An expedition to tag blue whales in New Zealand waters for the first time almost came up empty as warmer sea temperatures forced them out of some of their usual feeding grounds.
Photo: AFP / Biosphoto
NIWA marine ecologist Kim Goetz led the expedition in January to to tag up to eight of the animals, to help understand their foraging and migration patterns.
Their boat headed first to the seas of Taranaki where where deep cold water usually rises to the surface bringing up the rich nutrients the mammals feed on.
But the water was unusually warm, at 20°C to 22°C, and it was a La Nina weather pattern, so the cold water wasn’t welling up.
“That usually has implications for their prey like krill – and so they weren’t there,” Goetz says.
“This year was a particularly bizarre year."
A pilot from Golden Bay Air saw one animal near Farewell Spit, heading south, and Goetz and her team followed, towards the West Coast of the South Island. They hired a plane to search at the same time, finally spotting two whales.
“You really have one time to approach these animals and get the tag on,” Goetz says.
Blue whales can grow to a length of 30 metres, she says. “If these whales wanted to do some damage to your boat they would have absolutely no problem.”
The tags are fired onto the animal and if it doesn’t hit, the tag is lost. They transmit to a satellite every 45 seconds when the whale is at the surface, and last four to six months.
The expedition saw about a dozen whales in all but most were travelling at speed.
“If these animals aren’t feeding and are just headed somewhere there’s just no point in even trying [to get close to tag them.”
In the three weeks since tagging, one whale headed to the west coast of Auckland to stay near an underwater canyon, the other went to Taranaki, through Cook Strait and down the east coast to forage off Otago.
It’s not known if the blue whales around New Zealand migrate north and south, nor what route they might take if they do.
“We don’t know much of anything about their population, we’re just beginning to scratch the surface.”
The whales are going where they can get food, and if they do migrate, travelling further to get nourishment may affect them.
“So certainly there are implications but we don’t know now much of an oddball year this is.”
