Objectives

• 1) What factors affect the distribution of Niangua darters, with particular attention to how climate change may affect the distribution?
• 2) Does microhabitat selection of Niangua darters differ among seasons?

Overview

Understanding temporal and spatial habitat relationships is important to the recovery of the federally threatened Niangua darter Etheostoma nianguae, and other imperiled freshwater fishes, particularly in the face of projected climate and land use change. We evaluated microhabitat selection of adult Niangua darters at three Missouri Ozark stream reaches (mean= 503 m). Each reach was snorkeled (mean= 2.9 m/min) to identify Niangua darter locations where we measured nine instream habitat variables believed to be important to Niangua darter. These same variables were measured at three random locations within 100 m of each used location to represent available habitat. We used an information theoretic framework to develop models representing hypotheses related to Niangua darter microhabitat selection. We developed six models containing depth, velocity, substrate, distance to nearest cover, and cover size which we fit using discrete choice analysis. The model containing depth at 60% velocity had the lowest AICc value with all other models having a ΔAICc >4. During cooler months, adult Niangua darters selected deeper depths and slower velocities compared to warmer months. Selection for shallower/intermediate depths and faster velocities during warmer months may optimize feeding opportunities whereas deeper depths and slower velocities may maximize energy conservation during cooler months.