Habitat Use and Density of the Ouachita Darter in the Upper Ouachita River

Abstract: The Ouachita darter (Percina sp. nov.) is endemic to the fragmented Ouachita River drainage in southwest Arkansas and is considered a sensitive species by the U.S. Forest Service.  Characterization of habitat used by the species would facilitate management efforts, but it is not well defined.  Our objectives were to establish baseline sample densities and to identify the habitat used by Ouachita darters in the upper Ouachita River, Arkansas.  Mean sample density in the free-flowing section of the river from trawl surveys was 0.21 fish/100 m² compared to 0.51 fish/100 m² estimated from snorkeling surveys.  Trawl samples in the transition zone between Lake Ouachita and the upper river yielded an average of 1.36 fish/100 m².  Ouachita darters occupied shallow pool or moderately deep run/glide habitat, and selected for moderate water velocities over cobble/gravel substrates.  Adults used slightly shallower, faster water than juveniles.  We conclude that the Ouachita darter is a relatively rare darter in the upper Ouachita River, and that the transition zone between reservoir and river provides unexpectedly good habitat that may support a source population of Ouachita darters.  Maintenance of flows that create run/glide habitats with silt-free cobble/gravel substrate is important for conservation of the species.