Forest and Bird is calling for urgent action to better protect the endangered yellow-eyed penguin from fishing threats.
The conservation group claims the survival of the population "depends on what is essentially a guessing game".
That’s because in the 2017/2018 data period there were three reported incidents, but an observer rate of just 10.4 per cent, Forest and Bird says.
It therefore estimates 30 hoiho, or yellow-eyed penguins, died in the data period, due to set nets.
The incidents occurred in the East Coast South Island fishery and the Southland to Fiordland fishery.
The Yellow-Eyed Penguin Trust agrees with Forest and Bird that set nets pose a risk but believes the number of hoiho killed as a result would have been less than 30.
It says the Aquatic Environment and Biodiversity Annual review for 2017 estimated 17 birds would have died.
The trust said set nets are just one of the many threats facing the species, with starvation a particular concern this year.
"With only 10 per cent observer coverage in these fisheries we can never know the full picture of what is happening at sea. The survival of our mainland hoiho population depends on what is essentially a guessing game," says Forest and Bird’s chief executive Kevin Hague.
"Government proposals to create marine reserves and protected areas on the South Island’s east coast and a proposed new threat management strategy are positive steps but leave the threat to penguins from set net fishing wide open," he says.
A draft Hoiho Threat Management Strategy and accompanying action plan, currently open for consultation, don’t propose any concrete steps to protect the mainland population of hoiho from fishing threats, Mr Hague says.
"It’s time for the industry to stop resisting efforts for human or electronic monitoring on their boats, or otherwise stop using set nets in penguin habitat," he says.
Not all of the factors causing the decline of the hoiho are well understood, including disease, starvation and climate change-related issues, Mr Hague says.
"But the danger posed by set nets is well understood and we have to remove this threat from the hoiho’s environment to ensure they continue to live and breed around our southern coasts."
At the start of last breeding season, there were 227 nests counted for the genetically distinct mainland population, which takes in the southeast and southern South Island, Stewart Island and Whenua Hou/Codfish Island.
This was down from about 600 pairs counted around a decade ago.
'Incorrect' says MPI
The Ministry for Primary Industries says Forest and Bird's analysis is incorrect, as are their assumptions of bycatch of hoiho and the amount of observer coverage.
Over the past five years, a total of nine hoiho captures have been reported by commercial fishers and/or observed by Fisheries New Zealand Observers, says Stuart Anderson, MPI Director Fisheries Management.
As observers are not placed on all vessels, there is uncertainty regarding the number of total captures on un-observed vessels, Mr Anderson says.
Between a quarter and half of the high-risk fleet carry observers, depending on the year and area, not 10 per cent as suggested by Forest and Bird, he says.
"A full scientific reassessment of fishing-related hoiho captures will be completed next year. We expect that this will give us a much more reliable estimate of the impacts on hoiho from fishing (beyond just observed and reported captures)," Mr Anderson says.
Fisheries New Zealand is working alongside DOC, Ngai Tahu, the Yellow-eyed Penguin Trust to develop a strategy and five-year action plan to protect hoiho, he says.
"This work is coordinated, based on the best scientific information, and focussed on areas that will make the most difference to hoiho in the long run."
In the meantime, MPI continues its work to roll out electronic reporting and positioning to all fishing vessels, and place Fisheries New Zealand observers on board fishing vessels to ensure the ministry has robust information, he says.
Work also continues to improve fisheries risk assessment and identify further science information needed to support MPI in managing risk from fishing.
And it is engaging with fishers and researchers to share information and develop mitigation measures.
Other work includes developing operational procedures and vessel-specific risk management plans for set net vessels operating near hoiho habitat, including voluntary commercial set net closures such as that around Whenua Hou, Codfish Island, Mr Anderson says.
An update of the National Plan of Action for seabirds is currently with ministers awaiting their decision to publicly consult, he says.
Fisheries Inshore New Zealand, which represents commercial fishers, says Forest and Bird is scaremongering.
There were three yellow-eyed penguins caught, not 30 in 2017/2018, says chief executive Dr Jeremy Helson.
Official records show in 2016/2017 there were no yellow-eyed penguins reported to have been caught in set nets, but in 2015/2016 there were three.
"Fishing has a small impact on this population but is mitigating its effects and is also voluntarily supplying fish to rescue centres to feed the penguins," Dr Helson said.
"If Forest and Bird really wanted to save these birds they would put all their resources into the real and identified issues causing their depletion."
Dr Helson says these include starvation due to increased water temperatures. This is a sub-Antarctic species that is not coping so far North, he says.
The other issues causing the depletion of the penguins are disease, particularly avian malaria; predation from barracouda, great white sharks, sea lions and leopard seals; and human threats including dog attacks and tourism, he says.