Celtic Mist Scientific Report

During the 2023 season the IWDG conducted surveys onboard R.V Celtic Mist in Partnership with Fair Seas within two Areas of Interest (AOI) highlighted in the Revitalising Our Seas report: the Southwest Coast and Loop Head to Kenmare River AOI’s. This survey programme was designed to capture the maximum amount of data within these areas and increase our knowledge of the marine life within these sites.

Read the full report here: Celtic Mist Scientific Report

IWDG members joined us onboard throughout the season and were trained in cetacean survey techniques upon joining the vessel by IWDG’s full-time onboard biologist. Visual watches are undertaken by the marine using standard line transect methodology for cetaceans whenever sea conditions are suitable. Photo identification techniques were also undertaken and information was gathered on key anthropogenic impacts.

Overall results

During the 2023 season, which ran from between April and September, nine week-long surveys took place, with an addition three surveys focusing on the Shannon Dolphin population (data collected during these surveys were not included in this report). Surveys started in Kinsale, Co. Cork, and finished in Kilrush Co. Clare. In total, Celtic Mist travelled 3214.4 km, with 2332.9 km whilst observers were ‘on effort’ (Figure 2), the majority of which was conducted with two observers (2004.7km). Surveys were carried out in coastal waters over the whole of the southwest coastline, with effort concentrated around the departure/arrival ports of our surveys, including Cork Harbour, Bantry, Co. Cork.

Effort conducted per 100km² onboard Celtic Mist during 2023.

During the season we recorded 462 sightings of 11 different species of marine megafauna: seven species of cetaceans, two pinniped and two fish species. Common dolphins (Delphinus delphis) were the most sighted species making up 48% of the total sightings, followed by grey seals at 22%, and minke whales at 12%.

Key Findings

  • Species richness mirrored the Revitalising Our Seas report, with the highest levels of biodiversity observed within the Southwest Coast AOI.
  • Harbour porpoise sightings were low throughout the survey area despite both AOI surveyed including an existing SAC with harbour porpoise as a qualifying feature. Whilst further analysis is required to incorporate effort, this finding is part of a wider picture occurring in Irish waters, with declining numbers of harbour porpoise in inshore waters observed during other surveys within three separate SACs: Roaringwater Bay (O’Brien and Berrow
    2020), Rockabill to Dalkey Island (Berrow et al. 2021) and the Blasket Islands (O’Brien et al. 2022).
  • Numbers of large baleen whales were low in both AOI with only eight sightings of fin whales within the Loop Head to Kenmare AOI and no sightings of humpback whales recorded in the whole survey area. This year the IWDG’s Cetacean Sighting Scheme identified  northward shift in humpback whales, with most sightings reported in Co. Sligo and Co. Mayo. Effort corrected data from the surveys onboard Celtic Mist helps to confirm this change in distribution. It also highlights how different data collection methodologies can and should be used in combination with one another.
  • New data collection methodologies to map anthropogenic threats were trialled throughout the season. Marine litter and pots numbers were recorded and amendments to the data collection were made when necessary to improve protocols. Monitoring within candidate MPAs should include human impacts and these methods will continue onboard Celtic Mist in future seasons.

Volunteers and Crew

None of the data collection would be possible without the volunteers and crew who dedicate their time in all aspects of the trips, as well as the huge effort it takes to maintain the vessel. This year we had 66 volunteers come onboard the research surveys, including 16 skippers and first mates. Thanks to everyone who joined us onboard in 2023!

We also had five Fair Seas personnel join us onboard who assisted with data collection. Dr Donal Griffin, Fair Seas Coordinator summarised the spirit of Celtic Mist after he came onboard with us this year:

What stood out to me over the course of the week was not only the upbeat, positive, and cheerful attitude we all seemed to share, but how many times the word ‘volunteer’ cropped up in our conversations. The levels of volunteerism among the crew were through the roof.

What’s next?

Due to the success of last years surveys Celtic Mist these surveys have continued. This year we will be surveying the waters of the west coast. Concentrating on three new Areas of Interest (AOI)  including Galway Bay and Islands, Mayo to Shelf Edge, Donegal to Sligo AOI. All trips are currently fully booked but there is a waiting list for each survey. If you are interested head to our Sail with Us page.


Becky Dudley,

IWDG Science Officer