Sardines are slender silver fish with short dorsal fin, only one, no lateral line and no scales on the head. The body length is about 1530 cm (6 12 inch). Dense social groups migrate along the coast and feed on a large number of plankton. They lay eggs mainly in spring, and after a few days, the hatched eggs and young fish have been drifting with the tide until they become free-swimming fish. Sardines are all economic fish species, which can be eaten raw, dried, salted or smoked, and boiled into fish powder or fish oil. Rotating net is the most important fishing tool, especially purse seine. Many other improved rotating nets are also used, such as nets or weirs. Weir is a fixed enclosure composed of piles. Sardines become like this when they swim along the coast. Fishing is mainly carried out at night, when fish float on the water and feed on plankton; After catching, the fish are soaked in salt water and then transported to the shore. Sardines are mainly used as food, but fish can also be made into animal feed. The uses of sardine oil include making paints, pigments and linoleum, and it is also used to make margarine in Europe.