Summary In order to characterize distribution of Gulf of Mexico sturgeon in nearshore Gulf of Mexico (GOM) and compare distributions prior to and after hurricane activity, 187 Gulf sturgeon (Acipenser oxyrinchus desotoi) were tagged with acoustic transmitters in Ochlockonee, Apalachicola, Brothers, Choctawhatchee, Yellow, Blackwater and Escambia rivers to monitor marine movement along the GOM coastline from Florida (FL) to Alabama (AL). Nine juveniles (79–86 cm fork length, 3.4–5.2 kg), 22 sub‐adults (91–126 cm fork length, 4.5–17.1 kg) and 156 adults (130–210 cm fork length, 14.9–75.2 kg) were tagged between 2003 and 2005 and acoustically monitored each year between January and April, 2004–2008. Of the 187 tagged Gulf sturgeon, 72 adults, one sub‐adult and no juveniles were relocated in the GOM throughout the entire duration of monitoring between 2004 and 2008. Fish were relocated on average 1.5 km from shore in two very important foraging and over wintering areas, one of which is not currently protected under the critical habitat designation: Site A located geographically between Pensacola, FL and Gulf Shores, AL and Site B located between Mexico Beach, FL and Panama City Beach, FL. Sediment studies conducted concluded that substrate at Site A consisted of fine sand, shell and areas of silty mud and substrate at Site B consisted of shell hash and fine sand. Macro invertebrates, such as polychaetes: Hobsonia florida and Mediomastus ambiseta and mollusk: Ervillia concentric, all typical to the Gulf sturgeon diet, were present at both sites. Forty‐three tagged adult Gulf sturgeon were relocated at Site A and 27 adults and one sub‐adult were relocated at Site B, with two additional fish located in other areas. Individual fish movement in one direction ranged from 10 to 315 km each year. Several fish exited one river, over wintered in the GOM, and entered a different river. Identification of new, frequently used Gulf sturgeon habitat (Site A), outside of federally protected critical habitat, provided vital information that will aid in the future protection of coastal areas that support Gulf sturgeon during the winter and help with recovery efforts of the species.

Fifty egg mats and up to five D‐shaped plankton nets were deployed in the tailrace of Pinopolis Dam at river kilometer 77 on the Cooper River, South Carolina, to evaluate the spawning activity of shortnose sturgeon Acipenser brevirostrum. Spawning times were estimated by back‐calculation based on developmental phase. Eggs were collected on 17 of 21 d sampled continuously from March 4 through March 25, 2002, when water temperatures were 10–16°C. A total of 31 shortnose sturgeon eggs were collected from egg mats. An additional 338 shortnose sturgeon eggs and 1 newly hatched yolk sac larva were collected from plankton nets. A minimum of 20 spawning events occurred in the tailrace during the 2002 spawning season. No relationship between mean daily discharge and spawning date was observed. Shortnose sturgeon spawned more often during the night than at any other time of day independent of generation.

In this paper, we assess patterns in activity of Gulf of Mexico sturgeon Acipenser oxyrinchus desotoi over a 24-h period in the Pensacola bay system, Florida. Although seasonal migration of sturgeon is well documented, little information is available pertaining to daily variation in activity. We surgically implanted 58 Gulf sturgeon with acoustic transmitters in the Escambia (n = 26), Yellow (n = 8), Blackwater (n = 12) and Choctawhatchee rivers (n = 12) in June, July, September and October 2005. Gulf sturgeon location was monitored using an array of 56 fixed-station acoustic receivers. The relationship between frequency of Gulf sturgeon observations recorded on all acoustic receivers and time of day for all seasons combined indicated a strong diel activity pattern. Gulf sturgeon were frequently detected at night in all seasons with the exception of summer. Consecutive hourly observations indicated lateral movement of Gulf sturgeon between independent acoustic receivers on 15% of all observations of individuals. The use of an acoustic receiver array not only provides continuous data within a defined area, but also provides insight into nocturnal behavior of Gulf sturgeon not previously identified.