A team of international scientists have succeeded in satellite tagging ocean sunfish off the Irish coast in the first operation of its kind in Irish or UK waters.
They believe the project may provide vital information on climatic changes in the Irish and European waters.
According to Dr Tom Doyle of the Coastal and Marine Resources Centre attached to University College Cork, sunfish are the largest bony fish in the world and can grow to up to 3.1m from tip to tail fin. They can weigh up to two tonnes.
"They have a unique shape - that is flattened from side to side and stretched from top to bottom. Their body is truncated to such an extent that they are literally all head and no body - in fact their German name 'schwimmender kopf' means 'swimming head'," he explained.
According to Dr Doyle, sunfish are related to puffer fish and porcupine fish and while they are believed to swim as deep as 600-700m, they also spend large amounts of time at the surface with their large dorsal fin flipping from side to side.
Together with Dr Jon Houghton of the University of Wales Swansea and other researchers from both Wales and Germany, Dr Doyle spent over two weeks studying the movements of sunfish off Smerwick harbour on the Dingle peninsula in Co Kerry.
"Sunfish feed on jellyfish but we're not sure why they are seen in such large numbers off the northern side of the Dingle peninsula around Smerwick harbour and down to Brandon Head - last year we were seeing around four a day, this year we were seeing up to 20 a day.
"We're not sure why so many sunfish aggregate in this small area but one strong possibility is that it may represent a nursery ground for sunfish where juveniles can shoal and feed together; similar nursery grounds are found in Bali in Indonesia and off the Californian coast."
With logistics and technical support provided by Taighde Mara Teo and funding research from the Marine Institute and Údarás na Gaeltachta, Dr Doyle and his colleagues succeeded in catching and tagging two fine specimens.
"We used a cast net to catch them and bring them on to a Rib [rigid inflatable boat] and then we transferred them to a bigger boat provided by Pádraig Frank Ó Súilleabháin of Eco Tours who had a big tank on board and we were able to put them in that so as not to stress them while measuring them.
"This research has very important implications for Ireland as a whole as sunfish may represent a good biological indicator of climatic change; that is, if sunfish sightings increase dramatically it may be a clear sign that our waters are warming and our climate is changing," said Dr Doyle.