Researchers outfitted 169 seabirds with radar detectors to pinpoint vessels that had turned off their transponders.

Galicia has agreed to a cull of the creatures, which are turning up in unusually large numbers and feasting on the region’s key exportGalicia, in north-west Spain, has declared war on an apparently inoffensive creature that is putting livelihoods under threat.The region’s shellfish farmers say that an unusually large population...