R. Watson, N. R. Sumner, (1997). 864-868. paper published in proceedings of the International Congress on Modelling and Simulation
Simulation is used to improve the management of prawn fisheries by indicating patterns of fishing effort which prevent the harvest of under-sized animals, conserve sufficient breeding stock, and maximise the sustainable yield. Attempts to use conventional optimisation methods to find the optimum pattern of weekly fishing efforts have been ineffective because of the many extraneous local maxima. Through the use of global optimisation methods such as simulating annealing we have been able to find fishing effort patterns which maximise predicted catch values. Despite being continuous variables, the optimum levels of weekly fishing efforts usually assumed either values of zero or else the maximum fishing effort allowed. Sensitivity of the predicted maximum catch value and the pattern of fishing effort achieving this were examined for a range of parameter values representing the fishing (net selectivity and catchability) and biological (natural mortality and growth rate) processes. The greatest catch values obtainable were constant for a wide range of values of trawl net selectivities and catchability parameters, however, the optimum fishing season to obtain these maxima altered. In contrast, changes in biological parameters had a large effect on the maximum catch value despite compensation in the optimum pattern of weekly fishing efforts.