Basking sharks are moving northwards

THE huge basking shark is the latest creature to be seen moving northwards, another case of wildlife responding to climate changes.

These sharks are sometimes seen off the Irish coast, with regular sightings reported to the Irish Whale and Dolphin Group (IWDG).

Numbers, however, have declined, mainly because of over-fishing.

Conservation groups are noticing a “dramatic shifting” north from waters around the south of England to seas off the coast of Scotland.

Nearly 300 of the massive fish — the second biggest in the world after the whale shark — have been spotted in Scottish waters in the last six months.

This has led to calls for the species to be granted legal protection. The basking shark is protected in British waters, with maximum penalties of six months imprisonment for people that harm or disturb it, but is not protected in Northern Ireland or the Republic.

It is most frequently seen off the Mayo, Galway, Kerry, Cork and Waterford coasts and is occasionally caught accidentally in nets.

The main attraction in the basking shark is its liver oil, nearly 200 kilograms per fish. Blasket Island writer Tomás Ó Criomthain once told how such a shark dragged a currach for about a mile nearly drowning the crew. The reward, however, was that its liver provided light to the island for five years.

It is reckoned that between 1947 and 1975, more than 12,000 basking sharks were killed at Achill, Co Mayo, not including those killed at sea by Norwegian whalers.

Inevitably because of such high levels of exploitation, numbers dropped substantially and the Achill fishery closed in the mid-1980’s.

At present, the biggest threat to the basking shark comes from hunters who can sell the two-metre fins for prices up to €25,000.

These fins can not only end up in shark fin soup, but are also used as trophies in restaurants or status symbols in wealthy homes in Asia.

Despite their enormous size, basking sharks do not pose a threat to humans: they have tiny teeth and filter-feed on plankton. They can reach 36 ft in length and weigh up to seven tonnes.

In order to take in enough food, they must filter approximately 2000 cubic meters of water an hour — equivalent to an Olympic size swimming pool of water! For a fish that can take 12-20 years to reach maturity, over-fishing and persecution can have serious consequences. Gestation can take from 18 months up to three years and a litter is thought to consist of five to six pups.

Now, there are moves to safeguard the sharks’ future as their population increases in more northerly seas.

Using fin recognition, the survey for the Scottish Wildlife Trust (SWT) spotted 292 of the sharks from April to September this year in waters off the coast of Scotland.

Leading marine conservationist Colin Speedie, who carried out the survey, said the creatures were using waters around the Western Isles as breeding areas.

“Two Scottish basking shark ‘hotspots’ have come to light as a result of our survey work,” he said.

“These are in the Gunna Sound, between the islands of Coll and Tiree, and around the rocky island of Hyskeir, five miles south-west of the island of Canna.

“Our observations suggest sharks are gathering in these areas for courtship and may actually be using them as breeding areas,’’ Mr Speedie said.

He added that shark population is on the increase. “For the first time we are seeing a high proportion of large sharks, some over nine metres in length, and what are probably baby sharks in the same area,’’ he said.

Marine wildlife tourism in Scotland is growing, directly supporting more than 2,500 jobs and earning nearly €100 million a year.