Brilliant Basking Sharks in the UK

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Not long ago I was incredibly lucky and got amazing views of a basking shark off the coast of Shetland. Despite being the biggest fish to visit our waters, basking sharks are completely harmless. These huge filter feeders eat tiny crustaceans and fish by filtering water through their gills. One of approximately 40 species of shark that can be seen around the UK, many aspects of these gentle giants’ lives are still a mystery to researchers. Luckily, for both scientists and nature lovers alike, the UK has a number of basking shark hotspots. And August is one of the best times of year to see them.

Basking Shark Basics

So, what do we know about basking sharks? Let’s start with the basics. With lengths of up to 11 metres, they are the second biggest fish in the world after the whale shark. In appearance, the basking shark has the classic shark outline, with a triangular dorsal fin and tall, curved upright tail. The long, bulbous nose and eyes set well forward give them a much less threatening demeanour than, say, a great white shark, though.

As filter feeders, they find food by swimming along slowly with their mouths wide open. This filters enormous amounts of water through their gills, allowing them to extract zooplankton and other tiny creatures. Basking sharks feed closer to the surface on sunny days when this zooplankton is more concentrated near the top of the water column. This is what gave them their names, as it looks as though they are basking in the sun. In the UK, they are usually seen off western coasts between May and October. While whale sharks only inhabit tropical waters, the basking shark prefers temperate seas around the globe.

Secretive Sharks

There is still a lot we don’t know about basking sharks, though, and scientists have only recently begun to scratch the surface when it comes to their movements and behaviour. A tagging project carried out between 2004 and 2011 in the Western Atlantic found that these particular study subjects migrated south from their New England summer feeding grounds to South American coastal waters. Other studies have shown that while they do often move from surface waters to depths of up to 750 metres, they don’t hibernate in deep water as some once thought.

In the UK, it seems some of our summer visitors head as far as the Canary Islands in the autumn. However, evidence also suggests some stay year-round in British and Irish waters. NatureScot, in collaboration with the University of Exeter, has been tagging animals in the Inner Hebrides since 2012. They have found that some sharks return each year to the same area around the islands of Tiree and Coll. Previously, researchers had no idea if they had any fidelity to summer feeding grounds, or just went where the zooplankton took them.

Cairns of Coll — Sharks return each year to the waters around Coll in the Inner Hebrides

Although researchers have often seen courtship behaviour, with animals following each other nose to tail, they have never definitively recorded mating. Scientists know that basking shark young hatch from eggs inside the mother and are then born live. But they are unsure about the length of the gestation period and if they have preferred birthing locations, although Coll and Tiree could be candidates if they do. There is a lot more to learn about these enigmatic animals. We aren’t even sure about their current numbers, or how long they live, although it may be about 50 years.

Exploitation Past and Present

Sadly, being mysterious hasn’t stopped basking sharks from being overexploited by man. Because they are slow and relatively unbothered by humans approaching them, they are very easy to catch. Prior to the 20^th century, hunting had been something of a cottage industry in European waters. As with whaling, though, the advent of mechanised harpoon guns led to the killing of tens of thousands of sharks. From the 1930s on, boats fished out of the Clyde and various Hebridean locations. Large numbers of Norwegian ships also hunted Scottish waters.

This basking shark is swimming slowly along as it feeds

The main attraction was shark liver oil. This product had multiple uses including as a lubricant, in cosmetics and for lighting. One animal could yield over 200 gallons. Their rough skins were also used for leather, and in addition they were ground up for animal food. Gavin Maxwell, famous for writing Ring of Bright Water, about his beloved otters, attempted to set up a shark hunting business on the island of Soay, off Skye. In complete contrast to most people’s idea of him, he threw himself with relish into the killing side of the business, as recounted in his 1952 book Harpoon at a Venture. However, the business failed, and he eventually sold up.

Despite the last UK fishery closing in 1995, other countries still hunt basking sharks. Because the market for sharks’ fin soup continues to grow, fishing is still extremely lucrative, even though liver oil is no longer in such demand. As a result of a century of intensive overfishing, both here and around the globe, the International Union for Conservation of Nature (IUCN) classifies basking sharks as Endangered.

Good News, Bad News

Basking sharks do now benefit from a number of protections, however. In the UK, the Wildlife and Countryside Act amendment of 1998 banned hunting up to 12 nautical miles from shore. However, because tagging studies showed how little time they spend in inshore waters and how migratory they are, in 2005 they were added to the Bonn Convention on the Conservation of Migratory Species. This agreement commits signatory countries to preserving species that cross national borders.

On a smaller scale, in late 2020, the Scottish Government designated the Sea of the Hebrides as a Marine Protected Area. This small region, which spans from the west coasts of Mull and Skye across the Minch to Uist and includes Coll and Tiree, is extremely important for basking sharks, as well as minke whales. This zone could be even more important if, as suspected, they breed there. The designation recognises the importance of the area to biodiversity and the sharks and minkes in particular.

On top of the demand for their fins, however, basking sharks face other threats, both here and abroad. Two of the biggest dangers are entanglement in fishing gear and becoming bycatch. They are also vulnerable to boat strikes. Microplastics could pose another threat; as filter feeders it is possible that they may ingest large volumes of these tiny pieces of plastic. It isn’t yet understood how this will affect them in the long-term. How climate change will impact food availability is another area that needs more study.

UK Hotspots

To see these incredible creatures in the UK, west is definitely best between May and October. Look for the tell-tale triangular dorsal fin followed by a tall tail fin, moving slowly through the water. Calm and sunny days improve your chances.

The south and west coasts of Isle of Man are probably the best places in the UK to spot basking sharks, with an average of over 300 sightings a year. They often come remarkably close to shore, and you might even see courtship behaviour. The island was also the first place in the UK to protect them.

In Cornwall, places like the Lizard, Land’s End or any of the western headlands are good places to look. Wildlife spotting boat trips also run out of Penzance.

The Inner Hebrides Sea MPA was partly designated because of the large numbers of basking sharks that visit during the summer months. The west coasts of Mull and Skye, as well as Coll and Tiree, are particularly good. Boat trips run from places like Tobermory, Oban and Portree, but you can sometimes see sharks from the Calmac ferries operating around the area.

Calmac ferries can be good for spotting lots of marine life, including basking sharks

Other places to look include Shetland, the Isle of Arran, the Mull of Kintyre and Barra.