Rare Dolphin Threatened by Seismic Tests

credit: stuff.co.nz

The leading professional society for research on marine mammals, Society for Marine Mammalogy, has asked the New Zealand government to halt seismic survey in the habitat of the critically endangered Maui Dolphin (Cephalorhynchus hectori maui). There are only 55 individuals of this subspecies surviving in the wild. They are the world's smallest and rarest dolphins. They only live off the west coast of New Zealand's North Island and are closely related to the more numerous Hector's dolphin. It is not known if the two species interbreed, but they are identical in appearance. They breed slowly with females maturing late at around seven years and giving birth to a single offspring every two to four years.

While fishing is the primary cause of their death, scientists are concerned that seismic surveys harm their hearing and push them into unprotected areas where they are more exposed to the danger of fishing nets. Gillnets and trawling kill about 9% of the population each year or about 75 times the sustainable limit. The Society told the government that allowing testing in their habitat is inconsistent with the government's stated goal of allowing the species to recover. The extremely loud blasts of seismic surveying occur around the clock for weeks or even months at close intervals and are known to affect the behavior of whales, dolphins, porpoises and harm the fish on which they feed. Twenty-four cetacean species are known to science to suffer negative effects from marine noise pollution. While it may not be enough to kill a marine mammal outright, the chronic stress the extreme noise causes is debilitating, just as a human if debilitated by chronic stressors. Pre-natal damage to unborn dolphins is also possible which the Maui dolphins cannot bear if they are to avoid extinction. The Society earlier asked the government to ban gillnet and trawl fishing in the Maui's habitat. At the International Union for the Conservation of Nature (IUCN) convention last year 576 members voted to protect the Maui dolphin. Only two governments voted against the resolution, New Zealand's was one of them. Currently there is a ban on setting nets close to shore from Maunganui to Hawera, but harbors, which Maui's inhabit, are not subject to the ban. There is scientific backing for extending the ban farther south to Wanganui. Catch data shows net setting and trawling occurs illegally inside the protected area.