IWDG 2023 Sightings Summary Report

Sightings Summary Review 2023

During 2023, the IWDG validated 2,684 cetacean and basking shark sighting records, combining both casual and effort related sightings. This is the highest number of sightings handled by IWDG since the group was established in 1990 and represents an 8.6% increase on 2022. During this period 329 land-based effort watches were carried out from headlands throughout the four provinces. As with previous years, most cetacean sightings reported are mainly from inshore waters of 1-20km but a small number were from places like the Porcupine Seabight, Celtic Deep and offshore off the west coast, which increases the species diversity to include deep diving species such as pilot, sperm and beaked whales.

In order of frequency of sighting records, the 10 most commonly seen species were: 

Sighting summary 2023

The most frequently observed and reported species was the common dolphin with 571 records sighting records or 21.2% of all sightings validated by IWDG in 2023. Our smallest cetacean the harbour porpoise came in second place with 515 sightings.  Bottlenose dolphins took 3^rd place with 483 records (18%). Minke whales, our smallest rorqual, were again our most frequently reported baleen whale with 377 sightings (14%). The planet’s second largest fish and shark species, the basking shark had another good year with 156 sightings (6%), which was down slightly on 2022. Of our two large rorqual species, the humpback whale came in ahead of the fin whale, with 134 & 90 sightings respectively (5% & 3%).  Completing the summary of “usual suspects” was the mysterious deep-diving Northern bottlenose whale, who ordinarily wouldn’t feature on this summary, but for the sustained occurrence of a group of up to three specimens that were recorded regularly in Inner Bantry Bay between August 21^st and October 7^th.

The poor July result was due to a very wet and windy July, August wasn’t much better!

Sighting highlights 2023

Common dolphins were not only the most frequently reported cetacean species, they were also the most widespread. 2023 provided us with further evidence of their prospecting new areas and one such place is the Shannon Estuary, home to Ireland’s only resident population of bottlenose dolphins; where between January  and April they were recorded on 13 occasions in the Inner Estuary.  Unusually, many of the largest aggregations were from the northwest with a group tally of c.600 off Erris Head, Co. Mayo on May 12^th, 500 off Mullaghmore, Co. Sligo on June 20^th,  and c.400 in Broadhaven Bay, Co. Mayo on May 27th. But a group of c.300 off Portmuck, Islandmagee, Co. Antrim on Aug. 14^th suggest this expansion is not limited to the northwest.

Similar to 2022, a remarkable 27% of all harbour porpoise sightings came from Howth Head, Co. Dublin, from a single observer, whose land based photographic efforts have resulted in the establishment of a Harbour porpoise Photo ID catalogue, which is starting to produce interesting results in terms of documenting re-sightings of well-marked individuals, as well as several interactions suggesting “mating” behaviour among the areas harbour porpoises.  If we broaden the area to include all porpoise sightings in Co. Dublin, this represents 36% of all sightings of Ireland’s “smallest  whale” in 2023.

Harbour porpoise at Howth Hd. Co. Dublin being mobbed by Herring gull, Dec. 2023 © Dave O’ Connor

Figure 1. Harbour porpoise being mobbed by herring Gull 21^st Dec 2023, Howth Head, Co. Dublin, © Dave O’ Connor

Minke whales remain the only whale species that can be seen regularly in all Irish coastal waters. However, as usual the minke season kick started as early as late March with the expected build up in April along the south coast. While there were some impressive tallies in the west Cork and Kerry hotspots, the numbers in the southwest never reached anything like the dizzying heights of previous years. In fact the minke season peaked very quickly in May and June and after a poor July minkes numbers in the southwest seemed to thin out very considerably. That said the minke season was extended right up to the Christmas holidays with regular sightings of low numbers from Helvic Head, Co. Waterford.

2023 was the year our most charismatic whale, the humpback confirmed our suspicions of a very real range shift from the Irish Southwest to the Northwest waters.  Over the past 5 years the ratio of humpback sightings  in the northwest has almost doubled year on year, but as the numbers were still low, they didn’t really stand out. But 2023 saw the % of humpback sightings from the Northwest jump from around 19% to just over 60% and as many of these were animals we recognised from the WhaleTrack Project as regulars from Counties Cork and Kerry, we now have the evidence to confirm this change. Whether this is a temporary arrangement, or something more long term remains to be seen.

Figure 2: Map of all 2023 Humpback whale sightings © IWDG/WhaleTrack

The data shows no firm evidence of our largest coastal baleen whale, the fin whale following the humpbacks up the west coast as counties Cork and Waterford  between them accounted for almost 79% of fin whale sighting records in 2023. Having said that there were still fin whales showing up in some of the same areas where humpbacks were established in the northwest and it may only be a matter of time before the fin whales follow.

In Conclusion

Most sightings are submitted to IWDG online or on our free Reporting App, both of which require continuous support in order to keep abreast of the latest software updates and remain relevant. The impact of social media platforms such as Facebook, Twitter (now X) and Instagram on biological recording schemes is of ongoing concern. Up to relatively recently, www.iwdg.ie was really the only platform where people could show others what they were observing. However, now people will post their images or videos on their own platforms, and while a percentage of these will filter down to the IWDG, many presumably do not. Today’s image-rich social media environment has however greatly improved our ability to validate records to species level, which has improved from an historic 86.5% to 88% in 2023.

So, while the Sighting Scheme remains the country’s primary repository for validated cetacean sighting records, the state agency responsible for protecting our wildlife and habitats can’t assume that the biological recording schemes that underpin so much conservation and research can continue to operate indefinitely without central support. Goodwill, Citizen Science and a considerable voluntary effort can only take us so far, and a critical review of our sighting scheme remains a priority.

We’d like to take this opportunity to thank all our members for reporting their “casual” sightings to us, and to those effort watchers who put in so much dedicated time in carrying out more systematic watches from local sites. You have our respect and appreciation.

Humpback whales Aug. 7th 2023, bubblenet feeding, Donegal Bay © Gary Burrows

Pádraig Whooley – IWDG Sightings Officer