One of the world’s most endangered dolphin species is sliding towards extinction due to damaging fishing methods, experts have warned.
Also one of the world’s smallest marine dolphins, Hector’s dolphin lives only in waters around New Zealand, where its population has fallen from 30,000 to around 7,000 individuals since nylon fishing nets came into use in the 1970s.
A subspecies from New Zealand’s North Island, known as Maui’s dolphin, is particularly threatened. Classified by the IUCN as Critically Endangered, its population now numbers fewer than 100 individuals.
Unsustainable dolphin mortality
According to research conducted by Dr Liz Slooten of the University of Otago in New Zealand, commercial gillnets (long nets set vertically in the water to entangle fish) are drowning around 23 Hector’s dolphins each year along the east coast of New Zealand’s South Island.
With the sustainable limit for dolphin bycatch in the area estimated at just one dolphin a year, the current levels of dolphin mortality would reduce the Hector’s dolphin population by at least a further 14% by 2050.
Hector’s dolphin is also threatened by other fishing methods, including trawl nets, which are likely to kill just as many individuals as gillnets. This brings the number of dolphin deaths due to fisheries to at least 46 a year along the east coast.
Dr Barbara Maas, head of endangered species conservation for NABU International – Foundation for Nature, said, “An annual loss of this size will wipe out 62% of the population by 2050. Only a scattering of animals will survive, potentially pushing the population beyond the point of no return.”
As a coastal species, Hector’s dolphin is also highly vulnerable to a range of other threats, including pollution, boat strikes and marine mining.
More selective fishing methods needed
Although bans on gillnetting are already in force in some parts of New Zealand, the continuing high levels of dolphin mortality indicate that more work is needed to protect this rare species from extinction.
Dr Mass, who has been speaking at the World Conference on Marine Biodiversity in Aberdeen this week, recommended that the only way to prevent the demise of Hector’s dolphin would be “absolute protection against commercial and recreational gill-netting and trawling.”
She urges the New Zealand government to ban these fishing methods in waters up to 100 metres deep, and suggests that more selective fishing methods which do not catch dolphins, such as hook and line fishing and fish traps, should be used instead.
Read more on this story at the Guardian – Endangered dolphins near extinction.
Find out more about the World Conference on Marine Biodiversity.
Liz Shaw, ARKive Species Text Author