Almost half the breeding population of yellow-eyed penguins on Codfish Island, west of Stewart Island, have disappeared at sea, most likely because of commercial set nets, Forest and Bird says.
Forest & Bird chief executive Kevin Hague said the group was calling on the Government to gather those who work to protect the penguins, but also the fishing industry to agree an immediate set of actions to eliminate the risks from set netting in the penguins' feeding area.
"Unlike previous years where disease and high temperatures caused deaths on land, this year birds have disappeared at sea. There is an active set net fishery within the penguins' Whenua Hou foraging ground, and the indications are that nearly half the Whenua Hou hoiho population has been drowned in one or more of these nets.
"We are asking DOC and MPI what they intend to do to save our hoiho from extinction, because at current rates of decline we are on track to lose hoiho completely from mainland New Zealand. We have also written to the Minister of Conservation, expressing our concern."
However, Ministry for Primary Industries (MPI) says it is stepping up monitoring of the set net fisheries.
Almost every penguin killed in the set net fishery was killed on a boat that had an official observer on board, Hague said.
The first step was to get more observers onto set net vessels and prioritise putting cameras on set netting boats, he said.
Department of Conservation information showed only 14 yellow-eyed penguins were found on Codfish Island, down from 24 the previous year.
Forest & Bird said yellow-eyed penguins had also declined elsewhere this year. The Catlins had seen a drop of 10 per cent in nests and Otago Peninsula saw a small decline but not all areas have been searched yet.
The estimate for the entire southern east coast of the South Island was down 6 per cent.
However, it's not just yellow-eyed penguins at risk.