Cooperative Fish and Wildlife Research Units Program: Georgia
Education, Research and Technical Assistance for Managing Our Natural Resources

North American freshwater mussels have been subjected to multiple stressors in recent decades that have contributed to declines in the status and distribution of many species. However, considerable uncertainty exists regarding the relative influence of these factors on freshwater mussels. To evaluate the relative influence of natural and anthropogenic factors on freshwater mussels, we developed statistical models relating mussel species occurrence to various site- and landscape-level factors, including land use, stream size, the occurrence of drought, and reach isolation due to impoundment for 21 mussel species native to the Flint River Basin, Georgia. These models accounted for potential biases associated with both incomplete detection and misidentification of mussel species. Modeling results suggested that mussel species occupancy was strongly and negatively related to drought and reach isolation by impoundment. Mussel species were, on average, 4× less likely to be present following severe drought, but the negative effects of drought declined rapidly with increasing stream size. Similarly, mussel species were, on average, 15× less likely to occupy small streams that were isolated from mainstem tributaries by impoundments. This study provides insight into the effects of natural and anthropogenic factors on freshwater mussel populations and provides a useful tool for identifying locations within the lower Flint River Basin that may harbor populations of rare species or especially diverse mussel assemblages, thereby allowing managers to develop more informed and effective conservation strategies.