Odontaspis ferox is a species rarely encountered by humans because it is primarily distributed in deep offshore waters exceeding 100 meters. While this species has been found in various temperate and tropical seas worldwide, its distribution was believed to be limited to the Bay of Biscay in the eastern Atlantic. Consequently, scientists were astounded to observe its presence much further north in Ireland.

The discovery of the shark was thanks to the vigilance of a Swiss tourist who stumbled upon it and promptly notified Dr. Nicholas Payne, a prominent shark biologist and assistant professor in Trinity’s School of Natural Sciences. Dr. Payne, accompanied by Dr. Jenny Bortoluzzi and PhD candidate Haley Dolton from Trinity, as well as UCD scientist Kevin Purves, rapidly gathered measurements and samples before the tide advanced. Their aim was to gain insights into the biology and cause of death of this uncommon species.

Their research findings have recently been published in the Journal of Fish Biology.

Dr. Payne expressed his surprise, saying, “When a smalltooth shark washed up on the south English coast two weeks before the Irish one, we all found it highly unusual given the northerly location. The subsequent discovery of a second one in Ireland soon after raised even more concern.”

Further analysis revealed that the sea bottom temperatures across the Celtic Sea and The Channel were unusually elevated during the summer of 2022 and remained warmer than average throughout early 2023. This evidence led the researchers to suggest that the unseasonably warm conditions were responsible for bringing these individuals from lower latitudes into waters that were previously beyond their thermal range.

Considering the projections indicating a continued warming of sea temperatures around the UK and Ireland, the researchers anticipate an increase in sightings of this species and others traditionally associated with more tropical habitats.

Smalltooth sand tiger sharks, which pose no threat to humans, are currently categorized as “vulnerable” by the International Union for the Conservation of Nature. Although not specifically targeted by commercial fisheries, they face potential risks such as bycatch or pollution. The size of females in this species is typically around 15 ft, making the Irish specimen, a female, close to the upper limit of their size range.

The dissection of the shark was aided by Dr. Jenny Bortoluzzi, who expressed her excitement at the opportunity to collect numerous high-quality samples that contribute to our understanding of the species’ biology and ecology. She also noted the importance of public involvement, as this discovery was initiated by a member of the public. Encouraging public engagement can increase awareness and aid in future similar observations.

Despite gathering a wealth of data from the stranded sharks, the cause of their demise remains a mystery on this occasion. Their overall body condition was good, suggesting they were not malnourished, and there were no signs indicating recent capture or injuries on the Irish specimen.

The Irish part of this research project received support from Science Foundation Ireland and the Irish Research Council, while the UK component was funded by the Cetacean Strandings Investigation Programme, Research England, and the Natural Environment Research Council.