Shortnose Sturgeon in the Santee–Cooper Reservoir System, South Carolina

Abstract

The Santee–Cooper system in South Carolina, USA, is a complex of reservoirs, rivers, and canals. The endangered shortnose sturgeon Acipenser brevirostrum inhabits the rivers below the reservoirs and has also occasionally been reported anecdotally in the reservoirs themselves. During 1998–1999, we conducted a study to determine whether shortnose sturgeon were reproducing in the reservoirs, and if so, to evaluate habitat use and degree of separation from the riverine groups. Fourteen shortnose sturgeon were captured from the reservoirs, and all (even gravid females) appeared qualitatively less robust than riverine fish previously captured below one of the dams. Ten of the fish were implanted with transmitters and tracked at least once per week. Fish tracked in the upper reservoir, Lake Marion, stayed in the upper portion of that lake or in tributary streams flowing into it. We documented seasonal movements among four primary areas of upper Lake Marion and its tributaries. A spawning site on one of the tributaries, the Congaree River, was verified by collection of viable eggs. Genetic analysis demonstrated significant differences between samples from the Santee–Cooper reservoirs and three nearby coastal rivers. Cooper River samples, however, were not significantly different from reservoir samples, although appreciable differences in haplotype frequencies were observed. The need for a larger sample size was apparent. Although telemetry, spawning, genetic, and observational evidence suggests that the shortnose sturgeon in the reservoirs form a separate population segment, the results are not conclusive because possible downstream movement, especially of juveniles, through the dams has not been investigated.