New study shows Irish waters offer important refuge for endangered basking sharks

A NEW STUDY published today reveals that Irish waters have become an important habitat to the endangered basking shark.

Basking sharks are the second-largest shark species, growing to more than 11 metres in length.

Despite their size, they feed almost exclusively on tiny plankton filtered from seawater and are harmless to humans.

However, following centuries of targeted hunting and more recent pressures including accidental capture in fishing gear, ship strikes and habitat degradation, the species is now classified as endangered.

The study published today shows that Ireland’s waters provide an important seasonal refuge for the endangered basking shark, while the species has declined in many other parts of the world.

Drawing on almost 50 years of reported basking shark sightings around the Irish coast, researchers identified several long-standing hotspots where shark returns year after year.

The researchers also found that both the number of reported sightings and the size of shark groupings have increased over time.

This includes waters around the Blasket Islands in Co Kerry, the south coast of Co Cork, and the Inishowen Peninsula and Malin Head in Co Donegal.

The research, published in the journal Endangered Species Research, analysed 2,718 basking shark sightings recorded between 1978 and 2024 to investigate how the species uses Irish waters and the environmental conditions that influence its seasonal movements.

The study involved researchers from University College Dublin and the Irish Basking Shark Group.

It found that basking sharks return to Irish waters predictably each year, with sightings peaking during the spring and summer months, likely reflecting seasonal peaks in the plankton they feed on.

Lead author of the study and coordinator of the Irish Basking Shark Group, Dr Alexandra McInturf, remarked that the results “bode well for the status of their population and suggests that Ireland offers important habitat for this globally endangered species”.

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McInturf also noted that the study would not have been possible without thousands of sightings submitted by members of the public and that this “really speaks to the power of including members of the public in research and conservation efforts”.

Meanwhile, Dr Ruth Leeney, UCD School of Biology and Environmental Science and Irish Basking Shark Group, remarked that it’s “difficult to know what has driven the increasing number of basking shark sightings in Irish waters in recent years”.

She added that the increase “may be due, at least in part, to natural phenomena such as a shift in key feeding areas used by basking sharks in the northeast Atlantic, or changes in other behaviours”.

Speaking to The Journal, Leeney said there is a “long-standing interest” among the Irish public in reporting marine animals and that “this kind of study just wouldn’t be possible without those reports from the public”.

“It speaks to how important it is to ensure that that science isn’t just about scientists, but is about the public as well,” added Leeney.

She added that it is “remarkable” that there are so many basking sharks in Irish waters “given there was a hunt in Irish waters for basking sharks for so many years, and yet they’re still coming back”.

Meanwhile, Leeney said the study highlights that Ireland has a “responsibility to ensure that we maintain our ocean in a state that continues to support these habitats”.

“There are a lot of good reasons why we should maintain the health of our oceans, but this is just one more reason because we know globally, basking shark populations have disappeared completely from areas where they used to be very numerous”.

Leeney said the Irish Basking Shark Group also feel a “responsibility to publicise how important Irish waters are for the species”.

Elsewhere, Leeney described the basking shark as a “gentle giant” and noted that they are not associated with the “negative narrative of fear” that is attached to other sharks.

“Even though we know sharks kill very few people every year compared to other things like mosquitoes and hippos, sharks can often have a bad name.

“I think basking sharks turn that narrative on its head because they’re really large animals, but they are known to be gentle giants.

“They are plankton feeders, so they’re not top predators, and they’re beautiful to watch and something that people are very clearly fascinated by.

“The fact that we have them reliably in Irish waters, and have done so for the last few years, is a really exciting thing that has brought people here to see them.”