Stream Habitat and Mussel Populations Adjacent to AAWCM Sites in the Lower Flint River Basin

Freshwater mussel communities of the Flint River Basin (FRB) in southwestern Georgia are among the richest mussel assemblages in the southeastern United States. Declines in these populations appear to be associated with periodic droughts along with increasing water withdrawal for irrigation and other uses. Concerns about stream health and recognition of the need to manage water efficiently led to the development of Advanced Agricultural Water Conservation Measures (AAWCM). In 2012 and 2014, we examined the effects of AAWCM installed in operational settings on in-stream habitat, flow, and mussel populations in two watersheds of the lower Flint River Basin: Spring Creek and Ichawaynochaway Creek. Mussel abundance was relatively low in the sites sampled during the 2012 field season (in comparison to historic 1999/2001 surveys). In 2014, Spring Creek mussel abundance increased at sites adjacent to AAWCM farms and at two of three downstream locations. Increases followed the end of drought conditions and the apparent recruitment of mussels likely resulted from normal growing season stream flow. In 2014, Ichawaynochaway Creek mussel abundance remained constant or decreased at all sites. Historic surveys noted 2-11 mussel species at sampling sites. In 2012, 1-10 species were noted and in 2014, 0-8 species were noted. Abundance also declined from 8-1028 individuals per 100m reach to 0-629 individuals. Endangered species were rare at all sites and surveys. Rapid declines or extirpation of species at many sites occurred during the 1999-2001 drought, followed by an ongoing decline of surviving individuals through 2014. It appears that long-term declines in freshwater mussels continue in the tributaries of the lower Flint River. INTRODUCTION Freshwater mussel communities of the Flint River Basin (FRB) in southwestern Georgia are among the richest mussel assemblages in the southeastern United States. Historically, 29 species of mussels, seven of which were endemic, existed in the Flint River system (Clench and Turner 1956). Surveys conducted between 1991 and 1993 found that several Flint River tributaries within the Coastal Plain (lower FRB) continue to harbor diverse mussel faunas, numbering from 9 to 16 species, including several endangered species (Brim Box and Williams 2000). However, only 22 of the 29 species originally found in the Basin were observed during the 1999-2001 survey. The area in which the highest concentration of endangered species were found, and the most abundant and diverse communities were noted, was in the tributary streams of the Flint River flowing through the Coastal Plain portion of the watershed, the lower FRB.