Seán A. O'Callaghan

• Master of Science
• PhD candidate at Atlantic Technological University

Close‐range photogrammetry (CRP) is a well‐established technique to retrieve quantitative information from objects using photography. CRP is often used in morphology studies when the direct handling of individuals is unpractical or unethical, or to reduce processing costs and time. Although multiple software to extract quantitative information from...

Sowerby's beaked whale is a deep-diving cetacean species specialized to live in the deep waters of the North Atlantic, including offshore Irish waters. Sightings of Sowerby's beaked whales in this area are infrequent and a substantial increase in our knowledge of their presence comes from recent static acoustic monitoring (SAM) and passive acoustic...

Drones have become a crucial research tool across marine environments over the past decade, being specifically useful in marine mammal research. Fin whales (Balaenoptera physalus) have been monitored feeding along the Catalan coast, Spain (NW Mediterranean), since 2014. To overcome issues such as the distance between a whale and a research vessel o...

Photo-identification is a staple tool used in cetacean conservation studies since the 1970s to monitor individuals on a regional and ocean basin-wide scale to infer critical information about habitat use, suitability, and shifts. This technique has been extensively used on sperm whales globally since it was developed in 1982, initially using the ta...

Measurements from 106 stranded short‐beaked common dolphins along the Irish coast were taken between March 2017 and March 2023. Data were collected from the Irish Necropsy Project and Irish Cetacean Stranding Scheme. Total length measurements were gathered from 103 individuals where the tail flukes were still attached. These ranged between 96–238cm...

Animal morphometrics are essential to understand a species life history, as well as the ecological relationships of the species and the environment. This study explored humpback whale (Megaptera novaeangliae) maturity and body condition across the Northeast Atlantic using Uncrewed Aerial System (UAS) photogrammetry. We used morphometric data collec...

Social group cohesion can identify anti-predator tactics, since it is a protection measure in group living animals. Changes in group cohesion have been documented in dolphins exposed to vessel-induced disturbance which indicates a potential fear response. Dolphin group cohesion has previously been analyzed qualitatively since obtaining fine-scale s...

Sperm whales spatially segregate by sex and social behavior as they mature. In the North Atlantic, male whales move to higher latitudes as far as Svalbard at 80° N, while females and young whales typically remain around lower latitudes below 40–45° N. The Azores, Madeira, and the Canary Islands constitute important nursery grounds for female and yo...

The Lakes of Killarney are natural features of great importance to Ireland, both from a biodiversity and tourism perspective. Three interlinked glacial lakes occur in the Killarney Valley; Lough Leane, Muckross lake and the Upper Lake. These lakes provide an important habitat for a variety of fish species. However, there have been infrequent sighti...

Long-finned pilot whales (Globicephala melas) are a widespread, highly social deep-diving cetacean species ranging from the sub-tropics to the High Arctic. Information on this species’ life history at higher latitudes is limited. Opportunistic observations of pilot whale calves were made in the spring and summer of 2020, summer of 2022 and spring o...

The increase in the use of unmanned aerial vehicles (UAVs) in marine mammal research has raised concerns, as its potential impacts remain largely unknown. To assess the effects of disturbances on harbor seals by a DJI Phantom 4 Pro, behavioral responses were recorded before, during, and after UAV approaches at two colonies. GLMMs were applied to as...

Three male sperm whales (Physeter macrocephalus) stranded on the island of Andøya in northern Norway in 2020. This created an opportunity to do gross necropsies with a focus on stomach contents as the diet of sperm whales in Norwegian waters is poorly understood and also to study potential presence of marine debris. Four new prey types for sperm wh...

Ship strikes are a widespread conservation issue for many cetacean species globally. Population level impacts depend on the occurrence and severity of collisions, which may lead to life altering injuries or fatalities. Such impacts are a major concern for large, long-lived, and reproductively slow species like the fin whale. Since 2014, a seasonal...

Irish coastal waters are an important feeding area for marine mammals, seabirds and a variety of fish megafauna species. A multidisciplinary survey evaluated this feature in the summer of 2019.

North Atlantic right whales (Eubalaena glacialis) once occurred seasonally in Irish waters but in recent decades their presence has declined. This study reviews the existing literature to develop an understanding of the past distribution of North Atlantic right whales, their abundance, temporal occurrence, interspecies associations and apparent use...

Acoustic surveys on blue whiting (Micromesistius poutassou) spawning aggregations in the north east Atlantic have been carried out by the Institute of Marine Research (IMR) Norway since the early 1970s. The 2017 survey was part of an international collaborative survey using the vessels RV Celtic Explorer (Ireland), RV Tridens (Netherlands), FV King...

The WESPAS survey program is the consolidation of two existing survey programs carried out by FEAS. The Main Shelf herring acoustic survey has been carried out annually since 2008 and reports on the annual abundance of summer feeding aggregations of herring to the west of Scotland and north of Ireland from 54N to 59N. The boarfish survey has been c...