Evidence of large-scale spatial declines in recruitment patterns of southern rock lobster Jasus edwardsii, across south-eastern Australia

Abstract

Over the past 8–9 fishing seasons, recruitment has declined in all of the major rock lobster ( Jasus edwardsii) fisheries in south-eastern Australia. This has translated into declines in commercial catch rates. In some regions, this decline has been rapid. For example, catch rate in the southern zone fishery of South Australia has decreased by 65% from 2.1 kg/potlift in 2002 to 0.73 kg/potlift in 2008. While trends in recruitment and catch rate are spatially similar, contrasting regional signals are observed from puerulus settlement data which are used to predict future recruitment. Settlement has generally decreased in Tasmania, but some of the highest settlements on record were recorded in 2005 and 2006 in South Australia and Victoria. While historical management decisions may have contributed to the current status of rock lobster fisheries in some areas, simultaneous patterns of decline indicate possible large-scale environmental influences. Specific environmental factors remain largely unknown. However, we present data from an exceptional coldwater upwelling event observed during 2008 which suggests that growth rates in South Australia were significantly impacted. Overall, the results highlight the need for conservative TACCs in fisheries across south-eastern Australia in order to protect existing biomass and sustain rock lobster resources.