Species Distribution Models for a Native Imperiled Minnow and a Nonnative Sport Fish in a Western Ohio River

Abstract

Sport fisheries are frequent drivers of nonnative fish introductions throughout the inland waters of North America. These fisheries often value aggressive, large-bodied predators, and although they satiate angling demand they are also potentially problematic in systems that support imperiled species. The Tonguetied Minnow Exoglossum laurae is a rare species that maintains a disjunct distribution across small portions of four watersheds in the eastern and Midwestern United States, all of which are stocked with nonnative Brown Trout Salmo trutta for sportfishing. This study estimated habitat preferences for Tonguetied Minnow and Brown Trout in the Great Miami River, the westernmost drainage within the Tonguetied Minnow's range. Model data were based on eight water quality variables and seven stream habitat variables. Negative binomial regressions identified gradient, maximum water temperature, substrate, pool/glide habitat, total dissolved solids, and specific conductance as important predictors of the distribution of Tonguetied Minnow, whereas maximum water temperature and substrate were identified for Brown Trout. These reduced numbers of variables then served as input into maximum entropy species distribution models for Tonguetied Minnow and Brown Trout. Only gradient (model contribution [MC] = 46.9%; permutation importance [PI] = 11.6%) and maximum water temperature (MC = 44.2%; PI = 79.8%) contributed substantially to the species distribution model for Tonguetied Minnow, while maximum water temperature (MC = 63.4%; PI = 76.2%) and substrate (MC = 36.6%; PI = 23.8%) were important contributors for Brown Trout. Water temperature appears to exert the principal influence on the distributions of both species and supports the premise that these species share similar habitat preferences within the Great Miami River. Therefore, the Tonguetied Minnow is likely unable to avoid interspecific interactions, such as predation, posed by Brown Trout that are introduced for sportfishing, thus raising concerns about the conservation of this isolated and highly imperiled population.