Basking sharks are fascinating beasts who may just have launched the legend of Nessie

Published Date: 30 August 2010
By Kath Gourlay

Being classed as a hotspot for sharks doesn't always make for a tourist area, but visitors to the Western isles need have no worries. The bus-sized basking sharks cruising through the Minch this month have no interest in snacking on limbs or torsos. In fact, they're the ones who can be at risk, from the boatloads of tourists and film crews that gather to watch their activities.

"Basking sharks are slow-moving and harmless to humans and their sheer bulk makes them vulnerable when it comes to outmanoeuvring fast boats and the people in them," says Suzanne Henderson, marine advisory officer for Scottish Natural Heritage, Nets from fishing boats, and creel ropes are also a hazard, and SNH has published leaflets and water-resistant maps highlighting the areas around the West coast where large groups of these massive sharks are likely to be at this time of year. "These sites are really important, both nationally and globally, and consistently high numbers have been seen in the sound between Coll and Tiree, and the seas round Canna and Hyskeir," says Suzanne.

In recent summers, SNH recorded the presence of more than 80 basking sharks around Canna and even more around Coll. Shark expert Colin Speedie, who carried out much of the work, says that people have a lot to learn about the habits of these gentle giants.

"Basking sharks are huge – the size of a double decker bus – but they feed entirely on plankton. These minute creatures drift through the water and are filtered through comb-like gills in the shark's enormous gaping mouth.

In one hour an adult shark filters enough water to fill a 50m Olympic-sized swimming pool."

Basking sharks are most often seen in coastal areas during the summer and early autumn, when plankton are plentiful and they get their name from being seen "basking" at the surface of the water. The hotspot areas round the Western Isles are known to be mating sites and keen observers might get lucky and spot rare displays of courtship behaviour, such as "breaching" where huge sharks 20 or 30ft long and around six tonnes in weight leap clear of the water.

Another fascinating sight – again, rarely seen, though observed in the Western Isles – is when pairs of courting basking sharks swim along nose to tail for miles and miles in a seemingly trance-like state. This is the time, says SNH, when the sharks are most vulnerable and boat owners and fishermen need to be vigilant around these mating areas.

Previous generations were not so considerate. Basking sharks have been following the plankton drifts up the west coast for centuries, and in the 18th and 19th centuries were highly valued for the high oil content in their huge livers.

The curious story of a creature dubbed "the Stronsay Beast" suggests that a basking shark might have been behind the origins of the Loch Ness Monster legend. In 1808, an enormous carcass was found washed up on the Orkney island of Stronsay. It was measured in front of witnesses and found to be 55ft long. A drawing was made of it which is now in the Orkney museum. In the drawing, the massive creature appeared to have a very long neck.

Stronsay was a thriving herring fishing port, and trade flourished round the coasts and through the Caledonian Canal, where travelling fisherfolk told and retold the story.

A piece of the vertebrae stored in the Royal Museum of Edinburgh showed it was made of cartilage, not bone, so it had to be a shark. If the gill arches had fallen off and the soft tissue had rotted, then the backbone leading to the head and neck would be left looking just like a long neck with a huge body behind it.

Did "the Stronsay Beast" launch the legend of Nessie? We may never know.

Visit www.whalewatchscotland.com/trips for more information

This article was first published in The Scotsman on Saturday, August 28

http://living.scotsman.com/outdoors/Kath-Gourlay--Basking-sharks.6499739.jp