This report is a contribution to the Strategic Environmental Assessment (SEA5) conducted by the Department of Trade and Industry (now Department of Energy and Climate Change). Eight marine mammal species are known to occur regularly in this area: grey seal, harbour seal, harbour porpoise, white-beaked dolphin, bottlenose dolphin, Atlantic white-sided dolphin, killer whale, and minke whale. Long-finned pilot whales and Risso's dolphins are regularly seen in waters around Shetland. There are occasional at-sea records of at least a further five cetacean species (humpback whale, fin whale, sperm whale, striped dolphin and short-beaked common dolphin) and four pinniped species (hooded seal, bearded seal, ringed seal and walrus).