We conducted a study on the early breeding technology of the southern estuary in late March 1997 and succeeded in conducting research on breeding techniques for early breeding of the fish species in April 1997 and April 1998 in order to explore A complete set of mature techniques for the breeding of early-blooded seedlings is continuously improving the breeding of large-mouthed larvae in the South.
1 Cultivation pond conditions
1.1 Manual temperature-control cultivation pond: a total of 12 mouths, an area of ​​110m2, each mouth area of ​​9 ~ 10m2, depth of 0.8m, circular, according to artificial breeding hatchery structure and quality requirements for design, construction, and contiguous to build a regular rectangle; The red brick is used to form a 2m high heat preservation wall with a double arched thick plastic film insulation shed at the top; an artificial temperature increase facility is equipped with an auxiliary steam boiler, and a 40mm diameter steel pipe is used as a hot water delivery system; The heating system is connected.
1.2 Conventional cultivation ponds: A total of six areas, an area of ​​2000m2, pool depth of 1.5m, the pool weeks and the bottom of the pool are plastered with cement mortar. Supporting the corresponding intake and drainage systems, overflow screens and overflow pipes are provided at the outlets, and the amount of water in and out can be controlled at will. Most of the tanks are equipped with water spray pipes, and if necessary, they can be sprayed with oxygen.
1.3 Water source: The water source is the groundwater in the digging well. After being stored and aerated before use, the water quality is fresh and clean.
2 Cultivation methods
2.1 Frying stage: The whole process of fry cultivation is carried out in the greenhouse.
2.1.1 Preparation of fry before stocking: Check whether the water inlet and outlet systems are unblocked and whether the heating system is normal. After washing the fish pond, use 10ppm bleaching liquid to disinfect the fish pond and the surrounding heat preservation walls and sheds, and rinse thoroughly with clean water to drain all the water. Fill the pool with water and warm it to about 23°C.
2.1.2 Stocking Density: Because the greenhouse cultivation pool can artificially control the flow of water, it should be cultivated using the micro-flowing water method, and the stocking density should be 5,000 to 7,000 fry per 5 to 10 mm size per cubic meter of water body.
2.1.3 Feeding: Fry that has just been placed in a nursery pond is fed with cooked egg yolk. It is fed once a day in the morning, in the evening and once in the evening. Every time 100,000 fish fry are fed with 5 to 6 cooked egg yolks, the feeding method is Add the egg yolk to a thin syrup and slowly spill it into the pool. Two to three days later, as the individuals grow up, they gradually feed the blisters. The leeches were soaked in 5% saline for 3 to 5 minutes before being fed. Normal feeding 4 times a day, after the appropriate increase in the number of feeding. Daily feed sufficient amount to ensure that the pool has a higher bait density in order to facilitate the feeding of fry. According to our observations, the large-mouthed carp seedlings feed strongly at nighttime compared to the daytime, so the amount of feed at night needs to be appropriately increased. The water flow rate of the pool should be reduced when feeding, so as not to consume more energy when the fish fry.
2.1.4 Daily management: The daily management adheres to the duty shifting day and night, and mainly controls and monitors the water flow and water temperature. The water temperature should be maintained at about 23°C. The microfluidic state is always maintained in the pool, but as the fish grows, it is necessary to increase the flow appropriately to prevent the hypoxia pan. In water quality management, the bait is salvaged once in the morning and in the evening, and screens are washed. Pay attention to disease prevention and harm.
The fry is cultivated for 10 to 12 days, and the body length reaches 3 to 4 cm, and the survival rate reaches more than 90%.
2.2 Fish species stage: Fish species cultivation is mainly done in conventional cultivation ponds.
2.2.1 Preparation of fish species before lower pool: After the pond is cleaned and disinfected, the well water stored after the exposure is placed first. When the depth is 2/3, it is put into filtered adult pond water with certain fatness. .
2.2.2 Fish species stocking: When the outside water temperature reaches 15°C or more, the inch fish species in the greenhouse are transferred to a conventional cultivation pond and continue to be cultivated to the required specifications. In the first five days before the fish species emerged from the greenhouse, the water temperature in the cultivation pool was gradually reduced, and the daily decrease was 1 to 1.5°C until the temperature difference between the indoor and outdoor cultivation pools did not exceed 2°C. The stocking density is 90 to 110 tails/m2 of water.
2.2.3 Feeding: In order to explore the breeding effect of different types of bait, we used two groups of leeches and artificial compound feed (two in each, the same area and depth) in the first batch of cultivation in 1997 for comparative breeding experiments. When the fish ponds are just under the water tank, when the size of the fish species reaches 5cm or more, pools No. 1 and No. 2 (the No. 2 pool is the spare pool for the grading sub-pools) continue to use leeches as bait, and No. 3 and No. 4 pools (No. 4 ponds Grading pools are maintained in graded sub-pools. Artificial feeds are then started until the end of the batch.
Feeding of leeches: Set up a bait station at the depth of 80cm from the surface of the adjacent two ponds. Feed it twice a day in the morning and 4 times in the afternoon. There are a few feeds in the bait before feeding. Left bait is a degree, which can avoid the mutual existence of fish species due to insufficient food. Once in the evening, the amount of feeding is increased by 20 to 30% at one time compared to the daytime. The use of leeches as bait, after 16 days of cultivation, more than 80% of fish species specifications of 10cm or more.
Artificial compound feed tame food: The nutrient requirements of juvenile fish of similar species (carnivorous fish) should be self-formulated. The main raw materials are fishmeal, bean flour, starch, yeast powder, minerals and multivitamins, and the protein content is 47 to 49%. The method of domestication is: set up two bait stations in one pond of a fish pond, sink deep into the water at a depth of 50cm, and then place a square box of bamboo on the water surface of the bait, and put more water hyacinths and fish species in the box. Generally concentrated in the water hyacinth area underwater, but above the feed water hyacinth table to facilitate feeding and observation. At the beginning of taming, we use new fish and fish, pig lungs, etc., and stir the meat pulp into meat paste. Mix with the above-mentioned compound feed and mix with water to form a dough. Pinch into small dough and put it into the bait station and feed it. Temptation. On the first day, the amount of leeches accounts for 70%, artificial compound feed accounts for 30%, and after 10% of the blisters are reduced every day, after 6-7 days, the fish species have been fully adapted to the compound feed, and then the compound feed is processed into soft. Feed pellets, to complete the process of artificial domesticated feed. Daily feeding times can be up to 8 times during the tame period and 6 times after normal feeding. The daily feeding amount accounts for 3 to 5% of the fish's body weight and gradually increases to about 10% of the fish's body weight. After artificial diets were fed for 16 days, about 60% of the species had a size of 10cm or more.
2.2.4 Daily management: It mainly includes removing bait, regulating water quality, observing the feeding and activities of fish species, and grading and grading in separate ponds in time.
2.3 Prevention of fish diseases Usually, the prevention of fish diseases mainly maintains the cleanliness of the cultivation ponds, and attention is paid to water quality regulation. To ensure quality, do not feed rotten spoilage feed, leeches and other fresh live food after disinfection. Careful and meticulous operation to minimize fish damage. In our production practice, we found that common diseases of the early-stage propagation of large-mouthed puffers in the South include bubble disease, hydromycosis, trichodiasis, and myxosporosis.
2.3.1 Trichodinosis: mainly caused by worms, the symptoms are manifested by white parts of the body surface and mouth circles. The treatment method is that per cubic meter of water is mixed with 0.5 g of copper sulfate and 0.2 g of ferrous sulfate dissolved in water and then splashed in the whole pool. The curative effect is significant.
2.3.2 Myxosporidiosis: mainly caused by Myxosporidium. Symptoms are the appearance of cysts of different sizes on the body surface, ankles, and rays. The diseased fish swim slowly and the appetite decreases. The treatment method is to concentrate the diseased fish, soak it in the clarified 40ppm quicklime solution for 10 minutes, then transfer it to 0.7ppm solution of dipterex and soak for 10-15 minutes. With this method, the condition with lesser severity will be effective, and the severe disease can be cured after three consecutive use.
3 Results and Discussion
3.1 Results: Four batches of early-blooded breeds were bred before April 30, 1997. A total of 1.256 million fish species with a size of 3cm or more were cultivated, of which about 15cm large-scale species were 153,000, and the output value was over 250,000 yuan, and the profit was 163,000. yuan. In May 1998, 5 batches of early-reproductive breeds were cultivated, and a total of 1.518 million fish species with a size of 3 cm or more were cultivated. A total of 246,000 large-scale species with a total size of about 10 cm were produced. The output value was 31 million yuan and the profit was 229,000 yuan.
3.2 Summary and discussion
3.2.1 Through experiments, we believe that when fingerlings are transferred from greenhouses to conventional cultivation ponds, one should pay attention to adjusting the temperature difference. Generally when the outside water temperature reaches 15°C or more, they can begin to move into conventional ponds, but they must be adjusted about 5 days in advance. The difference in water temperature between the inner and outer greenhouses in the greenhouse is reduced (the temperature drop in the greenhouse does not exceed 2°C per day) so that the fish can adapt to the outside water temperature after exiting the greenhouse. Second, we must pay attention to climate change. During the period from April to May, cold waves often occur in the Sichuan Basin. When fish species are transferred, cold weather should be avoided to avoid abrupt climate change and sudden loss of water temperature.
3.2.2 The key to improving the survival rate of breeding is to invest in adequate feed and timely grading and grading in separate ponds. It has been observed that in the entire seedling cultivation stage, the southern bigmouth have the phenomenon of mutual cannibalism, especially the lack of food and the size of the same pool is even more serious when the disparity, the performance of eating small, strong and weak. To reduce this phenomenon and improve the survival rate and quality of seed, on the one hand, it is necessary to strengthen feeding management, pay attention to the rules of food intake, more accurately grasp the food intake, meet the feeding needs of the seed and minimize waste. , and pay attention to the quality of food, so fresh, palatable. On the other hand, it is necessary to sift through the sieving pool in a timely manner. The seedlings in the same cultivating pond should have the same specifications and moderate density. The fingerling pools are sifted and graded once in 7 to 10 days. When the fingerlings with large disparities are kept in separate ponds, the phenomenon of mutual grueling can be effectively reduced.
3.2.3 The problem of the type of food and the effect of cultivation. According to the control breeding experiment in 1997, the effect of the water pond was significantly better than that of the artificial compound feed pool. Calculated economically, each species of fish grows 500g, consuming about 3000g of water fleas, the local leeches cost 7.00 yuan/kg, and the cost of bait for every 500g of fish species is only about 21.00 yuan. The price of 500g of fish species can be calculated according to the tail. Up to 100 yuan or more is a good deal. And the quality of the bait used as a bait is stable, which reduces the processing and tame-food links. The feeding method is simple and easy. Therefore, in the future breeding of early-reproduction seedlings, we have always insisted on the cultivation method using leeches as the main food.
* Comrades Yang Yongji and Pang Weihong of the Mianyang Fishery Station participated in the research work and thanked them.