The blue mussel (Mytilus edulis) is a small, rope-farmed bivalve with a glossy blue-black, teardrop shell and plump, apricot-to-cream flesh inside. A filter feeder that hangs from socks and ropes in cool coastal waters, it needs no feeding — it strains its food straight from the sea, which is why it tastes so vividly of the sea. Sweet, faintly briny and savoury when steamed open, it is among the most sustainable and affordable shellfish in the world.