| SPATIAL AND TEMPORAL HABITAT SEGREGATION BY SPAWNING CATOSTOMIDS IN THE SAVANNAH RIVER, SOUTH CAROLINA AND GEORGIA |
| GRABOWSKI, T. B. (1) and Isely, J. J. (2). (1)Department of Biological Sciences, Clemson University, Clemson, South Carolina, 29634-0326, tgrabow@clemson.edu, (2)U.S. Geological Survey, South Carolina Cooperative Fish and Wildlife Research Unit, Clemson University, Clemson, South Carolina, 29634-0372. |
| Six catostomid species, including the imperiled robust redhorse, inhabit the lower Savannah River. Each of these species is dependent to differing degrees upon main channel gravel bars for spawning substrate. Catostomids in the lower Savannah River have ready access to only two main channel gravel bars. Despite the importance of these features, little is known about how the different species utilize gravel bars. We used visual observation, prepositioned grid electrofishers, and drift nets to determine the degree of spatial and temporal segregation in the use of this habitat over the course of two spawning seasons. We were able to evaluate spawning activity in three species: spotted sucker, notchlip redhorse, and robust redhorse. No temporal overlap was observed in habitat use by adult fishes. Adults of a given species were present on the bar for discrete periods of time (approx. 15-21 days) followed by a lapse of 14-20 days with no spawning individuals observed. Different species showed a high degree of spatial overlap on the gravel bar with similar requirements of substrate and flow. The order of species remained consistent between years. However, there was variability in the length of time each species occupied the gravel bar and the duration of the interludes between spawning species. The two gravel bars differ in the number of individuals of each species using them. Our preliminary conclusion is that only limited interference occurring among species and other factors such as habitat availability and density dependent effects, such as egg predation and intraspecific nest superimposition, may be effecting catostomid populations. |
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