Vallisneria 2003-2004

We compared nekton use of Vallisneria americana Michx. (submerged aquatic vegetation, SAV) with marsh shoreline vegetation and subtidal nonvegetated bottom (SNB) using a 1-m2 drop sampler in the oligohaline area of Barataria Bay, Louisiana. Mean densities of most abundant species were significantly different among six habitat types. Harris mud crab Rhithropanopeus harrisii, Ohio shrimp Macrobrachium ohione, blue crab Callinectes sapidus, daggerblade grass shrimp Palaemonetes pugio, white shrimp Litopenaeus setiferus (fall), rainwater killifish Lucania parva, naked goby Gobiosoma bosc, code goby Gobiosoma robustum (fall), speckled worm eel Myrophis punctatus (fall), and gulf pipefish Syngnathus scovelli (spring), were much more abundant, and species richness also was greater, in Vallisneria than over SNB. Vallisneria supported densities of most species that were similar to those in marsh vegetation, although naked goby and gulf pipefish were more abundant in Vallisneria, and speckled worm eel and saltmarsh topminnow Fundulus jenkinsi were more abundant in marsh. Within the Vallisneria bed, densities of Harris mud crab, rainwater killifish, and speckled worm eel were higher at sites near the marsh (SAV Inside Edge) than at sites more distant from the marsh (SAV Outside Edge), and Ohio shrimp (fall) densities were higher in the interior of the bed than along the edges. The mean size of blue crab was larger in marsh than Vallisneria and larger in Vallisneria than SNB. White shrimp did not differ in size among habitat types. Vallisneria beds may provide an important nursery habitat for young blue crab and white shrimp that use oligohaline estuarine areas. These SAV beds can provide an alternative structural habitat to emergent vegetation during periods of low water, because Vallisneria occurs in the subtidal and generally persists throughout the year on the Gulf coast. Species whose young thrive in low-salinity waters and also depend on structure would benefit most from Vallisneria habitat in estuaries.