Satellite tags to save dolphins

March 02, 2004
By Kim Griggs
In Wellington, New Zealand

New Zealand is aiming to use satellite tagging to try to save Maui's dolphins, the world's most endangered marine mammal.

New Zealand's public conservation agency, the Department of Conservation, (DOC), is testing the system by tagging three Hector's dolphins.

These animals are also endangered, but are more populous at around 7,000 than Maui's dolphins, which number less than 150.

If the trial of the satellite tags proves successful on the Hector's dolphins, then the critically endangered Maui's may also be tagged.

This, the DOC argues, would give it sorely needed information about where these small cetaceans range.

Mock-up of dolphin with satellite tagging

"Our efforts to save New Zealand's rarest dolphin are being hampered by what we don't know about them," said Rob McCallum, from the Department of Conservation.

Local conservation groups are vehemently opposed to the trial.

Netting ban

Maui's dolphins are now protected through a ban on the use of commercial set nets within four nautical miles of the west coast of New Zealand's North Island, where the dolphins are known to live.

In the past three and a half years, eight Maui's dolphins have washed up dead.

But since the netting ban came into force late in 2002, only one has been found dead.

The worry for the DOC is that the dolphins have been spotted well outside the protected area, as far as 15 nautical miles from shore and up to 100 kilometres south of the closed set netting area.

"We need to find out if Maui's dolphins move outside the current set netting closed area," said Mr McCallum.

"If so, we need solid evidence to show this and to determine how much of their time they spend in different areas."

Internationally, scientists have tagged other marine mammals, often with startling results.

Heaviside's dolphins, a close relative of Hector's dolphin in southwest Africa, were thought to be an inshore dolphin species.

Satellite tagging has shown that this dolphin species moves out to and back from the edge of the continental shelf, about 25 nautical miles offshore.

Ideal tags

To test the efficacy of satellite tracking on the South Island-based Hector's dolphins, the DOC plans to attach tiny satellite tags - two matchboxes in length and 50 grams in weight -to the dorsal fins of three dolphins.

The transmitters are attached with nylon-coated pins, with fasteners that are designed to eventually corrode and release the tag from the animal.

For the transmitter to work, it needs to be above water, so the trial aims to find out if the swimming style of New Zealand's small dolphins, which do not dive very deep but do not surface for long, will allow enough useful data to be transmitted.

Ban on use of commercial set nets has led to fall in dolphin deaths

Ann Rupley, technical sales manager at the tags' manufacturers Wildlife Computers, said dolphins were the ideal animals for the tags.

"They are a good platform for these tags because they do come up above the surface so often.

"They are exactly the kind of thing that this tag was designed for," she said.

But Dr Liz Slooten, a zoologist at the University of Otago who has studied New Zealand's dolphins for 20 years, has real doubts that the tags will provide the right information.

Other non-invasive research methods, such as acoustic, boat-based and aerial surveys, can give the same data without the potential for trauma and damage to the dolphins, she argued.

"All of these methods are absolutely standard methods used for doing whale and dolphin surveys not only in New Zealand but around the world. So there is no convincing argument for this work," she said.

"If there was a really strong argument ... I'd be out there doing it myself. I certainly wouldn't be objecting to it."

The tags, Dr Slooten and other opponents argue, will not give enough fine-scale detail to be able to pinpoint just where these endangered animals range.

Maori support

But Wildlife Computers' Ms Rupley disputes that, and says the average fix is plus or minus 350 metres or better.
"They may be as good as plus or minus 150 metres which is certainly close enough to get a pretty good fix on the animal."

For the local Maori tribe, Ngai Tahu, the plan makes good sense and they have given it their backing.

"We spent a lot of time thinking about and talking about this as anybody would," said spokesperson Robin Mautai Wybrow.

"We support the department 150 per cent in terms of what they are attempting to do, which at the end of the day, for us, is to look at how they can help our cousins in the North Island with the Maui's dolphin."

The trial is expected to start soon.

"With less than 150 Maui's dolphins left, we need to consider all means available to find out what we need to know to save this dolphin," said McCallum. "We can't afford to wait."

Reproduced from BBC Online
http://news.bbc.co.uk/1/hi/technology/3523337.stm