How to raise topmouth culter? Detailed explanation of key farming techniques
Topmouth culter, commonly known as white stripe, Heshun, and Taihu whitefish, is one of the well-known "Three Whites of Taihu." It has a large body, grows fast, and its flesh is white, tender, and delicious, making it a top-grade fish. It is very tasty whether eaten fresh or salted, and currently its price in the Jiangsu-Zhejiang-Shanghai market is relatively high; it will be one of the most popular farmed species in 2002. The resources of topmouth culter in lakes and reservoirs are dwindling day by day and cannot meet market demand. Therefore, research on the biological characteristics, artificial breeding, embryonic development, pond farming techniques, cage adult fish farming techniques, and key points for drug use of topmouth culter is very beneficial for adjusting the agricultural industrial structure, developing and utilizing new species, and protecting natural wild topmouth culter resources.
Living habits of topmouth culter
Starting in the 1970s, China mainly studied it as a harmful predatory fish, focusing on how to limit its population development in reservoirs. This fish lives in the upper and middle layers of water bodies, and wild whitefish are mainly carnivorous. In recent years, our practice has proved that topmouth culter can also eat artificial compound feed. The biological characteristics of topmouth culter are as follows:
1. Habitat habits: Topmouth culter is a fish that lives in large water bodies such as lakes, reservoirs, and outer ponds. Adult fish generally move in the middle and upper layers of open water, swim quickly, are fierce in temperament, and are good at jumping; juvenile fish live in groups in shallow water areas with relatively slow currents.
2. External traits: The mouth is superior, and the lower jaw is thick and turned upward; the tips of the lower pharyngeal teeth are slightly curved, the gill rakers are slender, the swim bladder has 3 chambers, and the middle chamber is round and large; there is a ventral keel from the base of the pelvic fin to the anus, and the dorsal fin has thick hard spines; the back and upper sides of the body are gray, and the belly is silvery white; the body is elongated and laterally compressed.
3. Feeding habits: The feeding frequency is high, and it feeds as usual even in severe winter and during the reproductive period. It mainly feeds on fish and is highly selective in food, mostly small and medium-sized fish in the middle and upper layers, such as anchovies, mullet, Coilia, and other fish, as well as insects, cladocerans, and copepods; it has a great chance of swallowing aquatic plants. As the individual grows, the feeding habits will change significantly; small individuals mainly feed on algae, aquatic insects, and so on, while those with a body length of more than 24 cm mainly feed on fish. The relationship between the total length of suitable prey fish and the total length of topmouth culter can be expressed as: Y=1/5 X (Y: total length of suitable prey fish; X: total length of topmouth culter; unit of length: cm). Under artificial conditions, after domestication, it can feed on fish paste, chilled fresh fish and shrimp, and artificial compound feed.
4. Reproductive characteristics: Topmouth culter has obvious anadromous spawning habits. In mid-May each year, it gradually enters the stage of sexual maturity. From mid-June to mid-July (from 10 days after Grain in Ear to 10 days after Minor Heat in the lunar calendar) is the peak spawning period, and it ends in early August. Male fish mature sexually at 2 winters of age, female fish mature at 3 winters of age, and sexual maturity of female fish at 2 winters of age is rare. The fecundity of female fish is 150,000-200,000 eggs/kg. Most spawning grounds are in the upper reaches of reservoirs and nearshore zones on the windward side of lakes. Due to differences in water temperature, water level, flowing water, and other conditions, spawning time is earlier or later. The spawning water temperature is 20-30°C, and the suitable spawning water temperature is 25°C. The suitable spawning water flow speed is 0.1-1.5 m/s. Each spawning act lasts about 2 hours, and the eggs are adhesive, light yellow-gray, with an egg diameter of 0.7-1.1 mm. The eggs develop on aquatic plants, gravel, and hard mud in shallow nearshore shoals of lakes, and larvae hatch after about 48 hours.
5. Growth: It grows rapidly and has a relatively large body size, with a maximum length of 10-15 kg, and common individuals are 0.5-1.5 kg. Under general conditions, the body length of topmouth culter grows fastest in the first year, followed by the second year. Starting from the third year, the annual increase in body length gradually declines. The annual weight gain rate also gradually declines. It can be expressed by the formula W=aLb, where W(g), L(cm). Under artificial conditions, after 8-10 months of rearing, 70% of seedlings about 7 cm long can grow into commercial fish of more than 0.5 kg. Fish of 1 and 2 years of age are in a period of vigorous growth, and those of 3 years of age and above enter a period of slow growth. After female fish reach sexual maturity, their growth rate does not decrease significantly, and female fish grow faster than male fish.
6. Age: Under general conditions, the age of topmouth culter can be identified by scales. The age of natural topmouth culter can reach 9 years. The relationship between the age of topmouth culter and body length and body weight is complex, but the body length of topmouth culter is directly proportional to scale diameter. It can be expressed by the formula L=a+bD.
Pond conditions for topmouth culter
The pond should be selected in a place with sufficient water source, good water quality, and convenient transportation and power supply. The area should preferably be 5-6 mu. If the area is too large, the size difference at harvest is large, and it is difficult to control the feed size during farming; if the area is too small, the yield is low. The water depth should preferably be more than 1.5 m, and about 1 m can also be used for farming.