Seasonal movement and size distribution of three commercially important Australian prawn species (Crustacea : Penaeidae) within an estuarine system

Three penaeid prawn species, Penaeus plebejus Hesse, Metapenaeus bennettae Racek & Dall, and M. macleayi (Haswell), were sampled using a beam trawl, at four sites for 16 months in the Noosa River, Queensland, and data collected are used to provide generalized life histories for the three species and to discuss the composition and timing of the commercial bait prawn fishery. P. plebejus individuals were recruited to the river throughout the year, M. bennettae between March and June, and M. macleayi between April and July. P. plebejus juveniles remained only briefly in the river and were most numerous at sites near the river mouth. There was no distinct period of migration of this species from the river. M. bennettae and M. macleayi individuals remained in the river until December and March, respectively, when, in the absence of obvious abiotic stimuli such as rainfall runoff and reduced salinities, there was a marked egress from the river. While in the river, both of these species could be caught through the zone of salt-water penetration up to 35 km from the sea, and both were most numerous in the southern half of Lake Cootharaba in a zone of approximately 19 × 10-3 mean salinity. Similarity between these and other distribution patterns recorded in topographically different rivers suggests salinity is an important determining factor in the distribution of these prawns.