The Surrounding Sea - Gower - page 123

FIG 65. Tub gurnard, the largest of the gurnards found around Gower. (Paul Kay)
Two years earlier, in July 2002, a fisherman caught a 3.6 metre thresher shark Alopias vulpinus off
Gower. Thresher sharks are often present in British waters and can come very close to beaches, and
have been seen swimming near Mumbles lighthouse. They will readily approach the shoreline following
schools of fish, such as mackerel and herring, and can enter shallow bays or narrow passes between is-
lands. Thresher sharks can often be seen swimming at the surface with their long caudal fin scything the
water, whilst actively feeding upon small fish that seem to 'boil' ahead of the shark. The elongated tail
is used as a specialised feeding tool, the shark first herding and then stunning fish with strong sweep-
ing blows. Infrequently they will also eat crustaceans and even seabirds. Overfishing is threatening the
thresher shark and populations are said to 'have collapsed' - in other words, they are close to commercial
extinction. Even 'recreational' fishing of this species therefore needs to be discouraged.
Other sharks recorded from the area include mako shark Isurus oxyrinchus , porbeagle shark Lamna
nasus andbaskingshark Cetorhinus maximus ,whichfeedsonplankton.Baskingsharksaremigratoryand
occurnearthecoastduringthesummer.ThereweresightingsoffGowerduringthelate1970sandaprob-
able sighting by a water-skier off Oxwich in 1984. There is an interesting historical record by Dillwyn of
agreathammerhead shark Sphyrna mokarran thatwascaughtinCarmarthen Bayin1839.Itsstuffedskin
was later sold for £28 as a sideshow curiosity. Dillwyn wrote to Henry de la Beche saying he had tried,
but failed, to procure the fish. This species is a very rare vagrant from tropical waters and only five were
recordedfromBritishwatersthroughoutthetwentiethcentury.Thestrangeshapeofthehead,fromwhich
the species gets its name, is thought to make the shark more sensitive to electrical signals, which they use
to detect hidden prey; common stingray Dasyatis pastinaca being a favourite food.
Sharks, rays and the related skates are distinguished from bony fish by their cartilaginous skeletons.
Species with long snouts are usually known as skates, while those with shorter snouts are called rays. A
hundred years ago British waters were packed with both skates and rays, including the common or blue
skate Dipturus batis , which can reach 3 metres in length. Today most species are in decline and the blue
skate is now listed as endangered. Their current status around the Welsh coast is unclear, although there