This report is a contribution to the Strategic Environmental Assessment (SEA7) conducted by the Department of Trade and Industry (now Department of Energy and Climate Change) and deals with the shellfish resources and their commercial fisheries within SEA7. Exploited species of shellfish are found in the SEA7 zone occupying all types of habitat and distributed over a considerable range of depths, from the littoral zone down to 1000m. These species provide important fisheries and make vital contributions to the economy of remote communities on the west coast of Scotland. The main species reviewed in this report are: Norway lobster; European Lobster; Crawfish; Edible crab; Velvet swimming crab; Shore crab; Red crabs; Giant scallop; Queen scallop; Cockle; Common mussel; Razor shells; Whelks; Periwinkle