Distribution of Gulf of Mexico Sturgeon in Relation to Benthic Invertebrate Prey Resources and Environmental Parameters in the Suwannee River Estuary, Florida

Abstract

The distribution of threatened Gulf of Mexico sturgeon Acipenser oxyrinchus desotoi (hereafter referred to as Gulf sturgeon) in the Suwannee River estuary, Florida, was examined relative to the distribution of benthic invertebrate prey and environmental variables (salinity, temperature, dissolved oxygen, and sediment type) to determine potential foraging areas within the estuary. Eighteen Gulf sturgeon (1,279–2,010 mm total length, 15.25–53.25 kg) were netted at the mouth of the Suwannee River during their spring upriver migration in 2001 and surgically implanted with ultrasonic tags. These sturgeon were subsequently tracked as they migrated seaward out of the Suwannee River and into the estuary in fall 2001 and as they returned to the estuary in spring 2002 to migrate upriver again. Invertebrates and sediment type were identified in diver-collected cores from the Suwannee River estuary during spring 2002. Thirteen of the 18 tagged Gulf sturgeon were relocated in the Suwannee River estuary. Eight were located from early November through mid-December 2001 (fall seaward migration), and 10 were located from mid-March through mid-April 2002 (spring upriver migration). Gulf sturgeon during fall 2001 and spring 2002 were associated with areas composed mostly of sand that contained high abundances of known benthic prey, primarily the brachiopod Glottidia pyramidata and, secondarily, amphipods Ampelisca spp. and brittle stars (Amphiuridae and Ophiactidae). Canonical correspondence analysis and examination of temperature and salinity at relocation positions of Gulf sturgeon during the fall 2001 and spring 2002 suggest differential use of the Suwannee River estuary during the two seasons. Compared with fall, sturgeon in the spring were found closer inshore, where the water was less saline and warmer, and they were concentrated in areas with greater abundance of their primary prey, brachiopods. Specific areas within the Suwannee River estuary therefore appear to be potential spring foraging habitats for threatened Gulf sturgeon.