Date of Award

1990

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

William H. Herke

Abstract

Juvenile penaeid shrimp were studied by a variety of methods in a southwest Louisiana, brackish marsh. Most of the work was conducted in two study ponds, one with a fixed-crest weir and the other without. In mark and recapture studies, both brown shrimp Penaeus aztecus and white shrimp P. setiferus were found to grow faster in marsh behind a fixed-crest weir. There was no apparent weir effect on mortality of either species. Brown shrimp emigrated an average of 12 d later from marsh behind the weir; white shrimp were sometimes delayed by the weir. The peak of brown shrimp emigration from both weired and unweired marsh peaked coincided with both new and full moons. I used four methods of estimating juvenile shrimp standing stocks and found that shrimp were usually less abundant in the weired than the unweired pond. The reduction in observed emigration of shrimp from a weired area was likely caused by restricted immigration past the weir. I used density estimates from the unweired study pond and a nearby marsh pond to confirm that export estimates in previous studies of the unweired pond were reasonable, although conservative, estimates of normal numbers of shrimp emigrating from similar marsh ponds. Graphic analysis, linear statistics, and superposed epoch analysis were used to study effects of environmental variables on white shrimp emigration. White shrimp emigration from the marsh was associated with decreasing temperatures, high water outflow, decreasing and/or low barometric pressure, and rainfall.

Pages

158

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