Others become entangled in fishing rope, a particularly grotesque phenomenon since the thick ropes can rub through a whale's skin and hit bone.

CNN: Endangered right whales appear to be on the rebound

During the journey back to Tobermory, the fishing boat's bridle, to which the tow rope was attached, broke.

BBC: Tobermory lifeboat in 11-hour rescue drama

The tow rope snapped, however, in heavy seas and the fishing boat went aground on rocks.

BBC: Tobermory lifeboat in 11-hour rescue drama