Marine mammal expert Dr Liz Slooten of Otago University has expressed concerns over dangers to whales and dolphins from sonar and seismic exploration for deep sea oil in Statoil’s permit zone off Northland.
“Gray’s and Cuvier’s beaked whales and sperm whales live off Northland’s west coast”, says Dr Slooten. “Beaked and sperm whales are sensitive to seismic sonar explosions for oil exploration that can damage hearing, which whales rely on to navigate, and they can be killed, if they’re very close to the sonic explosions”.
Dr Slooten says that having observers on oil survey vessels are “virtually useless” and do very little to protect whales.
“Overseas research has shown that observers on the seismic testing ships only see around ten percent of whales and dolphins in the area. That’s because sperm whales, for example, spend 45 minutes diving and feeding for every 10 minutes they comes to the surface to breathe.”
“Most of the whales that are sensitive to noise will be on the run or already be in deep trouble, before the observers can see them”, said Dr Slooten. “Seismic survey noise can be heard for at least 80 kilometres, but the observers can see whales and dolphins for only one or two kilometres, and then, only when they surface. Small species, like Maui’s dolphins are also very difficult to see if they are more than a few hundred metres from the vessel.”
About half of the world’s whales, dolphin and porpoise species live in our waters. They often travel huge distances around our country at different times of the year.
Dr Liz Slooten says there are three common responses from when whales are scared by sonar:
- fleeing to escape the sounds can push marine mammals into areas of other risks (eg netting)
- because sound travels further in deep water, whales may head for shallower and shallower water where the sonar noise becomes quiet more quickly, and end up beaching themselves
- beaked whales normally feed 1000-3000 deep off Northland and may panic and try to surface too quickly. This can give them the bends by not being able to depressurise. The worst result is death.
“There have never been extensive surveys of whales and dolphins off Northland’s west coast. That means there is no baseline data to see if things change with deep sea oil surveys or drilling”, says Dr Slooten. “However we do know there are unusual and rare species of whales and dolphin present from the animals that have beached along Northland west coast over the past few decades and from surveys carried out close to shore for Maui’s dolphins.”
A rare pygmy sperm whale beached earlier this year on the Raglan coast while seismic testing was being carried out on for oil and gas (1). The cause of death is unknown because the whale was quickly shot and buried before an autopsy could be carried out.
Some examples of the whale and dolphin species found off Northland are listed below with some brief information about them.
Pygmy Right Whale:
Pygmy right whales are rarely encountered (as of 2008 fewer than 25 “at sea” sightings of the species had been made) and consequently little studied. Until 2012 this species of whale were thought to be extinct.
Gray’s Beaked Whale:
Gray’s beaked whale is said to be the most common species of whale to beach in New Zealand and has stranded on Northland beaches.
Cuvier’s Beaked Whale:
In 2014, scientists used satellite-linked tags to track Cuvier’s beaked whales off the coast of California and found the animals dove down to 2,992 metres (nearly three kilometres) below the ocean surface and spent up to two hours and 17 minutes underwater before resurfacing. This was both the deepest and the longest dive ever documented for any mammal.
Beaked whales are very sensitive to noise and spend a lot of time in the deep sea which is also the area Statoil is targeting.
Sperm whales are the largest toothed predator and are found in several areas around New Zealand (including Kaikoura).
From the early 1700s through the late 1900s the species was a prime target of whalers. The species is now protected by a commercial whaling moratorium, although some have been taken under the guise of “scientific whaling” and is currently listed as vulnerable by the IUCN.
Pilot whales are among the largest of the oceanic dolphins exceeded in size only by orca (which is really a dolphin). Pilot whales some of the most common stranders here and overseas.
Pygmy Sperm Whale:
Pygmy sperm whales are found throughout tropical and temperate waters but are rarely sighted at sea, so most data come from stranded animals – making a precise range and migration map difficult. They are believed to prefer off-shore waters, and are most frequently seen in waters ranging from 400 to 1,000 metres in depth. The total population is unknown.
Dwarf Sperm Whale:
The dwarf sperm whale is the smallest whale species. It grows up to 2.7 m. The species makes slow, deliberate movements with little splash or blow and usually lies motionless when at the sea’s surface. Consequently it is usually observed only in very calm seas.
Risso’s dolphins feed on squid. Although Risso’s dolphin has stranded on northern beaches, mass strandings are infrequent.
Pygmy Killer Whale:
The pygmy killer whale is a small, rarely seen oceanic dolphin. Its name refers to the way it looks like an orca. This species was only discoverered in 1952. Data from strandings, which seem to be common in the species, indicates a diet of squid and small fish. They have been observed attacking, killing and eating other cetacean species including the common dolphin. The species is purely oceanic, so is at home in the deep waters of the Tasman Sea.
Several dolphin species are also found in the area, including common dolphin, dusky dolphin and Maui’s dolphin, which is only found in New Zealand and is Critically Endangered. Orca are also regularly sighted.