Rare drone footage shows basking sharks engaged in what is thought to be courtship behaviour off the Co Clare coast.

The footage, captured last month, shows up to nine sharks circling a rigid inflatable boat piloted by researchers from the Irish Basking Shark Group.

"It was methodical, orchestrated behaviour, as if they were doing synchronised swimming," said Simon Berrow from Galway-Mayo Institute of Technology and the IBSG.

The world's second largest fish is often seen feeding in this area in the spring.

"But we realised immediately that they were not feeding. This was something else, something special,"  Dr Berrow said. 

The basking shark is the world's second largest fish, typically reaching 8m in length.
(Image: Irish Basking Shark Group)

Basking sharks are harmless plankton feeders.

They are unprotected in Irish waters but the IBSG is working to change that.

Little is known about their courtship behaviour and reproduction cycles.

Nose-to-tail following, parallel swimming and breaching are all theorised as being linked to courtship. 

The research team collected a number of DNA samples during the encounter.

The IBSG were able to collect a number of DNA samples during the encounter. 
(Image: Irish Basking Shark Group)

"This spring we collected over 60 samples from sharks off West Clare. So to get a further opportunity to take more samples, in the same location but at a different time of the year, was just too good to miss," said Dr Berrow.

"By using the drone, we were also able to get a fantastic perspective of the shark from above. We were on a 6m rib and estimate that they were 6-8m in length. It was just such a humbling experience. Everyone on board will remember it."