Population and production estimates for decapod crustaceans in wetlands of Galveston Bay, Texas

The value of wetlands is reflected in the relative abundance and production of nekton, but these population variables have been difficult to estimate because of sampling problems, landscape complexity, tidal dynamics, and limited information on growth and mortality. We combined a landscape analysis of land-water patterns in regularly flooded wetlands of lower Galveston Bay, Texas, with data on small-scale (1-50-m) distribution patterns of nekton over the marsh surface to estimate population abundances of juvenile brown shrimp Farfantepenaeus aztecus, white shrimp Litopenaeus setiferus, and blue crab Callinectes sapidus. Using information on size frequencies, size-weight relationships, and growth rates, we estimated the wet biomass and production of these species from salt marshes and open-water habitats. In 17,673 ha of marsh complex (vegetation with a 150-m water buffer) in lower Galveston Bay, we estimated the standing crops (number/ha) at 19,382 for brown shrimp, 17,406 for white shrimp, and 16,726 for blue crabs, or 3.0, 2.2, and 4.2 times the standing crop estimates for shallow, open bay water. Annual production from the marsh complex was substantially higher than for open water and was estimated at 128 kg/ha for brown shrimp, 109 kg/ha for white shrimp, and 170 kg/ha for blue crabs.