The tiny Maui's dolphins are only found off the west coast of New Zealand's North Island Enlarge

Measures to protect one of the world's rarest dolphins have been denounced as a "death sentence" by campaigners.

Only 55 adult Maui's dolphins are known to survive off the coast of New Zealand but their numbers are being threatened by fishing and disease.

The NZ government has proposed extending a protection zone to save the tiny, black and white cetaceans.

But researchers say the actions don't go far enough and argue the Maui's could be extinct within 20 years.

The Maui's are the world's smallest and rarest dolphins and only found on the west coast of New Zealand's North Island.

New Zealand's failure to protect the world's smallest and rarest dolphin is a bitter blow to marine conservation”

Dr Barbara MaasNabu International

They are closely related to another native species called Hector's dolphins which survive in far greater numbers.

Net impact

In 2012 a survey commissioned by the New Zealand government's Department of Conservation found that there were approximately 55 Maui's left above the age of one.

They estimated there were around 20 breeding females. These give birth to one calf every two to four years.

Conservationists say the introduction of nylon filament nets in the 1970s has been a key factor in the decline of these dolphins.

The Maui's inhabit coastal waters up to a depth of 100 metres but have come into contact with trawlers and with fishermen using set nets which have proved particularly destructive to these animals.

dolphins surfing
Maui's and Hector's dolphins enjoy surfing the waves in groups

The New Zealand government has recently announced new restrictions on fishing, extending the ban on the use of set nets by 350 square kilometres.

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