First, biological characteristics
1. The sweet-smelling aquarium is mostly an annual one. Every year from February to May, when the water temperature of the river gradually rises to 10-15Â°C, close to the temperature of seawater, juveniles (2-3 cm in length) that have crossed the sea in the sea enter the estuary. Juveniles grow and develop in the river, with the development of the gonads, they also swim to the lower reaches of the river. In September-November, spawning with the larvae growth and water temperature continue to decline, young fish into the sea over the winter.
2, life habits also known as squid. It is said that this fish has the ability to "occupy the site." Wild ayu, which covers an area of â€‹â€‹about one square meter, plus the range of activities is only 2-3 meters.
3. The feeding habit of sweetfish is similar to that of other plant-eating fishes. It is an animal diet at the seedling stage, and it turns into a plant-eating and omnivorous as it develops. The larvae began to feed 4-5 days after hatching. Their body length was about 4 centimeters, and they began to eat cladocera and copepods and other small crustaceans, and continued until the upstream. During the journey to the river, feeding organs evolved, and feeding gradually changed to low algae.
4. The upper and lower limits of the growth of ayu are 10-27Â°C. In the range of 15-25Â°C, the growth rate is proportional to the temperature. Generally, the optimum growth temperature is 22-24Â°C, and the lower limit of winter is 2 - 3Â°C. The main growth period of ayu is summer and autumn, and the large one can reach about 500 grams.
5, Reproductive habits Ayu is a fish that is not breeding in autumn, and the spawning water temperature is within a period when the river water falls from 19Â°C to 14Â°C. The eggs are sticky, and the egg diameter is about 0.9-1.0 mm. Most of the broodstock died after spawning. The number of eggs laid can reach up to 130,000, with a minimum of 10,000 and usually 25,000.
Second, aquaculture technology is the beginning of artificial breeding of aquaculture in Japan, China's Zhejiang Province has been tested, Hebei Province has been successful breeding, Taiwan Province is more prevalent.
1. The selection of aquaculture depends on the conditions of water sources, water quality, baits, and management. The aquaculture site should be selected to have sufficient flow in the water source, generally reaching a flow rate of 27 liters per second, keeping the water temperature at an annual temperature of 13Â° C., PH value between 6.5-7.8, and the area where the feed is rich and pollution-free. The northern region should have wintering facilities.
2. Design of aquaculture ponds (1) Fish pond size: The pond size depends on the water source and the amount of water. Generally, each pond is suitable for 100-300 square meters.
(2) Fish pond structure: Round fish ponds have the best breeding effect. The circular fish pond will not cause dead spots, and it is easy to concentrate the dirt around the central drainage area, so it can be easily discharged in time to keep the water quality fresh. The circumference of the bottom of the pool should generally be maintained at a slope of 1/10 to 1/15 toward the center of the pool. When the pond area is 100 square meters, the thickness of the pool wall should be 15 centimeters and the depth of water is 60-90 centimeters. The pool bottom and the pool wall are made of stones or concrete, which is easy to attach natural diatoms and increase the unique aroma of sweet fish. .
3. When the stocking density and the amount of growing water are sufficient, an average of 400 fry can be stocked per 3.3 square meters. The growth rate of sweetfish is related to the farming conditions and management, and the product specification is 80 grams.
4. Baits and Feeding Methods The formula for accompaniment of ayu is fish meal 25, animal protein powder 5, chicken powder 4, soybean meal 10, rice bran 15, alfalfa 5, distillers grains 8, vitamin 15 and inorganic salt mixture 4. Solid fat 6, coarse corn flour 10.
Feeding methods mostly use the bait method. The number of feedings is mainly based on the environmental factors such as the stocking density, development stage, water temperature, water quality, and water volume of the fry. It has been observed that sweetfish should be cast in the morning and evening. Feeding amount is sufficient in dissolved oxygen, and the water temperature is 17% of fish body weight at 17-22Â°C. If the temperature is lower than 17Â°C and the dissolved oxygen is low, the feeding amount should be reduced.
5. Aquaculture management (1) Preparation for fry before entering into cultivation: Check and maintain all facilities before stocking, and pre-infuse about 15 days before seedling, so that the wall of the pond is covered with diatoms and replanted. .
(2) The selection and transportation of fish species is a rare species. Artificial seedlings are currently only available in several nursery sites in Zhejiang and Hebei. Seed transport can be used for long-distance transportation of automobiles. When the water temperature is 17-19Â°C, the density survival rate can reach more than 98%; the short-distance transport density can be increased.
(3) Before the fish fry in the fry of the fry stocking are put into the fish pond, they must be disinfected with a medicine bath to prevent the virus from being brought into the pond. The amount of antibiotics in the medicine bath is about 1/5 to 1/10 of the amount of water. On the day of stocking, the bait can be fed. The amount of feed depends on the health of the fry and the weather. After a few days, the amount of bait is gradually increased to about 15%.
(4) Cultivation management Fish fry weighing 5-6 grams are generally stocked in mid-March, and product specifications can be achieved by early June. The sweet fish has a feed rate of 2.5-3. Cultivation management mainly pays attention to the following aspects:
a. Feed more fresh, high nutritional value foods rich in animal protein to produce larger-sized products;
b, often pay attention to changes in water temperature, sweet fish intolerance of low temperature, water temperature is low, easy to cause indigestion, if conditions can be increased to the optimum water temperature or increase feed, but avoid feeding more fat-containing food;
c. Our observations that ayu are sometimes eaten from each other, so we must regularly patrol the pool to observe the feeding and activity of the cultivars in order to adjust the feeding amount in time;
d. Observe whether the activities of the fish in the pool are normal and changes in appetite. Check whether there is disease or not so as to avoid loss. In summary, the success of aquaculture depends on the level of environmental factors and the level of management system.
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