by Lucy Hunt
At the end of April we took the opportunity in the fine weather to get out tagging and sampling basking sharks in Kerry, where sharks had been reported for 2 weeks previous around the Blasket Islands! We were lucky to find basking sharks on all sides of Slea head and the Blaskets. For this trip we planned to also gender the leviathan sharks and I was excited, as I knew this meant I was going to be snorkelling with them. It was three summers previous I had had my first encounter with these sharks snorkelling off Bolus head with over 20 sharks in the water where plankton had amassed in a small inlet! It was an experience I wanted to relive only this time it would be better as I would be contributing to science. The slime samples we collected and the gender of the sharks, which I would observe, would be used for genetic studies. Once we had tagged and slime sampled sharks I would enter the water and snorkel with them to first note the tag number then gender them and catch what I could on camera! To identify a male shark we look out for a pair of claspers on the ventral surface near the anal fin these claspers are absent in females. A seemingly easy enough task but as with everything in the field there is always something to make it that bit more challenging!
As I was dropped in the water about five meters in front of the first shark approximately 8m in length- one of the largest animals I have ever been in the sea with, enveloped by the chilling Atlantic, the leviathan swam straight towards me angled slightly and swam by leaving me swimming frantically in it's wake to keep up and capture it on my digital camera. As it passed by I caught a glimpse of it's tag number 328 and videoed it's underside, which had about 8 lampreys on it making it impossible to distinguish claspers with the quick encounter I was allowed! I would have to scrutinise the video when back on dry land to determine its gender. Lampreys are parasitic fish that attach to basking sharks.
The giant shark glided by with effortless motion once more allowing another short lived observation of this fantastic species leaving me alone again in the Blasket Sound where my colleagues collected me and I was awarded with tea and biscuits and listened to intently on my encounter! Whilst telling my tale I was looking over my listeners shoulders only to witness one of the most incredible things I have seen - a basking shark breach clean out of the water! Everyone turned with cameras ready to catch the next breach but nothing happened. So we continued tagging in the area but the sharks seemed that bit more flighty than we had normally encountered and it was a bit more challenging for Nick our skipper to get to them without first scaring them off, he did a great job though as by noon Dr. Berrow had over 20 sharks tagged.
Just before heading out of the Sound for shelter from the wind on the south of Great Blasket I was looking towards land and lo and behold another breach - I was enraptured and a thrilled laughter overtook me when everyone turned and we all watched on as another shark breached twice!! A truly spellbinding experience to watch! This elaborate behaviour is often associated with mating and or ridding of parasites but we are still unsure.
We moved to the south of Great Blasket to get some shelter from the wind and spotted three sharks nose to tail swimming and another few sharks in the distance, once these sharks were tagged and slime sampled I hopped in the water to get some more gender information, again more lampreys hindering views. We then spotted two smaller looking sharks close to the rocks and went in for a look tagging and slime sampling one. The water was like a plankton soup hopping with activity in the recess where the sharks were scooping it up! GMIT marine biology student John Power and I immersed ourselves in the lively water to see if we could get any more info for the project, once in the water our faces tickled by the plankton which the sharks were after. Sea gooseberries (a type of small jelly fish) were iridescent with phosphorescent rays running down their bodies perhaps warning of their fate to come when all of a sudden a huge shark came out of the murkiness and straight for me and John, on noticing our presence it closed it's gaping mouth and turned away, John dove to observe more lampreys on another shark. Whilst we had been in the water the team on the boat were busy tagging other sharks nearby and witnessed another shark breaching!
We spotted more sharks further off and followed them out where they were nose to tail swimming and parallel swimming; behaviour also associated with courtship and mating! Once these were tagged and sampled we hopped in the water with what we thought was one shark yet there were two below this one - proving that for every one we see at the surface there may very well be many more beneath! We were able to see their tag numbers but not get below them to gender them as the sharks swam around us in circles reminding me of the predatory behaviour other shark species exhibit and in what seemed like an eternity I was encircled by three very large sharks their mouths wide open filtering the plankton rich water not leaving me with much space to exit the circle! Eventually they descended into the depths and I swam after them but once again was left behind.
The day edged on and I wanted to get some zooplankton samples to assess predator prey relationships so samples were taken in the presence of sharks and at our four other stations, which we had started to sample in 2010. On our return more sharks were seen and a minke whale amongst a feeding frenzy of sea gulls and gannets diving for sandeel. Then in the shelter of Coomenoule two more sharks appeared giving everyone the opportunity of donning a mask and looking in over the edge of the boat at these spectacular animals.
It was a very successful field day with great teamwork from all involved as we deployed over 35 visual tags, obtained 15 shark slime samples for genetic studies. Obtaining dorsal fin photos for the photo id catalogue and taking plankton samples for predator prey analysis and also in water observations. At least 60 sharks were seen in the waters around the Blasket islands as well as four minke whales and over 20 common dolphins before it was time to go home when the sun was setting over the Atlantic horizon.
Guidelines for swimming/boating in the presence of basking sharks
http://www.baskingsharks.org/content.asp?did=26602&rootid=6210