Barataria Bay 2005-2006

Nekton in the northern Gulf of Mexico often depend on marsh habitat and estuarine nursery areas during their life history, but patterns of habitat use and the underlying processes that drive these patterns are not fully understood. We examined small-scale (1-50 m) patterns of habitat use in Barataria Bay, Louisiana, between 2002 and 2006 by collecting nekton with a 1-m2 drop sampler. Habitat-specific densities were estimated for six habitat types at various distances from the shoreline into the marsh (Marsh1M = 1m and Marsh3M = 3 m into the marsh) and over shallow nonvegetated bottom, SNB (SNB1M = 1 m, SNB5M = 5 m, SNB20M = 20 m, and SNB50M = 50 m) seaward of the marsh. Habitat-specific growth rates also were estimated for brown shrimp Farfantepenaeus aztecus caged in SNB1M, SNB5M, and SNB20M. Nekton density patterns in Barataria Bay appeared to be clearly different from the Galveston Bay model, which predicts nekton distribution patterns relative to the marsh shoreline. Although densities in Barataria Bay were significantly higher in samples near the marsh shoreline (Marsh1M or SNB1M) for brown shrimp, blue crab, and white shrimp, highest mean densities were not always present in marsh edge vegetation. In addition, densities of brown shrimp and white shrimp in Barataria Bay declined much more steeply with distance into the marsh than in the model. Daily growth rates (1.0 - 1.2 mm TL day-1; 68 - 89 mg day-1) for brown shrimp were similar among SNB habitat types. Our results suggest that SNB in Barataria Bay may be relatively more important as habitat for fishery species than previously assumed.

The purpose of this study was to examine the small-scale (1-50 m) patterns of nekton distribution in lower Barataria Bay and test the generality of the Galveston Bay model of habitat-specific nekton densities.

Although a mesocosm experiment was conducted in 2002 and 2006 to examine shrimp growth, the whereabouts of these growth data are unknown as are collection data for drop samples taken in 2002. Therefore, this information is not included in the Final Barataria Bay 2005-2006 data set. Actual data set includes only 1-m2 drop sample collections for 2005-2006.

Rozas, L. P. and T. J. Minello. 2015. Small-Scale Nekton Density and Growth Patterns Across a Saltmarsh Landscape in Barataria Bay, Louisiana. Estuaries and Coasts 38(6): 2000-2018.

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Initially a two-way analysis of variance (ANOVA) on a subset of nekton data was used to explore that possibility and to look for differences in nekton abundance and environmental characteristics among locations/years.

Each sample was assigned a unique identification code. Field collected samples were tagged redundantly (e.g. one label inside of the collection vessel and a matching label attached to the outside of the vessel). The identifier and its associated information (e.g. date, location, habitat) was recorded on field data sheets. Once a sample arrived at the laboratory, the label remained with the sample throughout the various stages of sample processing. After data were entered into an Excel spreadsheet or similar database file, the information was printed out and compared against the field data sheets by two biologists. Corrections were made at this time and saved. The electronic file was also sorted and examined by the Lab Supervisor or other project personnel in a variety of ways to look for outliers, missing data, and other potential errors.

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