GREAT WHITE SHARKS IN CORNISH WATERS?
There are more than 30 different shark species which are either resident or seasonal visitors to British waters ranging from dogfish to the second largest shark species in the world.
The most recent footage of large marine creatures off the coast of Cornwall are most likely to be either a basking shark, mako shark, porbeagle shark or even a bottlenose dolphin.
The basking shark is a harmless filter feeder which can reach lengths of 11 metres or more.
Makos and porbeagles are from the same family as the great white shark and can reach lengths up to four metres while bottlenose dolphins measure around 3.6 metres.
However there's no reason why great whites wouldn't visit British waters. Our sea temperatures are well within their range (5C - 26C). In fact in some ways it is actually something of a mystery why they are not found around our shores.
It may be down to the fact that we have busy coastal waters and a large shallow continental shelf with very strong tidal flows.
In the Atlantic generally, great whites are incredibly rare and have been overfished for centuries further south in areas such as the Canary Islands and the Azores.
We've been fishing off the Cornish coast for centuries and to date no-one has ever caught a great white.
The nearest confirmed sighting was of a juvenile (2.1 metres long) which was caught off the coast of La Rochelle in France back in 1977.
One of the world's leading shark experts, Professor Len Compagno, in his book Sharks of the World has reportedly extended the potential range for great whites to the English Channel, North Sea and Irish Sea.
In Continental Europe they are occasionally spotted in the Mediterranean off Italy, Spain and Malta.
Theories why they may not be here include lack of sufficient food stock. Despite South West England having one of the world's largest populations of grey seals it is still not thought large enough to support a resident population of great whites.
In the last 20 years there have been approx 70 reported sightings of great white sharks in UK waters, however none of these have produced any conclusive evidence.
Whatever the true identity of these creatures it is further evidence of the rich marine life found around our shores and should be a cause for celebration rather than concern.
None of the most likely candidates pose any threat whatsoever to swimmers or surfers. Worldwide it has been estimated that more than 100 million sharks are killed every year while fatal shark attacks on humans can be counted on the fingers of two hands.
Sadly great white sharks - like many shark species - are now so endangered the chances of seeing one anywhere in the world is becoming rarer and rarer.
While no confirmed sightings have ever been made and until they are we must remain sceptical.
GREAT WHITE SHARK FACTS
Latin name: Carcharodon carcharias
Max length: 6.4 metres
Max weight: 3,312 kgs
Max reported age: 36 years
Appearance: Fusiform, conical snout, short gill slits (do not encircle head). First dorsal fin is large, second dorsal and anal fins are minute, caudal fin crescent shaped. Dorsal surface blue-grey to grey-brown, often bronzy, ventral surface white, boundary between two tones is abrupt. Small, dark spots may be present on flanks posterior to last gill slit. Most have a black oval blotch on axil of pectoral fin. Teeth are large, erect, triangular and serrated. Denticles are minute, and tightly packed, with three ridges and flat blades. Skin is smooth compared to many species.
Conservation Status: Vulnerable (VU) - Low reproductive potential, vulnerable to target bycatch fisheries. Protected in some parts of range, but enforcement is weak. Global status of Endangered may be found with further data. Overall population unknown, regional estimates suggest decline in abundance and average size. Placed on CITES Appendix II 2004.
Habitat: Mainly coastal and offshore areas of continental and insular shelves, also recorded off oceanic islands. Often close to surf line, shallow bays and offshore continental islands. Depth range: surface to ~1,875 m. Temp range: 7-27 °C.
Reproduction: Ovoviviparous - embryos hatch in uteri, females give birth to live young. Embryos nourished through oophagy (ingestion of unfertilised eggs). Embryonic sharks swallow own teeth, perhaps to reutilise calcium/minerals. Possible that females reproduce biennually, gestation time unknown, possibly up to 1 year. Litter sizes: 2-10 embryos, unconfirmed reports of up to 14 embryos.
Diet: Principle prey: marine mammals and fishes (including other sharks and rays), occasionally turtles. Birds and sea otters commonly found injured from encounters with White Sharks, but rarely ingested.
Predators: Humans represent the greatest threat, plus occasional predation by Killer Whales and larger sharks.
Behaviour: Movement on localised, regional and intercontinental scales. Capable of short, high-speed pursuits and launching clear from the surface. Patterns in movement and abundance may be linked to seasonal variations in surface temperature.
Sometimes use displays in order to discourage other sharks - most commonly "tail slap" (caudal fin out of the water and slapping the surface, propelling water usually in the direction of a second shark).
