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Genetic structure and diversity of barramundi in Papua New Guinea and implications for managing the fishery

John Salini, J Hughes, D Milton and D Hurwood

CSIRO Marine Research, CLEVELAND, AUSTRALIA

THEME: ASFB

Abstract text The aim of this study was to assess the extent of gene flow among populations of barramundi from different river systems in southern Papua New Guinea. Barramundi muscle tissues were analysed from the Fly River system, coastal areas and Daru Island west of Fly River mouth, Kikori River, Merauke and Mullins Harbour. We used a 300bp fragment of mitochondrial control region and six microsatellite loci to examine genetic structure. We used Fst statistics, assignment testing and genic differentiation analyses to compare: the population structure between locations; the relationship of coastal juveniles to adults and to compare similarities between locations. There was little evidence for population structure among samples from Merauke to the Kikori River or between juvenile and adult samples. However, the Mullins Harbour collection was significantly different from other samples and reflected its location in eastern Papua New Guinea, and separation from all other samples by unsuitable habitat. Mitochondrial DNA was highly polymorphic with 69 haplotypes identified from 192 fish. These results indicate a well-mixed population of barramundi with no evidence of recent population bottlenecks. This contrasts with fishery records that indicated a steady decline in commercial landings until the mid-1990s when the fishery became no longer viable.