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

Shea, C.P., P.W. Bettoli, K.Potoka, C.F. Saylor, and P.W. Shute. 2015. Use of dynamic occupancy models to assess the response of darters (Teleostei: Percidae) to varying hydrological and hydrothermal conditions in a southeastern United States tailwater. River Research and Appplications 31:676-691.


River regulation and water resource development are important problems threatening stream-dwelling fishes and other aquatic biota. During the past 100 y, most large rivers in North America have been altered for flood control, hydropower, navigation, or water supply development. Although these activities clearly provide important human services, their associated environmental disturbances can profoundly affect stream-dwelling organisms. Nowhere in North America is this more evident than the Tennessee River drainage in Alabama, Georgia, Tennessee, and Virginia, where the Tennessee Valley Authority operates 11 dams on the mainstem Tennessee River and 27 dams on major tributaries. We used multi-species dynamic occupancy models to evaluate the influence of site- and species-level characteristics on metapopulation dynamics rates for 15 darter species native to the Elk River, Tennessee. Modeling results indicated that darter colonization was strongly and positively related to water temperature and body size, but crevice spawning species were substantially less likely to colonize previously unoccupied study reaches. Modeling results also indicated that the risk of extinction was strongly and negatively related to stream temperature. Additionally, the presence of populations in neighboring upstream study reaches contributed to a lower risk of extinction for existing populations. A series of metapopulation simulations based on parameter estimates from the best-approximating models were conducted to evaluate the consequences of alternative hypotheses on darter dispersal capabilities. The simulation results revealed that failure to account for alternative plausible hypotheses of influential properties, such as dispersal, could mask the range of possible outcomes, both positive and negative. Our study demonstrates the usefulness of trait-based approaches and a metapopulation framework to assess the dynamics of darters in a heavily-regulated stream system. Results from our study will provide a baseline for evaluating the ecological consequences of alternative dam operations under an adaptive management framework.