Role of larval distribution and abundance in overall life-history dynamics: a study of the prawnPenaeus semisulcatusin Albatross Bay, Gulf of Carpentaria, Australia

The distribution and abundance ofPenaeus semisulcatusde Haan larvae in Albatross Bay was studied during the 6 yr from March 1986 to April 1992. The study is a component of an investigation into the causes of interannual recruitment variation. Protozoeae were found in a wide range of temperatures and salinities and in both the presence and absence of thermoclines and haloclines, although density of larvae was low in water warmer than 30°C. Two distinct peaks of larval abundance were evident: from January to March (summer), and from August to November (spring). Firststage protozoeae were rarely found during summer, although later stages were common, which suggests either that they were less catchable in summer or that most summer spawning was outside the study area. Three extended cruises during 1987 found high densities of larvae as far as 120 km offshore; these larvae represent wasted reproductive output since they are beyond the zone of effective spawning. The annual variations in abundance of larvae were compared with the results of parallel CSIRO studies of otherP. semisulcatuslife-history stages in Albatross Bay. There is poor agreement between larval numbers and the population fecundity index (a measure of egg production), but a stronger match with densities of postlarvae in the Albatross Bay estuaries, particularly in summer. This indicates that variable rates of egg hatching and early larval survival may be important determinants of successful recruitment to theP. semisulcatusfishery.