Effects of sampling effort, assemblage similarity, and habitat heterogeneity on estimates of species richness and relative abundance of stream fishes

Abstract

We estimated the sampling effort required to accurately estimate species richness and to detect changes in catch-per-unit-effort (CPUE) in four Great Plains, USA, streams. The number of sampled reaches (i.e., <1 km) required to estimate stream-segment (i.e., 20–28 km) species richness decreased with increased sampled reach length (i.e., 10, 20, 40, or 60 mean stream widths, MSW), whereas total sampling effort decreased with a greater number of shorter sampled reaches. Collecting all species in a stream segment required all sampled reaches (i.e., 10) of a length equal to 40 or 60 MSW. The number of stream reaches sampled with lengths equal to 40 MSW required to detect a 50% change in CPUE of common species (i.e., total abundance > 1% of total catch) with β = 0.80 ranged from 7 to 630 (mean = 99) and decreased with longer sampled reaches. A greater number of sampled reaches were needed to detect 90% of species richness and 25% changes in CPUE when Jaccard’s similarity of samples of stream fish assemblages and habitat heterogeneity was lower within streams. Our results suggest that homogeneous stream segments require more sampled reaches to characterize fish assemblages and monitor trends in fish abundance.

Site length for biological assessment of boatable rivers

“…In fact, the range in scores was slightly less for site lengths of 10 MWCW than longer sites, resulting in marginally smaller detectable differences for 10-MWCW site lengths (Table I). Fischer and Paukert (2009) and Utrup and Fisher (2006) reached similar conclusions for prairie rivers. Smith and Jones (2008) estimated that an optimized design for detecting species in small Michigan catchments would be (Table I), across a region with similar variability as the Oregon data (Hughes and Herlihy, 2007).…”

“…For example, in designs where a long sampling site is warranted for estimating spatially extensive characteristics, we strongly advocate sampling several shorter sub-sites, and keeping the data separate, to generate multiple data points that can be used to determine conditions at a smaller geographic extent (e.g. Cao et al, 2001;Hughes et al, 2002;Erős et al, 2008;Smith and Jones, 2008;Fischer and Paukert, 2009;Kanno et al, 2009). A split-geographic extent design, such as this, will provide data at two geographic extents, the smaller geographic extent also providing a means of estimating variability within the larger geographic extent, as long as the data are recorded by sub-site.…”

Intra-reach Headwater Fish Assemblage Structure

“…However, they did not report the similarity among assemblages within each reach or pool. Similarly, Fischer and Paukert (2009) collected nested samples of different effort (distances shocked) to determine effort needed to detect different assemblages between streams, but did not examine differences in local assemblages within streams. Espirito-Santo et al (2013) also examined fish assemblages at fine-scales within Amazonian headwater streams and were able to identify microhabitat associations and movements between the river and floodplain, but they did not discuss the similarity of assemblages within each reach.…”

A standardised sampling protocol for robust assessment of reach-scale fish community diversity in wadeable New Zealand streams

“…For instance, it has previously been established that fish species richness increases with the number of geomorphic units sampled (Gorman & Karr 1978;Angermeier & Schlosser 1989) and that effort, stream length, and stream area can all influence species richness and relative abundance at the reach-segment scale (e.g. Lyons 1992; Simonson & Lyons 1995;Patton et al 2000;Hughes et al 2002;Blocksom et al 2009;Fischer & Paukert 2009). Additionally, the level of effort required to effectively describe riverine fish species composition at larger watershed scales has also been investigated (Smith & Jones 2005).…”

“…Additionally, the level of effort required to effectively describe riverine fish species composition at larger watershed scales has also been investigated (Smith & Jones 2005). Information from such studies has been incorporated into methodologies to improve the quality and accuracy of data collected and, because these data are often used for management or conservation decisions, confidence in their accuracy and quality is paramount (Fischer & Paukert 2009). …”