Acoustic research helps fishery

Scientists and fishers will use deep ocean acoustic remote sensing techniques developed by CSIRO to help give long-term sustainability to the largest fishery in Australia's south-east.

The $1.2 million project is intended to underpin the Blue Grenadier fishery, located off the Tasmanian west coast and in western Bass Strait and involve the Tasmanian and Victorian fishers. It is jointly funded by the Fisheries Research and Development Corporation, CSIRO Marine Research, the Ocean Fresh Fisheries, Petuna/Sealord and will use Australia's National Facility for Marine Research, Southern Surveyor.

"The Blue Grenadier fishery is the largest fin fish fishery in southern Australia and a valuable component of the Australian SE fishery export," said Rudy Kloser, acoustic research scientist at CSIRO Marine Research.

"Through this project, we are looking at remotely sensed methods to estimate fishery stock size and the environmental triggers which influence stock spawning success that sets the pattern for harvests up to five years ahead," Kloser said.

"Our objective is to establish a cost-effective biological observing system which combines satellite data of ocean surface conditions with sub-surface acoustic and oceanographic and biological sampling from fishing vessels to help estimate current stock levels and predict future catch levels."

Gerry Geen, representing industry and also a co-leader of the project, said the project would provide a basis from which to apply for certification of the fishery as sustainable by the London-Marine Stewardship Council.

Certification promotes consumer recognition of species which are being sustainably fished.

In Australia, the western rock lobster has gained certification and in New Zealand, Hoki, the same species as Blue Grenadier, has achieved certification.

Geen said its most innovative element was the transfer of the acoustic technology to fishing vessels harvesting the stock.

"Industry has been harvesting from this fishery for the past decade and has a vested interest in knowing more about the fishery and how it replenishes itself,"

Geen said.

"The science and technology necessary to understand environmental conditions is at a point where we can work together to secure a sustainable future for the industry, the fishery and the ecosystem. Significantly, the on-going shipboard monitoring system will be critical in building a quantitative history of stock assessments to ensure sustainability."

Project industry partners are the Tasmanian and Victorian companies, Petuna/Sealord and Ocean Fresh Fisheries, which hold 80 per cent of the quota. Managed by the Australian Fisheries Management Authority, the fishery has a maximum catch allowance of 7000 tonnes a year (2004).

Blue Grenadier (Macruronus novaezelandiae) is caught by trawling at depths of 200-700m along the continental slope, linking the continental shelf to the deep ocean. They commonly grow from between 60 and 100cm and weigh from 1 to 3.5 kg when caught. A high quality white-fleshed fish is primarily exported currently to European markets.

Scientific stock assessments are used by fishery managers to determine sustainable levels of harvesting, based on recent harvest history, biological life history parameters and data from fishers and stock surveys which is then used to simulate and predict the extent to which a fishery can be sustainably harvested.

Central to the new assessments will be the use of industry-based acoustic methods complimented with a deep towed multi-frequency acoustic system. Remarkably sensitive at depths of up to 1,000 metres, it measures the strength of reflected sound from individual fish, distinguishing between different fish species. Combining the acoustic surveys with targeted ecological research will provide an estimate of the fish population in the survey area.