Survival of the fittest

The clear and calm waters of Reisafjorden, in Norway's Far North, have in recent years become the winter playground of the Scandinavian country's killer whale population. At three degrees Celsius (37 Fahrenheit), the cold water is perfect for the herring which, ahead of the spawning season in February and March, have fattened up and make a tasty dish for the hungry killer whales, also known as orcas.

But in the past 20 years, the herring migrated 300 kilometres (190 miles) north, leaving the Lofoten Islands in search of waters that remain under six degrees Celsius – the temperature required for them to reproduce. The Norwegian killer whales, which only occasionally feast on seals or smaller whales, have followed the herring.

"We believe that the global warming which is responsible for the rising water temperatures has pushed the herring further north," said Pierre Robert de Latour, founder of the organisation Undersea Soft Encounter Alliance, on board a whale-watching vessel.

In the long term, they're going to move even further north. If the stocks were to diminish it would be an environmental catastrophe for whales, orcas, sea birds and cod," he warns.

For now, the killer whale population along Norway's coast appears to be thriving. It's not unusual for several boats carrying dozens of amateur divers to converge in the same fjord, with both boats and divers coming within just a few metres of the giant mammals.

"Norwegian authorities aim to implement some recommended regulations of such activities," Haug said. "Whale watching is a good way of raising awareness and educating people about these animals and their life in the oceans, but too much could cause some problems," said Robert de Latour, himself a nature guide.

Fifteen years ago, Hollywood's most famous killer whale died in a Norwegian fjord. Keiko, a male orca captured in 1979 off Iceland around the age of two, spent most of his life in water theme parks before starring in the 1993 hit movie "Free Willy".

After a massive international campaign, Keiko was released into the wild in Iceland, before he headed for Norway – one of the only countries in the world that hunts whales, albeit not killer whales. He died in December 2003, at the age of 27.