Oyster reefs (Crassostrea virginica) are an important component of marine ecosystems and a highly valued fishery resource that may be essential habitat for many estuarine species. The Magnuson-Stevens Fisheries Conservation and Management Act (recently reauthorized in 2007) mandates that necessary measures must be taken to protect essential fish habitat; however few studies have assessed the potential for intertidal oyster reefs to serve as habitat. This research was designed to characterize the macrofaunal community of intertidal oyster reefs in a Gulf Coast estuary. Specifically, the nekton density of intertidal estuarine oyster reefs was compared to the nekton density of seagrass beds (Halodule wrightii) and marsh edge (Spartina alternifora) habitats. We hypothesized that there was no difference in nekton density among these three estuarine habitats. In May 2008, we collected 15 replicate intertidal oyster reef samples and 20 replicate marsh and seagrass samples from 2 sites in Corpus Christi Bay, Texas. Samples were collected using a 1-m drop sampler composed of 1-mm mesh. The enclosed area was swept with a dip net until all organisms were collected. Samples were rough sorted and fixed with formalin the field. In the laboratory, samples were quantified and identified to lowest possible taxon.
Results/Conclusions
Results suggest that there are significantly higher densities of fishes and crustaceans (nekton) using the intertidal oyster reefs (mean = 250.53 m-2 ± 31.07), than the adjacent seagrass (mean = 135.7 m-2 ± 13.16) and marsh (mean = 137.7 m-2 ± 31.67) habitats, which had similar densities. Multivariate analyses reveal that there are also community differences among habitats, with intertidal oyster reef having a different community structure than marsh and seagrass. Previous research has documented high densities, rapid growth, refuge from predation, and reduced mortality in both seagrass and marsh, characterizing it as essential fish habitat. Because we found high densities of fishes and crustaceans in intertidal reefs, there is strong evidence that this may be important habitat for juvenile nekton and may also be characterized as essential fish habitat. We also found a different nekton community structure on intertidal oyster reef, suggesting that different species from those found in vegetated habitats are using oyster reef and that this habitat may be critical for numerous estuarine species.
