Genetic structure of barramundi (Lates calcarifer) stocks from northern Australia

Barramundi, L. calcarifer, were collected from seven localities in the Northern Territory, the Daly, Finniss, Mary, Glyde, Roper and McArthur rivers and Blue Mud Bay, and from the Ord River in Western Australia. Barramundi were sampled seven times from the Daly and Finniss rivers over a 14-month period. In total, 46 loci were identified using starch-gel electrophoresis of enzymes and polyacrylamide electrophoresis of muscle proteins. Twelve loci were polymorphic at the P0.99 level. Most loci were in Hardy-Weinberg equilibrium. A contingency Χ2 analysis for homogeneity of alleles over all loci and all localities was highly significant (P < 0.001). Comparisons of data from adjacent pairs of localities revealed that the overall heterogeneity was attributable to heterogeneity among seven of the eight localities; the Daly and Finniss river areas were not significantly different from one another. No evidence of heterogeneity over time was found among the collections from the Daly River area. The considerable amount of heterogeneity observed suggests that each of these seven localities supports a genetically discrete stock of barramundi; this conclusion is consistent with the documented life history of Australian barramundi. The genetic heterogeneity of the stocks should be considered when management policies for L. calcarifer are being formulated.