A telemetry study was conducted in the Apalachicola River/estuary, Florida, to determine migratory behavior of anadromous Gulf of Mexico sturgeon. Ultrasonic (remote and mobile units) and radio telemetry gears were used to assess movements of sturgeon in both fresh and saltwater. Transmitter-equipped fish (N = 10) began fall migration between 22 September and 19 October 1987, and averaged 4.6 days to descend 152 Ian to the lower Apalachicola River where freshwater "staging areas" were utilized for periods of 0-20 days prior to moving into brackish river water. Three sturgeon continuously monitored during river exit spent 8-12 hours in brackish river water, apparently osmoregulating before making nocturnal exits to Apalachicola Bay. Ultrasonic monitoring was largely unsuccessful, although 3 sturgeon were tracked into saltwater and monitored in Apalachicola Bay for up to 4 hours. Ultrasonic remote sensors located in barrier island passes were partially functional and recorded sturgeon movement in West Pass. Seven of the radio-tagged sturgeon returned to the Apalachicola River in spring 1988. Smaller fish returned significantly earlier in the year than did larger ones.