At time of writing in early March 2025, our 2024/25 fin whale season is nearing an end. It looked like it was over by late January, with just a single fin whale sighting record off Helvic Head, Co. Waterford on February 8th however, effort watches since Feb. 25th by our local IWDG Cork group have documented a run of late season fin whale sightings off Knockadoon Head, east Cork, up to and including 6th March, 2025. This late flurry of sighting leaves open the possibility that the lack of sightings during February may have been weather related.
Fin whales have been recorded in every month in Irish coastal waters. Over the past decade 2015-2024 they have typically been present over at least nine months each year, running from June to the following February. In more recent years their season has if anything extended further with animals present over 10 months and on one year (2017) they were recorded over an 11-month period. So, it’s safe to say that fin whales are close to being present here year-round. Wherever they go once they leave our shores, the data would suggest it’s not too far away.
With humpback whales sucking so much of the oxygen out of the room in recent years, their larger rorqual relative, tends to get over-looked. So how has the “Greyhound of the Sea” fared here over the past 20 years? To answer this, I took a bit of a deep dive into our cetacean database and looked at two simple metrics, the first of which was the number of actual validated sighting reports (n=2,089), to see how they broke down over the years. The result was a fairly flat trendline (top chart) with some years better than others. I was curious to see how the same humpback data would look and it’s quite clear when plotted over the same period that their trendline is on an upward trajectory. So humpbacks, in Ireland anyway, seem to be doing much better than our fin whales.
Chart 1. Fin whale sightings over 20 yrs. Courtesy IWDG
Chart II. Fin whale Average group size over 20 yrs. Courtesy IWDG
But the number of actual sightings may not be that useful as a measure, as it tells us little about the numbers of animals present each year, or average group sizes. For instance, if we had just one fin whale sighting record in a year, but with a group size was of 1,000 fin whales, would we still consider this to be a good year?
By dividing the total number of animals by the total number of sightings, we get some idea of average group sizes each year, and when these are plotted (2nd chart above) it is fairly evident that although the numbers of fin whale sightings might be flat, average group sizes are getting smaller, which is consistent with what we are experiencing on the water. Even in areas with lots of feeding dolphins, seabirds and forage fish, it seems when fin whales locate these “sweet spots”, that they are simply not present in anything like the numbers we remember in years past. Whether this is down to the lack of sprat, or the right sort of sprat, with too many immature fish, is unclear; but it suggests that fin whales are more discerning than our pair trawlers.
When we think of large whale Photo ID, it tends to imply humpback whales and for good reason…. picking the low hanging fruit just reaps the greatest rewards! However, this simple technique can be used on any whale species; it’s just a lot less straightforward.
In December 2024 we received an email from Luana Millecamps, a former student on the IMBRSea masters course at ATU Galway in 2022. She explained how she was working with the NGO Mar Ilimitado in southwest Portugal, https://marilimitado.com/. Long story short, they have a fin whale catalogue and wanted to reach out to others in the region who also had strong images that could be used for photo ID matching. As is generally the case, we were only too happy to share our catalogue, as such opportunities don’t present too often with fin whales.
On December 19th we received an early Christmas present from Portugal in the form of an email telling us they’d potentially matched as many as four of our animals to their catalogue from the Sagres area of Portugal. Such a high number of matches surprised us, so we asked to take a look at their images, which we duly received and along with Andrew Malcolm we got to work on running their images through the Irish fin whale catalogue.
In summary, of their four “matches”, we agreed that one was a certain “No”, another was a possible, another was a probable, but one was a definite match with our #FWIRL023 dating back to Jan. 3rd 2005 (see composite images).
FWIRL023, a match to Sagres, SW Portugal…….can you see it?
So although this doesn’t confirm a link to a breeding area; it does however provide us with that all-important first international fin whale match, which may in time yield further results. It’s important not to try and compare this one meagre match with the myriads of matches among our 136 humpbacks…apples and oranges spring to mind.
Remarkably, almost nothing is known today about fin whale breeding areas in the north Atlantic, whereas we can give you chapter and verse on that of humpbacks. So, this is an important first step for this often seen, yet poorly understood species. As was the case with our long wait for the first match to an Atlantic humpback breeding area, who knows, perhaps this breakthrough will open the sluice gates for further long-distance matches. Let’s hope so.
Ireland -Portugal match…an important 1st step for our understanding of fin whales.
Our top tips for Photo ID of fin whales from boats are:
- Use a skipper with a proven track record of working around large whales.
- Approach the whale slowly at an oblique angle on the right side.
- To get useful ID images, you’ll need to use a good camera with a zoom lens. While your smart phone may get nice pictures or video, these are not that useful.
- If possible, and the whale is obliging, try to photograph the dorsal fin and flanks from both sides.
- Do not pursue the whale if it attempts to leave the area.
- As you will need to get close to capture the details on the dorsal fin and chevron area, you’ll ideally need to be within 100 mts of the whale and so we’d urge people serious about Photo ID to apply to NPWS for a license to film/photograph them. Applications can be emailed to wildlifelicence@npws.gov.ie
- Send any useful images to IWDG e: sightings@IWDG.ie at the highest resolution and we’ll do the rest.
We extend a big thanks to our colleagues at Mar Ilimitado and look forward to meeting you at the ECS conference in the Azores in May.
By Pádraig Whooley, IWDG Sightings Officer