Amateur fishermen also a threat to Hector's dolphin - study

There were about 7400 Hector's dolphins, about 1200 around the Banks Peninsula area.. Photo / Black Cat Cruises

Rules to protect the endangered Hector's dolphin from set nets in Akaroa Harbour may not go far enough, new research suggests.

Amateur fishermen have been allowed to use nylon mesh set nets, which can entangle the mammals and stop them surfacing for air, from April to September because it was previously thought dolphins only visited over summer.

But an Otago University study found the mammals were present in the harbour, on Banks Peninsula, near Christchurch, on almost half the days when set netting is allowed.

A three-strong team led by Professor Stephen Dawson, from the university's department of marine science, moored special acoustic devices in the harbour. The devices logged the dolphin's high-frequency signals over a year.

They recorded the presence of Hector's dolphins on 41 per cent of the days during the set netting season, despite their devices covering just 1 per cent of the inner harbour.

Prof Dawson concluded: "The concession offered to amateur gillnetters is not safe for the dolphins. A crucial problem for Hector's dolphins is that in several key areas the protection does not match the dolphins' distribution.

"The new research shows this is true in Akaroa Harbour, but it is also true offshore around Banks Peninsula, where aerial surveys have shown that the dolphins range much further offshore than the protection extends."

Akaroa is the largest harbour on Banks Peninsula and home to a valuable dolphin-watching industry, which takes visitors to see and swim with Hector's dolphins.

Prof Dawson said there were about 7400 Hector's dolphins, about 1200 around the Banks Peninsula area.

A large part of the population was essentially unprotected, he warned.

The research was published yesterday in the scientific journal Endangered Species Research.