This is the first volume of a three-volume field guide covering the species of interest to fisheries of the major marine resource groups exploited in FAO Fishing Area 31. The marine resource groups included are the bivalves, gastropods, cephalopods, stomatopods, shrimps, lobsters, crabs, hagfishes, sharks, batoid fishes, chimaeras, bony fishes, sea turtles and marine mammals. Fish families that are less important to fisheries are covered but with abbreviated accounts. The important families are treated in detail and include the species name, frequent synonyms and names of similar species, an illustration, FAO common name(s), diagnostic characters, biology and fisheries information, notes on geographical distribution and a distribution map.