Doctor of Philosophy (PhD)


Oceanography and Coastal Sciences

Document Type



Louisiana wetlands are disappearing at a dramatic rate, providing an impetus for identifying essential fish habitat (EFH) in this region. The distribution, relative abundance, biomass, length and food web dynamics of spotted seatrout, Cynoscion nebulosus, as well as the fish assemblage structure were examined in Barataria Bay, LA, in relation to habitat type and physical/chemical properties of the water. All fish were collected from three sites located along a salinity gradient, each contained the three habitat types of interest: marsh edge, soft bottom and oyster shell, and were sampled monthly from May 2003 to May 2004 with gillnets. Habitat preference of spotted seatrout was not easily defined by habitat type alone, but rather their distribution, relative abundance, biomass and length distribution were influenced by a combination of habitat and physical/chemical properties of the water. Stable isotope analyses suggest that individual spotted seatrout may not move widely throughout Barataria Bay, but rather they may exhibit some site fidelity with preference for salinity ranges within the bay. Salinity was also an important variable structuring the fish assemblage in Barataria Bay, resulting in a distinct composition of species at the oligohaline site as compared to the mesohaline and polyhaline sites. The fish assemblage structure also differed among habitat types and could generally be divided into three categories; those species only or mostly found at the marsh edge, those species found at all three habitat types, and a few species that had a higher affinity for soft bottom and oyster shell habitats. These results suggest that habitat type and physical/chemical properties of the water work in concert with one another to provide a diverse range of available habitats important to estuarine fishes. Despite the importance of incorporating habitat in fisheries management, it may not be possible to identify which habitats are essential versus which ones are temporarily occupied. This study demonstrates that identifying EFH is a difficult task and illustrates that an ecosystem approach may be the best method when working towards identifying EFH given the influence of the physical/chemical properties of the water and the species-specific habitat associations identified in this study.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

James H. Cowan Jr.