Changes in fishing effort efficiency under effort and quota management systems applied to the Western Australian rock lobster fishery

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Fishing efficiency changes in the western rock lobster fishery, Panulirus cygnus George, 1962, have been assessed to improve the reliability of the commercial catch rate–based breeding stock indices and effective effort that contribute to a length-based stock assessment model. The present study covers the fishery under transferable effort quotas from the 1980s to 2009, and under catch quota management from 2010. To evaluate the changes in effective effort and lobster abundance through these events, fishing efficiency has been determined using standardized abundance indices from six independent survey locations in offshore breeding stock areas. Catch rates from these independent surveys (instituted 1994) have been compared with industry catch rates on adjacent grounds to estimate effort efficiency increases in the breeding stock areas. The catch rate calibration revealed that the deep water breeding stock areas had efficiency increases of 2.7%–3.6% per annum under effort control, while the shallower water breeding stocks in the offshore Abrolhos Islands were less affected. The change to catch quota management resulted in a marked decrease in effort efficiency of around 30%; however, the short time series since this management change does not provide a reliable trend of efficiency changes. Factors influencing fishing efficiency, including the management system itself, are considered and the need for validation of catch-rate based management performance indicators is discussed. Our study highlights the benefits of using fishery-independent surveys to evaluate effort efficiency changes and in addressing the biases normally associated with abundance measures based on commercial catch rates.