Habitat utilization and biological characteristics of adult Atlantic sturgeon in two South Carolina rivers

Thirty-nine adult Atlantic sturgeon Acipenser oxyrinchus oxyrinchus (136-23 4 cm total length) were caught in gill nets fished at historical sturgeon-f ishing locations in the Combahee and Edisto rivers (South Carolina) during spring and fall 1998. All fish were tagged (with passive integrated transpo nders and darts), and radio and acoustic transmitters were surgically impla nted in 29 fish. When possible, gonad biopsies were taken for sex and matur ity-stage determination. Locations of telemetered fish were determined seve ral times per week from airplanes (radio) and boats (radio and acoustic). N ominal ages, based on microscopic examination of pectoral spine cross-secti ons, ranged from 7 to 20 years. Of the 28 fish for which sex was definitive ly ascertained, 21 (aged 7-15) were male and 7 (aged 15-20) were female. Al l fish moved out of the rivers during the period extending from October to November. Twelve fish returned the following spring (most in March), and ma ny took up residence at the same sites utilized the previous year. Fall and spring spawnings were documented based on histological examination of gona d biopsies and directed upriver movements of fish during both seasons. Habi tats used during summer were diverse and included the lower and upper estua ries, tidal freshwater, river, and perhaps even the ocean, as some fish lef t the system entirely. One male was captured in two successive springs and was in spawning condition (running ripe) both years.