Habitat Suitability of the Carolina Madtom, an Imperiled, Endemic Stream Fish

—The Carolina madtom Noturus furiosus is an imperiled stream ictalurid that is endemic to the Tar and Neuse River basins in North Carolina. The Carolina madtom is listed as a threatened species by the state of North Carolina, and whereas recent distribution surveys have found that the Tar River basin population occupies a range similar to its historical range, the Neuse River basin population has shown recent significant decline. Quantification of habitat requirements and availability is critical for effective management and subsequent survival of the species. We investigated six reaches (three in each basin) to (1) quantify Carolina madtom microhabitat use, availability, and suitability; (2) compare suitable microhabitat availability between the two basins; and (3) examine use of an instream artificial cover unit. Carolina madtoms were located and their habitat was quantified at four of the six survey reaches. They most frequently occupied shallow to moderate depths of swift moving water over a sand substrate and used cobble for cover. Univariate and principal components analyses both showed that Carolina madtom use of instream habitat was selective (i.e., nonrandom). Interbasin comparisons suggested that suitable microhabitats were more prevalent in the impacted Neuse River basin than in the Tar River basin. We suggest that other physical or biotic effects may be responsible for the decline in the Neuse River basin population. We designed instream artificial cover units that were occupied by Carolina madtoms (25% of the time) and occasionally by other organisms. Carolina madtom abundance among all areas treated with the artificial cover unit was statistically higher than that in the control areas, demonstrating use of artificial cover when available. Microhabitat characteristics of occupied artificial cover units closely resembled those of natural instream microhabitat used by Carolina madtoms; these units present an option for conservation and restoration if increased management is deemed necessary. Results from our study provide habitat suitability criteria and artificial cover information that can inform management and conservation of the Carolina madtom. Warmwater streams in the southeastern United States support substantial biological diversity on broad spatial scales (Meffe and Sheldon 1988; Lydeard and Mayden 1995). Because these systems are dynamic, management becomes a challenging task, compounded by the fact that fish often require conditions that differ from those of other aquatic species (e.g., flow conditions; Hubert and Rahel 1989; Aadland 1993). Particularly vulnerable to habitat loss, exotic species, and pollution, stream fishes in the southeastern United States are disproportionately imperiled in comparison with those in other U.S. regions (Wilcove et al. 1998; Jelks et al. 2008). In particular, disproportionate rates of imperilment and extirpation are occurring among benthic fishes (e.g., sculpins, darters, and madtoms Noturus spp.) as stream bottoms are often the first impacted habitat type (Angermeier 1995; Etnier 1997; Warren et al. 1997). Aadland (1993) also noted higher rates of imperilment for nongame species because they are generally less intensively managed than species of commercial and recreational interest. Endemic species are particularly susceptible to extirpation because their isolation increases vulnerability to both human activity and natural catastrophic events (Warren and Burr 1994; Burkhead et al. 1997). An understanding of habitat requirements is critical for conservation of endemic species. Habitat quality and quantity influence species diversity; a greater diversity of quality correlates to higher fish diversity (Gorman and Karr 1978; Schlosser 1982; Reeves et al. *Corresponding author: [email protected] Received December 10, 2008; accepted August 29, 2009 Published online December 31, 2009 325 Transactions of the American Fisheries Society 139:325–338, 2010 Copyright by the American Fisheries Society 2009 DOI: 10.1577/T08-238.1 [Article]