Assessing the effects of moving to maximum economic yield effort level in the western rock lobster fishery of Western Australia

Abstract

Abstract The western rock lobster ( Panulirus cygnus ) fishery has been facing significant economic pressure from increasing costs, lower prices as well as predicted reduced catches due to low recruitment. A maximum economic yield (MEY) assessment estimated the fishing effort that would maximise the net present value of profits over 2008/09–2013/14 was about 50%–70% reduction of 2007/08 effort. The assessment accounted for fixed vessel costs and the variable pot lift cost. An important component of this assessment was the use of puerulus settlement time series that provided a reliable predictor of recruitment to the fishery 3–4 years later. This can be contrasted to most MEY assessments that would use an average catch-effort relationship rather than taking into account the expected recruitment. This predictive ability has been particularly useful as there has been a period of unusually low puerulus settlements over the 5 years (2006/07–2010/11) including the lowest two settlements in the 40-year time series. Due to the low settlements, substantial management changes were implemented in 2008/09 and 2009/10 (44% and 73% reduction in nominal fishing effort, respectively compared to 2007/08) to maintain the breeding stock at sustainable levels by having a significant carryover of legal lobsters into future years of lower recruitment. These effort reductions provided a unique opportunity to assess the economic impact of a fishery moving to an MEY effort level over two years. The CPUE increased from 1.1 kg/pot lift in 2007/08 to 1.7 and 2.7 in 2008/09 and 2009/10, respectively. These CPUEs were much higher than the expected levels (1.2 and 1.1, respectively) if the 2007/08 effort had been maintained in these two years. The vessel numbers declined by 14% and 36% in 2008/09 and 2009/10, respectively, compared to 2007/08. The fishery profit increased by AUS$13 and 49 million for 2008/09 and 2009/10, respectively, compared to that estimated if the 2007/08 effort level had continued. This assessment demonstrates the economic benefits of fishing at a level close to that estimated for MEY under an input management regime. The management decision-rule framework is currently based on having the egg production above a threshold reference level to ensure sustainability and now a target reference point based on MEY principles is also being considered.