What is killing the octopus of Vila Nova de Gaia? That question has obsessed the Portuguese city, located just across the Douro river from Porto, since Jan. 2, when 1,100 lbs. (500 kg) of dead octopus were found on a 1.8-mile (3 km) stretch of local beach. The following day, another 110 lbs (50 kg) appeared; today there was just one expired creature. “It’s very strange that so many should be killed, and in such a confined area,” says Nuno Oliveira, director of the Gaia Biological Park, a nature refuge on the outskirts of Vila Nova de Gaia. “There’s nothing in the scientific literature for this kind of mass mortality among octopus.”Dead Octopuses Wash Up on Portuguese Beach