Artificial breeding and seed cultivation of Rugao hybrid blackfish in Jiangsu Province are practical new technologies
_Zhou Jianhong
The hybrid blackfish described in this article specifically refers to the offspring group distributed in the southern region of China (native to Hong Kong) as the mother, and the blackhead distributed in the north of the Yangtze River (Weifang, Shandong) as the father, and the offspring group propagated by artificial hybridization. Hybrid blackfish have the characteristics of strong disease resistance, fast growth, good intensive breeding performance, high yield and excellent quality, but the tolerance to low temperature is relatively weak. Since 2017, our city has begun to carry out the "South Fish North Culture" experiment, and after several years of trial breeding, it has been successful and has developed rapidly. At present, the breeding of this species has built the only whole industrial chain system of the blackfish industry in the country, and has become a beautiful business card of the local characteristic agriculture (aquatic products) industry in our city. In 2020, the total area of the enterprise breeding base will reach more than 2,800 mu, the annual aquaculture output will exceed 30,000 tons, the aquaculture output value will be 650 million yuan, and the total annual industrial economic volume of blackfish (including feed, blackfish deep processing output value, and blackfish product trade volume) will reach 1.648 billion yuan. In order to stabilize and ensure the quality and supply of cultured fry, ensure the quality and safety of breeding products, and realize the self-propagation, self-breeding and self-cultivation of breeding seedlings, we have specially established a hybrid blackfish artificial breeding and fry breeding base corresponding to the needs of industrial development and breeding fry in Zhongshan City, Guangdong Province, to produce high-quality seeds. To this end, the "Technical Specifications for Artificial Breeding and Seed Breeding of Hybrid Blackfish" (enterprise standard) with independent intellectual property rights has been formulated. The main technologies are introduced as follows:
1. Artificial breeding
1.1 Sources and selection of broodstock
1.1.1 The mother, the spotted snakehead originating in Hong Kong ("Hong Kong" ), has been specially bred and screened for use as a reserve parent.
1.1.2 The father, native to Weifang, Shandong, is specially cultivated and screened as a reserve parent.
1.1.3 Screening Requirements
Spotted snakehead, with a specification of more than 2 winter age, a weight of ≥ 750g/tail, and the original biological characteristics such as large head, tip, long body, and large tail fin area of individuals of the same specification are obvious. Snakehead, 2 winter age or older, weight 1000 ~ 1500 g / tail. Individuals who remain as broodstock are required to be disease-free, injured, physically strong, and energetic. The ratio of male to female is 1:1 to 1:1.2.
1.1.4 Transport of broodstock
The use of living water tank transportation, each ton of water shipment ≤ 250kg, water temperature control between 10 ~ 15 ° C, long-distance transportation 4 ~ 5 hours to change the water once, the immediate temperature difference when adjusting the water temperature on the way ≤ 3 ° C. Transport operations should be carried out with care and should not cause injury.
1.2 Broodstock rearing
1.2.1 Broodstock breeding pond: Broodstock breeding pond area of 1000±100㎡, water depth 1.5±0.1m, sediment bottom of the pond. A purse seine of 0.8 to 1.2 m is set up on the side of the pond embankment to prevent it from escaping. Use quicklime to routinely clear the pond for disinfection before stocking.
1.2.2 Broodstock stocking: Broodstock ponds are specially stocked for the intensive rearing of broodstock. Stocking density of 400±20 fish / mu, rearing tail weight of≥ 300g silver carp, bighead carp 100±20 to regulate water quality.
1.2.3 Broodstock feed: Feed broodstock
The main feed is commonly used snakehead commercial feed, after the spring, the water temperature rises to more than 18 ° C to be fed, rising to 22 ~ 28 ° C, the amount of food increased greatly. The feeding volume is 5% to 8% of the body weight of the fish.
1.2.4 Broodstock rearing management: mainly pay attention to prenatal rearing and postnatal care of broodstock. Frequently fill with new water, keep the water fresh, and feed enough high-quality feed to meet the nutritional needs of broodstock gonadal transformation and postpartum nutritional supplementation. In the middle or four corners around the broodstock pond, some suitable aquatic plants are planted to facilitate the broodstock to hide, eat and regulate the water quality.
1.3 Induced labour
1.3.1 Selection of male and female broodstock. Selective mature females and males induce labour in a ratio of 1:1 between male and female broodstock. Try to induce labor if necessary.
1.3.2 The water temperature of induced production is about 25 °C.
1.3.3 Induced delivery drugs and injectable doses. Types of inducing drugs, chorionic gonadotropin (HCG), diosterone (DOM). Injection dosage: Female fish :D OM3~ 4mg + HCG1000 ~ 1500IU/kg Male fish dose halved. A two-shot injection method is used. The first injection volume is 1/3 of the total amount, the second injection is 2/3 of the total amount, the needle spacing is 12 to 14 hours, and the broodstock spawn in estrus at 16 to 18 hours.
1.3.4 Spawning. Broodstock injected with induction drugs are placed in 1:1 pairs in a water-filled plastic foam box to spawn. Box size: 40cm× 60cm×30cm, water depth 25cm. Be quiet around the spawning area. Check the spawning situation in time, and once the eggs are laid, the broodstock are fished out and the eggs are collected.
1.4 Incubation
1.4.1 Hatchery. Cement pond hatching, hatchery size 5m×5m×0.3m, water depth 20cm. Shade rain shelters are set up in the incubation area.
1.4.2 Incubation Methods. The fertilized eggs are collected into a cement tank and aerated in still water, which is sterilized in advance. Incubation density 1~15,000 grains/m2.
1.4.3 Incubation management. During the incubation process, attention is paid to disinfecting the fertilized eggs to prevent water mold. During incubation, the water temperature should be kept between 20 and 28 °C, and the amplitude range should be controlled at about 2 °C to ensure that the water quality is fresh and the dissolved oxygen is not less than 4mg/L.
1.5 Emergence. After the fry colony can dive for 8 hours, the fry emerges.
2. Seedling cultivation
2.1 The seedlings are from April to July, and the water temperature ≥ 25 °C.
2.2 Seedling ponds. The area is 1500~2000m2, and the pond is separated by a grid. In advance, use a mesh of about 20 mesh (1 to 1.2 m high) to surround the fry pond to prevent frogs, snakes and rats from entering the pond. The water depth of the seedling pond is 1 to 1.2 m.
2.3 Water injection. About 6 days before the seedlings are injected with water, the depth of water injection is 1±0.1m, and the water inlet is filtered with a 120 mesh mesh bag.
2.4 Clear the pond for disinfection. After the end of the water injection, use tea bran 25 ~ 30kg / mu to clear the pond, 400g of copper sulfate per mu, 300g of ferrous sulfate, and add water to the whole pond to kill ciliate. On the third day of Qingtang, 400g of enemy insects and 1 bottle (100mL/bottle) of mebenzimidazole were sprinkled throughout the pond to kill worms and parasites. On the 4th day of the pond, the pond water is slightly colored, and the whole pond is sprinkled with chlorpyrifolith (40mL/mu) and water to kill zooplankton and aquatic insects.
2.5 Water. On the second day of Qingtang, 40± 10kg/mu of chicken manure is fertilized by packaging slow release. Each package of chicken manure 20 ~ 25kg, with a rope to pull well, and in the chicken manure bag inserted a few small holes, let the fertilizer release, and open the aerator, water after 4 to 5 days to test the water to release seedlings.
2.6 Seedling preparation. On the 4th day of clearing the pond, a small circle with an 80 mesh net in the upper air outlet, with an area of about 15 to 20 m2, is prepared for the release of fish fry (black sesame seeds). The mesh should be vertical, pressed, and covered with a shading net of about 10m2 to prevent strong sunlight and heavy wind and rain, and put 3 to 5 terrestrial grasses inside when conditions permit.
2.7 Seedling release. Test the water on the 5th night of clearing the pond. Take about 20kg of water (half a bucket) in the pond and put it in an indoor container, put 10 to 20 fry, and test the water for 10 hours to release the seedlings normally. On the 6th day of Qingtang (48 hours after the use of cypermethrin), the seedlings were released at a density of 100,000 to 150,000 fish per mu (in case of heavy storms and bad weather, try to shield the wind and rain). About 2 days after the fry descend into the pond, when the fish swim and sink, the purse seine in the pond is removed.
2.8 Feeding management. Fry are generally not fed after they are discharged from the pond. The lower pond is 4 to 6 days, and it should be replenished in time when the red worms in the pond are reduced. Every 3 to 4 days, a pond of rotifers should be sent, and a total of two ponds should be issued. But there is no need for an inner net, no need to put grass. When supplementing red worms, the first time with a 60 mesh screen silk screen, large individuals frozen for use. As the fry grew, they gradually switched to 40-mesh to 20-mesh sieve nets. The exact size depends on the fry size. However, all supplementary red worms must be filtered when entering the pond to prevent centipedes from entering the pond.
2.9 Sieving (commonly known as "sieving") divides the pond. When the fry grows to about 6 dynasties (1 dynasty body length of about 3.3 cm, the same below), it is necessary to pull the net up the fry, out of the sieving pond, according to the specifications of the fry to set the sieve position, it is best to distinguish half a direction (about 1.6cm) to sift out the fast-growing group (commonly known as "head stopper" to lengthen the next screening time. When sieving the pond, a small corner water surface should be surrounded by 60 mesh mesh mesh pieces in the pond, and the area depends on the number of fish, generally 20 to 30m2 (note that there can be no lack of oxygen in the water body in the purse seine) to concentrate the fish, which is convenient for "domestication".
2.10 Domestication and breeding. When taming food, make a circular food table, put the frozen and hardened stagnant water pods (or can use the seawater harvest insects), put the recovered live water pods (red worms) nearby, lure the fish swarms, reduce the amount of live water pods after the cluster, increase the amount of frozen water pods, and finally completely stop the live water pods, switch to fish syrup and feed the stagnant water pods, mix the stranded fish slurry with the "stagnant water pods" to make a "slurry mass", hang a ball on the side of the pool, when the feeding intensity increases, the stagnant water pods will be changed to powder, that is, the powder will be fed with "fish pulp", and the stagnant water pods will be scattered when the food is strong. Artificial powder is fed. When the fish is in a strong way to remove or expand the purse seine in time, sift once in 5 to 7 days, when the fish grows to about 8 directions, that is, use fish pulp to mix the granular feed of No. 0 material (Ø 0.6mm), and adjust with the growth of the fish body, and gradually increase the size of the feed granules to No. 1 material (Ø 1.0mm). The entire domestication and breeding time is about 40 days. Fry are sieved 8 to 10 times during the rearing phase. Fry are reared for about 60 days and emerge from the pond when they reach a size of 40 to 60 fish/kg.
2.11 Prevention of fish diseases. During the breeding process, it is necessary to disinfect the food field and tools with bleach powder or formalin every day. The use of antibiotics throughout the process is strictly prohibited, and generally bacterial VESs occur less often, and once they occur, they are treated with traditional Chinese medicine.
2.12 Fishing Transport. Fry transport oxygen bag transport, 48 hours journey, shipping density of 25000 fish / bag, air transport is more ideal. Fingerling transport. After 3 days of food stopping, the net is pulled and fished, and the live water truck is transported. Fish density per 1000kg water Shipment volume ≤300kg, per 1000kg of water plus 250g "antistress", shipping water temperature control between 15 ~ 20 °C. If the water needs to be changed once in 4 to 5 hours for long-distance transportation, the immediate temperature difference ≤ 3 °C when the water temperature is adjusted on the way. Transport operations should be carried out with care and should not cause injury.