Commercial fishing is a worldwide enterprise that involves the capture of ocean and freshwater fish, shellfish, and marine mammals, and their processing for market. Fishing equipment ranges from small boats whose nets are cast and hauled in by hand to factory ships equipped with the most advanced technologies for finding, harvesting, and processing huge quantities of fish. These large catches are made at heavy expense, however, not only in the cost of the equipment (some advanced fishing vessels are nearly as expensive as modern warships) and fuel, but also in the potential depletion of fishery resources. The major portion of the total fish harvest consists of relatively few ocean species, which are divided into two groups. Pelagic species--those which inhabit the near-surface layers of the oceans--include several species of herring, tuna, salmon, anchovies, pilchard, sardines, menhaden, and mackerel. Demersal species--fish that inhabit the areas near the ocean bottom--include cod, sole, halibut, haddock, hake, and flounder. Large catches are also made of a group of fish classed commercially as \Tshellfish\t--shrimp, lobster, scallops, oysters, clams, crabs, mussels, and squid. The most important marine mammal is the whale. Although \Twhaling\t is a specialized area within the fishing industry, it has lost most of its former importance. Almost all large pelagic and demersal fish catches are made over the continental shelf, the underwater plateau surrounding the continents and large islands. In these waters temperatures, water depths, and the currents that influence the quantities of available food create an environment that is highly favorable to the existence of large schools of fish. The animals living in and on the bottom of the continental shelf serve as additional food sources for demersal fish. Furthermore, most species spawn on continental shelves, and the main nursery grounds of many species are also in coastal regions. The main fishing grounds are located on the wider continental shelves of the mid and high latitudes. These include the Grand Banks, Bering Sea, and North Sea, the resources of which are exploited by many nations. THE DEVELOPMENT OF THE FISHING INDUSTRY Prehistoric peoples were hunters and food collectors, and they found much of their food in lakes, rivers, and shallow coastal ocean waters. Shellfish were the most accessible food fish, and the large shell heaps found throughout the world bear witness to the first fishing technique, the use of bare hands. During the Mesolithic Period (c.10,000 BC-6000 BC) certain cultures that depended almost entirely on a diet of fish developed primitive fishing technologies. The Scandinavian Maglemosian culture, for example, used stone-pointed fishing spears, stone fishhooks, fishing lines and nets, and bone harpoons. Improved equipment increased the size of catches, and preservation techniques were developed for drying, smoking, salting, and pickling fish. As larger fishing craft were built, vessels ventured farther into the oceans, and sea fishing developed into a well-defined vocation, with ports of supply, markets, and villages whose central occupation was the catching of fish. Early ocean fisheries were confined to the coastal regions of settled areas and to the Mediterranean Sea, which had been the traditional fishing grounds for large numbers of fish species, especially tuna. Gradually, the rich fishing regions of the Atlantic Ocean and the North and Baltic seas began to be exploited. The opening of these new fishing grounds had a significant influence on the spread of trade during the Middle Ages and on the establishment of new trade routes--for example, the herring fisheries in the southern Baltic and North Seas that helped to establish the \THanseatic League\t. The opening of the North Atlantic fishing areas around Nova Scotia and Newfoundland had a considerable effect on European history. First fished by the French in the early 1500s, by the beginnings of the 17th century fish from the North Atlantic fisheries became the principal source of New World wealth for England. PRINCIPAL FISHERIES The most important world fisheries are located close to land in waters less than 400 m (1,300 ft) in depth. The major fishing grounds are in the North Atlantic (including the \TGrand Banks\t and the Georges Banks off the New England coast), the North Sea, the waters over the continental shelves of Iceland and Norway, and the Barents Sea; in the North Pacific, particularly the Bering Sea, the Gulf of Alaska, and the coastal areas around Japan; and in the Pacific waters off the coasts of China and Malaysia. Other important fishing grounds are found off the Peruvian coast and off the coast of the southeastern United States. Fishing is often restricted to the spawning periods of a particular species, when the fish aggregate on spawning grounds. Fortunately, different stocks of the same species often have different spawning times on different grounds, and this fact enables the fishery to be extended over longer periods. For example, the Norwegian "spring herring" gathers for spawning mainly in January and February; the "big herring" (storsild) spawns in September to December. The herring stock size caught along the Norwegian coast has fluctuated throughout the centuries, and documents indicate that from about 1500 there have been four good herring periods, each lasting from 50 to 80 years. The last good period began about 1885 and declined rapidly in the late 1960s. At present, herring stocks throughout the North Atlantic are low, and their harvesting is regulated internationally through national quotas. Another example of a seasonal fishery is the Norwegian cod fishery, where cod migrating to the Norwegian coast to spawn are harvested in the winter, and immature cod from the Barents Sea are caught in the spring as they migrate to feed in the regions off the coast of Finnmark, the Norwegian province bordering the Arctic Sea. The local fisheries of the African coast, and many of those found elsewhere in the tropics, remain relatively undeveloped. The principal limiting factors are: first, the narrowness of the continental shelf, which limits the presence of demersal fish, and the existence of a straight coastline that offers few possibilities for good harbors; second, the high temperatures, which affect the keeping quality of the fish catch; and third, limited access to the interior, making marketing difficult. Fish landings are usually dried, smoked, or salted immediately. Major Fishing Countries Catches of fish and shellfish throughout the world have risen within the decade of the 1980s from about 77 million metric tons (1982) to over 90 million metric tons (1986). Almost half the catch, 40.5 million metric tons, is taken by Asian countries, principally Japan, which today captures the world's largest catches. The \TUSSR\t follows Japan; China is third, but with a catch only half the size of the Soviet catch; and the United States and Chile share fourth place. The total catch of marine fish and shellfish in the United States throughout the 1980s averaged about 3 million metric tons annually. About one-quarter of the marine fish catch is taken in the Northwest Atlantic, some 40% in the Southwest Atlantic and Gulf of Mexico, and another quarter in the Northeast Pacific and Alaskan coastal waters. Tuna and shrimp are the most valuable catches. The haddock fisheries of the New England coast is another important fishery, although haddock landings have decreased sharply in recent years because of overfishing. The same fishery yields cod and flounder. Salmon and halibut are harvested in the Northeast Pacific, and the anchovy fishery off the coast of California produces fish for processing and for live bait. About 250,000 fishermen are engaged in marine fisheries in the United States. Most U.S. fishing vessels are smaller than 50 gross tons and less than 20 m (65 ft) long. There are only a few hundred vessels of significantly larger size in the U.S. fleet. Principal fishing ports are San Pedro, Calif. (tuna), Kodiak, Alaska (crab and groundfish), and Cameron, La. (menhaden). The profitable crab fishery in the Bering Sea collapsed in 1983 and is not expected to yield higher catches until the mid-1990s. Much of the crab fleet were converted to trawlers, which yielded higher catches of Pacific cod and pollock in joint venture fisheries with foreign processors (mainly Japanese and Soviet). The catches of Pacific salmon have decreased in recent years despite increased efforts in release of smolt (young salmon) produced in coastal hatcheries. FISHING TECHNOLOGIES In most modern fishing fleets the basic fishing vessel is the trawler, equipped with a diesel engine and outfitted with a variety of equipment for fish finding and capturing. Echosounders and sonar devices detect the presence of fish in waters up to 400 fathoms deep (730m/3400 ft) and are also used to ascertain water depths and the roughness of the ocean bottom. Airplanes are used to scout scattered shoals of pelagic fish. Fish Harvesting The standard methods of catching fish involve either nets, hooked lines, or traps. Pelagic fish are most often harvested using purse seine nets, which are set in a wide circle around the shoal and then closed (or pursed) and drawn up. Straight drift or gill nets--whose mesh is just large enough to allow the heads of fish to pass through while trapping them at their gills--are used to catch salmon, tuna, cod, and other fish. (Since the 1980s, however, the use of immense assemblies of drift nets has exacerbated the overfishing of valuable fisheries and caused the accidental deaths of thousands of such non-commercial species as porpoises.) Demersal fish may be netted in otter trawl nets pulled along the ocean bottom, or with beam trawls that are used in more shallow waters, primarily for shrimp. In halibut fishing, hooked groundlines, called longlines, may reach lengths of many miles, with baited hooks attached at intervals of 6 to 9 m (20 to 30 ft). Floating longlines are used primarily in tuna and salmon fishing, as are trolling lines, shorter lines that are towed behind a moving boat. Lights may be lowered into fresh and brackish waters to attract fish, which are then sucked up into the ship by powerful vacuum pumps. Fish Processing Large fishing vessels on long voyages are equipped to keep their catch edible by storing it in refrigerated facilities or by quick-freezing it. A fully equipped factory ship will also have machinery on board for fish filleting and freezing or canning. Fish fillets are frozen at sea into large blocks weighing up to 45 kg (100 lb); these are later reprocessed on shore into individual portions. Some ships may also have facilities for drying and grinding fish into fish meal. Factory ships are huge vessels operated by crews of 500 to 650 and accompanied by their own fleets of smaller ships called catcher boats. FISHERIES MANAGEMENT As early as the 1890s it was acknowledged that fishery resources are limited and that they must be managed through international agreements. In 1902 the International Council for the Exploration of the Sea (\Lice\ls) was formed by the major European fishing countries. The founding of \Lice\ls led to several conventions for the regulation of fisheries by mesh size of nets and by quotas, in order to obtain "maximum sustainable yields"--the highest yields consistent with the maintenance of fish stocks. Although such conventions have been effective in the Northeast Atlantic, they have not operated as well in other regions. The extension of national jurisdictions over fisheries resources to a 200-naut-mile (370-km/230-mi) zone, beginning in the 1970s, has further limited the effectiveness of many international conventions. In the United States the Fishery Conservation and Management Act of 1976 places all marine resources from the coast to 200 naut mi offshore under U.S. jurisdiction. Management is effected through regional fisheries councils, which also grant permits to foreign countries to harvest specified quantities of certain fish species in return for a fee. Countries that have fished under U.S. license include Japan, South Korea, the \TUSSR\t, and Poland. In addition to these quotas for foreign fishing vessels, quotas on commercially important fish such as salmon have been set for the American fishing fleet, which is restricted in terms of both the total catch of any particular species and the season when such fish may be harvested. WORLD CATCHES In 1948 the total world fish catch was about 19 million metric tons (20 million U.S. tons). With the introduction of advanced harvesting technologies, the total catch rose to over 60 million metric tons by 1970. Although there have been major fluctuations, since 1970 the trend has been upward: almost 77 million metric tons in 1982, more than 92 million metric tons in the late 1980s. The causes for fluctuating--and, in some species groups, diminishing--catches are varied and include factors that are beyond human control: for example, the change in the ocean currents that caused the disappearance of the anchovy from the coastal waters off Peru (see \TEl Nino\t). Overfishing, which is the harvesting of a species to a point where it cannot reproduce itself in significant numbers, is partly responsible for decline of California sardines. Species that are now in danger of being overfished include cod, haddock, halibut, salmon, and several species of tuna and whale. International agreements and quotas are effective to some extent in preventing the extinction of some of these species. Beginning in the early 1980s, Japanese, Taiwanese, and South Korean fishing fleets began to use a new fishing technique to make large-scale squid catches in the North Pacific. Huge, 15-m-deep (50 ft) drift nets made of unbreakable nylon, each stretching 90 m (295 ft), are lowered off the boats each evening. Together, the nets from a single boat form a great wall just under the surface of the ocean. The nets drift all night, entangling any sea creatures that happen to swim into their meshes--not only the desired squid, but quantities of salmon, steelhead trout, and ocean mammals as big as seals. Illegal catches of immature salmon have appeared regularly in Asian markets. (Legally salmon belong to the country where they originated.) Because these fish have been taken before they can return to their native waters to spawn, the use of drift nets threatens the survival of the salmon as well as the steelhead trout populations in the northern Pacific area. As they "strip-mine" the ocean the nets kill vast numbers of unwanted species; for example, they may be responsible for the decline in the numbers of young humpback whales. Fishing nations in South Pacific regions have asked for an end to the taking of albacore \Ttuna\t with drift nets, and in 1989, the United Nations called for the end of drift net use in the South Pacific by the summer of 1991. Japan and Taiwan agreed; but in 1990, Asian ships had begun moving drift net operations to fisheries in the South Atlantic. FUTURE POSSIBILITIES Most present fishery resources are fished to their limits, at least for those species that have commercial importance. Many species exist, however, for which there has been no commercial demand, although some of these fish--notably whiting, hake, and pollack--offer great commercial possibilities if markets can be developed for them. Many of the pelagic fish now used for the production of fish meal may be sold for direct human consumption in the future. \Tkrill\t, a pelagic crustacean, exists in huge numbers in the Antarctic, where it is the principal food of whales. Krill resources offer great possibilities for exploitation, although when krill-processing technology is perfected, the fishing nations must agree on the optimal amount of the harvest. The improved cultivation of marine resources offers another possibility for increasing the number of food fish. Salmon have been artificially propagated in Norway and North America and in the Baltic Sea, and sea trout have been transplanted into coastal areas, where it is hoped that they will form less migratory, local stocks that can be easily harvested (see \Tfish farming\t). Lagoon cultivation of shrimp has been successful in Ecuador, which is now a large supplier of shrimp to the United States, and in China, Taiwan, and Indonesia. The cultivation of species of inland fish is also an advancing technology that may well provide an important protein source in the coming years. Felix Favorite and Taivo Laevastu Bibliography: Allen, P., ed., The U.S. Fishing Industry (1982); Johnson, D.M., The International Law of Fisheries (1987); Johnston, P. F., The New England Fisheries: A Treasure Greater than Gold (1984); Kawaky, J., ed., Commercial Fisherman's Guide, 3 vols. (1990); Laevasto, T., and Hayes, M. L., Fisheries Oceanography and Ecology (1981); Martin, R.F., and Flick, G.J., Jr., eds., The Seafood Industry (1990); Neilson, L. A., and Johnson, D. L., eds., Fisheries Techniques (1983); Royce, W. F., Fisheries Development (1987); Sainsbury, J., Commercial Fishing Methods (1986). See also: \TFish\t; \Twhaling\t; separate articles on individual fish species.