Winter coastal movement of Gulf of Mexico sturgeon throughout northwest Florida and southeast Alabama

Abstract

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.