Nature

Anyone with more than a passing interest in basking sharks, which it must be said is a curiously appropriate interest to have, may have been surprised to read a recent article in a UK newspaper.

It contained a claim the animals are migrating northwards in pursuit of plankton, their favourite food source. As a consequence they are now more likely to be seen in Scottish waters, such as the seas around Shetland rather than waters off south-west England or the Isle of Man.

In fact, whilst there may be truth in the fact plankton streams are heading north, there were over 240 sightings of basking sharks in Manx waters during the summer months of 2005 and interest is such that a new dedicated Manx Basking Shark website was set up in early 2005 along with a telephone hotline for sightings.

The basking shark is the second largest fish in the world, trailing only the tropical whale shark. However, despite their formidable size, over 13 metres in length and seven tonnes in weight, they feed predominantly on tiny plankton.

More shark sightings?

Perhaps, not surprisingly, they need to filter vast amounts of sea water in order to trap sufficient numbers of their favoured prey. Consequently they spend many hours swimming around close to the surface of the water with their cathedral-like mouths wide open.

It has been estimated an average sized shark (around eight metres) can filter sufficient sea water to fill a swimming pool in just one hour.

To achieve this, their gills have what are called gill rakers, brush-like structures which are covered in a sticky mucus which traps the plankton.

Of course this has a drawback. With every mouthful of food, the fish has to swallow gallons of snot for want of a better word. Fortunately, like young children, they seem peculiarly well adapted for this behaviour.

Indeed, the entire fish is coated in a mucus-like slime and divers who have come into close contact have reported not only does it smell distinctly fishy, but it's also rather tricky to remove from your wetsuit!

For most people contact is somewhat more distant.

Have you spotted more sharks?

Shark spotting has become almost a national pastime on the island during the summer months when numbers are at their peak. They can be seen in many locations, predominantly on the west coast of the island and remarkably close to shore.

The most common activity will be feeding, but sometimes mating behaviour can be seen and on a very few occasions you seen one breach - jumping out of the water altogether. Rather like a salmon but somewhat more spectacular!

Shark spotters are able to roughly gauge the length of the animals even from a distance, as the tail to the dorsal fin (normally the two most prominent parts of the shark above water) is half its overall length.

The basking sharks that live off the British coast are a local population, not seasonal migrants and whilst it is often claimed precious little is known about their lives, the situation is improving all the time.

Work is currently being carried out at Plymouth Marine Laboratory into what the sharks do in winter and research is also being conducted into how far individuals move.

Having said that, no-one is really sure where female sharks have their young, and the most authoritative work on their anatomy was carried out over 50 years ago.

The message it seems is simple. If you are lucky enough to see a basking shark around the island, report it. You could be helping to add to our knowledge about these gentle leviathans of the deep.

The basking shark hotline number is 01624 801 345