Duobao fish grows rapidly, and it only takes10 ~12 months from spawning and hatching to commercial fish selling (0.8 ~/kg). It is an excellent fish with great development prospect because of its high economic value, high bait conversion rate, strong disease resistance and low oxygen consumption. The female grows faster than the male, and the length of the female fish is obviously larger than that of the male fish. When the female fish reaches sexual maturity at the age of 2, the length of the male fish can reach 20 ~ 25.5 cm, and the female fish can reach 30 ~ 35.6 cm.
Facility conditions
The farm should be located far away from pollution sources, with convenient communication and transportation, sufficient electricity and fresh water. The water quality is clear and meets the national secondary water quality standard for fisheries (please consult the local fishery administrative department). Parent fish cultivation facilities include temperature control, light control, aeration, water intake and drainage, water treatment and other facilities and equipment. Parent fish breeding ponds can be made of wooden tanks (lined with rubber inner walls), glass fiber reinforced plastic tanks and cement tanks. There are square, rectangular, circular and octagonal pool shapes. The volume varies from10 ~100 cubic meters. The general-purpose volume is 20 ~ 60 cubic meters, and the pool depth is 0.6 ~1.2 meters. The water inlet is arranged at the top of the pool in the tangential or diagonal direction, and the central water outlet is arranged in the center of the pool. After circulating, the pool water is discharged out of the pool through the central drainage column. The drainage column outside the pool is composed of inner and outer sleeves, which can be matched with the central drainage column to freely adjust the water level and flow rate in the pool.
Seedling facilities should include seed culture room, biological bait culture room, aeration facilities, temperature control facilities, water treatment facilities including (ultraviolet disinfection equipment) and water intake and drainage facilities. Nursery ponds are divided into pre-cultivation ponds, post-cultivation ponds and intermediate cultivation ponds.
Pre-cultivation pond: round or square cement pond with an area of10 ~ 20m2 and a depth of 0.8 ~1.0m..
Post-culture pond: the area is 20 ~ 40m2, the water depth is1~1.5m, and there are independent water inlets and outlets; The bottom of the pool is inclined to the drainage hole at a certain slope to facilitate drainage.
Intermediate culture pond: round or square cement pond with an area of 30 ~ 50m2 and a depth of 0.8 ~1.0m, which requires good water circulation and sewage discharge functions.
Parent fish selection
There are two sources of parent fish: one is selected from wild populations; The second is to select from the breeding population. China is not the place of origin of Duobao fish, so it mainly relies on the second way to obtain parent fish. Under the general breeding conditions, only about 50% of the female fish ovulate in the production season, and other females either do not lay eggs, or lay eggs late, and the quality of eggs changes greatly, so the fry breeding farm should keep enough parent fish, usually >: 100 tail is appropriate. Duobao fish is hermaphrodite and lacks secondary sexual characteristics. The difference between male and female parents is gradually revealed through the periodic development process. Female individuals are larger, the body fullness increases before spawning, and the gonad bulges obviously; Male individuals are relatively small, with average body fullness at maturity and no prominent gonads. Parent fish should be complete in shape, normal in color, healthy and harmless, active, good in clustering, active in feeding, and appropriate in age and size. Female fish are required to be over 3 years old, weigh over 3 kg and have a body length of over 40 cm; The male fish is over 2 years old, weighs over 2 kg, and is 30 ~ 35 cm long. The male-female ratio of parent fish entering the pond is 1︰ 1 or 1︰ 1.5. Parent fish are allowed to be used until 6 years old. Parent fish are transported in foam boxes with low temperature insulation, and the temperature is about 10℃,1~ 2 fish per box. Parent fish transported in the current breeding season should generally be the next breeding season.
artificial insemination
Duobao fish spawns in batches and can spawn many times in each spawning season. After the eggs of Dolphin mature, they first enter the reproductive cavity, and then they can be fertilized by artificial insemination. Every female of Duobao fish has a regular ovulation interval, but the individual ovulation cycle is different: short 60 (4) hours, long113 (2) hours, and most of them are between 80 and 90 hours. When the temperature is12 ~14℃, the eggs must be squeezed within 10 hour after ovulation to ensure the maximum survival of the eggs. This time limit is affected by the water temperature. During artificial insemination, dry the fish and utensils first to prevent water and excrement from mixing. Then add 1× 105 eggs to 1 ~ 5ml semen, stir quickly and evenly to make the sperm and eggs fully contact, and then add a small amount of seawater after sedimentation and sand filtration, so that the volume ratio of semen, eggs and water is about 0.5:/kloc-0:/kloc-0: 00. Let it stand for10 ~15 minutes. After it absorbs water and swells, rinse it with clear water1~ 2 times, put it into a 2000ml measuring cylinder, and add seawater to separate the floating eggs from the precipitated eggs. Record the number of floating eggs, and put them into an incubator for incubation after disinfection. The egg diameter of Duobao fish is an important index of egg vitality. When the egg diameter is 0.9 ~1.1mm, the fertilization rate is high, while the fertilization rate is medium or low when the egg diameter is1.1.2mm, and the fertilization rate below 0.9mm is the worst. High-quality fertilized eggs are transparent and round, and the gap around eggs is small. The 1.2 division after fertilization is clear and symmetrical. If you need to transport the fertilized eggs of Duobao fish, the packing density depends on the transport distance, which is generally 3000 ~150000 eggs/L. During transportation, the oxygen-filled bag should be kept at a low temperature.
Hatching young fish
The fertilized eggs of Duobao fish are floating in seawater, so the conventional floating egg incubation method is adopted. Small glass tanks (25 ~130l) and large glass fiber reinforced plastic tanks (1~ 10m3) or cement tanks (10 ~ 20m3) are commonly used in incubation containers. One or more incubation cages can be placed in the incubation tank (or pool), and the incubation cages are generally about 80cm×60cm×60cm, so that they are in a floating state, and the upper opening of the incubation cages is about 10cm above the water surface. In order to keep enough oxygen in the incubator, the water in the incubator should keep circulating flow, and at the same time, a number of inflatable stones can be used to inflate the dissolved oxygen level in the incubator, so that the dissolved oxygen level in the incubator can be kept above 6 mg/L. At the same time, gas stones 1 piece are placed in the center of each incubator to keep the water flow and make fertilized eggs evenly distributed in the water. The daily water circulation of the incubator should be kept at 2 ~ 3 ranges, and the number of eggs deposited every day should be counted to suck out the eggs in time. When hatching, the following conditions should be met: the water quality should meet the second-class standard of national fishery water quality (consult the local fishery administrative department); Direct sunlight should be avoided, and the illuminance100 ~1000 lux, preferably 500Lux; Water temperature10 ~16℃, with12 ~15℃ being the best, and salinity: 28 ~ 35; pH7.8～8.2； Dissolved oxygen >; 6mg/L； Ammonia nitrogen < 0. 1mg/L。 According to the density of 300,000 ~ 600,000 grains /m3, the fertilized eggs are put into an incubation cage of 0.5 ~1m3 for incubation. Under the condition of12 ~14℃, fertilized eggs can hatch within one week. There are two ways to deploy the pond: one is to directly deploy the pond after collecting, washing and counting the hair eggs; On the other hand, the newly hatched fish with broken membrane are carefully moved into the feeding tank with smooth utensils, and the water and gas quantity are adjusted to ensure sufficient dissolved oxygen, and at the same time, the dead seedlings are removed, kept clean and hygienic, and enter the fry cultivation procedure.
Seedling cultivation
If you buy seedlings, you should buy seedlings of more than 5 cm. Before buying seedlings, you should investigate the parent fish germplasm, seedling quality and technical level of the seedling farm, and you must buy them from the national seed farm or the seedling farm designated by the government. It is required that the fry be in complete shape, without injury, disability, deformity and albinism. The specifications of the same batch of seedlings are neat, the eyes are located on the left side of the body, and the eye side is bluish-brown, with a little melanin, and the eye side is smooth and white. The fry body surface is bright and smooth, without scars, dark and red symptoms, with strong mobility, neat gills and no inflammation and parasites.
Seedling transportation: Stop eating and cool down well in advance before seedling transportation. Generally, nylon bags are used for oxygen shipment, and the transportation time should be within 20 hours. Firstly, about 1/3 sand filtered seawater is added into the bag, the fry are counted, packed into the bag, oxygenated and sealed, and then packed into a foam box or carton for transportation. 10 liter packaging bag, each bag can hold 50 ~100 fish fry with a total length of 5 ~10 cm; Full-length15cm fry, each bag can hold 30 ~ 50 fry. During the transportation of fry, it is necessary to avoid injuries, collisions, broken bags, air leakage, water leakage and lack of oxygen. When the water temperature is high or the transportation distance is long, a small amount of ice cubes should be added to the transportation bag to cool down and inhibit bacterial reproduction.
Conditions for entering the pond: the temperature difference of fry in the pond should be controlled within the range of1~ 2℃, and the salinity difference should be within 5. So as to reduce that stress reaction of fry due to environmental change.
The biological bait used in the cultivation of the fry of Duobao fish mainly includes marine Chlorella, rotifer and Artemia. Chlorella sp. in seawater is Pseudococcus sp. One-time culture method is often used in production. The batch and scale of culture are mainly determined according to the production process of Duobao fry, the needs of larvae and juveniles, the time and quantity of feeding. The rotifer is Brachionus plicatilis. Rotifers are generally cultivated by one-time culture and continuous culture, or by combining the two methods. Cultured rotifers must be fortified with nutrients, the main purpose of which is to increase the content of unsaturated fatty acids. There are two ways to strengthen. One is to feed rotifers with marine microalgae rich in EPA/DHA, such as Phaeodactylum tricornutum, Isochrysis, Chlorella, and Chlorella. Chlorella and Chlorella are the most common. The second is to use artificial enhancers rich in EPA/DHA, such as squid fish oil and fish oil. Intensive culture was carried out 6 ~12 hours before feeding fry. Artemia is hatched by Artemia incubator, and the larvae are separated and fortified with nutrition, and then harvested and fed to the larvae and juveniles of Duobao fish. The reinforcement of Artemia refers to the reinforcement method of rotifer.
Intermediate cultivation
60 ~ 70 days after hatching, the fry can reach 3cm, at this time, most of the fry have completed metamorphosis and gradually turned into benthic life. In order to improve the quality of cultured seedlings, it is necessary to transfer to the intermediate culture stage. It can only be used as commercial seed for breeding when it is more than 5cm. Soak and disinfect the seedling pond with bleaching solution before releasing seedlings, and then add filtered seawater for later use after washing. For 3 ~ 5 cm seedlings, the seedling density is1000 ~ 2000/m2. During the cultivation period, the feed requires balanced nutrition, and high-quality compound feed or self-made soft pellet feed can be used. Feed 8 ~10 times a day in the early stage of feeding, and gradually decrease to 3 ~ 4 times as the fish grows up. In order to prevent the pollution of residual bait, the water in the pond must be drained after each feeding, and the deposited residual bait and feces should be removed, and the oil film should be removed. The water exchange rate is 8 ~10 cycles per day. In general, the survival rate of young fish from the initial hatching to the commercial seedling stage is10 ~ 20%, which can reach about 30%.
Out-of-the-pond: The larvae of Duobao fish are usually drained and collected out of the pond, so the damage of the larvae out of the pond should be avoided during operation, and the quality and specifications of the larvae out of the pond should be tested.
Transportation: The transportation methods of fry include box-type or barrel-type container inflatable transportation and running water boat transportation, which can be selected according to the specific situation. The water temperature and salinity of transportation water can be adjusted in advance according to the requirements of developing water environment. Seedling transportation should stop eating for more than 1 day.
Fish stocking
To control and adjust the culture density, it is necessary to adjust the culture density according to the exchange capacity of pool water and the growth of fry in actual production. The following factors should be considered when controlling the breeding density:
When the exchange capacity of pool water is less than 6 ranges per day, the density should be reduced appropriately; When the exchange capacity is more than 10 range per day, the density can be increased as appropriate; The density can also be increased or decreased according to the amount of dissolved oxygen in the monitored water.
Fish are sampled and weighed every month to decide whether to adjust the density.
Make full use of the culture area, so as not to slow down the growth rate of fish in some culture ponds because of over-stocking, nor to waste the culture area because of low stocking density.
In order to ensure that excessive stress reaction will affect the growth of fish, it is necessary to make a full plan before each pond separation and dumping to ensure that the fish will be stable in one pond for at least a period of time before the pond separation operation.
Feeding and feeding
The basic requirement of Duobao fish for feed is high protein and medium fat. Compared with other carnivorous fish, its demand for fat is slightly lower. If you feed high-fat feed for a long time, it will reduce the function of the liver. In order to make the turbot grow healthily, it is necessary to feed the turbot with feed suitable for each growth stage. The protein content in the feed is required to be 45-56% in the seedling stage (including the juvenile stage); During the growth period, the content of protein in feed is 45-50%. The demand for fat of Duobao fish is low. The content of fat in feed is about 10% at the seedling stage and10 ~13% at the growth stage. The optimum C/P ratio (energy to protein ratio) is about 65% at seedling stage; With the growth of fish, the C/P ratio of feed in the growing period increased to 65 ~ 76%; The C/P ratio of feed used before leaving the pond reached 80%.
The feed used in the culture of Duobao fish should be suitable for the nutritional needs of different growth stages, which contains a proper amount of vitamins, minerals and highly unsaturated fatty acids. The feed used should be easy to feed, the feed particles should be well formed and not easy to collapse in water. When purchasing feed, it should be checked whether the feed label indicates the following contents: it should be marked with the words "This product conforms to the hygienic standard of feed" to indicate that the product conforms to the provisions of GB 13078; Indicate the guaranteed value of the main components, that is, the contents of crude protein, crude fiber, crude ash, calcium, total phosphorus, salt, water and amino acids; Indicate the standard number, production license and product approval number for the production of the product; Specification, model, net weight, production date, shelf life, name and address of the manufacturer, etc. In order to prevent pathogenic organisms from being brought into fish ponds from feed, it is suggested that wet granular feed and any fresh materials should not be used in industrial farming.
Because turbot belongs to a temperature-changing animal, its food intake varies greatly under different water temperatures. Generally, the daily feeding rate is 6 ~ 4% at the seedling stage, about 2% when it grows to100g, and about1~ 0.5% when it grows to more than 300g.