A collision between a boat and a basking shark has been recorded for the first time, meaning either that researchers were lucky to capture the footage or that the incidents are more common than previously believed. Experts say more monitoring is needed to quantify the problem and that boats should be forced to follow a code of conduct to keep the sharks safe.
Alexandra McInturf at Oregon State University and her colleagues tagged a 7-metre female basking shark (Cetorhinus maximus) off the coast of Ireland on 24 April with a device that records movement in three axes, depth, position and video.
McInturf says only one shark at a time was tagged due to the high cost of the sensors, and that they only stay on a shark for up to 12 hours at a time, so capturing a collision may be indicative of the frequency of incidents.
In the video, the shark can be seen feeding on the surface before making sudden evasive moves and then colliding with a boat. The animal then seems to panic and rapidly dive down and out to sea, stopping only when it reaches the seabed.
Images from a camera attached to a basking shark before, during and after a collision with a boat
Big Fish Lab at Oregon State University.
The tag automatically released around 7 hours after the collision and researchers noted that the shark did not resume feeding or normal behaviour in that time. Video showed visible damage to the shark’s skin, paint marks and abrasions but no apparent bleeding or open wound. The researchers do not know if it recovered.
The species is considered endangered around the world, but it congregates in large numbers off the coast of Ireland – where an area of 28,000 hectares of land and sea on the coast of County Kerry was recently designated as the nation’s first national marine park. A voluntary code of conduct that limits speed and proximity to sharks is followed by some boats, but McInturf would like to see this become mandatory and for larger studies of basking sharks to properly quantify the problem.
“We certainly see evidence of boat strikes on the sharks. We’ve seen a shark come back year after year that has these massive prop marks in its fin,” says McInturf. “This was the first glimpse into the fact that this actually could be a lot more prevalent than we thought.”
“I don’t want to villainise the fishing boats. I think it’s an honest mistake. However, I do think there needs to be legally enforceable codes of conduct around these animals,” says McInturf.
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