COLOMBO — When fishermen in southern Sri Lanka recently caught a giant oceanic manta ray, they needed a backhoe to haul it out of the water once they reached land. Weighing 800 kilograms, or nearly 1,800 pounds, the catch drew much local attention. It sold for 170,000 rupees, or about $470, and soon this endangered animal, Mobula birostris, was cut up into a pile of meat. This isn’t an unusual occurrence in Sri Lanka, where artisanal fishers catch and kill a large number of manta and devil rays, known collectively as mobulid rays, every year. A study published last year calculated that this an…