The importance of conserving recruitment pulses in rock lobster (Jasus edwardsii) fisheries where puerulus settlement is low or highly sporadic

Abstract

The commercial fishery for southern rock lobster (Jasus edwardsii) is South Australia's most valuable fishery resource worth in excess of AUS$100 million annually. Over the past decade, recruitment to the fishable biomass has decreased, which has translated to declines in commercial catch rates. In the Northern Zone fishery, catch per unit effort (CPUE) declined from 1.42 kg/potlift in 1999 to 0.67 kg/potlift in 2008, a decrease of 52%. Puerulus monitoring has been undertaken since 1996, with the period from settlement to recruitment estimated at ~4 years. In 2002, 2005 and 2006, spikes in settlement were recorded, which were predicted to enter the fishery as recruitment pulses in 2006, 2009 and 2010, respectively. Management decisions failed to conserve the 2006 recruitment pulse by setting total allowable commercial catches (TACCs) above actual catch estimates. However, in 2008, a conservative management approach was adopted with the TACC reduced from 470 to 310 t despite 403 t being landed in the 2008 season. In 2009, CPUE increased by 31% to 0.88 kg/potlift while fishing effort decreased by 42%. In 2010, CPUE increased further to 1.07 kg/potlift, the highest since 2000. The study highlights the importance of management decisions that conserve recruitment pulses in order to sustain lobster resources on which fisheries depend.