Attacks by killer whales: what is happening to boats near Gibraltar coast, why are orcas ramming yachts?

Concerns have been raised about a group of orcas lurking around boats following a recent reported incidents, including one where a skipper valiantly defended his vessel against a killer whale attack.

Greg Blackburn was at the helm of a 46ft Bavaria, with tourists Stephen Bidwell and Janet Morris on board, when it was rammed by at least six killer whales earlier this month around seven miles from Tangier, in Morocco.

The incident, which hasn't put Blackburn off from venturing back into the water, is not the only time sailors have experienced rough company in the area, with reports of a vengeful killer whale called White Gladis leading the charge.

Why are killer whales attacking boats?

Blackburn, 32, from Pontefract, West Yorks, said he had heard of at least six more boats that have been subject to orca attacks since his ship was targeted on 2 May. But there is a simple explanation - overfishing in the area, according to Blackburn.

He said: "I personally believe that they see boats taking their food reserves and they are simply trying to protect it as we would any harvest of our own. It's quite clear when you see the amount of fishing in the area and you learn from locals about the fishing skiffs that have been attacked. There has to be a reason why they are doing this - and I think it's because the blue-finned tuna they live on is becoming endangered."

And added: "There is a real risk of this behaviour becoming more of a problem. It's a concern for the future that if other pods engage with this one and the behaviour is passed on it could be come a problem on a much larger scale. There is still a high percentage of vessels getting through untouched by the orcas. When you look at it statistically, it’s just sometimes your luck runs out - as did mine."

Blackburn recommended anyone in doubt of going back into the water can put their mind at ease by checking orca watching sites that track their movements and get information about safe routes that have been used.

"The sheer power these animals possess is awe inspiring, the way they move through the water and work together as a team is something to behold. There’s nothing you can do in the situation but just wait until they have finished," said Blackburn, who along with Cambridge couple Janet and Stephen, had to endure an hour-long attack before finding safety.

Who is White Gladis?

White Gladis is the nickname given to what some researchers are calling one killer whale, dubbed the leader of the pack, who is teaching other whales how to go after boats.

It is thought that Gladis had a bad experience herself - possibly having been tangled up in illegal fishing nets or collided with a boat - leading to her aggression towards boats.