Endangered whales under Threat.

Research has shown 14 endangered Bryde's whales found dead in Auckland's Hauraki Gulf in recent years were killed by boats.

An autopsy on a 12-metre Bryde's whale found dead on Friday revealed massive injuries along half its body, said Massey University veterinary pathologist Stuart Hunter.

"It was clear that the whale had severe trauma, running all the way from the rib cage to near the tail of the whale, so it was most likely to be a large vessel that caused these lethal injuries," he said.

One of New Zealand's most endangered species, Bryde's whales are found in the Hauraki Gulf all year round, with ship strike posing the greatest threat to their life.

Auckland University marine scientist Rochelle Constantine has started tagging the creatures to investigate why they are so vulnerable, and found most swim quite close to the surface.

"We have deployed five tags so far and preliminary analysis shows that the whales are spending the majority of their time less than 10 metres below the surface," Dr Constantine said.

"This puts them within the strike depth of many vessels using the gulf."

The researcher urged captains of large ships to be more vigilant in watching out for the huge mammals.

"All vessels using the Hauraki Gulf pose a threat to whales so it is important that everyone using these waters is watching out for these large residents in Auckland's backyard," she said.

Whales re-colonising NZ waters

Scientists have discovered that southern right whales, hunted to near extinction in the 19th century, appear to be re-colonising mainland New Zealand calving grounds from a remnant population in the subantarctic Auckland Islands.

The endangered whales were rarely seen around mainland New Zealand for most of the last century, but small and growing numbers are slowly returning to the coast to give birth and raise their calves.

“With the increase in numbers observed around the Auckland Islands over the last decade, we think that some individuals are re-discovering the former primary habitat around the mainland of New Zealand,” says Professor Scott Baker of The University of Auckland and Oregon State University, who helped initiate the first study of the Auckland Island population in 1995.

The latest findings are based on genetic evidence from small skin samples collected from 707 whales over more than a decade. By comparing the DNA fingerprints of individual whales, the research has confirmed genetic differences between whales around Australia and New Zealand, and provides new insight into differences in the recovery of regional populations.

The results support the conclusion that the mainland New Zealand population was wiped out and that the returning whales are from the remnant subantarctic population. It revealed, for the first time, the movement of seven individual whales between the Auckland Islands and mainland New Zealand. “The seven whales that have been identified in both the Auckland Islands and the mainland are probably the first pioneers of this re-colonisation,” says Dr Baker.

The research has been published today in the international journal, Marine Ecology Progress Series, by scientists from The University of Auckland, New Zealand Department of Conversation (DOC), Australian Antarctic Division, Macquarie University, the Museum of Western Australia and Oregon State University.

“The results confirm the strong connection of right whales to regional calving grounds around Australia and New Zealand as a result of early maternal experience,” says lead author Emma Carroll, a PhD student from The University of Auckland. “This maternal fidelity contributed to the vulnerability of these local populations, which were quickly hunted to extinction using only open boats and hand-held harpoons.”

Maternal fidelity is a kind of cultural heritage passed from a mother to calf during the first year of life, as they migrate together from calving grounds to feeding grounds thought to be near the subantarctic convergences.

When right whales around mainland New Zealand were wiped out, this heritage seemed to have been lost, slowing the return of whales to their former habitat. Surprisingly, a remnant population that calves in the subantarctic Auckland Islands survived and has shown signs of recovery, with surveys in the 1990s revealing an estimated 1,000 individuals.

With increased numbers of southern right whales returning to the mainland shores, DOC is calling on the public to report sightings of this rare whale. “With the winter calving season upon us, we are once again calling for the public to immediately report sightings of southern right whales to 0800 DOCHOT” says Dr Laura Boren, the DOC National Marine Mammal Coordinator.

DOC also has a flickr gallery where the public can upload images of the whales, at www.doc.govt.nz/marinemammalsightings. Dr Boren reminds photographers not to get too close to the whales, however. “To keep both you and the whale safe, leave a distance of 50m or 200m if there is a calf present,” she says.

The research article, entitled “Population structure and individual movement of southern right whales around New Zealand and Australia”, with the unique identifier “doi:10.3354/meps09145”, will be available for free download from the Marine Ecology Progress Series website www.int-res.com/journals/meps/

Southern right whales are large, long-lived mammals that calve in shallow coastal areas where they were hunted intensively in New Zealand and Australia in the 19th century. The species was given legal protection by the League of Nations in 1935 but was subject to illegal whaling in the 1950s and 1960s. The current New Zealand population is estimated to be less than 5 per cent of its pre-whaling abundance.