Trout Growth and Mortality Following Water Quality and Flow Improvements on the Lower Saluda River in South Carolina

The lower Saluda River (LSR) supports a coldwater, put-grow-and-take trout fishery due to hypolimnetic releases from the Saluda Hydroelectric Project. The LSR has historically been noted for low flows (5.1 m3 sec-1) transitioning abruptly to peaking flows up to 509.7 m3 sec-1 with seasonally hypoxic water. Recent relicensing resulted in changes in the Saluda Hydroelectric Project operation that were intended to improve habitat conditions downstream. In a multi-year study, a combination of tagging and boat electrofishing was used to evaluate mortality, growth, and angler catch and exploitation rates of catchable rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta) stocked into the LSR. Each year electrofishing catch rates and angler tag returns of December-stocked catchable-sized trout peaked in December shortly after stocking and declined rapidly in subsequent months. More than half of the angler tag returns were reported from the uppermost reach of the river that contained most of the angler access. Mean annual mortality of stocked rainbow trout and brown trout was high (>95%), but harvest rates were low (<9%) for both species, indicating natural or post-stocking mortality was more influential than fishing mortality. Mean annual angler catch rates were poor, with only 13% of stocked rainbow trout and 4% of brown trout caught by anglers. Despite the poor survival of stocked trout, quality trout habitat was demonstrated by the presence of large rainbow trout (2.6 kg) and brown trout (3.1 kg), excellent (>17 mm mo-1) growth rates for both species, and the presence of small rainbow trout that were assumed to be wild. Because of these findings, several changes were made to the management of the fishery. A modification to the five-fish creel limit, whereby only one trout over 40.64 cm can be harvested as one of the five, was made to reduce exploitation of holdover fish. A 4-km catch-andrelease-only zone was also established to serve as a nursery for young-of-the-year fish and provide additional protection for the holdover population.

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