Basking sharks can grow up to 11m long. They are the UK’s biggest fish (and the world’s second largest). They feed on plankton – tiny plants and animals that drift around in the sea. They’re usually seen around Cornwall’s coast in the spring and summer when they’re feeding close to the surface. Their oddly shaped tail, which often appears above the surface, along with their lack of surfacing and diving, helps to tell them apart from cetaceans (whales, dolphins and porpoises).
Tips to avoid disturbing basking sharks:
Actions that scare, startle or panic:
- Getting too close
- Sudden movements
- Surrounding or crowding them
How to tell you’ve been spotted:
- A basking shark feeding at the surface suddenly dives
- Sudden tail movements and a rapid change of direction away from a boat or person. Basking sharks are have quite poor vision and are often focused on feeding on dense plankton. This means people may accidentally get too close and the shark will panic suddenly.
It’s too late and definitely time to move away if:
- It’s a while before the basking shark resurfaces and starts feeding
- They increase their swimming or travelling speed
- A basking shark lashes its tail – it may be about to breach or dive.
Follow the general guidelines and in particular:
- Keep clear of large groups – they are likely to be gathering to breed
- Avoid sharks swimming close together nose to tail, as you may disrupt courtship
- Keep clear of areas where they’ve been seen breaching
- Ensure all encounters are on their terms by, ideally, only being close to them if they choose to be close to you
- If you find yourself unexpectedly close, slow down or stop and allow them to pass. If safe, put the engine into neutral so there is no chance of injuring them with the propeller, as there may be others under the surface. Check carefully before re-engaging the engine.
How disturbance affects them:
- Basking sharks are slow moving and appear to be relatively unaware of other water users, making the possibility of a collision or injury from a propeller more likely. They can weigh up to 7 tonnes so a collision can cause serious injury to them and you!
- Basking sharks don’t breed until they are about 20 years old, so their long term survival could be put at risk if they are regularly disturbed at breeding time. They need to be in good health to breed successfully and regular disturbance during peak feeding times is likely to affect their health.
Basking shark code of conduct for swimmers, thanks to The Shark Trust