Shellfish

Shellfish is a colloquial and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater environments, some are found in freshwater. In addition, a few species of land crabs are eaten, for example Cardisoma guanhumi in the Caribbean. Shellfish are among the most common food allergens. Despite the name, shellfish are not actually fish, but are simply water-dwelling animals. Most shellfish are low on the food chain and eat a diet composed primarily of phytoplankton and zooplankton. Many varieties of shellfish, and crustaceans in particular, are actually closely related to insects and arachnids; crustaceans make up one of the main subphyla of the phylum Arthropoda. Molluscs include cephalopods (squids, octopuses, cuttlefish) and bivalves (clams, oysters), as well as gastropods (aquatic species such as whelks and winkles; land species such as snails and slugs). Molluscs used as a food source by humans include many species of clams, mussels, oysters, winkles, and scallops. Some crustaceans that are commonly eaten are shrimp, lobsters, crayfish, and crabs. Echinoderms are not as frequently harvested for food as molluscs and crustaceans; however, sea urchin roe is quite popular in many parts of the world, where the live delicacy is harder to transport. The term “shellfish” is used both broadly, specifically and broadly. In common parlance, as in 'having shellfish for dinner', it can refer to anything from clams and oysters to lobster and shrimp. For regulatory purposes it is often narrowly defined as filter-feeding molluscs such as clams, mussels, and oyster to the exclusion of crustaceans and all else. Although the term is primarily applied to marine species, edible freshwater invertebrates such as crayfish and river mussels are also sometimes grouped under the umbrella term 'shellfish'. Although their shells may differ, all shellfish are invertebrates. As non-mammalian animals that spend their entire lives in water they are 'fish' in an informal sense; however, the term ”finfish” is sometimes used to distinguish fish, animals defined by having vertebrae, from shellfish in modern terminology. The word 'shellfish' is both singular and plural; the rarely used 'shellfishes' is sometimes employed to distinguish among various types of shellfish. Archaeological finds have shown that humans have been making use of shellfish as a food item for hundreds of thousands of years. In the present, shellfish dishes are a feature of almost all the cuisines of the world, providing an important source of protein in many cuisines around the world, especially in the countries with coastal areas.