Sport fisheries have been primary drivers of introductions of non-native fishes throughout North American inland waters for more than a century. These fisheries tend to value apex predators, species that are often aggressive and large-bodied. While these introductions satiate angling demand, they are problematic in freshwater systems that harbor rare and endangered fauna. Tonguetied minnow (Exoglossum laurae) maintains a disjunct distribution across four watersheds of the eastern and Midwestern United States. In Ohio, tonguetied minnow is Endangered and is distributed along a ~60 km segment of the Upper Mad River, a headwater tributary of the Great Miami River drainage. The Upper Mad River is also annually stocked with ~11,500 brown trout (Salmo trutta) to sustain a popular sport fishery. Here we use Poisson regressions in combination with maximum entropy species distribution models to estimate in-stream habitat of both species in the Upper Mad River. Models were based on 15 water quality and stream habitat variables collected from throughout the Great Miami River.
Results/Conclusions
Poisson regressions identified water temperature, stream gradient, and channel type as important for tonguetied minnow, whereas water temperature, stream gradient, in-stream cover, riffle habitat, and total dissolved solids were identified for brown trout. Maximum entropy species distribution models based on the results from Poisson regressions found that only water temperature (49% model contribution for tonguetied minnow and 21% model contribution for brown trout) and stream gradient (50% model contribution for tonguetied minnow and 73% model contribution for brown trout) were important for each species. More specifically, cold water and high stream gradient were associated with the distributions of both species. Ecological constraints therefore likely prevent tonguetied minnow from escaping elevated extirpative risks resulting from interspecific interactions, such as predation, with introduced brown trout.