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Tory story

Tuesday, 03 May 2011 18:19
Sharks off Tory Island
Sharks off Tory Island
(c) Emmett Johnston

The North Donegal Coast was the set location for an interesting tagging tale with a remarkable 24 visual tags deployed and the first ever deployment of a Timed Depth Recorder (TDR) on a Basking Shark. These sophisticated pieces of modern technology are designed to investigate the basking sharks surfacing habits in Irish and north-east Atlantic waters.

It all began on Tuesday the 27th when the North Donegal shark team received an email from Tory islander Deirdre Sweeney. Deirdre reported 12 sharks near the islands Harbour entrance and more out in the sound.  The teams Rib 'Seashell' was readied with extra fuel and supplies stored for the longer than usual journey. Thursday the 28th brought calm sea's and light winds perfect conditions for the run to Tory island from Lough Swilly and of course for basking sharks to surface.

As soon as the team arrived at Tory they spotted their first shark of the day and they wasted no time in photographing the distinctive dorsal fin of the animal and deploying a visual tag. Within minutes more sharks started to surface along a distinctive tidal line 500m off the islands coast. What followed can only be described as a tagging spree, as 24 sharks received their new individually numbered identifies. The team also took a number of slime samples, recorded high definition underwater footage and captured numerous dorsal fin pictures. That not being enough the team decided that the time was right to deploy two of their QUB developed and Inishowen Development Partnership funded TDR's.

These prototype tags specially developed for this project were initially put out a trial basis for only a few hours. Two medium size sharks were chosen and deployment went perfectly. One tag (150.079mhz) was recovered two hours later with usable data and the other tag '150.137mhz' which was put on for a longer period was not recovered due to deteriorating weather conditions. We know the tag is still out there broadcasting because Donal Griffen from the North Donegal basking shark research team detected a signal off the tag near Tory Island by Yaggi antennae from Horn head 24 hours later.

For the final tale of shark number 475 with tag '150.137 Mhz' and the tags eventual recovery... you'll have to wait for the sequel !