WELLINGTON - The world's largest animal, which was almost hunted to extinction in the 19th Century, appears to be making a comeback in waters off New Zealand, New Zealand scientists revealed Monday.

The study of blue whales in the South Taranaki Bight, off the west of the North Island, showed that the creatures were passing through in numbers greater than expected, according to researchers with the government's National Institute of Water and Atmospheric Research (NIWA).

A blue whale swims in the deep blue sea off the coast of Mirissa, in southern Sri Lanka, April 5, 2013. The southern tip of Sri Lanka, where the deep waters of the continental shelf is close to the shore, is one of the few locations in the world to see dolphins, whales and other creatures of the deep. Since the end of the 25 years civil war in 2009, tourists are returning to the island to enjoy its natural beauty and catch a rare glimpse of the elusive blue whales, the largest creature that has ever lived. Picture taken April 5, 2013. [Photo/Agencies]

The blue whales had found an important food source there on their way to and from summer feeding grounds in Antarctica.

The study examined sightings of blue whales collected between 1979 and 1999, historical whaling data, strandings, foraging observations, and sightings recorded during two seismic surveys conducted in 2011.

It linked the increased presence of blue whales to a specific ocean movement that generated large clouds of plankton in the South Taranaki Bight.

Despite being more than 20 meters long and weighing more than 100 tons, the blue whale remains one of the world's most elusive creatures.

Sightings were rare and little was known about the distribution patterns of blue whales, NIWA marine ecologist Dr Leigh Torres said in a statement.

The study would significantly enhance understanding of the distribution and foraging grounds of blue whales in the Southern Hemisphere.

"Conventional wisdom has been that blue whales only transit through New Zealand waters while migrating. But this new information suggests that this is not an accurate understanding of their ecology," he said.

They appeared to be present in the Bight with "some regularity and density" to feed.

"Blue whales are huge and need to eat vast amounts of food, which are tiny plankton, to support their energy demands. But there are just four confirmed blue whale foraging grounds in the Southern Hemisphere outside of Antarctic waters. So, it's very important that we properly document and protect their foraging grounds."

However, he warned, the South Taranaki Bight was also the largest offshore natural gas and oil exploration area in New Zealand, with significant plans for expansion in the near future.

"Shipping traffic and seabed mining activities have been shown to impact blue whales directly, altering their behavior and degrading their habitat through acoustic disturbance and ship strikes," he said.

"We need to gain a better understanding of how and when blue whales forage here so that possible impacts can be avoided."