Blue Shark

Blue Shark
  • Scientific name: Prionace glauca
  • Size: Up to 13ft and 400lb. Typical boat caught in UK waters 5 – 8ft and up to 150lbs.
  • UK shore caught record: No record stands. Minimum qualifying weight set at 40lbs.
  • IGFA world record: 528lbs
  • IUCN Status: NT (Near Threatened)
  • Distribution: Blue shark has an extremely widespread distribution, being found throughout temperate and tropical waters across all the world’s seas and oceans, apart from the Arctic Ocean.
  • Feeds on: Fish, squid and cuttlefish.
  • Description: Sleek body with large eyes and pointed snout. Pectoral fins are long, as is the tailfin. The dorsal fin is relatively small. The body is dark blue on the back, blending to a lighter blue on the flanks and white to grey on the belly. The mouth has two rows of serrated teeth, with additional rows behind.

Blue shark is a large predatory species which has a wide distribution through all of the world’s seas and oceans, although they are absent from the arctic and polar regions. They are a pelagic species, generally swimming through deep water, looking for prey which consists of shoaling fish and squid. Blue shark can be either solitary or form into small groups. They are nomadic and cover great distances as they migrate around the world. Blue sharks are thought to use the gulf stream and Atlantic gyres in order to conserve energy as they travel through the seas. In British waters they are generally found in the slightly warmer water of the south west of England and Ireland, although they can turn up elsewhere and have been sighted to the north of the British Isles.

Feeding and Diet

Unsurprisingly, blue shark are hunters. They feed mostly mackerel and herring as well as squid and sometimes hunt larger fish such as cod, pollock and coalfish. Although blue shark generally swim slowly to conserve energy they are capable of fast bursts of speed when hunting.

Blue Shark Squid
A blue shark feeding on squid off the coast of Southern California.

Blue shark will occasionally scavenge and have been spotted following trawlers and eating the bycatch and gutted fish which are thrown overboard. They have also been known to attack the nets of trawlers when they are full of fish and being hauled back on board the boat.

Commercial and Recreational Fishing for Blue Sharks

Blue sharks are caught commercially with several million being caught each year across the world. The flesh of blue sharks is not highly regarded, but the skin is used for leather and the liver for oil. The dorsal fin is also used to make shark fin soup. After these parts of the shark have been taken the remainder of the carcass may be thrown back into the sea or processed into fishmeal. The extent of the commercial exploitation of this species was outlined in 2018 when a Spanish fishing vessel, the Virxen da Blanca, was detained by the Irish Naval Service and found to have 1,250 kilograms of shark fin on board, along with an incredible 164,250 kilograms of blue shark on board – the equivalent of around 5,000 individual blue sharks.

The blue shark has an uncertain future if commercial fishing for this species continues at current levels. In their last assessment the International Union for the Conservation of Nature classed blue shark as Near Threatened on a global basis and in European waters with a decreasing population trend. In the Mediterranean blue shark was placed in the highest risk category of Critically Endangered and the IUCN noted that there are no recovery plans or fishery management schemes in place to allow stocks to recover.

Commercially Caught Blue Sharks
Commercially caught blue sharks on sale at a fish auction in Vigo, Spain.

Blue sharks have always been present in UK waters in the warmer summer months, although they may be becoming more common due to warming seas. There are charter boats around the south and west of England, Wales and Ireland which specialise in taking anglers out to catch blue shark. Almost all of these charter boats fish on a strict catch and release basis in order to protect blue shark for future generations (the boat caught record of 218lb has stood since 1959). In Summer 2016 a 242lb blue shark was caught off the coast of Wales at Milford Haven. While the shark would have been eligible as a record catch it was returned to the sea after being photographed. In August 2017 an even larger blue shark was caught off the coast of Cornwall. This shark weighed 256lb and was again released after being photographed.

Attacks on Humans

Blue shark attacks on humans are extremely rare but have been recorded. In total, on a world-wide basis, there are four confirmed cases of fatal blue shark attacks on humans with twenty-five confirmed non-fatal attacks. In August 2012 a beach in Ceredigion, Wales was closed to bathers due to the presence of a blue shark. The shark was spotted swimming in between boats and came very close to the shore, swimming past tourists in just a few feet of water. Later in the same month another beach in West Dorset had to be closed for an hour and a half due to another blue shark.