Five of the Arctic's 19 polar bear populations are on the decline, the World Conservation Union's Polar Bear Specialist Group says.

All of the troubled populations are located in Canada, says the group, which includes Canadian polar bear scientists and international researchers.

A group of polar bear experts say many of Canada's populations are on the decline.
(CBC News)

The group says the western Hudson Bay's polar bear population has dropped by 22 per cent and the southern Beaufort Sea's by 17 per cent.

It is also concerned about populations in the High Arctic's Norwegian Bay and the Baffin Bay and Kane Basin bears, which are shared by Canada and Greenland.

A sixth Canadian polar bear population, in the southern Hudson Bay, is also heading for trouble, it says. An Ontario government study shows the body condition of the bears has declined sharply in the past 20 years.

The scientists says they expect the world's polar bear numbers to drop by 30 per cent or more within the next 50 years because of changing ice conditions and warmer temperatures.

The size and state of polar bear populations in the Canadian Arctic has been disputed by Inuit, who question some of the scientific findings.

They believe that polar bear populations are not in as much immediate danger as some scientists are suggesting, and that undue concern over numbers may cause limits on hunting the animals, a major source of food.

About 60 per cent of the world's estimated 22,000 to 25,000 polar bears live in Canada.