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Ocean health monitored by Irish Basking Shark Research

Saturday, 13 November 2010 18:09
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(c) Emmett Johnston

Irish Basking Shark Research may lead to monitoring of the health of the oceans.

Research on the basking shark, the second largest fish in the world, is of international significance and the potential is huge. This is according to Project Leader with the Irish Basking Shark Study Group, Dr Simon Berrow. "Since 2008 we have tagged nearly 250 sharks in what is now, by far the biggest basking shark tagging project in the world. Amazingly we have had fifteen re-sightings, over 6% of the sharks tagged, from local re-sightings seen two weeks later, near the tagging site, to those seen 69 days later and over 800km away in Scotland. This shows that some sharks stay in the same area for extended periods but we think there is a general northerly movement through the summer with sharks in Ireland moving through Irish coastal waters before heading into Scottish waters. This year we had basking sharks tagged in west Cork re-sighted in west Kerry and in western Scotland."

"These tagging studies have also enabled us to estimate the number of sharks in an area.  In 2009 and 2010 we estimated using mark-recapture modelling, around 200 sharks occurred in Trawbreaga Bay off the Inishowen Peninsular, Co Donegal. During this period basking sharks were also being reported in many bays and off headlands all around the Irish coast suggesting there were thousands of sharks in Ireland. When you consider global estimates of basking shark populations amount to only 20,000 individuals this means a high proportion of the world's basking shark occur in Ireland or global estimates are horribly wrong."

In addition to the tagging work, the Irish Basking Shark Study Group have pioneered a new method of obtaining samples for genetic and other analysis. "Our discovery of the potential of shark slime, or mucous, for providing samples for genetic, pollution and other studies requiring biologically active substances, was largely by accident" said Dr Simon Berrow, "but the potential of this discovery is huge. Suddenly we have a simple method of collecting samples without killing the animal enabling us to re-sample individuals over different time and geographical periods and when coupled with tagging, explore the opportunities for genetic tagging and other techniques". This new method may have important implications for other shark and fish species.

This important research will be presented at the European Elasmobranch Association conference held in the Marine Institute, Galway this week. "The basking shark is one of the most impressive species swimming in the world's oceans, and Ireland is without doubt one of the best places in the world to study them" said Dr Berrow. Why are basking sharks important ? They were killed in huge numbers in Ireland and elsewhere mainly for the oil in their liver but in recent times they are thought to be an excellent indicators of climate change. Basking sharks fundamentally go where zooplankton concentrates and filter huge quantities through their gill rakers. As zooplankton distribution will be affected by climate change, the distribution, abundance and movements of sharks will change to reflect these trends.  Tracking basking sharks may be far more effective than tracking zooplankton and provide one of the best indicators of the health of our seas and thus the planet.

<b>This important research has been funded by the Heritage Council during 2009 and 2010 under a Wildlife Research Grant.</b>