It should be very practical and comprehensive! High yield and High efficiency Culture of Grass Carp in Pond

Using the experience of aquaculture in the front line of production to promote the development of fishery and boost the benefit of industry.

Grass carp is one of the four major domestic fish in China, grass carp is also the main artificial freshwater fishes in China, its main food is forage, grass carp food chain is short, it can withstand coarse food, a wide range of feed sources, low culture cost, and grass carp grow fast, delicious meat, high economic value, is a kind of freshwater farmed fish that can bring greater economic benefits, therefore, its culture has been paid attention to by people.

1. Biological characteristics of grass carp

Grass carp belongs to the genus Ctenopharyngodon idellus of the subfamily Cyprinidae. Grass carp are commonly known as: grass stick, grass carp, oil carp, grass carp, white carp, grass carp, grass root, mixer and so on. Grass carp and herring, bighead carp, silver carp and crucian carp are called the six major freshwater fish in China, among which grass, silver carp, bighead carp and herring are the "four big domestic fish".

The head of grass carp is flat, the distance between the eyes is large, the mouth is curved, the mouth is under the mouth, the lower jaw is shorter, the upper jaw is slightly longer than the lower jaw, without beard.

The body is cylindrical, the abdomen is round, and the scales on the body surface are round and large.

Most of the fish are tea-yellow, the edges of the scales are grayish black, the back is turquoise, and the abdomen is grayish white.

Compared with carp and silver carp, the scales of grass carp are large and round, each scale has a black edge, and the lateral line is relatively straight.

The ventral and pectoral fins of the fin are orange, the caudal and dorsal fins are gray, and the dorsal fins are relatively short.

The tail of grass carp is flat on the side and the caudal fin bifurcates deeply.

The pharynx has 2 rows of throat teeth, which are comb-shaped and are mainly used for cutting grasses. Grass carp have no real teeth and masticatory function, so they can not stir and grind the feed after ingesting the feed, but swallow the feed directly into the esophagus.

Grass carp (Ctenopharyngodon idellus) is one of the typical herbivorous fish. Under the condition of pond culture, grass carp mainly inhabit in the middle layer of the water, lively, move quickly and swim very fast. Grass carp mainly feed on higher aquatic plants such as duckweed, ryegrass, hyacinth, hollowleaf, Malay, Sudan grass, goldfish algae, verticillium verticillata, floating sand, elephant grass and weeds, etc.

In addition, grass carp eat a lot, and the maximum daily food intake can reach 60%-70% of their body weight, but because grass carp has no stomach and is a stomachless fish, it is unable to produce enzymes to digest cellulose, so it has a very low digestibility to grasses, resulting in a very large amount of feces and easy to fertilize and water. The feed is mainly digested by digestive enzymes secreted by the liver, pancreas and intestines.

The intestinal tract of grass carp is 3 times of its body length, grass carp generally choose to start feeding unprecedented in the intestinal row, and food intake begins to increase in a state of hunger, but if the hunger time is too long, it will inhibit appetite and affect the growth of grass carp.

Grass carp like to live in clear waters in nature, usually live in lush water, artificial culture, not suitable for fat water should be thin water.

In the fry stage, grass carp in the pond mainly feed on zooplankton, such as chironomid larvae, cladocera and insects, as well as commercial feed. When the fish species gradually develop into adult fish, they can mainly feed on forage. Therefore, the best food in the fry stage is duckweed and artificial feed in the pond, and then it will gradually change from young grass to larger plant food.

Grass carp has strong adaptability to water temperature, and can survive in 0.5-38 ℃ water. The optimum water temperature is 20-32 ℃, and the most suitable water temperature is 27-30 ℃. The maximum food intake is at 27-30 ℃, and the food intake decreases when the water temperature is lower than 20 ℃. When the water temperature is below 5 ℃, it may stop feeding. When the water temperature is below 0.5 (freezing to death) or above 40 ℃ (heatstroke), it begins or is dying.

Grass carp has a certain adaptability to hypoxia. The growth and development can be normal when the dissolved oxygen in water is 5 mg / L, and the respiration is inhibited when the dissolved oxygen is 1.6 mg / L.

2. Feeding rule of grass carp

Grass carp eat less in the morning than in the afternoon, and eat the most in the evening. In fact, many fish like to eat in the evening, the reason is unknown. For grass carp fed with pellet feed, the grabbing of fish was very strong at the beginning of feeding, and the feeding slowed down after 30-40 minutes, and the feeding and food intake was very little after 1 hour, indicating that the feeding was basically over.

Grass carp begin to defecate after about 2 hours of feeding, so it is more appropriate to feed the second meal 3 hours after the first meal, otherwise, because grass carp are gluttonous, they can be excreted while eating, and a lot of feed will be wasted if the distance between meals is too short, and the bait coefficient will increase, which will directly affect the efficiency of fish culture.

In the high temperature season from July to September, the water temperature is 22-30 ℃, which is the suitable water temperature for strong metabolism of grass carp. During this season, grass carp begin to eat at 6-7 in the morning and like to eat at night. When intensive cultivation of grass carp, you can start feeding from 6: 00 or 7: 00 in the morning, feed every 3-4 hours, 3-6 times a day is more reasonable.

The water temperature is relatively low in spring and late autumn, about 15-22 ℃. It is reasonable to feed twice a day, from 9 am to 10:00 and from 4 pm to 5 pm. Under this kind of water temperature, grass carp mostly do not eat at night, probably because the decline of water temperature is related to not eating at night.

Relationship between food intake and dissolved oxygen in water of grass carp. Grass carp generally stop eating any feed when the dissolved oxygen is less than 3mg/L; the food intake is significantly reduced at 3-4mg/L, which is about half of the normal food intake; at 5-8mg/L, the food intake is in the normal state, there is little difference.

3. Nutritional requirements of grass carp

It is reported that the protein and amino acids needed in the growth process of grass carp are in a state of constant change. usually in the process from fry to fingerling, the formula feed should contain 30% 35% protein. In the process from the growth of fish to adult fish, the level of protein in the feed should be reduced to 25% 28%. Because grass carp is a vegetarian fish, high protein can easily cause hepatobiliary and fatty disease.

Make sure the feed is full of nutrients and is usually required to contain 40% carbohydrates, 20% crude protein, 8% cellulose and 4% crude fat. Green feed mainly refers to water grass, dry grass, elephant grass, ryegrass and Sudan grass and so on, and must ensure that it is fresh to facilitate the smooth digestion of grass carp. Reasonable supply of nutrients can ensure that they get enough nutrients, so as to maintain exuberant growth and eventually increase production.

4. The growth rate of grass carp

Grass carp is a large economic fish with fast growth. 2Mel grows fastest at the age of 3 years, so it is most cost-effective for grass carp to culture for 2 years. The growth rate slows down obviously after 4-year-old sexual maturity, so it is not cost-effective to raise grass carp too big.

(1) the growth rate of 3-year-old male and female individuals was similar. After 4 years of age, the growth rate of females is faster than that of males.

Usually the body weight can reach 3~5kg after 2 years in captivity. Under natural conditions, the maximum weight of grass carp can reach more than 50kg.

5. Species collocation and stocking density of grass carp.

The reasonable collocation and mixed culture of fish species is not only the decisive factor of increasing production, but also the main way to improve the benefit. Under relatively good conditions, the higher the stocking density, the better, and there is also a suitable value for the stocking density. When this value is exceeded, the growth conditions of stocked fish will become worse because there are too many fish released. At this time, the growth rate of light fish slows down, unable to achieve the purpose of increasing production, and a large number of fish die, resulting in significant economic losses.

In the ponds where grass carp are mainly raised, the amount of grass carp should be controlled at about 60-70% of the total amount. In the ponds with better conditions, 500,600 fish can be put per mu, and the maximum should not exceed 1000, with 200,300 silver carp, 50,100 bighead carp, 80,100 carp or crucian carp, and other fish can be matched appropriately.

When grass carp are cultured in ponds, it will often lead to excessive water quality due to excessive fecal discharge, which can easily lead to cyanobacteria or serious eutrophication, resulting in unsuitable survival. Therefore, silver carp must be mixed in ponds in order to purify the water quality and benefit each other. Many people reject the low value of silver carp, but do not realize that silver carp is the nemesis of cyanobacteria and must be mixed.

It is said that in a pond with rich feed, one grass carp can be matched with two silver carp, and if there are few feed sources, one grass carp can be matched with one silver carp or even two grass carp with one silver carp.

6. Feeding and management

An important link in the feeding and management of grass carp is the management of feed delivery. Because grass carps are gluttonous, they can be excreted while eating, excreting and eating at the same time, as far as possible to reach 70% to 80% full, but not too little or too much. Avoid being too full or hungry, and keep the food evenly for a long time. If you are often too full or hungry or "overeat", enteritis can occur easily.

It is best to use a feeding machine to feed pellet feed, so that the feed is scattered evenly and widely distributed, so as to avoid concentrated predation of fish in the pond, so that fish with small size and weak physique can not be eaten or not full. The use of expanded material can reduce this situation.

According to experience, the frequency of pellet feed is three times a day from March to April, that is, 08:30, 11:30 and 3 p.m., and four times a day from May to September, that is, 8 a.m., 11:00, 03:30 and 5 p.m., each time for about 30 minutes.

The best mode is to cultivate grass carp mainly with compound feed and supplemented by green feed in ponds. Compound feed can be hard pellet or floating expanded material, which requires comprehensive feed nutrition; green feed is fed with purple flowers, alfalfa, ryegrass, Sudan grass, dry grass, elephant grass, etc., requiring fresh and tender forage for grass carp digestion.

The amount of forage feeding should be flexibly controlled according to the weather, fish eating and water quality, and it would be better to finish it before evening every day. Grass carp generally stop eating from midnight to early morning, which may be related to dissolved oxygen, but they like to eat grass food and feed in the middle of the night. In the summer high temperature season, grass carp should not eat night grass as far as possible, so as not to increase oxygen consumption and hypoxia due to energy digestion at night.

7. Water quality regulation

The water quality of grass carp is very important. If possible, fresh water should be added frequently to keep the water quality fresh and hygienic, so as to increase the vitality of the water, increase the dissolved oxygen, increase the proliferation rate of plankton, and meet the bait needs of silver carp and bighead carp. To stimulate the rapid growth of grass carp.

Equipped with and frequently open the aerator to increase oxygen to keep the water quality fresh and the dissolved oxygen normal.

Sprinkle 10-20 kg of quicklime per mu every half month or month to clarify the water quality. Or apply water quality improver to keep the water quality good for a long time.

The transparency of the water body had better be kept at 25-30 cm.

8. Disease control

Grass carp have many diseases, and intensive ponds are more prone to epidemic outbreaks. These diseases can cause a large number of deaths of adult fish and fish species, resulting in a decline in aquaculture production. Usually, the prevalence of some grass carp diseases will bring great economic losses to farmers.

The common diseases in grass carp culture include enteritis, red skin disease, hemorrhagic disease, Gill rot disease, septicemia, hepatobiliary disease and so on. Usually these diseases are not a single occurrence, the occurrence of a disease is usually accompanied by two or more complications. And the occurrence of these diseases is usually with the increase in temperature, the risk of disease increases.

These diseases must be controlled in the process of large-scale grass carp culture, especially in summer and autumn when the temperature is relatively high.

Prevention and cure measures

1. Fish disease is mainly prevented, which is also the key to intensive culture of grass carp. Therefore, in the whole breeding process, most of the energy should be put on the prevention and control of fish diseases and strictly control the disinfection of each link.

2. The main reasons for grass carp to get sick are deterioration of water quality, aging, mildew of feed, outbreak of seasonal bacteria and parasites, etc. Because grass carp are fond of food and eat a large amount of food in fish, the most effective treatment is of course oral administration plus topical use.

3. In the process of feeding concentrate, try to feed green feed once a day or every other period of time to satisfy the grass carp's herbivorous nature and avoid the occurrence of hepatobiliary disease. If there is not enough green feed, the feed can be stopped for 1 day every 7-10 days to reduce the load of fish liver and gallbladder and reduce the risk of hepatobiliary disease.

4. Vaccination can be used to prevent and control the occurrence of fish disease.

5. limit appetite: grass carp are gluttonous, as long as the environment is suitable, the appetite is basically uncontrolled, the summer and autumn with high water temperature is the peak of grass carp growth and the largest amount of food, especially in the high temperature season to limit the amount of grass carp to eat, generally feed to 70% to 80% full, every day insist on fishing out the remaining material.

6. Disinfection of pool water: from May to September, it is best to disinfect pond water once a month. Commonly used drugs and their dosage: bleaching powder 1 g / m3 of water, mixture of copper sulfate and ferrous sulfate 0.7 g / m3 of water, trichlorfon 0.5-1 g / m3 of water, quicklime 20 kg / m3 of water, etc., the effect is better when all kinds of drugs are used alternately.

7. Feeding bait: from May to September, Chinese herbal medicine was regularly fed, and the bait made of immune enhancer was used for health care. The bait was mixed in the feed 1-3 times a month for 2-3 days each time.

8. The treatment methods of related diseases refer to the types of diseases they suffer from. Due to the limited space, please refer to the relevant articles.

(Liu Wenjun)