The Isle of Man might be famous for its onshore races, but the basking sharks that inhabit the surrounding Irish Sea are busy making their own laps of this small British dependency. Kayaker Craig Whalley encountered a trio of the ocean giants while cruising past Fleshwick Bay, along the island's southwest coast.


This particular corner of Mann becomes a hotspot for basking-shark sightings every year, typically between mid-May and mid-August. During the summer months, calm seas and warm weather promote healthy blooms of plankton in the area – and the hungry basking sharks follow close behind. In fact, schools of up to a hundred have been seen in these waters!

Despite ranking among the ocean's largest fish (second only to whale sharks), these animals are harmless filter-feeders. They do have hundreds of tiny teeth, but it's actually their complex gill rakers that sieve passing food from the water. As a shark swims forward – displaying its signature open-mouthed gape – water is moved over the rakers, which collect food in their comb-like branches. It's a passive way to feed, but also extremely effective: a single basking shark can filter 2,000 tons of seawater per hour. 

All that feeding keeps them busy, and it's unusual to spot a closed-mouthed basking shark – but when it does happen, the resulting images are superbly derpy.

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According to Whalley, the three sharks that cruised past his kayak ranged from three to four metres (roughly 9-13ft). Basking sharks can reach a whopping ten metres in length (though unconfirmed measurements suggest they get even bigger than that), and the average for an adult falls somewhere between six and nine metres (22-29ft). Given those size ranges, it's possible Whalley's sighting included sub-adult sharks.

Encounters with smaller juveniles are incredibly rare, and scientists are still working to find out why. (The smallest free-swimming basking shark ever documented was just shy of two metres long.) One of the possible reasons for this is that females – who can carry their young for up to three years! – move far offshore to pup.

If you look closely at Whalley's images, you'll notice a curious loiterer near the pelvic fin of one shark (located on the animal's underbelly). That eel-like creature is a sea lamprey, one of several types of animals known to cling to basking sharks. 

Image: Craig Whalley/Facebook
Image: Craig Whalley/Facebook
Image: Craig Whalley/Facebook

Lampreys cannot cut through basking shark skin, which is lined with tough modified scales called dermal denticles. However, it seems their presence can be annoying enough to explain one of the basking shark's most interesting habits: breaching like whales. Jumping and crash-landing is a great way to rid yourself of parasites ... and unwanted hitchhikers. 

The sharks don't pose a bite risk to humans, notes Whalley in an interview with BBC News, but they should still be treated with caution: they are, after all, multi-ton wild animals. "You should never approach them but let them come to you," he said. "I positioned myself in a visible line of plankton and they swam right underneath my kayak. They are such beautiful creatures, it was fantastic."

Local experts also recommend that divers keep clear of any social schooling, so as not to disturb the sharks' natural behaviour. Similarly, boats should never approach within 100 metres of a basking shark. 

As for the timing of it all, Whalley chalks his encounter up to luck. "It's just being at the right place, at the right time!" he wrote on Facebook.



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