SPECIES COMPOSITION AND DISTRIBUTION OF COMMERCIAL PENAEID PRAWN CATCHES IN THE GULF OF CARPENTARIA, AUSTRALIA, IN RELATION TO DEPTH AND SEDIMENT TYPE

To describe the distribution of the commercial penaeid species caught in the Gulf of Carpentaria, species composition data were drawn from s tudies conducted in the gulf between 1977 and 1992, supplemented with data from commercial catches monitored by fishers trained in species i dentification. The catch is made up of eight species in four commercia l species groups. Three species account for most of the catch: the ban ana prawn Penaeus merguiensis (about 41%) and the tiger prawns P. escu lentus (24%) and P. semisulcatus (23%). Three others, the endeavour pr awns Metapenaeus endeavouri (8%) and M. ensis (3%) and the king prawn P. latisulcatus (1%), are found in commercial quantities but usually a s incidental components of catches. Two species, the black tiger prawn , P. monodon, and the red-spot king prawn, P. longistylus, are caught only occasionally. At a fine spatial scale (six-nautical-mile grids), each species group was found to consist largely of just one species, a nd the ratio of one species to another within a species group were rel atively stable over time. By using these ratios in combination with fi shers' logbook data, it was possible to refine annual catch statistics for the gulf to the level of species rather than, as in the past, jus t to species group. The spatial distributions of individual species we re found to be related to depth and/or sediment type. Catches of P. me rguiensis were mainly from the eastern and southern gulf, and in water s shallower than 20 m, but were not associated with any particular sed iment type. The brown tiger prawn, P. esculentus, was most abundant in the southern gulf and shallower parts of the western gulf (<35 m deep ). The sediments in these areas were sand or muddy sand. In contrast, the grooved tiger prawn, P. semisulcatus, was most abundant in the nor th-eastern gulf and the deeper parts of the western gulf (>35 m deep) where sediments were mud or sandy mud. The blue-tailed endeavour prawn , M. endeavouri, was the most widespread of the species in the gulf, b ut, like P. esculentus, it was most abundant in the south-eastern gulf and shallower parts of the western gulf, where sediments were either sand or muddy sand. The red endeavour prawn, M. ensis, was more limite d in its distribution, with highest abundance in the north-eastern gul f and in the deeper parts of the western gulf (35-45 m). Here, the sed iments were more than 60% mud.