Genetic population structure of species in the South East Fishery of Australia

A summary is given of allozyme, mitochondrial DNA and microsatellite data for commercially important species (13 fish and 7 shellfish) in Australia's South East Fishery, including contiguous waters and the Tasman Sea. For most fish species, genetic population differentiation was limited and in about half the studies was non-detectable. Striking population differentiation was recorded for gemfish. For fish species, on average only 2-3% of the total genetic variation could be attributed to population differentiation within southern Australian waters. In shellfish, similar to5% of variation arose from population differences. The reduced differentiation of fish populations may be due to a longer larval period and greater adult mobility. Although there was evidence that the Tasman Sea acts as a barrier to gene flow, with most fish species showing significant differences between Australia and New Zealand, the degree of differentiation was small (only similar to2%). The limited genetic differentiation observed for most species is attributable to the lack of major oceanographic and environmental barriers to gene flow, together with influential current systems; it necessitates large sample sizes for good genetic tests. However, significant genetic stock structuring is apparent for several fish and shellfish species-particularly for coastal species, where isolation by distance may explain some of the data. Any evidence for genetic stock structure must be factored into plans for sustainable management.