The hoiho - or yellow-eyed penguin - is one of the rarest penguins in the world, with only 143 known nests on mainland New Zealand including on Stewart Island.
Doc says that without a serious turnaround, the 2024 Bird of the Year winner could become extinct within 20 years.
The 2024/25 nest counts across Otago, Southland and Stewart Island show a decline of 80 percent since 2008/09.
Doc said there were fewer than 100 chicks on Stewart Island and mainland New Zealand, and there was no guarantee of their long-term survival.
Hoiho have a low reproductive rate and low juvenile survival. It is expected less than 20 percent of these chicks will survive to adulthood, Doc added.
Doc said the declining numbers were a result of multiple threats including disease, introduced predators, human disturbance, a significant shift in adult diet, fisheries bycatch, and marine predation.
Te Rūnanga o Ngāi Tahu hoiho recovery representative Puawai Swindells-Wallace had visited nesting sites from Waitaha (Canterbury) down to Rakiura (Stewart Island) and seen first-hand the hard work conservation rangers and volunteers were doing to try to save this species from extinction.
"We have some really good people on the ground, but with such a large range to cover, it is extremely challenging," Swindells-Wallace said.
"Hoiho are a taonga species for Ngāi Tahu and it is unthinkable that we could lose them - we don't really know what impact that could have on the whole ecosystem.
"We need to collectively increase our capacity to support the hoiho to regain their rightful place on our beaches and in our moana."
They were coined 'the people's penguin' and won the Bird of The Year competition in 2019 and 2024, but recent mainland hoiho/yellow-eyed penguin nest counts have experts worried.
The Yellow-eyed Penguin Trust (YEPT) recently appointed Anna Campbell to lead the organisation, with a focus on innovation to accelerate restoration of coastal ecosystems.
"Nest and chick numbers are critically low on mainland New Zealand," Campbell said.
"Now is the time to come together, be bold and brave - collaborating can enhance our potential to protect the hoiho.
"We are committed to a future where hoiho thrive in the natural environment."
