By Pauline Askin

SYDNEY (Reuters) - Balancing in small boats in choppy Antarctic waters, sometimes for hours and covered in ice, Australian researchers shot at endangered blue whales with an airgun to tag the giant creature with satellite tracking equipment.

During a seven-week voyage the scientists from the Australian Antarctic Division tagged the world's largest creature and then tracked the rarely seen whales using sonar attached to special buoys to gain an insight into the threatened species.

Little has been known up to now about the habits of blue whales, which despite their huge bodies - the heart of a full grown adult is the size of a small car - were hunted to the brink of extinction in the 1900s and still remain endangered.

"This kind of detailed movement hasn't been collected yet, so that's really important," Virginia Andrews-Goff, a member of the research team and expert in whale tagging, told Reuters.

"We're using the biopsy samples and the photos to work out individual identities. In the future that individual information will lead to getting an idea of the abundance of Antarctic blue whale and how well they're recovering from whaling."

Among the many mysteries surrounding blue whales - which can grow up to 30 meters (98 ft) long and weigh 170 tonnes (374,800 lbs) - is their number. Several thousand are believed to exist throughout the world, but more precise data is lacking.

The mechanics of the scientific venture were challenging, as tagging could only be deployed using air guns at closer range. Taggers underwent intensive firearms training and a fitness program to build core strength and thigh muscles in order to stabilize themselves in the small boats and shoot accurately.

"We were tagging, taking biopsy samples and taking photos...So you could be out on the water for four hours at a time," said Andrews-Goff.

"We were heading out in conditions that were below 0 degrees Celsius (32 Fahrenheit). Sometimes it was snowing, sometimes the ice would actually freeze on you."

The method, which is non-lethal and has the potential to be adapted for use with other whale species, was announced on Wednesday at a news conference in the southern island of Tasmania.

"The achievements of this non-lethal research method clearly show it is not necessary to kill whales in order to study them," Environment Minister Tony Burke said in a statement.

The group plans to present their results at this year's meeting of the International Whaling Commission, the international body set up to manage whales.

(This story corrects paragraph 2 to say tagging, tracking took place over 7 weeks, not 3 years)

(Reporting by Pauline Askin, Editing by Elaine Lies and Michael Perry)