The cod is a large marine fish with khaki green back with small, yellowish spots and a creamy silver underbelly. It has a distinctive barbel under its chin. It is a versatile fish with good flavour and cooking properties. The young are called codling and are of a size to be sold whole. There is an obscure variety called torsk. Cod is related to hake, haddock, coley, ling, pollack and whiting. In common with haddock, the cod has been overfished and is an endangered species. There is much pressure on the British public to eat other fish in its place. Some supermarkets are now even offering free fish to promote other perfectly edible, better than edible, types of fish. So that if you go to the fish counter and ask for cod you might be asked if you would like to try megrim or coley instead.
Much cod is dried. The original treatment of whitefish, particularly cod, was to dry them, in which form it is called stockfish. The water content is reduced to less than a fifth so that the ratio of dried to fresh fish is 5 times. As salt became more readily available the practice changed and the fish was only partially dried before being coated in salt. The ratio of fresh to dry weight of salt cod is only about 3½. Large amounts of salt cod are produced particularly by Newfoundland in Canada, Norway and Iceland and much is exported to Portugal, where it is extremely popular, France, Spain and Italy.
Salt cod is much eaten during Lent in Catholic countries, it must be soaked for 24 hours or more before use, with occasional changes of water. It can often be purchased ready soaked on Fridays.