Progress

Project timetable and progress

Tagging with Pop-up Archival Transmitting (PAT) tags has been carried out in 2001 and 2002 (10 tags each year). The tags have been programmed to “pop up” at intervals of 3, 6, 9 or 12 months in order to get a full picture of the sharks’ seasonal movements. Plans to use new pop-up "Telephone Tags" in 2003 were delayed, but 3 were deployed in 2004 despite low numbers of basking sharks being sighted in the south west.

As the field work has progressed, details of the tagging locations have been posted on the map below. As the tags pop up, further information will be added to this website.

Basking shark tagging during the 2001 and 2002 field seasons.

10 sharks were tagged in the summer (May – July) 2001, 5 in the south-west off Plymouth, 5 in the Clyde Sea, a further 10 sharks were tagged in the summer of 2002 (one with two tags programmed to pop-up at different times) off Plymouth and Cornwall.

Map 1
Numbers and locations of basking sharks
tagged in 2001 (black) and 2002 (red)

Tag recoveries: To date, data have been recovered from six of the ten tags deployed in 2001, two tags were recovered physically, providing minute-by-minute details of diving behaviour (one for 8.5 months), the others have popped up and sent summary data back via satellite. Three of the 11 tags deployed in 2002 have so far popped-up on schedule and successfully sent data back via satellite.

Map 2
Positions and dates of the first 8 tags to pop up.

Findings so far:

Basking sharks tagged in UK waters in the summer remain on the European continental shelf through the winter and do not appear to make trans-oceanic migrations.
Contrary to earlier hypotheses, basking sharks do not hibernate on the sea-bed during winter.
Tagged basking sharks have moved extensively within continental shelf waters and there does not appear to be separate sub-populations off Scotland and south-west England.

Movements of five basking sharks tagged with PSAT tags in the northeast Atlantic for periods between may 2001 and June 2002. (See Sims et al., 2003 for full details)

Sharks 3 and 4 were tagged in Scottish waters, sharks 1,2 and 5 were tagged off Plymouth.

Map 3

Shark 3: 31 July to 20 September 2001.
Shark 1: 24 May to 7 August 2001.

Map 4

Shark 4: 28 July to 5 January 2002
Shark 2: 24 May to 7 December 2001
Shark 5: 25 May to 7 December 2001

Publications

David W. Sims, Emily J. Southall, Anthony J. Richardson, Philip C. Reid, Julian D. Metcalfe. Seasonal movements and behaviour of basking sharks from archival tagging: no evidence of winter hibernation, Marine Ecology Progress Series, Vol. 248: 187–196, 2003

Available online from: http://www.int-res.com/journals/meps/