Comparison of Fish Communities at Random and Nonrandom Locations in a Sand‐Bed River

Abstract

Surveys based on nonrandom site selection, or convenience samples, are often a necessary part of large-scale monitoring programs to help minimize costs. The reliability of convenience samples to inform managers about distributions or population status of imperiled species is questionable, however, because the samples may not be representative of the whole population. We compared fish community data from 20 nonrandom, long-term monitoring sites for Rio Grande Silvery Minnow Hybognathus amarus with those from 20 randomly chosen samples collected during two surveys (one in summer, one in autumn) in the Rio Grande, New Mexico. We compared the species richness, community composition, and the catch per unit effort (CPUE). Fish species compositions, which were similar between both sets of summer and autumn surveys, were nearly identical in the autumn surveys. Similarly, we found consistent Rio Grande Silvery Minnow CPUE between surveys; summer random surveys estimated 0.32 fish/100 m 2 sampled, whereas summer nonrandom surveys estimated 0.37 fish/100 m 2 sampled. In autumn, both surveys showed a marked decline in Rio Grande Silvery Minnow; random surveys found 0.08 fish/100 m 2 sampled (95% confidence interval 0.04-0.18), whereas the nonrandom surveys failed to collect any Rio Grande Silvery Minnow. Both surveys showed a reduction in species richness between summer and autumn with a corresponding increase in dominance by Red Shiner Cyprinella lutrensis and a decline in Rio Grande Silvery Minnow. We failed to find any meaningful differences in either fish community or Rio Grande Silvery Minnow CPUE between random and nonrandom sites, suggesting that the long-term, nonrandom locations currently used to monitor the Rio Grande Silvery Minnow population are representative of the middle Rio Grande. We believe our results are applicable to many monitoring programs in systems with a homogeneous distribution of mesohabitats; nonetheless, we recommend that managers assess potential bias in monitoring programs based on convenience samples.

The emblematic minnows of the North American Great Plains: A synthesis of threats and conservation opportunities

“…Beginning with adults, habitat degradation (often in the form of longitudinal fragmentation) and flow alteration interact to truncate upstream adult migration through physical barriers or reducing flow connectivity. The linkage between habitat and flow is unidirectional for reproduction, with habitat degradation (often driven by longitudinal fragmentation due to dam construction) eliciting changes to the natural flow regime which disrupts spawning cues (Archdeacon, Henderson, Austring & Cook, ; Durham & Wilde, , , ). Ichthyoplankton downstream drift is disrupted by the interaction among flow, habitat and water quality.…”

“…Results from our review show that the threats to PBS species are multifaceted and inherently interlinked ( Figure 10). To conceptualize threats across the life history of PBS species, we broadly follow the five categories of anthropogenic drivers highlighted by Dudgeon, Arthington and Gessner (2006) to the natural flow regime which disrupts spawning cues (Archdeacon, Henderson, Austring & Cook, 2015;, 2009a. Ichthyoplankton downstream drift is disrupted by the interaction among flow, habitat and water quality.…”

Quantifying Seining Detection Probability for Fishes of Great Plains Sand‐Bed Rivers

“…Archdeacon et al. () speculated that not capturing the Rio Grande Silvery Minnow, also federally listed as threatened, at some sites in the Rio Grande River by seining could be attributed to low detection probability. We did not encounter Arkansas River Shiner in the Cimarron River and, for modeling considerations, assumed absence.…”

“…Not surprisingly, sand-bed streams are characterized by diverse instream habitats and highly variable and extreme physicochemical conditions (Matthews and Hill 1979;Fausch and Bestgen 1997;Dodds et al 2004). The high conductivity of the water in sand-bed streams of the Great Plains limits the use of electrofishing; thus, seining is the most common fish sampling gear in wadeable areas (e.g., Widmer et al 2010;Marsh-Matthews and Matthews 2013;Archdeacon et al 2015;Hoagstrom et al 2015;Wilde 2016).…”

“…Diminutive fishes that occur in Great Plains streams, which include a number of cyprinids of conservation concern (e.g., Arkansas River Shiner Notropis girardi, Peppered Chub Machrybopsis tetranema, Rio Grande Silvery Minnow Hybognathus amarus: Worthington et al, in press), are often the focus of research and monitoring efforts (e.g., Hoagstrom et al 2008;Wilde and Durham 2013;Archdeacon et al 2015;Perkin et al 2015;Pennock et al 2017). Despite recent advances, quantifying stream fish detection probability in sand-bed streams of the Great Plains has received little attention by researchers (but see Falke et al 2010Falke et al , 2012.…”