Larval ecology of penaeids of the Gulf of Carpentaria, Australia. I. Assessing the reproductive activity of five species of Penaeus from the distribution and abundance of the zoeal stages

Abstract

The distribution and abundance in the Gulf of Carpentaria, Australia, of the three zoeal (= protozoeal) stages of Penaeus merguiensis, P. esculentus, P. semisulcatus, P. latisulcatus and P. longistylus are described. All species were largely coastal in distribution. The zoeae of P. semisulcatus were the most abundant and widespread penaeid larvae in the Gulf, with highest densities in the north-western and south-western areas. Those of P. merguiensis, the next most abundant, were found only in coastal areas in the north-eastern, north-western and southern Gulf. The larvae of P. esculentus and P. latisulcatus were next in abundance with largest numbers in the north-western and south-western Gulf and a small area of the north-eastern Gulf. Zoeae of P. longistylus were very rare and found only in the southern Gulf.

The reproductive dynamics of these species have been inferred from the occurrence of the zoeal stages. All species showed a high degree of variation in reproductive activity throughout the year; both the timing and relative heights of the peaks varied by species within and between geographic subdivisions of the Gulf. Two seasonal peaks of reproduction were common in P. merguiensis, P. semisulcatus and P. latisulcatus in most areas, while single peaks were seen for P. esculentus and P. longistylus. No lunar periodicity of zoeal occurrence or reproduction was evident for any of these species. The spawning of P. merguiensis was in relatively shallow water, in as little as 10 m and generally less than 30 m; P. semisulcatus had the deepest spawning depth, rarely less than 20 m but extending to 50 m and most commonly around 40 m.