Juvenile White Shrimp Growth, Mortality, and Emigration in Weired and Unweired Louisiana Marsh Ponds

Abstract To study effects of marsh weirs on shrimp ecology, over 6,000 juvenile white shrimp Penaeus setiferus were marked with fluorescent pigments and released into two coastal Louisiana marsh ponds, one with a fixed-crest weir at its only opening, the other without. Marked white shrimp were recaptured as they emigrated toward the Gulf of Mexico from each pond. White shrimp growth was about 0.3–1.4 mm/d and 0.4–2.5 mm/d in 1983 and 0.3–0.4 mm/d and 0.5–0.7 mm/d in 1984 in the unweired and weired ponds, respectively. Growth was significantly greater in the weired pond. Mean time from release to emigration ranged from 31.5 to 47.4 d in the unweired pond and from 30.2 to 59.9 d in the pond with a weir. White shrimp emigrated significantly sooner from the unweired pond than from the weired pond in most experiments, but whether the weir actually delayed emigration was unclear. Peaks in emigration were associated with the occurrence of cold fronts. Instantaneous monthly mortality rates (Z ) from release to re...