James Dell

Variation in the EAC and impacts on the mesoscale distribution and availability of east-coast pelagic species

Supervisors: Dr Alistair Hobday (UTAS) and Dr Chris Wilcox (CMAR)

The east coast of Australia is bounded by the East Australia Current (EAC), Tasman Sea and Coral Sea . The EAC is the most dynamic of these ocean regions, and supports a valuable fishery harvesting a number of pelagic species, including sharks, tunas and billfishes. The distribution of these species within the east Australia systems is spatially and temporally variable. In addition, these species are not restricted to these systems and are believed to belong to larger, pan-Pacific stocks. Physical forcing of the EAC appears to be predictable several years in advance, yet the influence on the distribution of pelagic species is unclear.

More than a decade of data on species abundance and distribution has been collected through logbooks completed and analysed through the cooperation of the fishery, management and science organisations. Previous work has investigated variations in catch per unit effort (CPUE) at time scales of seasons and years, and to a lesser extent, movement patterns of some species. Remotely sensed and model driven data are also available on a suite of physical variables known to be correlated with the movements of pelagic predators. There is also great amount of knowledge held by the resource users, the fishers, which is at present under utilised.

The project will develop and evaluate Bayesian statistical models describing and predicting the availability of large pelagic species in the Tasman Sea , focussing on Yellowfin tuna. This will be achieved by pursuing a better understanding of the habitat preferences at various temporal and spatial scales, focusing on the mesoscale features (eddies, filaments and temperature fronts) of the EAC. Links between the archived logbook data, oceanographic information and the expert/local knowledge held by the fishers will be used to inform the models. Model output will allow trends and patterns of fish availability to be viewed in context of both the oceanography and the status of pelagic stocks in the adjacent regions of the South West Pacific.