NZ: More accurate information on orange roughy –

NZ: More accurate information on orange roughy Published:  25 July, 2007

SCIENTISTS are using advanced technology to survey orange roughy on the Chatham Rise – and early results reveal better information for determining the fishery’s stock size than ever before.

Commissioned by the Ministry of Fisheries, NIWA scientists are using a device built by scientists at Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO) that combines a fishing trawl net with a high-resolution video camera and acoustic equipment.

As the vessel moves along, scientists record acoustic echoes alongside images of orange roughy and other fish. This allows the ‘target strength’ for orange roughy to be determined, which in turn helps measure the amount of orange roughy present.

Until now, identifying orange roughy has been difficult – largely because orange roughy have an oil-filled swim bladder that produces a much weaker acoustic signal than the typical air-filled swim bladders of most fish. So when signals come in, it’s not clear whether they are from orange roughy or another kind of fish.

This new technology helps solve the identification problem and complements other acoustic research that New Zealand’s Deep Water Fishing Group is undertaking in collaboration with NIWA and CSIRO.

Ian Doonan, on board NIWA’s research vessel, the Tangaroa, says this is the first time simultaneous images and acoustic echoes have been collected in a large group of spawning orange roughy – and the footage is impressive.

“We’re able to identify orange roughy so clearly that we can see them diving in reaction to the net.

“The results will improve estimates of acoustic orange roughy biomass for both New Zealand and Australian waters. Essentially, that means more reliable information on the amount of orange roughy in the area.

“It will also help feed into more accurate assessments of stock numbers across the board.”

Ministry of Fisheries deepwater fisheries manager, Stefan Leslie, says this type of research has a key role to play in terms of helping make more informed decisions about the management of orange roughy.

“It’s a fishery that has been important for decades – providing jobs and export earnings for New Zealand along the way. To ensure this can continue, we need better information and this type of research is helping us achieve that.”

Ministry of Fisheries chief scientist, Pamela Mace, adds that the work is also a reflection of a large co-operative effort between government, trans-Tasman science organisations and the fishing industry’s Deepwater Group – all working together to develop an efficient and informative research programme.

The Chatham Rise is an area of ocean floor to the east of New Zealand stretching for some 1000 kilometres from near the South Island in the west, to the Chatham Islands in the east is published by Special Publications. Special Publications also publish FISHupdate magazine, Fish Farmer, the Fish Industry Yearbook, the Scottish Seafood Processors Federation Diary, the Fish Farmer Handbook and a range of wallplanners.