Macro-Benthic Prey and Physical Habitat Characteristics in a Western Gulf Sturgeon Population: Differential Estuarine Habitat Use Patterns

Gulf sturgeon, Acipenser oxyrinchus desotoi, is a threatened species throughout its northern Gulf of Mexico range with Mobile Bay, Alabama, as the recognized eastern and western population break.  Recovery requires strategic species and critical habitat protection. We examined three Gulf sturgeon habitat attributes in the Pascagoula River estuary: sediment grain size, depth, and benthic prey density (spatially [river, west and east zones] and seasonally [fall and spring]) relative to occurrence. Gulf sturgeon occupancy patterns indicated adults pulse through the system in both fall and spring (river-west-offshore islands) compared to longer/more variable occupancy for juveniles and sub-adults (river-west). There was almost no occupancy of the east zone by any size class.  Significant seasonal differences in water quality, physical habitat, and benthic characteristics were noted that weakly explained Gulf sturgeon occupancy patterns.  Expected seasonal water quality characteristics drive immigration and emigration patterns; however, direct comparisons of physical drivers and benthic density patterns were weak at best and suggest alternate hypotheses to explain the differential estuarine habitat use patterns. The most parsimonious explanation based on multiple weights-of-evidence suggests reduced use of the eastern distributary habitat is based on synergistic effects of urbanization/ industrialization; numerous examples occur in the east zone of the estuary.