Electrofishing Effort Requirements for Assessing Species Richness and Biotic Integrity in Western Oregon Streams

Abstract

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 10 h. The rapid protocol occasionally underestimated species richness by missing vagile, 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.

The Index of Biological Integrity and the bootstrap: Can random sampling error affect stream impairment decisions?

“…Moreover, the fact that IBI confidence interval length was not related to community evenness suggests that IBIs sensitivity will be driven more by the presence or absence of these rare taxa per se, rather than a skewed community distribution. This observation contradicts the contention, made by several authors, that the failure to capture all species present at a site does not significantly affect IBI score (Steedman, 1988;Fore et al, 1994;Reynolds and Herlihy, 2003), and suggests that managers may want to carefully weigh trade-offs between minimizing sampling effort and obtaining a sample that accurately portrays maximum species richness.…”

Distribution patterns and trophic characteristics of salmonids and native species inhabiting high altitude rivers of Pampa de Achala region, Argentina

“…Such low fish richness appears as a characteristic attribute of high altitude streams in Pampa de Achala area. Based on morphometric characteristics (mean width = 8 m), we were confident that our sampling design fit within recommended efforts to obtain a representative description of fish community, covering in most cases between 30 and 40 channel widths (Lyons, 1992;Reynolds et al, 2003;Temple & Parsons, 2008). Most streams belong to headwaters basins, and therefore first and second order streams become the dominant riverscape.…”

Assessing the ecological status in species-poor systems: A fish-based index for Mediterranean Rivers (Guadiana River, SW Spain)

“…Furthermore, the characterization of species´ abundances is largely more complex and difficult to standardize than the description of species´ presences-absences. Key issues in sampling methodologies like sampling effort or methods have immediate consequences on bioassessment results (Lenat, 1993;Reynolds et al, 2003), so the simplest the information needed the more confident the results. This also has economic implications for the implementation of bioassessment programs, since the more information needed the higher the cost of recording it while a cost-efficient method is always desired (Schmutz et al, 2007a).…”