Seasonal migration of Gulf sturgeon in the Suwannee River, Florida

The movements of 67 Gulf sturgeon Acipenser oxyrinchus desotoi equipped with radio transmitters were monitored in the Suwannee River, Florida, from March 1989 through August 1992. The objectives of this study were (1) to determine the seasonal movement patterns and distribution of Gulf sturgeon while in freshwater, (2) to document relationships between water temperature and Gulf sturgeon movement, and (3) to determine whether springs were used as thermal refugia by these fish. Gulf sturgeon were detected entering the river from mid-February through April; they moved upstream at an average speed of 3.5 km/d to areas where they remained until October or November. Gulf sturgeon moved no more than 0,6 river km (on average) upstream or downstream from their established summer area. Gulf sturgeon began leaving the Suwannee River from mid-September through early November and moved downstream at an average speed of 6.2 km/d; all fish returned to the Gulf of Mexico by early December. Water temperatures associated with spring and fall migrations averaged 22.1 ??C (range, 16.0-28.0??C) and 21.3??C (range, 16.9-26.8??C), respectively. Gulf sturgeon were frequently close to springs throughout the warmest period, but none were located within a spring or the thermal plume emanating from a spring.