Habitat use and movement patterns of adult robust redhorse released in the Oconee River, GA
July 2007 - December 2008
- Georgia Department of Natural Resources
- Georgia Power Company
- USFWS Region 4
The status and fate of the adult population of robust redhorse Moxostoma robustum in the Oconee River, GA, has been the subject of much investigation (e.g., Jennings et al. 1996, 1998, Freeman 1998, Jennings et al. 2000, 2003, 2004a, 2004b, 2005) and discussion by the Robust Redhorse Conservation Committee (RRCC) for more than a decade. The central issues in recent discussions include habitat use during spawning and non-spawning periods, movement pattersn, the apparent reduction in the number of individuals spawning annually at the Avant mine site, and a steady decline in catch rates during brood stock collection. There is increased concern among RRCC members about the fate of the robust redhorse population in the Oconee River. Radio telemetry has been used successfully to document dispersal rates, movement patterns, and habitat use of hatchery-reared juvenile robust redhorse released in the Oconee (Hess et al. 2001) and Ocmulgee (Jennings and Shepard 2003) rivers. The use of radio telemetry to evaluate movement patterns and habitat use of adult robust redhorse in the Oconee River has been considered in the past, but was never undertaken for a variety of reasons. However, recent dramatic successes with radio telemetry studies of adults in the Savannah (Grabowski and Isley 2006) and Pee Dee (R. Heise-NC Wildlife Resources Commission, personal communication ) rivers have renewed interest in the use of this technique to address long-standing questions about habitat use and movement patterns of adult robust redhorse in the Oconee River. Accordingly, I propose to use radio telemetry to conduct a long-term (i.e., minimum of 1 year; second year dependant on additional funding) assessment of habitat use of adult robust redhorse stocked in the Oconee River. The specific objectives of this study are to 1) compare habitat use and movement patterns of stocked fish during specific periods (i.e., pre-, spawning, and post-spawning) of the year; 2) use radio tagged robust redhorse as guide fish that might lead to unknown spawning aggregations or population centers; and 3) determine the detection probability of radio-tagged individuals. This work will provide long-term data on dispersal behavior, habitat use, and movement patterns of adult robust redhorse released into the Oconee River. Although some of the fish used in this study may have been produced in a hatchery and grew to adulthood in the wild, they are expected to behave as naturally spawning adults. Therefore, the behavior of the radio-tagged fish should allow for inference about the seasonal habitat use and movement patterns of wild-produced adults in the Oconee River and elsewhere. Further, the tagged fish may lead to undiscovered spawning sites in the Oconee River. An estimate of the probability of capturing (i.e. detection probability) adult robust redhorse, if one is present, can be incorporated into estimates of population size. Taken in total, this information should allow for new inferences about the status and prognosis of the adult robust redhorse population in the Oconee River and facilitate better management decisions for restoring or enhancing this species.