Polyodons pathuln was originally a large-scale freshwater economic fish unique to the United States. It can weigh up to 40 kilograms and is mainly distributed in the Mississippi River Basin. It belongs to the order of Oystercatcher, Odontodidae, and Paddlefish. It is a rare animal of the same family as the Chinese white plover. The Xiantao Fisheries Research Institute, under the guidance of the Hubei Provincial Aquatic Products Bureau, introduced paddlefish fertilized eggs from Missouri, USA, in April 1990, and hatched and experimented successfully. The paddlefish were settled in China and the paddlefish is now learning biology and breeding techniques. Make a brief introduction. 1 Biological characteristics 1.1 Shape characteristics Paddlefish is a cartilaginous fish. There is a long kiss shaped like a spoon, which accounts for about 1/3 of the body length. The trunk is streamlined, flat on the side of the tail, scales are degraded, and the surface is smooth, the eyes are very small, the mouth is not stretchable under the kiss, and the plum blossom-like pattern is covered by the lid. The pectoral fins are smaller, the lower ones, the ventral pelvic fins, the dorsal fins starting behind the pelvic fins, the caudal fins are fork-shaped, asymmetric, with long upper leaves and short lower leaves. Body color: The back is grayish black, with shallow sides, abdomen grey, fins grey and black (see photo). The newly hatched larvae have no kisses and their body length is about 8-9mm. After being raised for more than one month, the kiss is fully developed. The 10-15cm body cubs are like duckbills, such as the elephant ear. The body is crystal-clear and swim-specific. It is especially popular for fish lovers. 1.2 Ecological habits Paddlefish is a kind of pure freshwater fish that can live in inland rivers, lakes, and ponds all year round. It does not need to swim like a Chinese sturgeon. The temperature range is extremely wide, and it can survive in 0-37°C water bodies. In China, it can both heat and winter. Living in the middle of the water, it is docile and easy to fish. The pH is suitably in the range of 6.5-8. Dissolved oxygen in the water body is required to be above 3mg/L. When the pond is deficient in oxygen, it will float at the same time with the head lice, which is slightly inferior to the oxygen tolerance of the white peony. 1.3 Dietary and growth spawning species feed on zooplankton for life. Open diet of larvae is mainly small-scale horns, but also eat egg yolk, fish meal, shrimp powder and so on. Before the cockroach is fully developed, the feeding method is swallowing. If there is not enough feed, juveniles will prey on other fry smaller than the fish, and they will even be able to eat together and eat together. Up to 13 cm in length, the plankton can be filtered and the chironomid larvae are accidentally eaten. In captivity, buoyant foods, which are generally eaten and zooplankton in size, when feeding, the squid often flipped the body, belly upside down, and rode for bait. Paddlefish grow fast. In the year of the fishery in Hubei, the total length can reach 50-60cm and the weight can reach 700g-1000g. Second-instar fish, with a total length of 67-80cm, weighing 2-3kg, and third-instar fish can reach more than 5kg. 1.4 Breeding characteristics Paddlefish are mature earlier than Chinese sturgeon and Daphnia magna. Male sexual maturity is mostly 7-9 years, females are mostly 8-10 years. In 1974, the Soviet Union imported paddlefish from the United States, and in 1984 received the first batch of paddlefish. Paddlefish ovary accounts for 15-25% of body weight. The female ovulation reaches 3500 capsules/kg, the egg diameter reaches 2-2.5mm, and the eggs are grey and black. In the natural environment, paddlefish reproduce in March and June, requiring the water temperature to rise to 16°C and the rising water flow. Eggs are sticky and often adhere to gravel. The incubation period is about 6-7 days. In 1963, the first successful spawning of paddlefish in the United States was successful. The main point is the selective maturation of broodstock, injection of fish pituitary gland or luteinizing hormone-releasing hormone analogue (LRH-A), to promote estrus, after oviposition, insemination, detackification, hatching, so as to obtain fry. 2 Breeding Techniques 2.1 Scallop Nursery The newly hatched paddlefish larvae have large umbilical sacs and are shaped like crickets. They are slow to move and they are often lying and lying. They need to be changed from vertical swimming to horizontal swimming after 3-4 days. At the same time, they are feeding. After we failed to raise the seedlings through cages, loops, and directly under ponds, we only designed aquaculture techniques for sinks. Practice has proved that this move is the key to improving the survival rate of fry. 2.1.1 sink conditions. Area of ​​about 10 square meters, rectangular, 1 meter wide, 1.2 meters deep, smooth wall, built into the drainage and anti-escape facilities, requiring good water quality, non-polluting, non-toxic and unbeatable, water source must be filtered before entering the tank, at least can be exchanged per hour once. Where conditions permit, it is best to have deep wells supporting the water temperature can be adjusted between 16-28 °C, the dissolved oxygen in the tank needs to be maintained at 5mg / L or more. 2.1.2 Technical Management. One spoonful of barramundi seedling density, generally 200 / m +2, 5cm seedlings put 100 / m2. 2 Open food should be filtered by 60 mesh sieve after the zooplankton, more than four times a day, with a slight excess of the feed in the sink for the degree, until the seedlings grow to 2cm can be directly fed large blisters. 3 spray water oxygenation or aeration oxygen to prevent floating head. 4 often wash the filter window to prevent flooding to escape the fish. 5 special management, make records. It will be cultivated in about 30 days. Seedlings can grow to 6-8cm and the survival rate is about 55-80%. 2.2 Pond Breeding After mastering the adaptability of paddlefish and its adaptability to temperature, the traditional scientific fish farming method can be used to breed 3-5cm paddlefish fry into 20-30cm fingerlings. The technical points are as follows: 2.2. 1 pond conditions. The area of ​​3-5 acres, depth of 1.5-2 meters, convenient drainage and irrigation, each pool is equipped with a 1.5-kilowatt aerator. 2.2.2 clear pond disinfection. Lime water clear pond, acres of 300-400 kg, kill fish, aquatic plants, bacteria and predators. 2.2.3 fish under the red worm. Fish seedlings before the pond 3-4 days before the application of base fertilizer, per mu large grass or manure 400-500kg, and increase soymilk 5kg per mu, prompting the Cladocera species after a large number of breeding, you can fish. 2.2.4 Reasonable and sparse. In general, about 500 mu fish are cast. If large-scale fish species above 40cm are to be reached, the stocking density should be adjusted between 200-300 tails. 2.2.5 Strengthen feeding. Feeding granular feeds with adequate palatability is generally done with "four settings." If it can be done to keep the fertilizing material to keep the plankton's sustained peak, it can make it grow faster, less incidence, survival rate of 90%. 2.3 adult fish breeding 2.3.1 main spatula. In 1992, the main breeding experiment was conducted in our laboratory. Mu 25-30 cm paddlefish 50-70 tails were put in, and fish species such as spotted earthworms were used. At the end of the year, net production was 152 kg and the tail weight was about 3 kg. In addition, more than 4,000 species of spotted squid were harvested in Mu and more than 4,000 yuan were harvested in mu, which has achieved very good results. 2.3.2 spawning spatula. That is, paddlefish is used as a flower pot and is raised in various types of aquaculture water to increase reserve of paddlefish broodstock without occupying too much water. For example, in 1991, in the city's fishery breeding grounds, 20 second-incubation paddlefishes were reared in grass broodstock ponds and reared for 9 months. In November, the largest individual was 4.8 kg with an average tail weight of 4.1 kg. In recent years, we have spawned the paddlefish in the broodstock ponds of the fork and tail fish, which not only improved the water quality environment of the fish back to the fish pond, but also enabled me to obtain a number of paddlefish parent fish. 2.4 Discharge of lakes and reservoirs The size of lakes and reservoirs for spatula breeding should be greater than 40 cm to increase the survival rate. Since 1991, we have released 2,200 paddlefish in a row of lakes with an area of ​​8,000 mu per mu of 78 kg of adult fish. The paddlefish has grown to more than 2 kg in the current year. At present, individuals are around 5-6 kg. In March 1993, we stocked 20-30cm paddlefish 5000 in Shenjia Lake, Wuchang County, with 6.25 tails of Muping. At the end of the year, more than 3,000kg of nets were excreted at the time of fishing. Individuals were about 2.5kg, and annual yields of small lakes were achieved. 15kg of data.
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