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Abstract
Penaeid prawns represent some of the most economically important crustaceans exposed to exploitation. The eastern king prawn, Penaeus (Melicertus) plebejus, is a valuable endemic species for Australia, widely distributed along the east coast. Penaeus plebejus exhibits great mobility and long-distance migration behavior. Accurate stock delimitation is important because the species distribution transcends management jurisdictions of the three eastern states. Furthermore, the species is targeted for stock enhancement, which requires an accurate understanding of geographic differentiation for a responsible enhancement program. One of the most important considerations when releasing captive bred prawns into natural systems is the maintenance of the genetic structure of the wild population. Novel species-specific microsatellite loci were developed, and thirteen selected loci were used to assess the geographic structure and population connectivity of the species throughout its geographical range. Our data showed consistency with the current single stock hypothesis, where south-east Queensland is the active breeding population that supplies the majority of recruitment to other localities. Several pairs of locations showed small but statistically significant differentiation, however the inferred dispersal between the sampled locations are adequate for the eastern king prawn to be considered as a single panmictic population. Highly variable mitochondrial control region (mtCR) was used to examine the reproductive performance of wild-caught female broodstock in the production of hatchery cohorts for restocking. We showed that mtCR can be a useful tool for tracking lineages and provided clear genetic evidence that unequal contribution and underproducing females can be common even in wild-caught broodstock. This highlights the importance of monitoring the genetic composition of hatchery cohorts prior to release in stock enhancement. Finally, we used partial pedigree data to provide genetic evidence that null alleles are very common and often at significant proportions in P. plebejus. Null alleles can cause problems in population studies; however, regression analyses of the population data with and without null allele adjustment showed that the presence of null alleles had no significant impact on our inference on the geographic structure of the species. The implications from this study are that P. plebejus is panmictic, and significant dispersal throughout the range suggested a need for a ooperative management approach from the eastern states of Australia. Close genetic monitoring of the final genetic makeup of the hatchery cohort is essential to ensure genetically appropriate cohorts can be used in stock enhancement of the species.