Summarize the economic value of fish.

A: Fish is the main body of aquaculture and has outstanding economic significance. The world's annual fishing output is close to 654.38 billion tons. Except for 30% used as feed, 70% is human food. Fish is delicious, high-quality food with high protein, low fat, high energy and digestibility, rich in nutrition and high in protein. 16%~25%, significantly higher than milk and eggs, and equivalent to chicken, beef and mutton and pork (19.3%~20.3%). In addition, there are essential and easily absorbed fats, calcium, phosphorus, iron, lysine, thiamine, riboflavin, nicotinic acid, ascorbic acid and multivitamins in fish. In addition to being eaten fresh and processed into "sea beef" (fish protein concentrated in meat tissue), shark fin (shark fin), fish belly (swim bladder) and fish lip (shark and ray's kistrodon cartilage), fishery products have also been developed and comprehensively utilized, providing raw materials for industrial and pharmaceutical production. Fish scale can be extracted and made into fish scale, fish scale gum, guanosine hydrochloride, caffeine, xanthine, fish scale soy sauce, calcium phosphate fertilizer, etc. Sharks and shark skins can be made into exquisite leather products. The advantages of fish skin are easy dyeing and low cost, which is only 1∕ 10 of snake skin, so it is very popular with consumers. The utilization of fish viscera is varied: fish liver (cod, shark, flounder, etc. High fat content can be used to extract cod liver oil, which is a commonly used nutritional drug for medical treatment and prevention and treatment of human diseases; Testis can produce protamine; Fish pancreas can extract insulin, and bonito and tuna produce the best quality insulin. Fish bile is the raw material for extracting bile pigment calcium salt, which can be used as bile salt for bacterial culture medium and for making artificial bezoar. Fish oil extracted from deep-sea fish contains highly unsaturated fatty acids, which can be used in medicine to reduce cholesterol in human blood. Eicosapentaenoic acid (EPA) extracted from fish oil can be made into a new drug for preventing and treating cerebral thrombosis-coagulation regulator. The treated fish oil can be made into solidified fat with special flavor and good stability, which can be used to produce artificial fish butter. Preparation of urethane and epoxy resin coatings: Leather can be yellowed by fish oil treatment, and it can be used to separate low-priced iron in ore flotation as lubricant and waterproof agent. Pure blood and viscera contain river poison, which can inhibit the activity of cholinesterase in human blood and paralyze the peripheral and central nervous system. The river toxin injection made from it can treat spasm, traumatic pain, neuralgia and pain relief of patients with advanced cancer. Hippocampus and Syngnathus are traditional Chinese medicines, which have the effects of nourishing, tranquilizing, resolving hard mass, relaxing muscles and activating collaterals. Fish heads, bones, bones and other wastes and inedible miscellaneous fish are often used to produce fish meal or liquefied products by biological fermentation. In some developed countries, fish meal is an indispensable additive to increase the output of pigs and poultry industry. Small fish such as mosquito-eating fish, scale fish, betta fish, wheat-ear fish, bonito fish and Pelteobagrus fulvidraco can ingest a large amount of boron. Boron is the natural enemy of mosquito larvae, which has a positive effect on controlling and preventing mosquito-borne encephalitis, yellow fever, malaria and filariasis, and indirectly benefits mankind.