Fish Community and Habitat Assessments within an Urbanized Spring-Fed Stream of the Edwards Plateau

Spring systems along the Edwards Plateau of Central Texas are historical and contemporary diversity hotspots for endemic fishes.  Flows of spring systems are dependent on karst aquifers, which are depleted by excessive groundwater withdrawals.  Purpose of this study was to establish relationship between spring flow and biotic integrity in the Comal River system, a large spring system located in an urbanized area.  Objectives of this study were to quantify spatial and temporal patterns in fish community densities, fish-habitat associations, and fish densities and habitat associations related to spring flow.  Given that spring habitats range from wadeable to non-wadeable waters, we combined seining and SCUBA techniques to quantify fish community and habitat associations. To date, densities of spring fishes and habitat associations were quantified under a region-wide drought.  Densities of spring fishes, most notably the federally-listed Etheostoma fonticola, decreased during a declining hydrograph, but seasonal reproduction by E. fonticola cannot be excluded as a possible mechanism in the decline.  Study results will guide conservation efforts in protecting the spring system from excessive withdrawals from the underlying aquifer.