In 2007 the Minister of Fisheries for the Commonwealth of Australia directed all Commonwealth managed fisheries should be managed with quantitative Harvest Strategies (HS); computerized decision rules using pre-agreed data to adjust catch levels. A mechanism for setting catch levels was needed immediately but international assessments would take decades to develop and of doubtful accuracy for the peripheral Tasman & Coral Sea stocks of tuna and billfish. Dr Prince was requested to participate on the Harvest Strategy Working Group established for the Eastern Tuna and Billfish Fishery.
Dr Prince designed the Spawning Per Recruit (SPR) Decision Tree using the logic of Virtual Population Analysis (VPA) to assess trends in size and catch rate data without reliance on quantitative population models. Harvest Strategy Evaluation by CSIRO confirmed the utility of the approach and found that the HS usefully becomes more precautionary with data uncertainty. The Harvest Strategy has been published by the Australian Commonwealth Government as an example of an approved Harvest Strategy and is being implemented as designed. Dr Prince has gone on to extend the SPR-Decision Tree concept to assessing data-poor fisheries in general.