As pressure on coastal marine resources is increasing globally, the need to quantitatively assess vulnerable fish stocks is crucial in order to avoid the ecological consequences of stock depletions. Species of Sciaenidae (croakers, drums) are important components of tropical and temperate fisheries and are especially vulnerable to exploitation. The black-spotted croaker, Protonibea diacanthus, is the only large sciaenid in coastal waters of northern Australia where it is targeted by commercial, recreational and indigenous fishers due to its food value and predictable aggregating behaviour. Localised declines in the abundance of this species have been observed, highlighting the urgent requirement by managers for information on fine and broad-scale population connectivity. This study examined the population structure of P. diacanthus across northwestern Australia using three complementary methods: genetic variation in microsatellite markers, otolith elemental composition and parasite assemblage composition. The genetic analyses demonstrated that there were at least five genetically distinct populations across the study region, with gene flow most likely restricted by inshore biogeographic barriers such as the Dampier Peninsula. The otolith chemistry and parasite analyses also revealed strong spatial variation among locations within broad-scale regions, suggesting fine-scale location fidelity within the lifetimes of individual fish. The complementarity of the three techniques elucidated patterns of connectivity over a range of spatial and temporal scales. We conclude that fisheries stock assessments and management are required at fine scales (100's km) to account for the restricted exchange among populations (stocks) and to prevent localised extirpations of this species. Realistic management arrangements may involve the successive closure and opening of fishing areas to reduce fishing pressure.

Protonibea diacanthus microsatellite genotypesThis file contains the individual genotypes used for the paper entitled "Strong population structure deduced from genetics, otolith chemistry and parasite abundances explains vulnerability to localised fishery collapse in a large Sciaenid fish, Protonibea diacanthus".Protonibea diacanthus_Microsatellite data_Dryad entry.xlsxProtonibea diacanthus parasites dataThis file contains the individual parasites assemblage and abundance used in the paper entitled "Strong population structure deduced from genetics, otolith chemistry and parasite abundances explains vulnerability to localised fishery collapse in a large Sciaenid fish, Protonibea diacanthus"Protonibea diacanthus_Parasites data_Dryad entry.xlsProtonibea diacanthus otolith microchemistry dataThis file contains the individual otolith microchemistry data used for the paper entitled "Strong population structure deduced from genetics, otolith chemistry and parasite abundances explains vulnerability to localised fishery collapse in a large Sciaenid fish, Protonibea diacanthus"Protonibea diacanthus_Otoliths data_Dryad entry.csv