Dear All

            As you may have heard there was a large thresher caught 3.5 miles south of the Runnel Stone yesterday.  As far as I can tell it could be the heaviest ever recorded.  Here is the info I have sent out to the media.

            Regards, Doug

Biggest Thresher Shark Ever, caught off Cornish Coast (again).

Roger Nowell, skipper of the inshore trawler F.V. Imogen (PZ110), was out fishing for squid and John Dory in the English Channel to the south of the Land’s End peninsula when on his echo sounder he spotted a shoal of scad (or horse mackerel) near to the bottom.  He shot his trawl, and hauled up a surprise catch, for amongst the fish was a large thresher shark. 

It was a female Common Thresher shark (Alopias vulpinus).  Thresher sharks are one of the largest of the 28 types of sharks found in British waters.  They are not common but are caught from time to time around our coasts, especially in the central Channel and off the coasts of Devon and Cornwall.  However when it was landed at Newlyn Fish Market it was found to weigh a monstrous 510 kg (1122 lb); making it one of the heaviest thresher sharks ever caught anywhere in the world and the second giant from Cornish waters in a few weeks.

The world angling record for the Common Thresher is a mere 348 kg, though larger ones are known to have been caught possibly weighing more than 450 kg. Although few records are kept of those caught by commercial fishing vessels.  However at half a tonne this is an amazing fish.  A related but different Bigeye Thresher (Alopias superciliosus) was caught on rod and line in Hawaii in March 2007 and that was 952 lb (433 kg).

The Cornish shark was a female and remarkably stout.  It may prove on gutting to have been pregnant or to have been feeding well and stored lots of energy in its liver.  These sharks have between two and four young at a time each around 150 cm and 6 kg in weight.



It was by no means the longest ever caught at 475 cm (15 foot 10 inches), as they can grow to 573 cm (18’ 9”) and have been said to reach 610 cm (20’).  In fact, one of the first sharks recorded in Britain was a seventeen foot thresher, which was caught between Calais and Dover in 1569, (and subsequently went on show in Fleet Street, London).

Thresher sharks are easily recognised by their long tail, which is about the same length as their body.  They have very sharp teeth but small mouths and are very unlikely to attack humans, as they normally prey on shoals of pilchards, herring and mackerel.  They may fish in twos or threes, or on their own, but often use their tails to scare the fish into a tight shoal before attacking.  A few years ago one was seen in Mevagissey Harbour, Cornwall, stunning a shoal of anchovies with its tail before feeding.  The Newlyn fish seems to have gone into the trawl while busy hunting the horse mackerel.

They are wonderful and fascinating fish and we have a small population around our coasts, mainly in the central and western Channel, but they are very vulnerable to fishing, taking a long time to grow and producing so few young at a time that they have difficulty replacing losses from the stock.  For this reason most anglers no longer land the sharks they catch but attempt to release them again alive and unharmed, sometimes after attaching a marker tag for future identification.  Several large threshers were caught and released by anglers this summer off the Isle of Wight and the Dorset Coast.  The Cornish stocks seem to be having an unfortunate period at the moment with one getting trapped in the bottom lines of a chain of lobster pots of Charlestown barely a month ago (14th October 2007).  At 400 kg that was also one of the largest recorded.

Douglas Herdson, UK Marine Fish Recording Scheme, National Marine Aquarium, 22.10.2007

Notes:-

1. This shark was marketed by W. Stevenson and Son of Newlyn.
2. It was bought by Julian Smart of Smart’s Prime Fish for £255 (50p per kg)
3. The National Marine Aquarium maintains the UK Marine Fish Recording Scheme which collects and collates reports of rare, uncommon and unusual marine and estuarine fish around the British Isles.  Douglas Herdson can be contacted on 01752 275216 or Douglas.Herdson@national-aquarium.co.uk.
4. See list of largest thresher sharks caught below

Largest Thresher Sharks

Common Thresher (Alopias vulpinus)

Newlyn Shark - (21.11.2007)

            475 cm TL (15’ 10”), weighed 510 kg (1122 lb)

Charlestown Shark – (14.10.2007)

            Weighing 340 kg gutted (thought to be 400 kg entire) (said to be 15’ to 20’).

Heaviest

World Angling Record – 348 KG 1983 in New Zealand

One of 363.8 kg (802 lb) caught in New Zealand in 1981 was not accepted for a record because of the way it was caught.

Said to have been some caught of over 900 lb (409 kg) but no definite weights.

A related Bigeye Thresher (Alopias superciliosus) was caught in Hawaii earlier this year (30th March 2007) which weighed 952 lb (433 kg), but again while this was a Hawaiian record, it was not accepted for an international angling record.

Longest

Known to grow to 573 cm (18’ 9”)

Claimed to 600 or 610 cm (20’)

Even first known for Britain, caught between Dover and Calais in June 1569, was 17’ (520 cm)

Douglas Herdson
Information Officer
National Marine Aquarium
Rope Walk
Coxside
Plymouth  PL4 0LF
UK


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