Introduction to the Biological Characteristics of the Topmouth Culter (Culter alburnus) from the Yangtze River

The topmouth culter, commonly known in Guangdong as "Yangtze Heshun," in the middle reaches of the Yangtze as "qiaobai" or "white fish," and in the lower reaches of the Yangtze as "Taihu white fish." In recent years, many people in our province have passed off the bigeye culter, i.e. the "Pearl River Heshun," as "Yangtze Heshun" @#@136@#@ to sell to farmers, with the result that even after four years of intensive culture they could not reach the market size of 8 liang to 1 jin. Since last year, Hainan culter and qingshao culter have been passed off as "Yangtze Heshun"; although they grow somewhat faster than the bigeye culter, they are slower than the genuine topmouth culter, and it is very difficult to raise them to a large market size of over 1 kg, with the sales market limited to a few seafood restaurants in Guangdong. In areas north of Hunan, the purchase price for adult fish of 0.5 kg is only 5-8 yuan/kg; for those over 1 kg, the purchase price is 20-30 yuan/kg; for those over 2-3 kg, the purchase price can reach 40-60 yuan/kg. Large-size commercial fish are in short supply, and in the Northeast or Northwest, large-size chilled fresh fish sell at almost the same price as live fish. Therefore, for culturing Heshun, the first choice should be genuine original broodstock fry of the topmouth culter and the Mongolian culter from the Yangtze River system. The topmouth culter belongs to the order Cypriniformes, family Cyprinidae, subfamily Culterinae, genus Culter. It has long enjoyed the reputation of being a "fine famous fish of the Yangtze" and the first of the "Three Whites of Taihu," and is listed as one of the four famous freshwater fish of China. The topmouth culter has delicate flesh, a delicious taste, and rich nutrition, and the whole fish can be used as medicine, with the effects of stimulating the appetite, strengthening the spleen, promoting diuresis, reducing swelling, and nourishing, strengthening the body, and benefiting the brain; it has therapeutic effects on emaciation and edema, postpartum cramps, weakness and debility, and poor memory, and is highly praised by gourmets. The product sells well throughout the country and even in Southeast Asia, and the price has remained high: the pond-side price for fish of 0.5 kg body weight is 36-40 yuan/kg, and for those over 5 kg body weight the pond-side price reaches 60-80 yuan/kg. In recent years, many discerning farmers in China have begun artificial culture of the topmouth culter. The author summarizes the practice of large-scale artificial breeding and grow-out at this farm, and draws on the experience of colleagues, to compile this material, for the reference of farmers only. 1. Morphological characteristics The topmouth culter has an elongated, laterally compressed body, with the dorsal surface of the head flat and straight; the mouth is superior, and the mouth cleft is almost perpendicular to the body; the lower jaw is firm and thick and upturned, protruding beyond the front edge of the upper jaw, and lying on the same plane as the upper jaw and the dorsal surface of the head. The head and tail are upturned, and the whole fish is shaped like a guandao (halberd), hence it is also called the "guandao" fish. 2. Distribution Wild topmouth culter is found throughout the lakes, hill ponds, reservoirs, rivers, and fish ponds connected to large water bodies in the areas of China's four major river systems: the Yangtze, Yellow, Heilongjiang, and Pearl rivers, with the highest yields especially in the Yangtze River system from the Dongting Lake area to the Taihu Lake area; the topmouth culter produced in Xingkai Lake in the Northeast is also very famous. Pond culture of white fish is developing rapidly in Guangdong, Zhejiang, Jiangsu, Anhui, Hubei, and other regions. 3. Living habits The topmouth culter is a large and medium-sized freshwater economic fish of the middle and upper layers; it moves swiftly, is good at jumping, has a fierce temperament, and is easily startled; when a net is drawn, it can "fly" over barriers more than 1 m high. Adult fish caught in the wild are very difficult to keep alive, and are mostly transported and sold as chilled fresh fish. After wild adult fish are domesticated and bred into mature broodstock, the first-generation original fry produced by artificial breeding have greatly reduced wildness, and the adult fish can enter the aquariums of restaurants and hotels completely in live form. 4. Living environment The topmouth culter is a eurythermal fish, with a survival water temperature of 0-38°C, a feeding water temperature of 3-36°C, an optimum water temperature of 15-32°C, and a best growth water temperature of 18-30°C; the breeding water temperature is 20-32°C. The topmouth culter has extremely strong adaptability and disease resistance, and can survive in water bodies large or small; from lakes and reservoirs of hundreds of thousands of mu to cement ponds of a few square meters or cages of a few square meters, fry can all be raised into adult fish or even mature broodstock. The topmouth culter has strong stress resistance, fewer diseases, and can tolerate low oxygen; even if the four major Chinese carps in the same pond die from floating due to oxygen deprivation, the topmouth culter will not necessarily die floating. Of course, high dissolved oxygen in the water can improve feed utilization, speed up growth, increase culture density, and enhance disease resistance. With a water depth of 0.5-10 m, fresh water quality, a transparency of more than 30 cm, a pH of 6.5-8.5, and an area of 1 mu to hundreds of thousands of mu, or cages or ponds, all are suitable for culturing adult topmouth culter. 5. Growth characteristics The topmouth culter grows rapidly and is easy to raise extensively; its body size is relatively large, with the largest individual reaching over 15 kg, common wild individuals being 1-10 kg, and artificially cultured fry reaching 0.6-1 kg in one year and 2-3 kg in two years. Generally speaking, growth is slower from the fry stage to a body weight of 100 g, somewhat faster from 100-200 g, faster from 200-300 g, fastest from 300-2500 g, and gradually slows down above 3000 g. In the same batch of topmouth culter fry, the growth rate is relatively uniform; male and female fish feed all year round (including in the severe winter season), and there is little difference between individuals; female fish also feed as usual during the breeding season, and their growth rate will not slow down because of reproduction. 6. Feeding habits The wild topmouth culter is a fierce carnivorous fish that feeds mainly on live fish; during the fry stage it feeds mainly on plankton and aquatic insects, and above 50 g it mainly swallows small fish and shrimp, and also swallows a small amount of tender plants. For original fry produced by artificial breeding, from the beginning of the transition from the endogenous nutrition stage to the exogenous nutrition stage all the way to the sale of commercial fish, artificial feed can be fed throughout the whole process, such as soybean milk, yellow powder, eel feed, silkworm pupa powder, peanut bran, soybean cake, or minced fish, fish paste, fish pellets, etc. Above 3-4 cm, full artificial compound feed can be fed, preferably floating feed, as well as aquatic plants such as duckweed, azolla, tender grass, and tender vegetables, etc. Of course, after re-domestication, they can also eat live fish again. There is not much difference in growth rate between feeding high-quality artificial feed and feeding live fish.