Cyclical winds are pushing colder, nutrient rich waters closer to the surface, leading to bottlenose dolphins, like this, and whales to be stranded (Image: NOAA) Cyclical weather patterns have driven more than 150 whales and dolphins to become stranded on Australian and New Zealand beaches since the weekend, scientists say.
Research by the University of Tasmania's department of marine biology has shown that mass strandings are cyclical and caused by westerly winds increasing in strength every 12 years over the Southern Ocean.
Marine biologist Dr Karen Evans said the study, presented to the Australian Marine Sciences Association annual conference in July, has shown strandings have a 12-year cycle, and the peak is being reached now.
The research shows cyclical westerly and southerly winds pushed sub-Antarctic waters north, drawing colder, nutrient-rich waters needed by whales and dolphins closer to the surface.
"You get an increase in the number of whales [around Tasmania and Victoria] and therefore a higher likelihood of animals to strand," she said.
Learning about beaching
Meanwhile Australia has announced it would establish a national whale strandings database to help find the causes of mass strandings.
Federal environment minister Ian Campbell said the new national database would take past research work "to another level with a strong, well-resourced national approach".
"Strandings are fairly frequent along the coasts of Tasmania and in Bass Strait at this time of year and in New Zealand, but unfortunately we do not know why it happens," Campbell said.
More than half of a 42-strong pod of whales that beached at Maria Island to the southeast of Australia's island state of Tasmania at the weekend were heading out to sea after a desperate rescue mission by about 80 volunteers.
The remaining animals, identified as long-finned pilot whales, have died, bringing to at least 117 the toll of beached whales and dolphins to have died in Tasmania since the weekend.
A mass beaching of whales and dolphins at King Island in the Bass Strait between mainland Australia and Tasmania at the weekend has resulted in the deaths of 73 long-finned pilot whales and 25 bottlenose dolphins, the state's environment department said.
"We've had about 80 people on Maria Island, including volunteers, Parks and Wildlife Service staff and Marine Conservation staff all working on a major effort which saw 23 of the stranded animals successfully saved," said environment department spokesman Warwick Brennan.
"They put large mats under the whales, dug trenches and gradually eased them into the water and supporting them while they became buoyant before moving them out to deeper water.
"The latest reports are that the rescued whales haven't been sighted again at this stage, which is a really good outcome."
New Zealand whales are doing it too
In New Zealand rescuers succeeded in returning to the sea 20 of the 21 pilot whales found alive on a beach near Whangamata on the North Island's east coast, and put down the last one.
Up to 70 volunteers including conservation department staff kept the last of the live whales afloat until they were strong enough to swim away.
But more than 50 of the pod of 73 whales, which lay undiscovered on isolated Opoutere beach until Monday, had died.
Conservation department area manager John Gaukrodger said there were no signs the refloated whales were returning to the beach.