Modeling the dynamics of eastern rock lobster, Jasus verreauxi, stock in New South Wales, Australia

Rock lobster, Jasus verreauxi, have been fished off New South Wales, Australia, since the late nineteenth century. Since 1994-95 (1 July 1994 to 30 June 1995) the fishery has been managed under an output-control scheme with an annual total allowable catch (TAC) of 106 metric tons (t). Estimates of catch and catch per unit of effort (CPUE) have been developed from data collected from the commercial fishery for the period 1903-1936 and the period from 1969-70 to 1993-94. A production model was fitted to these data by using a robust observation-error estimator that minimizes the median of squared differences between log-observed and predicted CPUEs. A bootstrap resampling procedure was incorporated into this robust estimation method to estimate stock parameters and their uncertainties. The virgin biomass of the rock lobster was 4084 t (its 5(th) and 95(th) percentiles being 2553 and 6400 t). The stock biomass decreased substantially until 1990-91. Since 1992-93, it has stabilized and has probably increased owing to the large decrease in the allowable catch after 1988-89. The stock biomass in year 1995-96 was likely to have been between 15% and 30% of the virgin biomass (75% confidence interval). The implications from using different estimation methods on assessing this lobster stock are discussed.