Distribution, seasonal abundance, and ecology of juvenile northern pink shrimp, Penaeus duorarum, in the Florida Bay area

The Florida Bay area of south Florida contains important nursery grounds used by juvenile northern pink shrimp, Penaeus duorarum, before their emigration to the offshore Tortugas Growds. Early juvenile shrimp were sampled in the bay area from 1965 to 1968; maximum concentrations of early -juveniles were in the western bay; few occurred in the eastern bay. They occurred year-round and were most abwdant from late summer to early winter, in seagrasses. Initial distri- bution of the early juveniles in the bay is effected by the flooding tide, which transports planktonic postlarval shrimp into the shallow nursery grounds where they settle as epibenthic postlarvae. The movement of postlarvae into the bay is apparently facilitated by the rise in sea level from about April to October. Variations in sea level control the areal extent of the shallow nursery grounds and may determine the abwdance of early juveniles in the bay, and the sub- sequent commercial production of adult shrimp on the offshore Tortugas Grounds. The postlarvae probably actively select areas of shoal grass, Halodule wrightii, for initial benthic settling. The early juveniles are closely associated with shoal grass as the primary habitat and may depend upon this species for sur- vival. Optimum habitat for early juveniles is characterized by 1) relatively open marine water circulation with daily tidal exchange, and 2) broad intertidal or subtidal beds of shoal grass with high blade densities. Shoal grass, often favored by environmental disturbances, may be a critical factor in recruitment success of pink shrimp.