Fin whales are filter feeders, like blue whales and humpbacks. They eat small schooling fish, squid and krill and can take in 70 cubic metres of water in one gulp. In the Antarctic they eat only krill. They sometimes use their high speed to circle a school of fish, compacting it into a tight ball, then swim into the ball with mouths open to scoop up the fish.

Fin whales are unique among cetaceans in that they all have asymmetric markings - a large white patch on the right side of the jaw while the left side is grey or black. No one knows why this is so.

Like the blue whales, fin whales were too dangerous to hunt until the invention of the explosive harpoon. But they were quickly depleted by modern whalers. They were given full protection in the Antarctic and the North Pacific in 1976 but illegal catches by the Soviet Union continued, further depleting the species.

When the modern coastal whaling industry began in Japan, fin whales were very important with catches peaking at 1,000 a year in 1910 and declining afterwards. Catches continued throughout the second world war averaging 300 a year from 1940-45. Catches fell below 100 a year for the first time in 1961 and ended in 1975 with a catch of 11.

Amazing facts:

- It has been calculated that during the feeding season it takes a fin whale about 3 hours to meet its daily food requirements, about the same time humans take in cooking and eating.

- The sounds fin whales make are so pure and regular that when they were first heard they were thought to be man made sounds for submarine detection.

- It was once called the razorback whale by whalers because of its sharply ridged dorsal fin.