All but two Adelie penguin chicks have starved to death in their east Antarctic colony, in a breeding season described as "catastrophic" by experts.
It was caused by unusually high amounts of ice late in the season, meaning adults had to travel further for food.
It is the second bad season in five years after no chicks survived in 2015.
Conservation groups are calling for urgent action on a new marine protection area in the east Antarctic to protect the colony of about 36,000.
WWF says a ban on krill fishing in the area would eliminate their competition and help to secure the survival of Antarctic species, including the Adelie penguins.
WWF have been supporting research with French scientists in the region monitoring penguin numbers since 2010.
The protection proposal will be discussed at a meeting on Monday of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR).
The Commission is made up of the 25 members and the European Union.
Adelie penguin breeding habits
- Adelie penguins are the most southerly breeding bird in the world.
- They are found along the Antarctic coast, and breed from October to February
- They typically lay two eggs in nests made of stones, and parents take turns to incubate the eggs
- Breeding adults may have to travel up to 30-75 miles (50-120 km) to catch food to then regurgitate for their chicks
- See more on Adelie Penguins
Source: National Geographic and Antarctica.gov.au
"This devastating event contrasts with the image that many people might have of penguins," Rod Downie, Head of Polar Programmes at WWF, said.
"The risk of opening up this area to exploratory krill fisheries, which would compete with the Adelie penguins for food as they recover from two catastrophic breeding failures in four years, is unthinkable.
"So CCAMLR needs to act now by adopting a new Marine Protected Area for the waters off east Antarctica, to protect the home of the penguins."