The basking shark – a gentle giant

There are several varieties of basking shark throughout the world but only one species — Cetorhinus maximus — occurs in British waters.

The basking shark is the world’s second largest fish (the whale shark is the largest), growing up to 15m (50ft) long and weighing up to 5 tons (5080kg). The name basking comes from its habit of swimming on or near the surface.

In the hot summer of 1976 a dinghy regatta off Brighton was visited by a small group of baskers. The scenes that followed were reminiscent of the film Jaws (still showing in cinemas at the time).

Unaware that the sharks were completely harmless, paddlers panicked, dinghies capsized and the local lifeboat was launched. No one was hurt and the sharks continued on their way.

clip_image002 Basking sharks occur throughout the east Atlantic but are commonest off Iceland and Norway. During the summer they appear all around the British Isles and are most often sighted in the south-west English channel.

Scientific name: Cetorhinus maximus

Maximum weight: About 5 tons (5080kg)

Average weight: About 1 ton (1020kg)

Maximum length: 15m (50ft) Life-span: Unknown

Scientific name: Cetorhinus maximus

The typical basking shark pose – swimming along with its gigantic mouth wide open, filtering water through its long gill slits. Another prominent feature is its front dorsal fin, visible from a considerable distance.

Baskers use their gill rakers to sieve plankton from the sea water Baskers use their gill rakers to sieve plankton from the sea water. In the winter, when the shark hibernates, these rakers disappear. They grow back in the spring when the fish begins feeding again.

Shark for sure

It is a deep sea species, rarely found in less than 35m (115ft) of water. When the shark appears off the coast of Britain it is usually in groups ofthree or four, but the schools of baskers that gather far out in the ocean to browse on plankton can number over 200.

In the past the basking shark’s size and docile behaviour meant it was often mistaken for a whale – or even a ‘sea serpent’. It swims silently along at about two knots (just over 2mph), filtering water through its almost permanently open mouth.

It is easily recognized by its long snout and the five very large gill slits on either side of its head. Attached to the arches of these gill slits are long bristle-like gill rakers which strain plankton from the water. The shark can filter up to 1.5 million litres (330,000 gallons) of water every hour.

During the winter months, when there is virtually no plankton in the water, the shark sheds its gill rakers, stops feeding and moves into deeper water to ‘hibernate’. When it re-emerges at the surface in the spring it has grown new rakers.

Like most sharks it produces live young, but litters rarely number more than two pups, and the gestation period may be as long as two years. Baskers are slow to mature, taking as long as ten years to reach reproductive age.

Size setback

Sadly, this shark’s great bulk means it is vulnerable to becoming tangled in fishing nets. There is a report of a basker of onh moderate weight blundering into tei strings of feathers being worked by anglen on a West Country charter boat.

In seconds there was total mayhem a; the shark, doubtless terrified, rolled th< whole lot around its body… and dived!

Rods arched, several broke and two more were wrenched overboard. Only those anglers with a knife at hand to cut the tau lines had rods which escaped unscathed.

Hunted species

Since this huge animal is a plankton feeder it doesn’t take a baited hook — and even if I did there would be almost no chance o landing it.

The shark’s gentle nature means it can bi approached easily and offshore fishermai can get within a few yards of the fish t< watch its majestic swimming motion.

Unfortunately this also makes it evei more vulnerable to commercial hunters who kill it for the oil in its liver and for it, fins. In Europe, where the shark has n legal protection, the market for shark mea is expanding. In the meantime, baskin; shark numbers continue to decline — an( sightings of this fascinating fish are sadh becoming much rarer.