January 28th, 2016 (Nina Hindmarsh). A foraging ground for a population of pygmy blue whales congregating 40 km north of in the South Taranaki Bight is the subject of a study being conducted until mid-February.
The project is funded by National Geographic and is made up of an international research team of scientists and in collaboration with the Department of Conservation. The project is led by marine mammal expert Professor Leigh Torres of Oregon State University.
The team onboard the NIWA research vessel Ikatere, aim to determine the “when, where and who” of the estimated population of around 50-100 whales feeding on a dense patch of krill.
Little is known about the world’s largest animal, and blue whale sightings are rare as they normally travel alone or in pairs.
Only four confirmed blue whale foraging grounds in the Southern Hemisphere have been confirmed, outside of Antarctic waters.
The pygmy is a subspecies of the blue whale. It reaches about 24m in length, and is smaller than the other subspecies.
Dr Torres previously worked as a research scientist for NIWA for six years, when it was believed blue whales were only passing through New Zealand waters while migrating. In 2012 Dr Torres led a team of researchers who observed a large congregation feeding in the South Taranaki Bight.
“Blue whales don’t usually aggregate,” she explains. “You don’t usually find that unless they’re feeding. So I started looking at old whaling records of sightings that had been reported, and sure enough all the records led me to the blue whales aggregating in this area. I then started looking at oceanography and asking, ‘why would these whales be there? Is there a food source?’ Sure enough, there had been some ocean studies in the seventies and eighties that said krill aggregate in the dense patches in the area.”
With heavy industry activity in the particular area of ocean, Dr Torres said its important to get a better understanding of the whales feeding patterns in order to manage vessel traffic, oil and gas and potential seabed mining.
“All these things can potentially cause harm to whales in different way, so it’s important to determine how important the feeding ground is to the whales,” she said.
She said the large mammals needed feed in order to achieve their large migrations. “So they really need to have these predictable sources of food we really need to know more about how often they’re there, and what the population size is.”
Golden Bay Department of Conservation ranger Mike Ogle is also part of the team. He said it was important to understand their migration patterns.
“Once we have a better idea of the status of the species we can monitor it and put more resources into it if needed.”
Dr Torres said the survey was made up of acoustic and visual components.
Scientists have deployed five hydrophones to the ocean floor which record vocalisation and give an idea of their location.
The visual survey includes photo ID of the individual whales and their markings, which are then matched to determine population size.