The status of the western rock lobster, Panulirus cygnus, fishery and the effectiveness of management controls in increasing the egg production of the stock

Abstract

In 1993, managers were concerned about the decline in the breeding stock of western rock lobster and introduced controls to raise egg production from the stock to those levels experienced in the late 1970s and early 1980s. The release of setose female lobsters (those with ovigerous setae) and of nonsetose female lobsters larger than a maximum legal size was required, the minimum legal carapace length (CL) was raised by 1 mm during the migratory phase between November and January, and the number of pots (traps) fished was reduced by 18%. Between 1993 and 1999, increases were observed in the indices of egg production obtained from research surveys and in the estimated released catches of setose female lobsters and of nonsetose female lobsters larger than the maximum size. From these and other fishery data, an age-structured model was developed to determine the status of the fishery and the effectiveness of each management control. By 1999, egg production of the stock had increased to 134% of the target level and 22% of the virgin level. Protection of setose female lobsters was the most effective control, followed by the reduction in pot usage, and then maximum legal size.