Occurrence of stocked shortnose sturgeon Acipenser brevirostrum in non-target rivers

A federal/state program was conducted to evaluate the use of hatchery-produced shortnose sturgeon Acipenser brevirostrum for supplementation or restoration of this federally endangered species. A total of 97 483 sturgeon of various ages was stocked into the Savannah River ( source of the initial broodstock) during 1985-1992. Of these, 18 213 were marked in some manner, and tag retention studies were conducted concurrently. Data on tagged fish capture was obtained from directed sampling and from commercial fisheries bycatch. During 1997-2000, 10% of the adult shortnose sturgeon population in the Savannah River was identifiable as hatchery-reared. Based on tag loss estimates, actual contribution of stocked fish to the population is believed to be approximately 38.7%, excluding any contribution from the 79 270 unmarked fish stocked. In 1995, hatchery fish began to be captured in non-target rivers. During 1997 2000, identifiable stocked fish comprised 7.4% of the adult population in the Ogeechee River, Georgia. In 1995-2000, 10.6% of the adults in the Edisto River, South Carolina were identifiable as stocked fish. Shortnose sturgeon were first reported in the Edisto River in 1994, and the first juvenile was captured in 1998. It appears that fish stocked into the Savannah River emigrated and colonized the Edisto River, and that they also substantially supplemented the Ogeechee River population. Other stocked fish have been detected in the Cooper River ( South Carolina) and in Winyah Bay ( 278 km north of the mouth of the Savannah River). Although shortnose sturgeon have not been shown to imprint on natal rivers, these data support the hypothesis that some fish stocked into the Savannah River failed to imprint on that river and began wandering.