European Spider Crab

Photo: BuceoPortosub · CC BY-SA

The Ons sector hosts one of Galicia's most spectacular wildlife events — the massed moult and mating aggregation of European spider crabs in late spring and early summer, when thousands of animals gather in shallow water in dense, climbing piles. Outside aggregation season solitary individuals are still common across the entire reef, serving as important prey for large cephalopods and otter populations on the islands above.