Eastern king prawn dispersal in eastern Australia: new information from particle tracking

The eastern king prawn (EKP) is found from Queensland down to Gippsland Lakes in Victoria, and evidence of spawning females suggest that these individuals are largely supplied from Queensland. Lagrangian particle tracking... [ view full abstract ]

The eastern king prawn (EKP) is found from Queensland down to Gippsland Lakes in Victoria, and evidence of spawning females suggest that these individuals are largely supplied from Queensland. Lagrangian particle tracking experiments were undertaken using the OFES ocean model from 1980-2008 and have allowed us to explore the inter-annual variability in EKP transport and quantify the source populations of larval EKPs along the east coast of Australia.
Larval EKPs were tracked from release through to settlement. Settlement time was based on growth-degree-days, and larvae were thinned according to negative exponential mortality. Both forward and backward simulations were done. Forward simulations had release locations between Fraser Island and Port Stephens to assess dispersal and backward simulations had arrival locations between Clarence River and Gabo Island to quantify the origin of EKP from known adult populations.
Modelling revealed EKP larvae typically settle after 19-21 days in the plankton, and will disperse at a rate of 36-55 km/d. Both forward and backward simulations showed that southern Queensland can supply EKP larvae for the entire NSW coast, but supply to southern NSW is highly variable due to variability in the strength and eddies of the EAC. This variability means that spawning sites in northern NSW are an important source of EKPs, as a higher proportion of larvae released at these sites reach southern NSW. Our modelling also showed that many larvae do not make it to coastal areas at all, with larvae a mean distance of 300 km from the coast at time of settlement. A comparison between simulated larval supply and fisheries landing data shows a correlation between larval supply and harvested EKP biomass.
This research shows that NSW spawning of EKPs is important for dispersal of larvae to higher latitudes, and that recruitment and subsequent catch of this species at its southern extent is higher dependent on the variability of the EAC. This has implications for current stocking efforts of the EKP in NSW.