence length or watershed size. Our results should offer insight into species richness and relative abundance accumulation rates when using a one-pass backpack electrofishing sample in Ozark Highland streams of Arkansas.