Reynolds, L., A.T. Herlihy, P.R. Kaufmann, S.V. Gregory, and R.M. Hughes. 2003. Electrofishing effort requirements for assessing species richness and biotic integrity in western Oregon streams. North American Journal of Fisheries Management 23:450-461. WED-01-123
We examined the sampling effort required in wadeable western Oregon streams at base flow to estimate fish species richness, percent abundance, and biotic integrity when employing three persons and one backpack electrofisher. Reaches were oversampled longitudinally and data were recorded separately for each habitat unit, allowing us to treat each habitat unit separately during data analyses. The median values of species richness from Monte Carlo simulations of the data indicated that a stream reach 40 times its mean wetted width was adequate to estimate 90% of species richness (i.e., all common species) in western Oregon fish assemblages. A reach length of 40 wetted channel widths was also adequate to precisely score an index of biotic integrity developed for western Oregon. However, where 40 channel widths are less than 150 m, we recommend a minimum distance of 150 m to ensure that sufficient numbers of individuals are captured, rare habitats are encountered, and riparian conditions do not fully determine channel morphology. In addition. at four sites we compared a rapid (4-h), one-pass sampling protocol of reaches 40 channel widths in length with an intensive, three-pass electrofishing protocol lasting more than 0 h. The rapid protocol occasionally underestimated species richness by missing vague, cryptic, or rare species, but it usually estimated species richness, percent abundance. and the IBI as well as the intensive protocol. The rapid protocol and quantitative fish population estimates tracked the same trends in population size at one site for 5 years.