Densities of Penaeus aztecus, Penaeus setiferus, and other natant macrofauna in a Texas salt marsh
Habitat-related densities of natant macrofauna were compared between vegetated and nonvegetated areas in a Spartina alterniflora marsh on Galveston Island, Texas. The most abundant macrofauna were crustaceans, Palaemonetes pugio, Penaeus aztecus, Penaeus setiferus, and Callinectes sapidus, and small fish, Gobiosoma bosci, Lagodon rhomboides, Leiostomus xanthurus, Fundulus similis and Micropogonias undulatus. Excluding residents P. pugio, G. bosci and F. similis, most of the macrofauna were transient juveniles of estuarine-dependent species. Among crustaceans, P. pugio, P. aztecus, and C. sapidus were significantly more dense in vegetated habitat, but P. setiferus was not consistently moreabundant in either vegetated or nonvegetated habitat. Of 29 species of fishes, 14 were usually in vegetation, 11 were more often on nonvegetated bottom, and 5 were indifferent to either habitat. Much seasonal variability in abundances of P. aztecus, P. setiferus, and C. sapidus, but not P. pugio, could be attributed to changes in temperature, salinity and water-level. Strong selection for vegetated habitat by P. aztecus was related to the historical water-level pattern coinciding with seasonal periods of marsh flooding. Apparently, high seasonal tides during the spring and fall facilitated access to vegetated habitat in the marsh and exploitation by transient P. aztecus. In contrast, strong selection for vegetation by P. pugio, abundant year-around in the marsh, was not similarly influenced by seasonal changes in water-level. Overall, habitat-related densities and physical interactions suggest that marsh physiography together with differences in tides may greatly determine the extent to which certain estuarine macrofauna utilize marsh habitats.