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Overlap between marine megafauna and maritime activities is a topic of global concern. Basking sharks (Cetorhinus maximus; CM) are listed as Globally Endangered under the IUCN, though reported sightings appear to be increasing in Ireland. While such trends in the region are welcome, increasing spatiotemporal overlap between CM and numerous water users poses an increased risk of boat strikes to the animals. To demonstrate the risk and impact of boat strikes on marine megafauna, we present camera-enabled animal-borne inertial measurement unit (IMU) data from a non-lethal boat strike on a CM within a proposed National Marine Park in Ireland. We tagged a ~7-m female CM in County Kerry, Ireland, which was struck by a boat ~6 h after tag deployment. Comparison of pre-strike data with 4 h of video and ~7.5 h of IMU data following the boat strike provides critical insight into the animal’s response. While the CM reacted momentarily with an increase in activity and swam to the seafloor, it quickly reduced its overall activity (i.e., overall dynamic body acceleration, tailbeat cycles, tailbeat amplitude, and vertical velocity) for the remainder of the deployment. Notably, the animal also ceased feeding for the duration of the video and headed towards deep offshore waters, which is in stark contrast to the pre-strike period where the animal was consistently observed feeding along the surface in shallow coastal water. This work provides insight into a CM’s response to acute injury and highlights the need for appropriate protections to mitigate risks for marine megafauna. [ABSTRACT FROM AUTHOR]

Abundance estimates are crucial for implementing effective conservation measures for large marine megafauna - particularly cetaceans. When combined with robust research methodologies, citizen science can provide a very useful tool to monitor large baleen whale populations, especially given their migratory nature, with individuals covering large areas typically exceeding the capacity of single research teams. The Irish Whale and Dolphin Group has been collecting humpback whale photo-ID data in the inshore waters of Ireland since 1999. The Group curates a catalogue that contained 120 individual humpback whales up to 2022. Most of these data were obtained through citizen science and the catalogue was built following robust methodologies and strict data-quality protocols. We used this photo-ID catalogue to derive the first comprehensive abundance estimates for the species in Irish waters using mark-recapture modelling techniques. We applied two approaches: (1) open population maximum likelihood mark-recapture models based on the POPAN formulation; (2) a multi-site mark-recapture model selection framework based on Bayesian inference. The first method yielded a humpback whale superpopulation size of 154 ± 9 (95% CI = 138-172, CV = 0.06) between 1999-2022, with annual abundance ranging between 2 ± 1 and 77 ± 8 individuals. The second approach provided annual abundance estimates from 3 ± 2 to 76 ± 11 for the same period. This study supports the idea of an increased presence of humpback whales in inshore Irish waters, especially during the last decade. Despite this increase, results also highlight the apparently very small size of the North Atlantic humpback whale subgroup occurring in the inshore waters of Ireland. [ABSTRACT FROM AUTHOR]

The article offers information on Short-Beaked Common Dolphins (Delphinus delphis) Observed Bow-Riding Basking Sharks (Cetorhinus maximus). It mentions bow-riding and lateral surface observations are incidental, they do demonstrate that common dolphins seek out and associate with species of interest when possible, seemingly to engage in playful behaviour.

Knowledge on the ecology of humpback whales in the eastern North Atlantic is lacking by comparison with most other ocean basins. Humpback whales were historically over-exploited in the region and are still found in low relative abundances. This, coupled with their large range makes them difficult to study. With the aim of informing more effective conservation measures in Ireland, the Irish Whale and Dolphin Group began recording sightings and images suitable for photo-identification of humpback whales from Irish waters in 1999. Validated records submitted by members of the public and data from dedicated surveys were analysed to form a longitudinal study of individually recognizable humpback whales. The distribution, relative abundance and seasonality of humpback whale sighting records are presented, revealing discrete important areas for humpback whales in Irish coastal waters. An annual easterly movement of humpback whales along the southern coast of Ireland is documented, mirroring that of their preferred prey: herring and sprat. Photo-identification images were compared with others collected throughout the North Atlantic (N = 8016), resulting in matches of two individuals between Ireland and Iceland, Norway and the Netherlands but no matches to known breeding grounds (Cape Verde and West Indies). This study demonstrates that combining public records with dedicated survey data is an effective approach to studying low-density, threatened migratory species over temporal and spatial scales that are relevant to conservation and management. [ABSTRACT FROM AUTHOR]

The article presents a study which investigated long-distance matches of bottlenose dolphins in Donegal Bay, Galway bay and Clew Bay in Ireland using photograph-identification catalogues. It is stated that dolphins from around the Irish coastal waters must be considered highly mobile and transient to relate its implications for the conservation and management of the species. The authors concluded that the resighting rate is high given that the sample size of individual bottlenose dolphins was relatively small.

Although killer whale (Orcinus orca) predation on humpback whales (Megaptera novaeangliae) is rarely witnessed, resultant scars on humpback flukes provide evidence of non-lethal interactions. Humpback whale photo-identification catalogs from the North Atlantic were used to evaluate humpback flukes (n = 10,957) for the presence and severity of killer whale scarification (e.g., rake marks, teeth indentations, missing tissue). Flukes were coded as none, light, moderate, or severe based on the extent of scarring. Even with increased sample sizes, especially for Norway and Iceland, the distribution of high-latitude humpbacks with killer whale scarring was consistent with prior studies: Atlantic Canada (21.7%), West Greenland (15.5%), Gulf of Maine (13.5%), Iceland (combined with East Greenland, 9.3%), and Norway (7.9%). For the first time, scarring rates are presented based on data from Ireland, Scotland, and England (11.0%) as well. Scarring frequencies generally differed between the eastern and western North Atlantic despite the co-occurrence of all migrating humpbacks in low-latitude breeding grounds, suggesting the occurrence of killer whale interactions in the distinct feeding grounds or along northward migration routes. While it was not possible to determine exactly where these interactions took place, the likelihood of a killer whale encounter and subsequent scar acquisition was greatest for humpbacks that feed in Atlantic Canada. [ABSTRACT FROM AUTHOR]