Sea hares and thresher sharks

November 22nd, 2007

An uncommon Sea Hare, Aplysia fasciata, has been discovered in September, October and November in the UK. Another unusual and exciting find was a large common Thresher Shark, found in Cornwall.

Aplysia fasciata, rarely seen in the UK, is larger than the common species Aplysia punctata, reaching up to 40cm long (rugby ball sized!) and can weigh up to 2kg! It is usually found on the Atlantic coasts of France, Spain, Portugal and West Africa. Sea hares are large herbivorous sea slugs, feeding on a wide variety of seaweeds. They have a small internal shell and when disturbed, release a cloud of purplish ink. Aplysia fasciata is very dark brown to black in colour. As well as the sea hares themselves, large egg masses, up to 30cm have also been found on the Devon coast.

A skipper, while fishing in the English Channel, south of Land’s end, hauled up a large, female common thresher shark (Alopias vulpinus). It was found to weigh 510 kg (1122 lb) and was 475 cm (15’ 58”) long, although thresher sharks are known to grow to 573 cm (18’8”). Thresher sharks are one of the largest of the approximately 28 sharks found in British water. Thresher sharks have long tails, the same length as their bodies and use these tails to move the fish, usually pilchards, herring and mackerel into tight shoals before attacking. There have been other thresher shark findings recently in Cornwall such as the large shark found in Charlestown which was approximately 400kg (881lb) and 463 cm (15’ 20”) long.

Added by

Jellyfish in November

November 19th, 2007

This month, there have been a number of jellyfish sightings including the String Jellyfish in Cornwall and the Mauve Stinger in the North Channel.

The String Jellyfish Apolemia uvaria, is not actually a jellyfish but belongs to a related group Siphonophora and is related to the Portuguese Man o’ War. They were reported in large numbers and have been spotted off Plymouth sound in the last 4-5 weeks. These unusual creatures have not been recorded in Plymouth or Cornwall before. They are usually found in oceanic waters and have a nasty sting.

Recently, there have been several sightings recorded in the North Channel, North West Ireland and Western Scotland of the jellyfish Pelagia noctiluca, more commonly known as the mauve stinger.

Photo: Steve Trewhella

The mauve stinger can grow up to 10cm in diameter; its tentacles can extend up to 3m and are covered in nematocysts. Its colour varies from mauve-brown to purple and pale red and the exumbrella or the outer surface of the mushroom-shaped bell is covered in nematocyst-bearing warts, pink or mauve in colour. Nematocysts, also called stinging cells, contain small poisoned tubes that deliver its sting. Pelagia noctiluca usually feed on sea squirts and other small jellyfish.

These species also have a nasty sting so approach with care!

Like this photo? Find out more about this photographer here.

Added by