After the highs of 2024 which broke all previous basking shark records with 357 validated sightings, it was always going to be a difficult year to beat and so it transpired with 186 sightings so far in 2025. While acknowledging that the calendar year still has some way to go, when it comes to Cetorhinus maximus their season by now is as good as run and in the coming weeks any additional sightings will have little impact on the year’s figures. But even with a 48% decline on last year, it was still what we’d consider a good shark year, ranking 4th over the past 20 years.
As with recent years, the main concentration of sighting was between March and May along the Celtic Sea and West coast. This was followed by the expected decline in June and July, but with an uptick in sightings related to courtship or “Torus” events which were recorded most frequently along the Clare coast. So although the majority of sightings over the season were feeding related, the largest aggregations once again tended to be later in the season, with more accurate counts being made possible with drone footage, which enables us count many sub surface animals, that would otherwise pass unnoticed.
We can distinguish between feeding and Torus events simply by establishing whether the mouth is in an open (feeding) or closed (torus) position. A few noteworthy counts were c.100 sharks on August 11th off the Bridges of Ross, Co. Clare, with up to 60 off nearby Loop Head on Aug. 14th. During many of these late season encounters, breaching was routinely observed and on a few occasions individuals breached synchronously. However, the Banner County had no monopoly on these large gatherings and the biggest feeding aggregation recorded was on April 11th in area between Turbot Island and InishTurk that was estimated at anywhere between 70-150 sharks.
Basking shark breach Loop Hd, Co. Clare 14/08/2025 © Conor Rowlands
Basking shark with lamprey Loop Hd, Co. Clare 12/08/2025 © John Glynn
In recognition of the growing importance of Irish waters for this species our colleagues at the Irish Basking Shark Group (with IWDG support) delivered the International Basking Shark conference in August 29-31 in ATU Galway, which was a great success, blending both the scientific and cultural elements of this iconic species. It should be stated that our good fortunewith this species may well be at the expense of other former UK hotspots such as the Isle of Man, Hebrides and Cornwall, all of whom are reporting record declines. Clearly our coastal waters are providing suitable feeding and perhaps even breeding conditions for this ocean grazer…..if only we could report such positive news for other marine megafauna.
A few months back I was contacted by Kinsale Yacht Club to see if I was available to give an autumn talk on my favourite subject ….Whale Watching. Last week while making final arrangements, I was asked unprompted by the Club official about the lack of whales and dolphins in west Cork waters that had been commented on by club members during the season. If there was ever proof needed that things are changing fast here, the fact that even weekend sailors are noticing it, is quite telling. So just how bad are things?
Well, a quick glance at IWDG sightings data shows that our cetacean sightings are down 21% on the year to date. Some of this decline may in part be explained by the temorary demise of our Reporting App which for a number of technical reasons has had to be retired. But the website as our primary reporting tool is working just fine and so there is clearly something else going on that can’t easily be explained by weather, as it wasn’t that poor a summer.
A deeper delve into our three main whale species show humpback sightings are down 20%, and while fin whales are holding their own, sightings of our most regularly recorded whale the minke are down 16%. These declines are hard to pin on climate change given that adjacent UK waters are similarly impacted and they’ve never recorded so many large whales.
Humpback #HBIRL47 under the shadow on Ben Bulben, Donegal Bay, 13/07/2025 © Tom Ormond
Not only are we recording fewer whales this year, but we are noticing a very real shift in their distribution as their preferred southwest feeding areas have switched to the Northwest. So far this year the waters between Sligo and Donegal have for the 3rd consecutive year enjoyed a record number of fin and humpback whale sightings, with 41% of fin whale and 44% of humpbacks records coming from Donegal Bay this year.
Now you could always make a case that given the vast migrations species like humpbacks undertake to breeding areas in the Cabo Verde or Caribbean, that a few additional days swimming up the Irish west coast is no big deal for a highly mobile marine mammal. The key point however is that this is an area where historically IWDG received very few, if any, large whale sightings. And many of these humpbacks are individuals we’ve recorded in previous years in west Cork and west Kerry. So not only are we seeing fewer whales, but when we do, they are in completely new areas. This is unusual behaviour for animals that typically demonstrate strong site fidelity to feeding areas.
As the years go by I find myself spending more and more time looking at the sightings data rather than producing it, so I took advantage the recent spell of high pressure to grab my optics and visit my favourite headland, the Old Head of Kinsale, where I started carrying out regular watches back in the late 1990’s. Everything was perfect, with calm seas and clear skies and nothing but my spotting scope between me and the big blue. Throughout the watch I saw areas of splash and surface disturbance off to the east of the lighthouse. There were blue fin tuna shoals boiling over a vast swathe of water. Only at the end of the watch did I pick up a small group of common dolphins, but just as everyone was telling me, not a single whale of any species was seen after 100 minutes watching in near perfect conditions, on what used to be one of Ireland’s foremost whale watch sites. Such a result would have been unthinkable at any time in the la
Fin whale with common dolphins, Donegal Bay 28/09/2025 © Joey Batt (Dublin-drone)
st 25 years. No tuna and lots of whales in west Cork, seems to have become no whales and lots of tuna, and in a relatively short time. Everything is it seems changing and fast.
Clearly whales being highly mobile can switch to areas with better feeding opportunities. There would be some relief if we knew for fact that this was all down to climate change resulting in warming waters and pelagic fish pushing north in search of colder SST’s. It’s a convenient argument, but one that is not supported as of yet by any evidence. We do need to explore the very real possibility that the reason our whales are deserting certain areas, is not so much that the pelagic fish on which they depend have also pushed further north, rather they’ve been pushed to a far more dangerous place. The brink.
Let’s hope that in the season ahead our fishing fleet, both over and under 18 mts, leave sufficient forage for other marine predators.
Big thanks to all our recorders who have sent us in sighting reports and images which enable us build on both the Irish humpback and fin whale Photo ID catalogues under our Whale Track project. Our Reporting App has as mentioned had to be decommisioned due to ongoing support issues with the various platforms, but rest assured our IT team are working on what is called a PWA (Progressive Web Application) which we hope to start to work on shortly. We’ll keep you posted on how this developes and may even be asking some of you to help us with testing when the time comes. In the meantime please continue
report any cetacean or basking shark records on www.iwdg.ie using the Report a Sighting link on the homepage.
By Pádraig Whooley, IWDG Sightings Officer