Ocean fisheries

Oceans occupy 71 percent of the Earth's surface. They are divided into five major oceans, which in decreasing order of size are: the Pacific Ocean, Atlantic Ocean, Indian Ocean, Southern Ocean, and Arctic Ocean. Over 70 percent of the world catch from the sea comes from the Pacific Ocean. ==Pacific Ocean==

The Pacific Ocean is the largest of the world's oceans, extending from the Arctic in the north to Antarctica in the south. Covering 169.2 million square kilometers, it is larger than all of the Earth's land area combined. The Pacific contains 25,000 islands (over half the islands in the world), most of which are south of the equator. The Pacific's greatest asset is its fish. The shoreline waters of the continents and the more temperate islands yield herring, salmon, sardines, snapper, swordfish, and tuna, as well as shellfish. ==Atlantic Ocean==

The Atlantic Ocean is the second-largest ocean covering 106.4 million square kilometres with a coastline of 111,000 kilometres. It occupies about one-fifth of the Earth's surface. The ocean has some of the world's richest fishing resources, especially in the waters covering the shelves. The major species of fish caught are cod, haddock, hake, herring, and mackerel. The most productive areas include the Grand Banks of Newfoundland, the shelf area off Nova Scotia, Georges Bank off Cape Cod, the Bahama Banks, the waters around Iceland, the Irish Sea, the Dogger Bank of the North Sea, and the Burdwood Bank of the Falkland Islands. Eel, lobster, and whales have also been taken in great quantities. Because of the threats to the ocean environment presented by oil spills, marine debris, and the incineration of toxic wastes at sea, various international treaties exist to reduce some forms of pollution. • Biomass distributions for high tropic-level fishes in the North Atlantic, 1900 - 2000 ==Indian Ocean==

• The Indian Ocean is the third largest ocean, covering 73,556,000 square kilometres, or about twenty percent of the water on the Earth's surface. Small islands dot the continental rims. The ocean's continental shelves are narrow, averaging in width. An exception is found off Australia's western coast, where the shelf width exceeds . The average depth of the ocean is 3,890 metres (12,760 feet). The remaining 14% is layered with terrigenous sediments. Glacial outwash dominates the extreme southern latitudes. The warmth of the Indian Ocean keeps phytoplankton production low, except along the northern fringes and in a few scattered spots elsewhere; life in the ocean is thus limited. Fishing is confined to subsistence levels. Its fish are of great and growing importance to the bordering countries for domestic consumption and export. Fishing fleets from Russia, Japan, South Korea, and Taiwan also exploit the Indian Ocean, mainly for shrimp and tuna. Endangered marine species include the dugong, seals, turtles, and whales. Oil and ship pollution threatens the Arabian Sea, Persian Gulf, and Red Sea. ==Southern Ocean==

The Southern Ocean is the fourth-largest ocean, covering 20,327,000 square kilometers. It is typically between 4,000 and 5,000 meters deep with only limited areas of shallow water. The Antarctic continental shelf is narrow and unusually deep, its edge lying at up to 800 meters, compared to a global mean of 133 meters. The Antarctic Circumpolar Current moves perpetually eastward — chasing and joining itself, and at 21,000 kilometers is the world's longest ocean current, transporting 130 million cubic meters per second — 100 times the flow of all the world's rivers. The Antarctic ice pack fluctuates from an average minimum of 2.6 million square kilometers in March to about 18.8 million square kilometers in September. Fauna: squid, whales, seals, krill, various fish Increased solar ultraviolet radiation resulting from the Antarctic ozone hole has reduced marine primary productivity (phytoplankton) by as much as 15% and has started damaging the DNA of some fish. Illegal, unreported, and unregulated fishing, especially the landing of an estimated five to six times more Patagonian toothfish than the regulated fishery, likely affects the sustainability of the stock. Long-line fishing for toothfish causes a high incidence of seabird mortality. The International Whaling Commission prohibits commercial whaling south of 40 degrees south (south of 60 degrees south between 50 degrees and 130 degrees west). Japan does not recognize this and they carry out an annual whale-hunt which they say is for scientific research. See Southern Ocean Whale Sanctuary. The Convention for the Conservation of Antarctic Seals has limited seal-hunting. The Convention on the Conservation of Antarctic Marine Living Resources regulates fishing in the region. ==Arctic Ocean==

The Arctic Ocean is the smallest of the world's five major oceans and the shallowest. Almost completely surrounded by Eurasia and North America, it is largely covered by sea ice throughout the year. Its temperature and salinity vary seasonally as the ice cover melts and freezes; its salinity is the lowest on average of the five major seas, due to low evaporation, heavy freshwater inflow from rivers and streams, and limited connection and outflow to surrounding oceanic waters with higher salinities. In summer the icepack shrinks about fifty percent. ==See also==