Most fisheries are marine, rather than freshwater; most marine fisheries are based near the coast. This is not only because harvesting from relatively shallow waters is easier than in the open ocean, but also because fish are much more abundant near the coastal shelf, due to coastal upwelling and the abundance of nutrients available there. However, productive wild fisheries also exist in open oceans, particularly by seamounts, and inland in lakes and rivers.
Most fisheries are wild fisheries, but increasingly fisheries are farmed. Farming can occur in coastal areas, such as with oyster farms,[1] but more typically occur inland, in lakes, ponds, tanks and other enclosures.
There are fisheries worldwide for fish, mollusks and crustaceans, and by extension, aquatic plants such as kelp. However, a very small number of species support the majority of the world’s fisheries. Some of these species are herring, cod, anchovy, tuna, flounder, mullet, squid, shrimp, salmon, crab, lobster, oyster and scallops. All except these last four provided a worldwide catch of well over a milliontonnes in 1999, with herring and sardines together providing a harvest of over 22 million metric tons in 1999. Many other species as well are harvested in smaller numbers.
