Technical points of how to raise sea bass healthily

Sea bass, also known as sea bass and seven-star perch, belong to the order Perciformes and Fataceae in taxonomy. Because they breed and grow along the coast, they are different from freshwater California perch and osmanthus bass, so they are also known as sea bass. Sea bass is a fierce carnivorous fish, which naturally feeds on small fish and shrimp, and artificial culture takes high-grade expanded material as the staple food and uses a small amount of fish larvae. Sea perch is a widely salty fish, which has the characteristics of fast growth, wide adaptability and strong disease resistance. Healthy culture techniques are introduced as follows.

Pond requirements and seedling release preparation

1. Pond. The area of each pond is 8-12 mu and the water depth is about 2 meters. The pond is too small, the water body is narrow, and the dissolved oxygen is insufficient, so it is difficult to produce high yield; the pond is too large and deep, which is disadvantageous to the production operation. The pond had better set up intake and drainage gates, respectively leading to the inlet and drainage rivers, do not reuse aquaculture water, so as to avoid secondary pollution.

2. Mechanical equipment. Every 1.2-1.5 mu of water is equipped with an aerator, which is the basic condition for high-yield culture; ponds need to be equipped with pumps to ensure that new water can be replaced at any time, and ponds without intake and drainage gates are more necessary; in addition, diesel generators should be equipped to prevent power outages and ponds from lack of oxygen.

3. Clear the pond. The ponds used for raising perch go through dry ponds, desilting and exposure, especially the old ponds that have been farmed for many years. Sterilize once half a month before seedling release, apply 150jin of quicklime per mu or disinfect with 20ppm bleach with appropriate amount of pool water. If there is no dry pond exposure, but also use tea bran to break and soak the whole pond to thoroughly remove wild fish.

4. Plug in the network. Divide the pond with a fine net to make it easy for fish fry to eat.

5. Cultivate water. After disinfection, the pond was filtered with fresh water (about 80 cm), and some compound fertilizers were applied to cultivate plankton.

II. Selection and cultivation of fish fry

1. Choose and buy fish fry. From the beginning of December to March of the following year, the fry needed for sea bass culture in Guangdong are basically hatched and desalinated in Fujian and transported directly to Doumen, Zhuhai, to be temporarily raised and sold in cages, usually 2-3 cm in size. The uniformity of selecting seedlings does not have to be greedy. In addition, we should pay attention to the "black body" fry, which has a low survival rate due to transportation stress.

2. Stocking fish fry. The general stocking density is about 8000 fish / mu, and it is generally chosen to release the fry at noon on a sunny day (when the water temperature and dissolved oxygen are higher to reduce the discomfort of the fry). The fry are disinfected with water and put into the prepared grid. Because there are many baits in high-density culture, and perch seldom look for the leftover bait at the bottom of the pond, a small amount of crucian carp, tilapia or carp (omnivorous) and a small amount of silver carp (filter feeding) should be put in per mu after net removal, so as to reduce water pollution and increase culture efficiency.

3. Fish fry cultivation. After releasing the fry, it is necessary to fully increase the oxygen (preferably at the bottom of the loose air stone). Generally, no bait is given on the first day, and the feeding begins gradually after a day, requiring fixed-point and regular meals, and the water spider is the best bait for opening. It is also possible to mix part of the eel feed with fish syrup. When the fry is 5-6 cm, it can be fed gradually, and anti-enteritis drugs should be added appropriately in the fry stage. As the fry grows up, the grid is gradually removed.

III. Management and disease control

1. Daily management

Bait: perch is easy to overeat, so the amount of feeding should be properly controlled, which is helpful to reduce the cost, reduce the occurrence of gastrointestinal diseases and water pollution. Bait to achieve a fixed point, timing, quantitative, generally feed 2 meals a day, respectively at 6-7 o'clock in the morning and 6-7 pm in the evening, generally build a bait bridge in the pond, feeding normally to 80% full. In case of high temperature and changing weather, the amount of bait should be reduced appropriately, and the feeding and health status of the fish should be observed every time, so that contingency measures can be taken in time.

Water quality management: high-yield culture of sea bass, that is, high-density culture, it is very important to maintain fresh water quality and sufficient dissolved oxygen. The main methods are:

Change water frequently, especially in the middle and later stages

In order to increase oxygen frequently, the aerator can be started properly in the fry stage, and the times of starting aerator become more and more frequent with the growth of fish, especially in the high temperature weather and the later stage of culture, all aerators should be started to keep the dissolved oxygen in pond water sufficient.

With the application of biological agents, high-density culture brings a large number of residual bait and excreta at the bottom of the pond, the decomposition concentration of harmful substances is high, and a large amount of oxygen in the water is consumed, especially in high temperature weather. Proper application of biological agents can effectively degrade ammonia nitrogen and nitrite and maintain good water quality, which is most easily ignored by farmers.

Do a good job of disinfection and insecticidal work, generally once every 15 days, depending on the frequency of fish eating.

Patrolling the pond: during the day, we mainly observe the increase and decrease of eating to judge the health of sea bass. Generally, the discomfort of fish is the first to react on eating. In addition, we inspect whether there are fish swimming, and there are generally a small number of fish swimming before a large number of cases. This is the best time to see a doctor and take medicine, and it is also a critical period. At night, especially at 2-3 o'clock in the middle of the night, the operation of the aerator should be inspected.

Anti-theft: fish theft occurs every year, so we must pay attention to guard against theft in the middle and later period of culture. the general way is to keep adequate lighting in fish ponds at night, fences in fish ponds and ample monitoring equipment.

2. Disease control

(1) ammonia nitrogen and nitrite poisoning: in high temperature weather, the ammonia nitrogen in the water is high, and even nitrite is produced, which will lead to dead fish when the perch is poisoned by hypoxia and food is reduced seriously. Main symptoms: Gill dark red, eating less. Prevention and treatment methods: release flocculant to absorb ammonia nitrogen in water, release bottom treatment agent to reduce ammonia nitrogen; release part of old water and inject new water, avoid directly flushing pond bottom dirt to accelerate the death of fish; pay attention to biological agents before the disease.

(2) Enteritis: the abdomen of the diseased fish is dilated, the anus is red and swollen, and there is a yellowish mucus outflow from the squeezed abdomen. It is mainly caused by feeding metamorphic feed or excessive feeding. During the treatment, the diet should be reduced first (it is better to stop feeding a meal), and the bait mixed with general antimicrobials can be cured for 3-5 days.

(3) Hemorrhage: the base of pectoral fin and dorsal fin of diseased fish is red, swollen and congested, the movement of diseased fish is slow, and the food intake decreases. The disease is a viral infection with strong infectivity. The mixed bait of ribavirin and norfloxacin can be used for 6 consecutive days. At the same time, the pond was sprinkled with strong chlorine throughout the pond, once a day for 3 consecutive days.

(4) Water mildew: this disease often occurs in winter and spring when the water temperature is low. The gray cotton-like mycelium is attached to the wound of the diseased fish, and the fish is weak and dies slowly. The disease spreads quickly after infection. Prevention can draw part of the groundwater to maintain salinity, and add more water to maintain the water temperature. The disease is easy to occur in a specific environment, to change the pond water environment and maintain adequate nutrition of fish to improve disease resistance is the most effective control measures.

(5) rotifer, oblique tube worm, Polycondensed disease: it mostly occurs in the body surface and Gill filaments of fish in the middle breeding stage. The symptoms are emaciation, blackening and erosion of the mouth, which occur all the year round. Water exchange is often used in prevention to improve water quality. The mixture of copper sulfate and ferrous sulfate (5:2) of 0.77-1ppm can be used to sprinkle evenly throughout the pond, or 20-25ppm formalin can be used to sprinkle the whole pond. General parasites are easy to cause secondary bacterial infection, so it is generally necessary to disinfect after killing insects.

(6) Hepatobiliary syndrome: the main manifestations are reduced eating, gradual swimming of fish and unknown death. The main reasons are frequent drug delivery under high-density culture, chronic accumulation of toxic and harmful substances in the fish, leading to organ dysfunction and tissue damage, long-term overfeeding, metabolic disorders or even metabolic disorders caused by long-term overload of fish liver. Prevention and treatment is mainly to regulate and control the water environment, scientific feeding, regular feeding with some liver-soothing and cholagogic Chinese herbal medicine has a certain preventive effect.

IV. Current misunderstanding of aquaculture

Some farmers mistakenly believe that "the more feed, the more fish", and do not know that excessive feeding will lead to a decline in the digestion and absorption rate of feed, long-term this will even lead to disease, so over-feeding causes waste. We suggest that the feeding of puffed materials should be kept at 70% or 80% full (the feeding rate of fish slows down obviously, and 70% of 80% of fish do not eat). We might as well do the math: generally, 28000 jin of new fish are produced in a pond, 1000 packs of materials (20kg/ package) are used, and they are farmed for 10 months. If users feed an extra 10 jin of food every day, the results will be as follows:

Coefficient of normal feed: 28 jin / bag

The coefficient of multiple feeding is 28000 / (1000 × 0.25 × 30 × 8) = 26.4 jin / bag.

Waste: 140 × 608400 yuan.

In short, healthy sea bass farming can only make money by selecting good seedlings, adjusting water, using good materials and preventing good diseases.