Semi-intensive cultivation is mainly to add some low-protein forage or agricultural and sideline products (
In the process of intensive production, fish almost completely depend on high protein (>: 20%) feed in compound feed.
Semi-intensive culture and intensive culture are both edible fish, such as grass carp, carp and catfish. And the yield is much higher than that of coarse fish. In the case of rough tillage, its yield is generally between 2.5-7.5 kg/m2, equivalent to about 1665-4995 kg per mu; The yield of semi-intensive cultivation is slightly higher, with an average yield of about 10 kg/m2, equivalent to 6700 kg per mu. In intensive farming, the yield of commercial fish can be several tens or even hundreds times higher than that of ordinary ponds, and the cumulative yield per mu can reach 3- 1.5 thousand kg. It is suitable for large and medium-sized waters with small water level difference, rich natural bait and shallow bottom. The specific method is: according to lakes, reservoirs and some navigable rivers. In the topography of the river branch, one end of the net is inserted into the bottom of the water, connected with the stone dragon, and one end is exposed out of the water, and fixed by piling. In this way, lakes and reservoirs are enclosed into several blocks with a certain area and shape, and the area can be large or small, so as to create a semi-artificial ecosystem, which combines intensive cultivation with rough cultivation, natural bait with artificial feeding, and is intensively cultivated like a pond. The yield per mu of fenced fish farming is generally 250 ~ 300 kg, and the high yield is above 800 kg.
(1) water quality conditions; Setting fences in open lakes and troughs to raise fish is easy to be polluted by industrial and agricultural sewage or influenced by water quality changes caused by the decay of aquatic plants. Therefore, in front of the fence, we should consider the pollution situation of the water area and its adjacent areas. Please refer to the water quality indicators in Table 6 for the requirements of water bodies in the fenced area. That is to say, in the breeding season, the dissolved oxygen in water should reach 6-8mg/L, the concentration of (H+) should reach 3.16-100 nmol/L (pH 7-8.5), the oxygen consumption of organic matter should not exceed 12mg/L, and the highest annual change of salinity should not exceed 4. There are no toxic gases and heavy metal ions in the water. In addition, from the perspective of biological monitoring, wild fish and shrimp in the waters can live normally all the year round.
(2) Water condition: The fish culture area requires the bottom of the swing (river) to be flat and the bottom mud to be moderate in hardness. Swing (mouth) is much less, narrow but not wide, which can not only reduce the fence cost, but also play a good role in keeping fish. The area of fish farming in lakes should generally be below 500 mu; River fish farming area should generally be below 50 mu. The water quality of such a water body is easy to stabilize, and it is also convenient for fishing, and the oxygen supply is sufficient and uniform. The water area is too small, and the water quality is not easy to be self-purified and stable; If it is too large, the bait is scattered, fishing is difficult, and the water in the middle of the river is easy to lack oxygen, so the yield is relatively low. .
(3) Hydrological conditions: The water depth of lakes and rivers is required to be 2-3 meters, and the annual water level change shall not exceed 1 meter. There is no record of drought and flood in the breeding season in history, so it is easy to set up fences in such waters. The water is too deep to pile; The water level changes too much, so it is easy for fence facilities to escape without roof during flood. The flow rate of aquaculture water should be 0.05-0. 1 m/s, and it is easy to be washed away when the water passes through the fish-blocking facilities. The water flow is too slow, the water exchange is poor, and the water quality is easy to deteriorate or lack oxygen.
(4) Navigation traffic and geographical location conditions: There are not many traffic and civilian vessels that need to enter and leave the aquaculture waters, which can reduce the probability of breaking the net and breaking the net to escape fish. But it is best to have roads on land, and fish products can reach the sales market by land and water transportation. If conditions permit, the fenced fish culture base is best in the suburbs near big cities.
(5) Weather and bait resource conditions: The fenced area is required to be rich in natural bait. In addition to abundant plankton, there are dense aquatic plants such as Sophora alopecuroides, black algae and POTAMOGETON malayi at the bottom of the lake or river, and benthos such as snails, mussels and mussels can be seen everywhere. This can reduce the amount of artificial bait and improve the stocking density of fish. If natural bait resources are abundant, the use of commercial bait can be reduced, and the utilization rate of mixed bait can be greatly improved due to the complementary effect of bait.
Fish farming in running water. High-density running water fish culture is to make use of the water potential, choose the drop terrain, build shallow fish ponds, divert water to flow by itself, concentrate large-scale fish species, and carry out high-density artificial feeding and intensive cultivation. This mode of production has the advantages of small floor space, simple equipment, fast fish growth and high yield. Generally, fish released from March to April with a weight of 70 ~ 150g will reach a weight of 0.8 ~ 1.0kg by mid-kloc-0/October, with a yield of more than 200kg per square meter of water. Where there are cold springs or warm water resources, it is especially suitable for promoting running water fish culture. The main cultured species are Rainbow Group, Tilapia, Carp and Grass Carp. Intensive and high-density intensive farming in artificially controlled water bodies has the advantages of short cycle, fast growth, high yield, high benefit and high commodity rate. Generally speaking, running water fish culture is about 40% more productive than conventional fish culture, which is a new aquaculture technology promoted throughout the country. There is much to be done in running water to raise fish. First, because there are many reservoirs, rivers, streams and other water resources in China, running water fish farming can be carried out as long as conditions are created. Second, the water from running fish ponds can also be used to irrigate farmland, which is multi-purpose and does not waste water resources.
(1) Site selection of active pool. The flowing water fish pond requires sufficient water, excellent water quality, stable water level and suitable water temperature, and the water temperature is between 15-30℃ in May and June. It needs plenty of sunshine, high dissolved oxygen and convenient feed and fish supply. Fish ponds should be built near the natural drop, where reservoirs and irrigation canals can flow and streams can flow by themselves, or beside the pollution-free perennial mountain spring water system, or near the power plant, and waste hot water can be used to run water. These running waters can be used to raise fish, which can reduce production costs and improve economic benefits.
(2) The shape and area of the pool. The living water fish pond is preferably round, oval or fan-shaped. The benefit of square pond culture is not good, because it is difficult for the running water in the pond to reach the dead corner. The walls of the swimming pool are made of bricks or stones. Smooth the surface with cement, level the bottom with concrete, and make the roof firm. A slope is built at the inlet and outlet to guide the water flow to the bottom, so as to divert the whole pool water, ensure the exchange of water flow at the bottom of the pool and ensure smooth sewage discharge. The fish pond with gravity water source covers an area of 40- 100 square meter, and 20-40 square meters need power to lift water as water source. Fishing facilities should be installed at the entrance and exit of fish ponds. The net depends on the size of the fish species, and the outlet and outlet should be designed separately.
(3) Fish stocking. Running water fish culture is beneficial to promote water exchange, increase dissolved oxygen in water and enhance fish metabolism and digestion and absorption. Appropriately increasing stocking quantity can also increase water yield. The main types of running water fish culture are grass carp, carp, tilapia and other edible fish. Grass ponds can be mixed with 10% carp or bream. Grass carp culture specifications should be large, with tail weight 150-400g and 5- 10 tail per square meter. The fish culture specifications in Liyutang are neat and large, the tail weight is 100- 150g, generally 25-35 fish per square meter, and the fish species gain 8- 150g. Tilapia has strong disease resistance and short breeding cycle. After 40 days of culture, tilapia with a tail weight of about 30 grams can get about 100 grams of commercial fish. Tilapia is best kept alone, because the fishing time is different from other fish.
(4) Feeding management. In natural water, surface water has high dissolved oxygen and water temperature, so surface water should be used as much as possible. The amount of running water should be large and the flow should be small. Excessive flow rate not only increases the physical consumption of fish, but also brings difficulties to feeding. Grass fish pond, mainly green feed, such as aquatic plants, dry grass, pumpkin leaves, bean leaves and so on. , properly supplemented by concentrated feed and carp pond: mainly concentrated feed, such as barley, compound feed, artificial compound pellet feed for running water fish farming, etc., and the feed coefficient is generally around 2. Feed the fish at 3% of the weight every day for the first few days, and gradually increase to 5%-7% with the growth of the fish, and feed it every 2 hours during the day 1 time. The fry should be disinfected with quicklime before going to the field, and the dosage per square meter is 120g, which is scattered all over the pond. Before the fry were put in, they were soaked in 3% salt solution for 5 minutes, and grass carp were vaccinated for immune prevention. Discharge pollutants regularly. Take/kloc-0 every two days or/kloc-0 every day. And often patrol the pool, often check the fish culture facilities, and often observe the feeding and growth of fish.