Discharge and Habitat Mediated Effects on Fountain Darter Etheostoma fonticola Reproduction

Purpose of this study was to assess reproduction of the federally listed Fountain Darter (Etheostoma fonticola) by effects of reductions in surface flows and expected associated changes in aquatic vegetation taxa in the Comal and San Marcos Rivers, Texas. We predicted that reproductive response variables, such as GSI, ovarian stage, and fecundity would be greatest in high flow environments and within vegetation types more closely approximating current understanding of habitat associations for this species. Sampling was conducted January to December, 2014 within low to high flow environments and in areas of no vegetation and short to tall vegetation types. Reproductive periodicity and effort were quantified using methodologies specific to darters and supported through histology. GSI, occurrence of late vitellogenic oocytes, and fecundity were similar among flow environments and microhabitat types, with a few exceptions indirectly related to water quantity. Observed responses in reproductive investment and clutch production likely represent adaptations to physical environments within a spring system that is not without historic variation in flow conditions. Further work is required to characterize the effects of reduced surface flow conditions on recruitment potential.