Dobao fish, also known as southern turbot, Atlantic desert turbot, American desert turbot, belongs to the bony fish, flounder order, flounder suborder, turbot family, turbot subfamily, turbot genus, is a deep submarine fish, is the largest of many turbot flounder fish in the Americas, naturally distributed in the United States North Carolina to the southern gulf of Florida, Texas south of the strait is also distributed.
The morphology of the dolphin is similar to that of the brown turbot in China, the body side is flat and oval, both eyes are located on the left side of the head, the left side of the body is light brown, there are irregular spots, the abdomen color is lighter, and it can change with the surrounding environment in order to hide the body and avoid predators. Dobao fish are broadly salty fish and can usually survive in both seawater and freshwater. Females grow faster than males and reach sexual maturity at two ages. Males typically have a lifespan of two years, with the longest-lived males reportedly in South Carolina reaching more than 3 years. In the case of the same age, the body weight of the female is significantly greater than the weight of the male, and a three-year-old female adult can reach about 25 cm. In natural waters, adults can grow up to 75 cm, females grow faster than males, second-instar fish can reach sexual maturity when the males reach 20 cm to 25.5 cm in length, and females can reach 30 cm to 35.6 cm. If artificial breeding is carried out, its growth period is significantly shortened, the effect is faster, and the benefit is better. In natural seas, the dobao fish has the ability to ambush and prey. Juvenile fish mainly use crustaceans as bait, and as the fish continue to grow, they gradually feed on a variety of fish, usually including spotted mullet, striped mullet, white mullet and grass shrimp.
Duobao fish has the characteristics of fast growth, excellent quality, wide adaptability, strong resistance to stress, and the meat is delicate and rich in nutrients, and is recognized as an excellent farmed fish. Since the early 1990s, the United States began to study the breeding and breeding technology of multi-treasure fish, and has made breakthroughs in physiological, ecological, artificial breeding and breeding technology, and the breeding of multi-treasure fish has become a new breeding industry that has developed rapidly in the United States. After the introduction of this variety into China, it has great development value and has broad prospects for development.
Breeding of multi-treasure fish
1. Selection of seedlings and seedlings
(1) Specifications: Duobao fish and brown turbot are relatively close in breeding technology, and it is easy to grasp in production. Generally, when the seedlings grow to more than 5 cm, they can be entered into large ponds for stocking. The size of more than 8 cm is best to put seedlings, at this time the physique of the seedlings is enhanced, the disease resistance is improved, the adaptability of the fry after entering the pond is strong, and the survival rate is easily improved.
(2) Seed selection: When purchasing seedlings, pay attention to the selection of fry with complete body shape, normal body color, no deformity, no bleaching, no damage to the fins, and rapid swimming, with a well-proportioned size, no pathology, and no parasites for the gills.
(3) Seedling release time: outdoor breeding, the water temperature above 18 °C to start releasing seedlings, to April to May of each year is appropriate. Because the water temperature is low too early, the fry is difficult to adapt to, and even reduces the survival rate of the fry; too late it affects its growth into a commercial fish in the same year.
(4) Stocking density: pond culture, stocking 500 to 800 fish per mu; pond cage culture, each 3 m × 3 m × 1.5 m cage stocking 100 to 200 fish; sea area cage culture, each 3 m × 3 m × 3.5 m cage stocking 300 to 400 tails; factory greenhouse culture, about 20 fish per square meter stocking.
2. The choice of pond
The existing shrimp pond can be used for breeding with a slight modification, requiring a water depth of about 1.5 meters, sufficient water source, fresh and pollution-free water quality, and better inlet and drainage facilities. Before releasing seedlings, it is necessary to carry out pool bottom treatment, dry pond dredging, loosen the bottom of the pool, and weather exposure for more than 10 days. 30 cm ~ 50 cm of inlet water, disinfection treatment with bleach powder, the effective chlorine content in the pool water is more than 10ppm, and the bleach powder containing 25% to 30% of chlorine is generally applied more than 40 grams per cubic meter of water.
Nurture management
1. Water quality and water exchange
The quality of aquaculture water is related to the success or failure of aquaculture. In the whole process of breeding, attention should be paid to carefully observing the changes in water temperature and water quality, and regularly measuring water temperature, dissolved oxygen, salinity, pH value, ammonia nitrogen, sulfide concentration, etc. The regulation of water used for pond aquaculture can be controlled by adjusting the amount of water exchanged. The size of the water exchange is proportional to the water temperature.
2. Bait nutrition and processing
Dobao fish are carnivorous benthic fish. Stir the vitamins and flour well, then mix with fishmeal and yeast powder, then add fish oil to mix well, add fresh fish, shrimp (or frozen fish and shrimp crushed), the above mixture together into the pelletizer and stir to make pellet feed. The raw materials for processing wet pellet feed are mainly mackerel, sardines, mackerel, noodle fish, green scale fish and other miscellaneous fish, which require good freshness, poor freshness or too long freezing time. In the process of farming, vitamin C, vitamin E and multivitamins can be added to the feed to strengthen the nutrition of fish and prevent the onset of disease due to nutritional deficiencies. It should be noted that the processed bait should be fed on the same day, and the rest should be properly frozen and stored. The maximum storage time should not exceed 2 days to prevent spoilage.
Commercially available baits that meet nutritional requirements can be used. Note that when the water temperature is low or high, the number of baits and the amount of bait can be appropriately reduced. In principle, there should be no residual bait, and bait cannot be thrown before the medicinal bath.
Multi-treasure fish disease prevention and control
1. Find out the cause of fish disease
(1) Water temperature change: fish belong to thermostatic animals, can not regulate body temperature, fish body temperature with the living environment water temperature rise and fall and change, sudden changes in water temperature, will cause fish death. Generally, when the body temperature of juvenile fish changes by more than 2 ° C and the adult fish exceeds 5 ° C, the fish is in a stress state, and it is most likely to die at this time.
(2) The content of dissolved oxygen in water: the oxygen consumption of fish is higher. The amount of dissolved oxygen in the fish living environment is often in a state of insufficient, especially in the case of high-density aquaculture, hypoxia often occurs, and fish are prone to disease. Therefore, it is important to take some oxygenation measures according to the actual situation. Suitable dissolved oxygen is generally 4 mg / L ~ 12 mg / L, the most suitable 8 mg / L ~ 9 mg / L.
(3) COD: less than 3 mg/L. If the ammonia nitrogen and COD content in the water is too high, the water quality is corrupt and prone to disease.
(4) pH: 6.0 ~ 9.5 is appropriate, the best is between 7 and 8.2. In the process of breeding, as long as you pay attention to frequent observation and testing, it is easier to grasp.
(5) Salinity and temperature: strong environmental adaptability, is the obvious advantage of multi-treasure fish over other fish. Its suitable salinity ranges from 0 to 60, the optimal 5 to 35, and it can even be grown in fresh water. The water temperature survival range is 1 °C ~ 35 °C, and the suitable range of aquaculture is 18 °C ~ 30 °C.
(6) Bait: Fish also tend to "get sick from the mouth", so what kind of bait to choose is very important. The allocation of fresh bait and matching bait should pay attention to the combination and freshness of nutrition, and avoid pollution during processing. Feed protein requirements are 32% to 48%, and the optimal 38% to 48%. Breeding for 8 months to 12 months can generally reach about 600 grams to 800 grams.
2. Preventive measures for fish diseases
(1) Stocking density: The stocking density of fry should be appropriate, and the stocking density is too large, resulting in an increase in the amount of bait and fish excrement, reducing the amount of dissolved oxygen and deteriorating the water quality.
(2) Water exchange and decontamination: With the growth of fry, it is necessary to gradually increase the amount of water exchange, generally 5 days to 10 days old daily water change, water exchange 30% ~ 50%; 11 ~ 20 days old daily water change twice, water exchange 40% ~ 60%; 20 days to 30 days old daily water change 2 times, water exchange 50% ~ 70%. Every 1 to 2 days to absorb sewage, the pond should be dredged at the bottom of the pond every year, and the indoor cement pond should be sucked in time to remove impurities.
(3) Filtration and purification: The greenhouse breeding water should be at least purified by sand filtration, and the fine sand particle diameter of sand filtration is 0.15 mm to 0.25 mm, and the thickness is about 60 cm.
(4) Strengthen the management of baiting: during breeding, the nutritional requirements of juvenile fish and adult fish must be met, and the freshness of bait should be good and the nutrition should be complete. Multivitamins, vitamin E, vitamin C and minerals can be added if necessary. Seedlings must be rinsed with fresh seawater before feeding with biological bait, and disinfected with antibiotics when there are bacteria. The number of feedings per day is determined according to the needs of the fish. Feeding bait should be qualitative, quantitative, timed and positioned. In principle, there can be no residual bait.
(5) Drug prevention and treatment
(1) Fish body disinfection: whether the purchased fry have diseases or injuries, they must undergo a medicinal bath; the seed breeding stage is sorted, and the medicinal bath is also carried out after the pond is poured. Commonly used disinfectant drugs are formalin, copper sulfate, ferrous sulfate and so on. Formalin concentration 1× 10-4 to 2× 10-4 medicinal bath for 60 minutes to 120 minutes, can prevent bacterial diseases and parasitic diseases; copper sulfate 5× 10-7 × 10-7 plus ferrous sulfate 2× 10-7 ~ 3× 10-7 can prevent ciliate. The use of potassium permanganate is strictly prohibited in the prevention and treatment of polyporangate drugs, because the respiratory system of turbots is very sensitive to potassium permanganate, and there have been many cases of turbot deaths due to the application of potassium permanganate.
(2) Pond disinfection: regular water disinfection, the most commonly used is to sprinkle quicklime, per acre of 1 meter deep pond dosage of 10 mg to 20 mg, can play a role in sterilization, improve water quality. In addition, it can also be sterilized with bleaching powder with a concentration of 5×10-7.
Estimation of aquaculture benefits (calculated at 200 yuan / kg)
1, pond culture: each mu can be stocked 500 ~ 800 tails, the survival rate of 80%, breeding for 6 months to 12 months average of 0.5 kg / tail ~ 0.8 kg / tail, per mu can earn 60,000 yuan ~ 100,000 yuan.
2. Pond cage culture: each 3 m × 3 m × 1.5 m cage stocking 100 to 200 tails, the survival rate is 80%, the average of 6 months to 12 months of breeding reaches 0.5 kg / tail ~ 0.7 kg / tail, income of 0.8 million yuan ~ 20,000 yuan.
3. Cage culture in the sea area: each 3 m × 3 m × 3.5 m cage stocking 300 to 400 tails, the survival rate is 80%, and the average of 6 months to 12 months is 0.5 kg / tail ~ 0.7 kg / tail, and the income is 20,000 yuan ~ 40,000 yuan.
4, factory greenhouse breeding: 20 tails per square meter, survival rate of 80%, breeding 6 months to 12 months to reach 0.5 kg / tail ~ 0.8 kg / tail, income of 1600 yuan / square meter ~ 2500 yuan / square meter.