Population Density and Instream Habitat Suitability of the Endangered Cape Fear Shiner

Abstract

Abstract.-The Cape Fear shiner Notropis mekistocholas is an endangered minnow endemic to the Cape Fear River basin of North Carolina; only five populations remain, all of which are declining. Determining the population densities and habitat requirements of the species is critical to its survival and restoration planning. We conducted population surveys (four sites) and instream microhabitat suitability analyses (six sites) on the Rocky and Deep rivers to (1) estimate the population density of Cape Fear shiners, (2) quantify the use, availability, and suitability of microhabitats, and (3) determine whether physical habitat alterations were a likely cause of local extirpations and whether instream habitat limits the occurrence and density of this species. Density ranged from 795 fish/ha to 1,393 fish/ha (4,768-7,392 fish/km) at three of the sites surveyed and was too low to be estimated at the fourth site. The fish most frequently occupied riffles and velocity breaks at moderate depths over gravel substrates. It occupied microhabitats nonrandomly with respect to availability; the microhabitats occupied were similar between spawning and postspawning seasons but shallower during spawning. Comparisons of suitable habitat among sites where the fish is extant, rare, or extirpated suggest that suitable substrate (gravel) is lacking where the fish is rare and that suitable microhabitat combinations, especially with respect to water velocity, are rare at all sites. Potential reintroduction sites where the species is rare or extirpated were shallower than extant sites, and one site where the fish is extirpated contained suitable physical habitat but lacked adequate water quality. Another site where the species is rare would require substrate alteration to improve conditions. The survival and recovery of the Cape Fear shiner is dependent on the protection of remaining suitable physical habitat with approaches that consider instream habitat, water quality, and biotic interactions as well as human uses and alterations of the river, riparian zone, and watershed.

Sampling Characteristics and Calibration of Snorkel Counts to Estimate Stream Fish Populations

“…Our fish density estimates are within the ranges of those obtained for other riverine fishes (Ensign et al 1995;Hewitt et al 2009), although notable differences exist. Hewitt et al (2009) estimated density of the endangered Cape Fear Shiner Notropis mekistocholas in the Cape Fear River basin, North Carolina, to range from 795 to 1,393 fish/ha using the strip-transect count method. Our strip-transect counts (unadjusted for efficiency) for all shiners were 439.1 and 455.8 fish/ha for the summer and fall, respectively.…”

“…Our strip-transect counts (unadjusted for efficiency) for all shiners were 439.1 and 455.8 fish/ha for the summer and fall, respectively. The difference in density estimates between our sampling and that of Hewitt et al (2009) may be due to study site differences, as our sampling was conducted in a high-gradient mountain river (lower productivity) versus their sampling in a Piedmont river (higher productivity), reflecting actual population differences rather than variation in sampling efficiency. Ensign et al (1995) estimated mean densities of 5-272 fish/ha for Black Jumprock Moxostom cervinum, 3-163 fish/ha for Roanoke Logperch Percina rex, and 79-2,360 fish/ha for Roanoke Darter Etheostoma roanoka over various sampling sites using line-transect distance sampling.…”

Modelling riverine habitat for robust redhorse: assessment for reintroduction of an imperilled species

“…Survival of an imperilled species often hinges on identifying suitable habitat and understanding how to conserve this habitat (Rosenberger & Angermeier 2003;Hewitt et al 2009). Habitat assessment is a tool applied in this study to identify suitable habitat for species reintroduction.…”

Mortality, Dispersal, and Habitat Use of Stocked Juvenile Muskellunge in Two Western North Carolina Rivers

“…Availability of suitable habitat may also impede stocking success (e.g., Mittelbach 1981;Hewitt et al 2009;Brown and Bozek 2010), and habitat degradation has been cited as a primary obstacle to the creation of successful Muskellunge fisheries (Kerr 2011). Availability of suitable habitat in a stocked system can be especially critical for Muskellunge and other species that are known to exist in low population densities (Dombeck et al 1984;Hewitt et al 2009;Kerr 2011) and that are selective in the types of habitat they use (Hanson and Margenau 1992;Wagner et al 2015). Furthermore, habitat suitability can be directly linked to both dispersal and mortality, contributing to (1) increased dispersal if fish are required to search for suitable locations or (2) increased mortality if inadequate habitat increases vulnerability to predators.…”