Due to the influence of natural factors and artificial fishing, most fish can't complete the whole life process and die. So it is difficult for us to know its physiological life, only its ecological life. The usual practice is to judge the life span of the largest individual (fish grows for life, and the older the individual, the older it is), such as scales, otoliths, fins, gill bones, gill cover bones, vertebrae, etc. Generally speaking, the life span of fish is related to its individual size and sexual maturity age. The bigger the fish, the later its sexual maturity and the longer its life span. From this point of view, whales, the largest fish in the world, should have the longest life span. Unfortunately, so far, people know nothing about its life. It is reported that European herring living in the Caspian Sea and the Black Sea can weigh up to 1 1,500 kg and live for more than 1 1,000 years. The life span of China Yangtze paddlefish is also close to 100 years. Many small fish, such as freshwater fish, fake tiger fish, herring and whitebait, have a life span of only about one year. Although the life span of fish varies greatly among species, most fish live between 2 and 20 years, and 60% of them live between 5 and 20 years. The fish that can live more than 30 years will not exceed 10%, and only 5% will live less than 2 years. Among the freshwater fishes in China, the life span of anchovy, whitebait, octopus, Pelteobagrus fulvidraco, silver carp and sand carp is between 2 and 4 years. The life span of herring, grass carp, silver carp, bighead carp, crucian carp, snakehead, red fish and mandarin fish is mostly 7-8 years, and some of them can live to 10 years. Marine fish have a short life span. In addition, the same kind of fish lives in different environments and has different life spans. For example, Pseudosciaena crocea can live for 29 years in the coastal areas of Zhejiang, but usually it can only live for 17 years in the coastal areas of Fujian and Guangdong, and only live for 9 years in the eastern waters of Hainan.