Fish Community and Habitat Assessments Within an Urbanized Spring Complex of the Edwards Plateau
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Spring complexes within the arid region of the Edwards Plateau are diversity hotspots and evolutionary refugia for numerous aquatic fauna. Within the last 100 years, anthropogenic modifications and uses of spring complexes are associated with imperilment of aquatic fauna. Purposes of this study were to assess biotic integrity (i.e., regional and natural species composition and diversity; Karr and Dudley 1981) of the fish community and to quantify current community structure and habitat associations within the Comal springs complex, the greatest discharge spring within the Edwards Plateau region of central Texas and located within the urban landscape. Fishes and habitats were quantified among wadeable and non-wadeable areas and among six reaches of the Comal springs complex seasonally for one year. Twenty-five species and 23,318 fishes were observed. Spring-associated fish richness (S) was six, comprising 77% of the total catch per unit effort. Compared to reference conditions and to historical records, species richness and relative abundances suggest that the Comal spring complex has high biotic integrity despite extremely low flow conditions and rotenone treatment in the 1950s and habitat modifications (e.g., low head dams, land use conversion, bank stabilization) and high recreation use since the 1950s. However, the fish community was not homogenous among all reaches. Within two reaches of high recreational use, spring-associated fish richness and relative abundances were lower than other four reaches but still maintained high relative abundances of the federally-listed Fountain Darter. Fish-habitat associations were similar to reported habitat associations for most fishes. A notable exception was observed for the Fountain Darter, which had a more ubiquitous distribution and was not strongly associated with vegetation as previously found. Into the future, this study can be used as a baseline to monitor and assess threats to the Comal spring complex.