Heatwave prompts surge in basking sharks

Record numbers of basking sharks have been spotted off the coast of Britain and Ireland after the recent hot weather boosted levels of their favourite food: zooplankton.

Last year there were only 26 sightings of the 11-metre sharks in two and a half months off the most southerly headland of Cornwall. This year more than 900 sightings have been recorded since the beginning of June.

“Last year we had a really poor year because of the weather. But even though temperatures have obviously picked up, we never expected to see the sharks in such large numbers,” said Tom Hardy of Cornwall Wildlife Trust, who is co-ordinating the south-west basking shark project.

The trust uses 40 volunteers working in half-hour shifts for 10 weeks to record sightings. The volunteers have also recorded sharks breaching the surface of the water five or six times. “That is very rare,” said Hardy.

Off the coast of Ireland, a record number of sightings was also recorded in June, with 248 basking sharks counted last month by the Irish Whale and Dolphin Group.

Conservationists believe one of the reasons for the high numbers could be unseasonably warm weather increasing the amount of zooplankton. Basking sharks – the world’s second largest fish – use highly developed senses and will travel hundreds of miles to seek out the densest patches.

Simon Berrow, of the Irish Whale and Dolphin Group, is carrying out a pioneering tagging project to find out more about the elusive sharks and has been taken aback by the numbers.

“In a three-day period we tagged more than 100 sharks in just one bay in north Donegal,” he said. “You only ever see five or six of these creatures on the surface, which doesn’t reflect what’s going on under the water.”

Around the coast of the Isle of Man, another basking shark hotspot, 400 sightings have been recorded since the beginning of May.

‘”We saw a lot more in May than is usual and after a couple of quiet weeks sightings are picking up again,” said Fiona Gell, marine wildlife officer for the Isle of Man government.

Basking sharks can weigh up to seven tonnes, but despite this they have tiny teeth and pose no threat to humans.

They have also been turning up in unexpected places this year. A rare sighting off the coast of Felixstowe caused a flood of wildlife watchers to head for the Suffolk coast last weekend. Extremely little is known about the species, and their seasonal and annual movements are a mystery to biologists. The high number of sightings is encouraging news for basking shark specialists who will meet at a conference over three days next month.

The 47 local wildlife trusts across the UK, the Isle of Man and Alderney are working to identify basking shark hotspots and hope that this summer’s bumper crop of sightings will strengthen their call for further protection of the species.

The trusts would like to see some of these areas turned into marine conservation zones, a new type of protected area being introduced through the Marine and Coastal Access Bill currently going through parliament. This could result, for example, in speed restrictions being imposed on boats in the area.

“One of our principal aims is to ensure there is no loss in the population size of these magnificent creatures,” said the the wildlife trusts’ marine policy officer, Lissa Goodwin.

“The fantastic number of sightings we have seen this summer show how crucial it is to protect these basking shark hotspots in the future.”