Recovery of a reservoir fish community from drawdown related impacts

Par Pond, a 10.5-km² reservoir in South Carolina, was drained over a period of 3 months to less than 50% of its former surface area and volume; it was maintained in that state for approximately 3.5 years. The drawdown resulted in significant reductions in fish abundance and number of fish species, changes in the relative abundance of fishes, and changes in the size structure of individual species of fish. An important factor contributing to these changes was complete loss of the original littoral zone. Within approximately 9 months of the refill of Par Pond to its former level, the fish community had recovered in terms of number of species and overall fish abundance, and had nearly recovered in terms of species composition. However, size structures after refill were different than before the drawdown: large individuals were fewer and small individuals greater in number. Factors contributing to the recovery of the Par Pond fish community included recolonization from refugia, high reproductive rates of resident species, and the shelter for small fishes provided by inundated terrestrial vegetation and rapidly regrowing aquatic vegetation. These results suggest that at least some reservoir fish communities are resilient to disturbances of their physical habitat and, in this respect, resemble stream fish communities.