We compared nekton density, composition, and biomass in fall 2009 and spring 2010 among three major habitat types (marsh, SAV=submerged aquatic vegetation dominated by Vallisneria americana, SNB=shallow nonvegetated bottom) commonly found throughout the Mobile-Tensaw River Delta (MTD) using 1-m2drop samplers. In the sampling design, habitat selection was based on vegetation composition. Sample locations (TR=Tensaw River, CB=Chocolatta Bay, and BC=Below Causeway) were selected based on their degree of tidal connectivity with the wider estuary (BC > TR > CB). Nekton distributional patterns varied among both locations and habitat types. Species richness was greater at BC than CB. The young of most estuarine-dependant fishery species (e.g., white shrimp, blue crab, gulf menhaden) were more abundant, and had more biomass, at BC and TR than CB. Estuarine residents (e.g., riverine grass shrimp, rainwater killifish) dominated the nekton in CB. Within locations, mean densities and biomass of abundant species were concentrated in vegetated (marsh, SAV) habitat types, and most species associated with vegetation structure were more abundant in SAV than marsh. Tidally unrestricted areas of the MTD may provide an important nursery for fishery species such as white shrimp, blue crab, gulf menhaden, and southern flounder. Additional studies will be needed to determine if these fishery species represent strong conduits for cross ecosystem transfer of energy and nutrients between the MTD and northern Gulf of Mexico.
Rozas LP, Valentine JF, Martin C, Steele L. 2011. Use of Shallow Estuarine Habitats by Nekton in the Mobile-Tensaw River Delta, Alabama. NGI (Northern Gulf Institute) Meeting. Poster.