Estimating the Effective Spawner Numbers in Tiger Prawn Fisheries Using Genetic Methods

David Peel, Jenny Ovenden, Tony Courtney, Heather Podlich, Kaye Basford and Cathy Dichmont

THEME: ASFB (Poster)

The brown tiger prawn (Peneaus esculentus) trawl fisheries located in the Gulf of Carpentaria and on the Queensland coast export over $150m worth of product annually and provide significant regional employment. The process of fisheries stock assessment that is used for sustainable management is expensive and often inaccurate. Usual approaches include computer modelling, the monitoring of catch and effort data, tagging experiments for mortality and growth rate estimation, standardisation of catch rates, and a host of other biological studies. We believe that it may be possible to use genetic information to augment fisheries stock assessment by estimating the number of breeding adults that successfully contribute recruits to the fishery (Ne). There are a number of methods available all based on certain genetic measures including examining the variance in gene frequency change across generations, comparing expected versus observed linkage disequilibrium and looking at the numbers of heterozygotes. These methods have been successfully applied in the literature to terrestrial animals, usually in a conservation scenario, where the populations are reasonably small. In this work we examine the effectiveness of extending the use of these methods to larger populations and applying the methods to a commercially harvested species. A pilot study has commenced on the Moreton bay brown tiger prawn population and a number of simulation experiments have been completed to compare the methods and software produced. These simulations and the general methodological approach shall be discussed.