Monitoring fish biodiversity in rivers and streams: A review of sampling effort requirements

Biological conservation requires effective monitoring and an accurate understanding of biodiversity patterns. It is important to examine how stream ecologists have quantified fish richness because it is a fundamental measure of biodiversity. Despite its importance, stream ecologists have generally not appreciated the influence of sampling effort on richness measures. Here, we review the global English language scientific literature to determine how much sampling effort is required to estimate fish richness at stream site. Effort can be defined in spatial units (e.g. the sampling distance along a stream), temporal units (e.g. the amount of time that should be spent capturing fish), or biological units (e.g. the number of individual fish that should be captured to optimize species detection). We hypothesized that effort requirements for different systems relate to study context like stream size and local species richness. We reviewed 47 studies: 25 investigated distance requirements, 17 investigated sampling intensity, and five investigated both concepts. The median distance required to effectively sample a stream reach was 46 and 52 times the width of a given stream to measure 90 and 100% of species richness, respectively. Local species richness and local stream widths did not explain variation in sampling effort requirements, suggesting that other local factors may relate to sampling requirements. Biologists and resource managers interested in developing fish biodiversity monitoring programs should consider sampling effort requirements in their protocol designs and may need to perform pilot studies to determine a suitable level of effort for their local context.