A Spatial Representation of the Tiger Prawn (Penaeus Esculentus) Fishery in Shark Bay, Western Australia

N. G. Hall, R. A. Watson, (2000). 212-230.   Paper published in proceedings of the Australian Society for Fish Biology Workshop Proceedings: Fish Movement and Migration, Albury, Victoria, Australia, 1999

The fishery for brown tiger prawns, Penaeus esculentus, in Shark Bay, Western Australia, experienced reduced recruitment in the early 1980s. It is considered that this decline resulted from recruitment overfishing. The measures subsequently implemented to reduce fishing effort on the tiger prawns were constrained by the objective of maintaining the harvest of western king prawns, P. latisulcatus. which was the dominant species in the catch. A series of spatial closures was applied to different regions within the fihery in an attempt to reduce effort on brown tiger prawns, yet maintain catches of western king prawns. The closures were intended to take advantage of the spatial structure of the fishery and the migration that occurs between fishing grounds. Until now, a subjective approach has been used, in consultation with the fishing industry, in determining the appropriate closures. A compartmental delay-difference model has been developed to represent the spatial structure of the brown tiger prawn fishery and to describe the distribution of the prawns through consecutive months of the fishing season. In the absence of explicit inJonnation on the rates of migration between fishing grounds, the model represents the migration rates as parameters, and estimates these, together with catchability and recruitment parameters, from the observed monthly catch rates within the fishing grounds. Using this model, a more accurate time series of annual recruitment indices has been calculated for the Shark Bay tiger prawn stock.