The Canadian government, supporting the UN's International Maritime Organisation ruling, has told containerships off the southeast coast of Nova Scotia to avoid a designated area where a rare species of whale breeds.

The area known as Roseway Basin, is 80 kilometres offshore and attracts 10 per cent of the right whale population, which now totals 350, reported The Canadian Press.

Containerships accidentally kill whales as the slow-moving animals loll on the surface, unable to get out of the way before a ship hits them, said the news agency. There were 22 North Atlantic right whale calves born this year, continuing a trend that has seen more than 20 born every year since 2001 and giving hope that the species can avoid extinction.