Trade of bivalve mollusks is an economic activity of crucial importance in many coastal areas in the world, particularly in developing countries, which continue to account for the bulk of world exports of fish and fishery products, including bivalves. Toxic episodes caused by the presence of marine biotoxins, produced by some phytoplankton species, have a direct impact on the production and commercialization of marine bivalves worldwide, on Shellfish harvesters and the aquaculture industry and on coastal economies and on human health. Clams, cockles, and ark shells constitute the economically most important group of bivalves. Oysters are the second most important group of bivalves in terms of production and trade Scallops are highly priced bivalves. Global production of scallops has constantly increased in recent years, from 1.8 to 2.5 million tonnes between 1997 and 2010. Toxic episodes have detrimental economic impacts on Shellfish harvesters and the aquaculture industry and on coastal economies and on human health.