Larval ecology of penaeids of the Gulf of Carpentaria, Australia. II. Hydrographic environment of Penaeus merguiensis, P. esculentus, P. semisulcatus and P. latisulcatus zoeae

Abstract

The abundance of larvae of P. merguiensis, P. esculentus, P. semisulcatus and P. latisulcatus in the Gulf of Carpentaria shows both spatial and temporal heterogeneity. Most of the larvae of all four species were found where the water was less than 50 m deep, with temperatures and salinities greater than 26ºC and 31 respectively. However, the mean temperatures of the waters in which the larvae were found varied significantly between some species. The mean temperatures and salinities of the waters was as follows: P. merguiensis 29.2ºC, 32.3; P. esculentus 28.4ºC, 33.1; P. semisulcatus 27.9ºC, 33.2; P. latisulcatus 27.3ºC, 33.0.

While the range of temperatures in which all four species were found was between 21.5 and 30.6ºC the ranges of salinities were more varied and may reflect the biogeographic distributions of the species. The three widespread species were found over large salinity ranges: P. merguiensis and P. semisulcatus, 27.8-34.9; and P. latisulcatus, 28.6-34.9. The Australian endemic, P. esculentus, was found in the most restricted range, 30.1-34.2.

The temperatures and salinities of the waters in which the larvae were caught reflect conditions suitable for reproduction, as well as growth and survival of the larvae. The means of the temperature and salinity may be near larval optima and the ranges similar to tolerances. These differences should be taken into account when assessing abiotic influences on larval mortality both in the field and in culture.