The huge sharks who come to Scots seas looking for love

Published on 07/01/2010 21:51

TWO basking shark hot spots have been discovered in Scotland's seas.

• This basking shark may look scary, but the gaping mouth is only catching plankton – its only food source Picture: PA

The two sites on the west coast have four times as many of the creatures – the world's second-largest fish – than anywhere else in the UK.

Gunna Sound, between Coll and Tiree, and the sea around the islands of Canna and Hyskeir, are thought to be internationally important for basking sharks.

Often, they are seen in large groups at the surface, with 83 spotted in one day off Canna and 94 in one day off Coll.

The sharks can often be seen displaying courtship behaviour, such as breaching – where the creature leaps clear of the water. Experts say this suggests both areas are important for sharks looking for a mate.

During courtship, two or more sharks can be seen swimming nose to tail or in contact with each other, in a trance-like state.

A new Scottish Natural Heritage (SNH) report has interpreted data collected along the west coast of Scotland between 2002 and 2006 by the Wildlife Trust's Basking Shark Project. Set up because so little was known about basking sharks, the project has surveyed the western seaboard of the UK over nine years.

SNH marine advisory officer Suzanne Henderson said: "It is very exciting to find out that the west coast of Scotland is one of the best places to spot these majestic animals. The figures show how important these sites are nationally, and possibly globally."

Basking sharks get their name from their trait of swimming close to the surface, where their main food source, plankton, is abundant, so they appear to be basking in the sun.

They can grow up to 11 metres long and can weigh as much as seven tonnes. They can live for 50 years.

For generations, they were hunted for the high oil content of their large livers. More recently, they were hunted in European waters for their colossal fins, which can sell in east Asian markets for 30,000.

Colin Speedie, a shark expert who did the research for SNH, said: "They are huge – the length of a double-decker bus – but they feed entirely on plankton, tiny animals that drift through the water.

"These minute creatures pass through their enormous gaping mouth and are filtered out by their comb-like gills. In one hour, an adult shark filters enough water to fill a 50m Olympic-sized swimming pool."

To reduce the risk of accidental collisions and highlight the hot spots, SNH is producing a leaflet and poster. These will be sent to boat clubs and training centres in the spring. The report will also consider what action could be taken to look after basking sharks in the waters off the west of Scotland, if climate change, offshore developments, fisheries, or marine tourism became an issue.

Dr Rebecca Boyd, marine policy officer with the Scottish Wildlife Trust, said: "It is excellent news that these giant sharks seem to be making a comeback, and Scotland has become so important to them for feeding and mating."