Project number: 2010-047
Project Status:
Completed
Budget expenditure: $614,243.87
Principal Investigator: Anya Waite
Organisation: University of Western Australia (UWA)
Project start/end date: 14 May 2010 - 29 Jun 2012
Contact:
FRDC

Need

Lack of knowledge of Western Australia’s fisheries oceanography fundamentally limits understanding of the recruitment of Western Rock Lobster, Panulirus cygnus, in a fishery worth $200-300 million/year to Australia. The life cycle of P. cygnus includes a planktonic “phyllosoma” larval stage that can be transported ~1500 km offshore, via ocean currents. Development then continues at sea for up to 11 months, before juveniles (“puerulus”) cross the shelf to recruit to coastal reef areas. Critical to improving management of this fishery is an understanding of oceanographic mechanisms driving coastal recruitment. The last three years of puerulus settlement have been low, with the latest (2008/09) the lowest in 40 years. This recent low settlement remains unexplained by environmental drivers previously identified as important, so its cause represents a key unknown for managers assessing the fishery’s sustainability. We will test the hypothesis that variation in settlement is driven by variation in food availability during the open-ocean stage of the phyllosoma larvae. We suggest that ocean productivity, particularly the nitrate-driven classic food chain supporting diatoms, and copepods, (as the ultimate prey of phyllosoma), limits phyllosoma growth and survival in their oceanic phase. Our work targets the peak autumn/winter plankton bloom in the Leeuwin Current, quantifying oceanographic parameters crucial to modelling rock lobster larval dynamics and attempting to link these directly to the food chain on which the phyllosoma as active predators, rely very heavily upon for survival.

Objectives

1. Analyze phyllosoma densities, sizes, genetics at four latitudes (Rottnest-Shark Bay, WA)
2. Analyze offshore food web structures supporting phyllosoma growth at sea
3. Assess potential for Leeuwin Current autumn/winter bloom to support phyllosoma growth

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