Fishing industry, worldwide economic activity that includes the production, marketing, and conservation of fish, shellfish, and related products, such as seaweeds. Fish are an important source of protein, and two-thirds of the world's catch is used for human consumption; one-third is used in making animal feed and industrial products. Oceans supply most of the world's catch; rivers and lakes supply a small percentage, and fish farms—enclosed areas on land or in the natural bodies of water—supply a still smaller portion. Ocean fish include herring, sardines, and tuna, which are caught near the surface, and flounder, cod, and pollack, which are found near the ocean floor. Freshwater fish, which are found in lakes and rivers, include carp and catfish. To control overfishing and enforce conservation laws, in the 1970s most countries that border the sea established fishery conservation zones that extend 200 mi (320 km) from a country's coast.