Vegetation associations of the endangered fountain darter Etheostoma fonticola

Abstract

Aquatic vegetation provides many services for aquatic habitats and fish communities. The federally listed fountain darter Etheostoma fonticola, found only in spring systems of the San Marcos and Comal rivers in central Texas, is reported to associate with vegetation for feeding, reproduction, and refuge. Descriptions of associations with vegetation range from preferred to exclusive, whereas other studies describe fountain darters found outside of vegetation. The purposes of this study were to quantify fountain darter occurrences and abundances among vegetated habitats using the concept of obligate and facultative habitat use. Wadeable and non-wadeable habitats among multiple reaches of the San Marcos and Comal rivers were sampled with seines and SCUBA diving methods in the spring and fall from 2014 to 2019. Fountain darters were often associated with aquatic vegetation but demonstrated both obligate and facultative tendencies. Fountain darters occurred in vegetation more than expected among wadeable and non-wadeable habitats in the majority of reaches within the San Marcos and Comal rivers. Among vegetation taxa, they were positively associated with bryophytes and negatively associated with Texas wild rice, but associations with other vegetation taxa varied by river and were possibly influenced by other variables. Current vegetation management in both rivers includes the removal of non-native species and restoration of native vegetation, so understanding the patterns of fountain darter associations with vegetation can guide future management and restoration efforts of these spring systems.