CATCH PREDICTION FOR THE BLUE SWIMMER CRAB (PORTUNUS PELAGICUS) IN COCKBURN SOUND, WESTERN AUSTRALIA

摘要

Commercial catches of Portunus pelagicus Linnaeus in Cockburn Sound, the second largest blue swimmer crab fishery in Western Australia, fluctuate markedly between fishing seasons. The stock also supports an important recreational fishery as it is close to the Perth metropolitan area. The prediction of each season's catch would remove uncertainty and aid management and marketing of this valuable species. This study produced a robust and cost-effective catch-prediction index based on juvenile abundance. The densities of seven age/sex categories of Portunus pelagicus in three regions of Cockburn Sound, derived by research otter trawling between 1999 and 2005, were examined to determine which best corresponded with the commercial blue swimmer crab landings in the following fishing season. The majority of age/sex categories correlated well with subsequent commercial catches, with the "all 0+ females and males" category producing the best prediction index. This category was then split into individual regions and month combinations and re-analyzed to determine the minimal level of effort required to produce a reliable catch-prediction. The resulting index, which uses "all 0+ females and males" sampled in only the northern and middle regions of Cockburn Sound between May and August accurately predicts the subsequent commercial catch in the following year and has predicted a catch of 1011 for the 2005/06 fishing season.