Influence of harvest refugia on penaeid prawn population dynamics and sustainable catch

Harvest refuges have frequently been proposed as fishery management tools for species with sedentary adults and dispersive juveniles but less often for species with a highly mobile adult phase. In this paper, I use a population model to investigate the potential of using harvest refuges for managing species with both dispersive juveniles and mobile adults using the penaeid prawn Penaeus latisulcatus as a model. Maximum harvest occurred when only a very small proportion of the habitat (2-3%) was fished very heavily (F = 10). When only a small percentage of the habitat was trawled, harvest increased as fishing mortality increased, but when trawling was more extensive, harvest peaked with a relatively low fishing mortality. This supports recent contentions that by themselves, marine reserves are insufficient to manage a fishery effectively and that they need to be used in conjunction with effort restrictions. Sensitivity analyses indicated that adult, juvenile, and larval mortality are all near thresholds that qualitatively change model behaviour, but provided their values remain below the threshold, it is not important to know them accurately to determine the best harvest regime.