Africa's only species of penguins, commonly known as the black-footed penguin, is at risk of extinction as its main food source of small fish has migrated away, experts say.

Global warming of ocean waters has seen sardines and anchovies moving south to cooler waters, leading to a catastrophic drop in the numbers of African Penguins seen along South Africa's west coast, they report.

The population of the flightless birds, long a tourist attraction around Cape Town, has plummeted 90 percent since 2004, according to the country's Department of Environmental Affairs.

Also found in Namibia, the black-footed penguin is Africa only native penguin species. It is also known as the jackass penguin, for its loud braying call.

South Africa's largest penguin colony contained a million birds in the 1930s, but today the country and Namibia together host less than 100,000 penguins.

The African Penguin was declared endangered by the Worldwide Union for Conservation of Nature in 2010.

The southern movement of anchovies and sardines means the penguins must swing farther south to catch their prey which weakened the adults as a result.

They either die or they abandon their chicks, researchers say.

Seven years ago, in an effort to halt the decline in penguin numbers, four main fishing grounds stretching some 12 miles across the penguins' main hunting areas were closed.

That brought objections from the fishing industry, since sardines and anchovies are the biggest component of the industry.

Whether it's climate change, fish migration of some other factors driving the decline in penguin numbers has been hotly debated for years.

While most researchers blame the decrease in penguins on the disappearance of fish from their normal hunting grounds, experts in the fishing industry disagree, saying modeling suggests predators, nest flooding, heat stress and human development may be behind the decline or at least make it worse.

Penguin biologists want the closure of the fishing grounds to continue for at least several more years, while scientists working for the fisheries are urging an end.

"These sorts of issues must be teased out and the assumptions clearly understood," says Dr. Rob Crawford, who heads the penguin biology research.

The South African government has brought together a panel of international experts tasked with reviewing the impact of the closure of fishing grounds and to make recommendations for future decisions.

"There's a lot at stake," says Ross Wanless of the conservation organization BirdLife South Africa. "We need to act now. "