Shark Tagging off Scilly

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Above: Paul Whittaker with Porbeagle Shark, one of only 7 tagged off Scilly

MV Sapphire pelagic trips often combine seabirding with research into shark movements via a tagging program. The two activities are complementary since chum is used to attract both seabirds and sharks. Seabirders may be lucky enough to witness a shark being tagged.

We have been tagging Blue Shark around the Isles of Scilly since August 1996. In this time we have tagged and released 456 Blue Sharks and 7 Porbeagle Sharks. We have had 20 recaptures of Blue Shark:

Tag no. 13468 was tagged on 5th August 2001 and recaptured on 2 September 2001, 85 miles southwest of Breast, France.
 

Tag no. 20315 was tagged on 20th July 2002 and recaptured on 29 January 2003, 1130 west of The Azores.
 

Tag no. 021108 was tagged on 10th July 2003 and recaptured on 27 September 2003, 20 miles southwest of The Lizard.
 

Tag no. 021113 was tagged on 10th August 2003 and recaptured 10 January 2005, 70 miles north of Madeira.
 

Tag no. 021467 was tagged on 20th August 2003 and recaptured on 12 May 2005, 150 miles west of The Azores.
 

Tag no. 021831 was tagged on 14th August 2004 and recaptured on 5 April 2005, west of Porto, northwest Portugal.
 

Tag no. 021464 was tagged on 12th July 2004 and recaptured on 18 June 2005, 760 miles west of The Azores.
 

Tag no. 021465 was tagged on 2nd August 2004 and recaptured on 19 October 2005, 450 miles southwest of The Azores.
 

Tag no. 012105 was tagged on 21st August 2005 and recaptured on 10 August 2006, 270 miles southwest of The Cape Verde Islands (not shown on map).
 

Tag no. 20324 was tagged on 22nd August 2002 and recaptured on 1 June 2007, location not given (not shown on map).

Tag no.  25782 was tagged on 27th August 2007 and recaptured on 15th November 2008, 560 miles southwest of The Azores.

Tag no.25789 was tagged on 27th August 2007 6.25 miles south of St.Mary`s. It was recaptured on 18th April 2009 550 miles west of The Azores. It had travelled at least 1673 miles in 600 days.
 
Tag no.21929 was tagged on 31st July 2005 5.25 miles south of St.Mary`s. It was recaptured on 11th April 2009 670 miles west of The Azores. It had travelled at least 1855 miles in 1350 days.

Tag no. 025793 was tagged 30th August 2007 7.25 miles south of St.Mary`s. It was recaptured on 10th December 2009 280 miles east of The Azores. It had travelled 920 miles in 833 days.

Tag no. 025405 was tagged 9th August 2009 8.5 miles south of St. Mary`s. It was recaptured on 14th August 2010 140 miles south west of The Azores. It had travelled 1318 miles in 370 days.

Tag no. 025397 was tagged 21st August 2010 4. 75 miles south east of St. Mary`s . It was recaptured on 28th September 2010 120 miles west of Cape Finisterre. It had travelled 462 miles in 38 days.

Tag  no. 025376 was tagged 15th August 2010 3.75 miles south west of the Bishop Rock lighthouse. It was recaptured on 11th December 2010 80 miles south west of Lisbon, Portugal. It travelled 738 miles in 118 days.

Tag no. 025497 was tagged 23rd August 2010 4.25 miles south east of St.Mary`s. It was recaptured on 12th March 2011 700miles south west of The Azores. It travelled 1821 miles in 201 days.
Tag no. 025502 was tagged 21st July 2001 6 miles south of St.Mary`s. It was recaptured on 4th September 2012 650 miles west of The Azores. It had travelled 1720 miles in 410 days.

Tag no. 0255557 was tagged 8th September 2011 5 miles south east of St.Mary`s. It was recaptured on 21st January 2013 160 miles south west of Madeira. It had travelled 1520 miles in 501 days.

Recaptures

Fig 1. Map showing recaptures of Blue Shark tagged off Scilly 

When a Blue Shark is caught its weight is recorded and a numbered tag inserted just below the dorsal fin. Upon subsequent recapture the shark again will be weighed so that the growth rate can be determined for the period that the shark was at liberty. Also, by recording the location of each capture we can understand more about shark movements. If a number of anglers catch the same shark, then we are able to produce a more definite migration pattern. Furthermore, if a non-gravid female is caught and later recaptured gravid, then we know that between times the shark has mated. Using this information, a breeding-area could be set up where both angling and commercial fishing is prohibited.
 

Tagging in previous years has already shown that the majority of Blue Sharks caught around the British Isles are females, whereas the majority caught off the eastern seaboard of the USA are males. This could well have something to do with breeding, which further tagging would confirm.
 

Shark tagging plays an important role in conservation. There is not a never-ending supply of stock that anglers and commercial fishermen can continue to exploit. Fish in general, and sharks in particular, are very slow to reach maturity. Comparatively speaking, they breed late in life. Continual slaughter of stocks will hasten the demise of these truly unique creatures.
 

Shark species management on the part of the national fisheries bodies is non-existent. Tagging hopes to highlight some of the problems and provide the scientific means by which to introduce shark species management.

Blue Shark prior to being taggedTagged Blue SharkImage by Joe Pender 

Contact Paul Whittaker psmwhittaker@hotmail.com for details of the Shark Trust.



Tagged Blue Shark