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Issue 52 | May 2009
An acoustic tag attached
to a gulper shark
A greeneye spurdog shark tagged near Port Lincoln in South Australia, has surprised Hobart scientists by swimming all the way to Portland in Victoria.
The spurdog was one of 50 deep-sea sharks fitted with acoustic tags in a no fishing area at the edge of the continental slope. Southern dogfish and whitefin swellsharks were also tagged and tracked using an array of seabed acoustic listening stations placed 400 metres deep.
'The fishing closure is designed primarily to protect vulnerable bycatch species such as the southern dogfish which is severely depleted over much of its range and nominated for protection under the Environment Protection and Biodiversity Conservation Act', says fishery biologist, Ross Daley from the Wealth from Oceans Flagship (WfO). 'But the closure will only work if the sharks stay in the box.'
And did they?
Deployment of an acoustic
listening station
Data downloaded from the acoustic listening stations in March 2009, showed most of the greeneye spurdogs moved large distances from the tagging box, while swellsharks stayed inside most of the time. Patterns in southern dogfish are less certain because relatively few were tagged, although they have astonished scientists by ascending hundreds of meters off the sea floor at night, presumably to feed.
'The more we study sharks, the more we appreciate about their capability to swim great distances and to make complex migrations to feed', Ross says.
The next phase of the research is a proposed project, co-funded by the WfO, and the Fisheries Research and Development Corporation, to expand the tagging work and conduct a survey between Brisbane and Hobart to locate additional areas for protecting deep sea sharks.
Two more years of study will determine whether a closed-area network can be an effective part of deep-sea shark management plans developed by the Australian Fisheries Management Authority and the Department of Environment, Heritage and the Arts.
A tagged shark returning to deep water
