Britain’s largest fish is back for the summer. RSPB England’s Beth Markey gives the low down on these widely misunderstood gentle giants

One of our favourite seasonal visitors, the basking shark, is back in UK waters for the summer.

As mysterious as they are colossal, basking sharks are famed globally for their unique appearance and elusive behaviour. And it’s not really hard to see why. Basking sharks are the size of a double-decker bus, with a gaping mouth that opens a metre wide to reveal impressive specially adapted bones to allow water to pass through and filter out food.

Historically they have been mythologised as sea monsters. But these days, we know basking sharks as harmless giants of the ocean. If you’re spending any time off the British coastline between May and October, you may even be lucky enough to spot one.

 

Second largest fish in the world

The second largest fish in the world (second only to the whale shark), basking sharks can grow up to an enormous 12 metres and weigh seven tonnes.

But don’t be fooled by their magnitude. Basking sharks are mild mannered, dining on zooplankton, small fish and invertebrates – humans are far too big and fleshy for their tastes. In fact, they are passive feeders, meaning that they simply swim with their mouths wide open and wait for the food to come to them.

Basking sharks have a global conservation status of vulnerable on the IUCN Red list and they remain one of the most heavily protected species across Europe. But there was a time, in recent history, where these gentle giants were hunted nearly to extinction for meat, for oil from their enormous livers, which make up 25 per cent of their total body weight, and for their fins.

The last basking shark fishery in British waters closed in 1995, at a point when the population was in dire straits. They remain endangered in the Northwest Atlantic. However, they are now protected in England under the Wildlife and Countryside Act 1981, the Countryside Rights of Way Act 2000 and more widely, the Common Fisheries Policy and the UK Biodiversity Action Plan.

 

A migration that puzzles

For decades, scientists have pondered the movements of basking sharks. Despite spending their summers in abundance around the British Isles and the Eastern coast of USA, very little was known about their winter journey.

In 2009, researchers finally cracked it when they applied tracking tags to 25 sharks. It turned out that the stealthy giants made their way across the equator and travelled to extreme depths, as low as 3,200 ft. This has continued to mystify scientists, as they don’t need to travel nearly as far to find the right conditions to sustain their needs. Perhaps they do it to breed – but nobody knows.

Basking sharks can be found across our coasts, but they have preferred hotspots including the coast of Cornwall, the Hebrides and the Isle of Man. On a sunny day, plankton will rise to the surface along with these sharks, making it perfect conditions to spot them.

The Shark Trust advises that you keep a respectful 100m distance between yourself and basking sharks. Harming, harassing or recklessly disturbing a basking shark can carry hefty fines and up to 6 months in jail.

 

What other sharks can we find in UK waters?

Shortfin mako shark – the fastest shark in the sea, shortfin mako’s can move at speeds of 50mph and measure up to an impressive 14ft. Although rare, these sharks can be found off the south and west coasts.

Blue shark – another migrant, blue sharks can grow up to nearly 4 metres and travel in schools.  Blue sharks can be spotted off the south west coast, although generally they stay around ten miles offshore.  

Common thresher shark – although not a frequent visitor, the common thresher visits during the summer and is identifiable by its uniquely large tail¸ which it uses to stun prey. They tend to stay far offshore but have been known to come inland.

Frilled shark – these bizarre looking sharks are also known as lizard sharks. However, you are very unlikely to see one in the wild as they are found as deep as 1,200m. Very little is known about its life cycle or feeding habits.

Greenland shark – one of nature’s strangest phenomenon’s, Greenland sharks can live to 400 years old, making them the longest living vertebrate on the planet. They are found in very deep water around the UK, so your chances of running into one is nil.

Porbeagle shark – porbeagle’s can be found across the UK in deep water and quite a way offshore throughout the summer. Measuring up to 12ft, they are powerful creatures and can weigh up to 600lbs. Porbeagles are also known as mackerel sharks, based on their feeding habits.  

 

Find your nearest RSPB reserve here: https://www.rspb.org.uk/reserves-and-events/reserves-a-z/

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