Abundance of macrocrustaceans in a natural marsh and a marsh altered by dredging, bulkheading, and filling.
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Indices of abundance of macrocrustaceans during March-October 1969 in West Bay, Tex., were determined for day and night and statistically compared between 1) a natural marsh area, 2) upland and bayward canal areas of a housing development, and 3) an open bay area. Significance levels of 5% or 1% were used in the statistical comparisons. Catches of brown shrimp, Penaeus aztecus; white shrimp, Penaeus setiferus; blue crab, Callinectes sapidus; and pink shrimp, P. duorarum, were significantly greater at night than during the day at one or more stations in the marsh. More grass shrimp, Palaemonetes sp., were caught at night than during the day, but the differences were not statistically significant. Individuals of each species appeared to migrate into the more shallow areas of the marsh at night. At night, brown shrimp and blue crabs were significantly more abundant in the marsh and bayward canal areas than in the upland canal and bay areas, white shrimp were significantly more abundant in the marsh area than in the other three areas, and pink shrimp were significantly more abundant in the marsh than in the upland and bayward canal areas. During the day, brown shrimp were significantly more abundant in the bayward canal area than in the upland canal and bay areas, while pink shrimp were significantly more abundant in the marsh area than in the upland canal area. The generally lower catches of each species in the open bay and upland canal areas when compared with the marsh and bayward canal areas were attributed to: 1) permanent loss of intertidal vegetation in the housing development; 2) low abundance of detrital material and benthic macroinvertebrates in the open bay and upland canal areas; and 3) eutrophic conditions in the upland canal area.