Wellington, Sep 7 (IANS): The populations of the Hector's dolphin, living only in the waters off New Zealand, has decreased by 80 per cent in the last 50 years, an environmental organisation revealed on Thursday.

It is estimated that there are currently only some 9,000 Hector's dolphins (Cephalorhynchus hectori) left, after a drastic population decrease from the 50,000 estimated in 1970, which has placed it on the list of endangered species of the International Union for Conservation of Nature, according to Sea Shepherd New Zealand, the environmental organisation which launched a campaign to save the marine mammals.

"Many of the small sub populations are as isolated and vulnerable as the North Island Hector's (Maui)" said Michael Lawry, Managing Director of Sea Shepherd New Zealand.

"Hector's disappeared at such a rapid rate last century and with very little public knowledge, it was truly a silent slaughter in our inshore waters. There's a greater public awareness now but still a problem that can't be solved by petitions and submissions," Efe news quoted Lawry as saying.

He also claimed that the connections the New Zealand government has with "some big fishing companies" might be helpful in solving this issue.

The "Operation Pahu", referring to the Hector's dolphins name in Maori language, a word which imitates the sound the dolphins make when surfacing to breath, aims to protect the mammals from illegal fishing or unregulated trade, the organisation said in a statement.

A large number of these dolphins die from being trapped in fishing nets as they are unable to swim up to the ocean surface to breath.

During the campaign, activists, in collaboration with indigenous people and local scientists, will patrol the southeastern coasts of the South Island to monitor human activities in the dolphin's habitat.

The Hector's dolphin, grey with whitish spots, usually grow to some 1.4 meter in length.