Scientists track, tag deep-sea sharks for first time

April 19th, 2008 - 4:51 pm ICT by admin  

Washington, April 19 (IANS) Deep-sea sharks have been tagged and tracked and their habitats precisely mapped for the first time to test the conservation value of areas closed to commercial fishing. Scientists from the Commonwealth Scientific and Industrial Research Organisation’s (CSIRO) flagship recently fitted acoustic tags to 50 gulper sharks, swell sharks and green eye dogfish near Port Lincoln, South Australia.

They will track the shark’s movements in a closed area designed to protect the gulper shark - a severely depleted and protected species under the Environment Protection and Biodiversity Conservation Act 1999.

“Half of the fish harvested in Australia’s south-east fishery come from a thin belt of water along the south-eastern continental shelf at depths of 200-700 metres,” said says CSIRO scientist Alan Williams.

“This rich belt yields prime table fish such as blue eye trevalla and pink ling, but is also home to several shark species vulnerable to over-fishing.

“The fishery has taken steps to reduce its impact on sharks by putting in place a network of three closed areas located off South Australia, Tasmania and New South Wales,” Williams said.

The research applied tagging techniques never before tested at such depths and developed new handling practices to minimise stress caused by the tag and release process, reports Sciencedaily.

The closed area, which covers approximately 1,200 square kilometres and is mostly in 200 to 1,000-metre depths, was mapped from the Marine National Facility Research Vessel Southern Surveyor.

Multi-beam sonar was used to draw the contours of steep rocky banks, narrow muddy terraces and submarine canyons on a previously blank area of seabed.

A towed underwater camera system was used for fine-scale observations of seabed habitats and communities, fish behaviour and habitat use, and to estimate fish distribution and abundance.

The sharks will be tracked for the next three years by a network of 24 acoustic listening stations moored 100 metres off the complex and steep seabed.

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