Australasian Science: Australia's authority on science since 1938

Gillnets Threaten Penguins

A global review of penguin bycatch has highlighted the serious risk that fishing nets pose to the survival of many of the world’s penguin species, including Tasmania’s little penguins and New Zealand’s iconic yellow-eyed penguins.

After albatrosses, penguins are the most threatened group of seabirds, with ten of the 18 penguin species threatened with extinction. Of the world’s 18 penguin species, 14 have been recorded as by-catch in fishing gear. Three penguin species are of particular concern: yellow-eyed (endangered), Humboldt (vulnerable) and Magellanic penguins (near-threatened).

Lead reviewer Dr Ursula Ellenberg, who has a joint affiliation with La Trobe and Otago universities, said that set nets – walls of fine nylon mesh used to catch fish by the gills, and hence widely known as gillnets – are causing most penguin deaths. “In Tasmania around 10,000 gillnets are registered, with many more unregistered, and in New Zealand waters around 330 commercial boats use gillnets, in addition to many recreational users. Diving birds like penguins are unable to see the fine mesh underwater, and become entangled and drown.”

Forest & Bird’s seabird advocate Karen Baird, who contributed to the review, said that yellow-eyed penguin numbers have dramatically declined in recent years, with only 246 breeding pairs left on New Zealand’s South Island in 2015–16. They face a number of threats, including fishing nets, climate change, predation and habitat degradation. “The deaths of penguins in set nets is one threat that could be easily avoided,” Baird said.

Little penguins in Australia are also affected, particularly in Tasmania because of gillnetting. While spatial closures have been implemented around some penguin colonies in Tasmania, many colonies remain exposed without such protection.

The review found that little penguins were at moderate risk of becoming bycatch in fisheries. However, co-author Dr Eric Woehler of BirdLife Tasmania said that “we will never know the true, horrific scale of penguins drowning as fisherfolk never report these incidents”. He said that immediate prohibition of gillnets would ensure that the conservation status of little penguins would not deteriorate in the future.

“The aim of such management is to make sure that nets are not set in areas that are important foraging hotspots for threatened penguins. Setting the net at night can considerably reduce the bycatch of penguins since these are visual hunters and mostly forage during daylight hours.”

Ellenberg said the review, published in Endangered Species Research, recommends a number of other actions to tackle the problem, including the presence of fisheries observers or video monitoring on vessels to monitor bycatch, and managing set net fisheries in important penguin foraging areas to reduce bycatch deaths.