Chilly seas could be keeping basking sharks away from Northern Ireland's waters as the plankton they feed on fails to bloom.
The fish – which can grow to the size of a double-decker bus – appear to be giving our seas a miss as water temperatures are lower than normal.
Northern Ireland's first sighting came on Saturday when a single shark was recorded at White Rocks beach in Portrush.
The Irish Whale and Dolphin Group (IWDG) says it has only validated 19 records this year, compared to 84 for the same period in 2012.
"The figures do point to a steady decline in sightings... but it is too early to speculate on the drivers that may be underpinning the decline," the IWDG's Padraig Whooley said.
Meanwhile, the Marine Conservation Society charity said it has received hardly any reports.
"Divers are telling us that the water temperature is 10 or 11 degrees centigrade. But at this time of the year it should be nearer 13 degrees," said Dr Jean-Luc Solandt, MCS senior biodiversity officer. "This means that the plankton are not blooming in the usual quantities."
Last year more than 170 sightings were reported to the website: www.mcsuk.org/sightings.