Salmon culture
Squid, local name is three fish, three fish, etc., belonging to the é²±-shaped head, é²±, é²¥. Squid is a valuable food fish, its meat is delicious, nutritious, high fat content, Chinese and foreign famous, creating a high exchange rate.
The eel is widely distributed, and it is distributed in the Bohai Sea, Yellow Sea, East China Sea and South China Sea. It is an anadromous fish and lived in the sea for most of its life. Every year from April to May, sexually mature fishes cluster into rivers for the reproduction of the river, forming a salmon production period for each river. Since the 1970s, due to severe damage to resources, it has become extremely rare to fish in the upper and middle reaches of the Yangtze River. In order to protect and restore the resources of squid, artificial breeding of squid has also emerged while relevant departments have taken protective measures.
(I) Characteristics Fishes have a flat body side and a long garden shape. Kiss the tip, mouth big end position. The upper jaw has a short cut in the middle. The abdomen has large, sharp, serrated rib scales. Caudal fins deep fork-shaped, body and head gray-black, with a slight bluish-green luster on the upper side, abdomen silvery white. No sideline fish. Scales smaller.
Carp is a famous warm-water anadromous fish. It reaches the breeding season every year. It enters the rivers of the Pearl River, Qiantang River and the Yangtze River for genital migration. The eel that enters the Yangtze River reaches Yichang as far as possible, but the number is very small, mainly distributed in Jiangsu, Anhui, and Ganjiang along the Yangtze River. The squid that enters the river often activities in the middle and lower layers of the water and has a strong swimming ability. After the broodstock laid their eggs, the fish scattered and then they left the sea to get the bait and winter. Juveniles grow and develop in some sections of the Tongjiang Lake and the mainstream of rivers. From September to October in the autumn, the temperature of the water drops, and the water level of the rivers and lakes begins to decline. The young squid descends along with the river water, descends into the sea, grows to sexual maturity in the ocean, and then participates in upstream reproduction.
Squid is a filter-feeding fish and feeds on plankton, but at different stages of its life history, the type of feeding and the intensity of feeding are different. Young calamus before the river reaches the sea mainly eats cladocera, copepods, rotifers, hexapods, shrimp, microcystis, diatoms, green algae, etc.; pups descending from the river into the sea, along the coast Bait migration, the main intake of marine copepods, followed by the garden sieved diatoms, aphids, six-limb larvae and shrimp and so on. Carp grows faster, and after two months of incubation, body length can reach 6.0 cm. Females grow much faster than males. The eel is mature enough to reach maturity at 3rd age, about 46.5 cm in length when sexually mature, and 42 cm in males. Before the first maturity, it grew fastest and gradually slowed down later. The spawning period lasts from late May to late July. The spawning grounds in the Yangtze River system are mainly distributed in the middle reaches of the Minjiang River in Jiangxi Province. Most of the spawning grounds are sandy or pebbled; the flow velocity is about 100 m/s; and the flow rate is 1200-1800 cubic meters per second on the river section. Two to three days after the flood peak is the spawning peak of the eel. The water temperature at the time of spawning is 25-32°C and the optimum temperature is 27-30°C. Brooders generally prefer to spawn in the evening or early morning. The proportion of eggs is slightly larger than that of water. In still water, it often sinks to the bottom of the water, and the flowing water floats in the upper layer of the water. The number of eggs in common individuals ranges from 1.5-2.5 million eggs, and the largest number is more than 3 million, which is a type of spawning.
(II) Artificial propagation
1, broodstock fishing. Many of the parents used for artificial breeding come from natural, mature salmon and are captured as soon as the spawning season approaches. The fishing gear commonly used is a three-layer gauze net with a woven fabric and a net length of 60 meters and a height of 2 meters. The cable diameter is 0.25 mm, the internal net is high and relaxed, and a pocket is formed during operation. Select the squid during the flood season and watch the patrols after the nets. When the storm is calm, there are fish nets. The upper stalks are shaken and the floats are pulled down. Fish should be taken immediately. Take care when picking fish. The action is light and fast. Take the fish without leaving the water and try to touch the fish as little as possible. Captured fish are immediately kept in the cabin and constantly changing or flushing to prevent lack of oxygen or injury.
2. Insemination and incubation. Artificial insemination is often performed on the river bank, and the captured broodstock are bred in river water or stocked in a cabin for use. If the male and female fish are caught first, their semen can be stored in an ice bottle and dry artificial insemination should be performed immediately when there are female eggs that have fertilized eggs.
The insemination eggs obtained are transported in nylon bags and transported to the ring or other incubators for hatching. Incubation water requires dissolved oxygen to be maintained above 4 mg/l, a pH of approximately 7.0, a water temperature of 27-33°C, and a flow rate of approximately 0.3 m/s. Under normal conditions, fry can be hatched after 14-17 hours.
(three) seed cultivation
1, fry cultivation. Artificially hatched fry are of weak constitution and are easily injured during collection and transportation. In order to improve the survival rate of fry, living conditions similar to those of the natural environment can be created, that is, the fry to juvenile stage cultivation is still carried out in the hatchery ring, with a density of 0.6-1.2 million per cubic meter of water. The water in the loop maintains the same early flow rate as it did during hatching, and gradually slows down later. Dissolved oxygen should be kept above 4 mg/l.
Fry hatched on the third day after hatching. At this point, planktonic nets made from 50 mesh sieves were used to feed plankton. Daily feeds are given three times in the morning, in the evening, and in the evening. When the fry grows to 1.5 centimeters, the bait is filtered with a 1 mm hole screen, and the amount of feeding is about 1.5 times the weight of the fish. In order to keep the water in the pool fresh, it is necessary to use a leather tube to remove the dirt from the bottom of the ring every 2-3 days. The water inlet end of the tube should be wrapped with an appropriate density screen to prevent the fish from being sucked out. During the larval culture stage, the fish body is susceptible to trichoderma disease and causes a large number of deaths. Salt water can be used for spilling, so that the pool water can maintain the salinity of 1 Torr and can prevent and control it.
After 30 days of cultivation, the fry can be artificially released when it grows to more than 2.6 cm, or it can be transferred to a pond to cultivate large fish species.
2, fish species cultivation. A pond with an area of ​​1-3 mu and a water depth of 2-3 meters is generally used, and the stocking density is about 3,000 mu per mu. One week before stocking, the ponds should be disinfected thoroughly, and then 200-500 kg of basal fertilizer per acre pond. Three days before stocking, two kilograms of soymilk milled soybeans were sprayed per acre each day to breed plankton in the pond. After the squid fire piece is put into the pond, 1-1.5 kilograms of soybean milk is fed per acre per day to make the water quality appear dark greenish or light brown, and keep the zooplankton at a higher density to ensure that the squid has sufficient feed. The water source in the pond is better. It is best to set the aerator to maintain a stable and high concentration of dissolved oxygen in the pool water.
Trout species can also be cultivated in cement pools, where up to 40 can be stocked per cubic body of water and zooplankton can be fed daily morning and evening. 2-3 days to get rid of dirt at the bottom of the pool once, and inject new water to increase dissolved oxygen and regulate water quality. In order to prevent parasitic diseases such as trichodinosis, salty water can often be used to disinfect. If it is found to be infected, it can be treated with salt water. The method is to make the salinity of the pool water reach 1‰, and the fish body can return to normal after 2-3 days.
In places where conditions permit, after the fall, when the water temperature drops to 15°C, the carp species can be moved into winter indoors. The stocking densities at the time of wintering are approximately 10 per m3, the water temperature is controlled at 20°C or more, and one to two large and medium-sized zooplankton are fed every day, and the feeding amount is 1/10 of the body weight. When the outdoor water temperature rises above 17°C in the spring of the next year, it will be moved to the pond for culture. During the overwintering period, when the indoor water temperature is appropriate and the feed is sufficient, the weight of the carp species can be nearly twice as heavy as before the winter.
(4) In addition to artificial breeding, fish seedlings may be harvested naturally. Under natural conditions, generally in late July, when the fish fry grows 1.4-3.5 cm in total length and weighs 0.04-0.44 g, the body is long and grey and white, scales have formed or partially formed, but thin and transparent, long and thin. In still water, these fry swim quickly, but in the running water they drift with the water. When there is no strong wind on a sunny day, swim around the shoals before and after the dawn to sow the bait. When the weather is rainy or wet, swim to the depths of the water layer.
The carp seedlings are very similar to the seedlings and meal fry, and should be carefully identified before they can be distinguished. The eel's seedlings were in the terminal position, the snout was slightly longer, the eye spacing was wider, and the irritation was dry. After catching, the fish seed head liked to drill to the bottom of the container and the tail was swung vigorously. At this time, sorting should be performed in time. It can be harvested with a dense net, and the operation method is shoreline fence, with a net length of 200 meters and a height of 3 meters. The net is made of a net cloth made of PVC filaments. The type of fry caught must be carefully sorted, and the operation must be careful, the action should be light and fast, and slight carelessness can cause a lot of death.
The selected eel fry should be immediately placed in a holding tank containing 2 ounces of salt solution. The body of water holding the holding box should be large and the water quality should be clear. Drop density is about 500 per cubic meter of water. During the rearing period, zooplankton are also fed as bait, and the fry will be fed up and down. In order to change the water and feed during transportation, the survival rate can reach more than 98%. Transportation tools and methods can refer to the transport of domestic fish seed, and their density can be smaller.
(e) Ponds Food fish are mainly domesticated second- and third-instar catfish in ponds. Generally, the weight of the second instar carp can reach about 200 grams per tail, and the individual weight of the third instar carp can reach about 600 grams, which is a better product specification. The farming method is often polyculture, that is, about 30 breeding catfish per acre in a pond of farmed fish, or 50-80 fish per acre fish pond, and then mixed with appropriate amount of other fish species.
Since catfish is a filter-feeding fish and staple food plankton, especially zooplankton, it is possible to refer to the culture method of catfish. It is necessary to keep the pond water as fat as possible, and the amount of zooplankton in living pool water should be kept at 300/l. the above. Keep the amount of dissolved oxygen in the water above 3 mg/l. In ponds, organic fertilizer such as grass manure or regular human and animal manure may be piled up to cultivate zooplankton. If the fatness does not keep up, the amount of plankton may be insufficient, and quick-acting fertilizer and splashed soybean milk may be added to facilitate the normal growth of carp. .
The Institute of Freshwater Fisheries of Jiangsu Province raises squid in fish ponds. In early May, the stocking size was 16-20.8 cm 2nd instar carp, which was raised to the end of October. The average body length was 39.5 cm and the body weight was 596 g. The total length of 42.5 cm, weighing 710 grams, the survival rate of 100%.
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