Allozyme and mitochondrial DNA analysis of the tropical saddle-tail sea perch, Lutjanus malabaricus (Schneider), from Australian waters

Samples of Lutjanus malabaricus from four localities were examined for genetic variability at 10 polymorphic allozyme loci and, after restriction fragment analysis with five enzymes detecting polymorphic cut sites, in mitochondrial DNA (mtDNA). Twenty composite mtDNA haplotypes were found, with three common haplotypes occurring in 84% of individuals examined. Significant differentiation in haplotype frequencies between individuals sampled from the east coast of Queensland and those from the Gulf of Carpentaria and the North West Shelf suggests little, if any, movement of genes through the Torres Strait since its opening about 8000 years ago. Allozyme allele frequencies differed at one locus (PGM-1*) between samples from the North West Shelf and those from the Gulf of Carpentaria. These results are consistent with a recolonization, after the last ice age, of the more northern waters of Australia from a stock off the west coast. The observation of more nuclear than mitochondrial DNA differentiation may be partly a consequence of a female bias in sex ratios. The suggested presence of multiple stocks (North West Shelf, Gulf of Carpentaria, east coast of Queensland) of L. malabaricus, a dominant component of the northern Australian finfish fishery, should be considered in future management plans.