Common name: Blue shark, Porbeagle shark, Mako shark
Latin name: Prionace glauca, Lamna nasus, Isurus oxyrinchus
Record weight: Sharks are the largest fish commonly encountered in the inshore waters of the British Isles, and this is reflected in their record weights. Blue sharks are the smallest and commonest of our sharks with a boat record weight of 218lb, the shore record for all sharks is open at 40lb. Porbeagles are only just the largest sharks encountered with a boat record of 507lb. The mako is very slightly smaller at 500lb.
Distribution: Sharks are most common in the deeper water found around the West coast of the country. Here they move closer to shore during the Summer months when the water temperature rises. Generally though, most sharks are found some miles off-shore. All of the sharks found around the British Isles are common around much of the coast of Europe. Most fish follow the warmer water of the Gulf stream and the would-be shark hunter would be wise to plot the position of this warm current when searching for sharks.
Features: The blue shark, as the name suggests is a deep indigo blue, unlike the other two species seen around our coasts, which tend to be almost battle-ship grey. The blue is also much slimmer and the pectoral fins look almost out of proportion to the body, being much longer than those in our other shark species. Porbeagle and mako sharks are often mistaken for each other, as they share the typical stout body form of the larger 'mackerel' sharks. One way to tell the two species apart (although not recommended!) is to examine the teeth. The teeth of the mako have only a single point, whereas the porbeagle's teeth have three points.
Diet: All of the open water sharks found around the British Isles are primarily fish eaters. Few fish are large enough to withstand an attack by one of these sharks, but for the most part, they feed upon much smaller prey. Despite their ferocious appearance, mackerel and herring are the main prey of these sharks. These oily fish provide the sharks with the vital high energy food that they require to meet their energy requirements. Other fish, such as dogfish, cod and even flatfish will be taken when they are locally available. Whilst each of these sharks is theoretically capable of attacking humans there are no records of this in British waters and as most sharks are found some miles off-shore the risk to humans is very, very small.
Spawning: Relatively little is known about where and when sharks breed, although it is obvious that they have a long gestation period, probably lasting many months. All three species of shark give birth to live young. The eggs are fertilised inside the female and develop under the protection of the female. When the eggs hatch, the young fish remain in the female, feeding on their yolk sacks and when this is exhausted they then turn on each other, eating any unfertilised eggs and weak individuals. When they eventually emerge the fifty or so young are around 45cm in length and are fully formed sharks that can go on the hunt immediately.