The net box keeps fish
Last Update: 2021-01-08
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Net box fish farming is in natural waters, the use of synthetic fiber mesh or metal mesh and other materials assembled into a certain shape of the box, set in the water body, the fish high density in the box, with the help of continuous water exchange inside and outside the box, to maintain the environment suitable for fish growth in the box, the use of natural bait or artificial bait to cultivate species or raise commercial fish, this method of fish farming called net box fish. Net-box fish farming was originally a traditional farming method in Cambodia and other Southeast Asian countries, and has since been gradually promoted around the world, currently in Japan, Norway, the United States, Denmark, Germany, Canada, Chile and other countries on a larger scale.
since 1973, the relevant research institutions have made use of natural bait in lakes and reservoirs to cultivate large-size mackerel and mackerel species. Since then, there have been many units in the net box breeding mackerel, mackerel commercial fish, as well as baited net box breeding erythropoies, carp, grass fish and group head have been successful. The area of fish farming and the area of fish culture and the species of culture have developed rapidly. At present, the net box culture mackerel, mackerel has formed supporting technology, cultured carp, thyfish and other technologies have matured, mechanized net box fish supporting technology has been introduced; In 1988, the high yield record of net-box carp in Jilin Province reached 87t/m2; the maximum yield of metal-box fish in irrigation channels in Meishan County, Sichuan Province was l66.8t/m2); and the maximum yield of fish in the net-box fishing area of Mirror Lake in Heilongjiang Province was 361 kg (net production of 300 kg, 1991).
According to the characteristics of the development of freshwater net-box fish farming in China, it can be divided into two types of net-box fish farming industry, which can be divided into three types: first, the cultivation of fish species, the use of plankton in reservoirs and lakes, organic debris , bacterial flocculants and other natural food in the net box to cultivate large-size mackerel, mackerel species, the general output can reach 2000 kg / mu to 4000 kg / mu; Herring, mackerel, or the use of grass-based lakes, rivers rich in water and grass resources to raise herbivore fish, net-feeding mackerel, mackerel production of up to 3000 kg / mu to 5000 kg / mu, herbivore fish production can be 4000 kg / mu - 6000 kg / mu; three is fully fed with grain feed to produce commercial fish, main carp, thyfish and other food-eating fish, the general yield of mu can be more than 20t to 60t, high yield can be more than 100t / mu. In addition, in recent years, the development of net-boxed mackerel, largemouth bass and other meat-eating fish and other names, special, excellent species, although not very common at present, there will be greater development in the future.
Many advanced countries in the world attach great importance to marine net culture, in the past 20 years, it has carried out a comprehensive and systematic research, and achieved fruitful results, and has been widely used in Norway, Chile, the United Kingdom, Denmark, the United States, Canada, Australia, Japan and other countries. In recent years, with the progress of science, the development and application of new technologies and new materials, the development of seawater net boxes is faster.
Its development trend is mainly reflected in: sea water net box culture range is expanding, from near shore to offshore, the frame material of the net box is constantly upgraded, using high-strength plastic, plastic steel rubber, stainless steel, alloy steel, steel and other new materials;
the form of tank farming from fixed floating development to floating, lifting, sinking, etc. , the volume of the box from dozens of cubic meters to thousands of cubic meters or even tens of thousands of cubic meters, the annual single fish production of the box from a few hundred kg to nearly a hundred tons, the expansion of breeding varieties to dozens of species, almost all kinds of market demand, high economic value; Integrated breeding of fish, crabs, shellfish and other varieties, aquaculture management towards the automatic development, the general use of automatic baiting, water quality analysis, underwater monitoring, biometrics, fish grading, automatic fish absorption, garbage collection and other automatic devices, and in the seed
, fish disease prevention and immunization, full-price with bait, netting materials anti-ultraviolet, anti-fouling and other aspects of accelerated development and application.
, China's marine net box breeding started late, is still mainly in the shallow sea bay floating raft-type net box breeding. In recent years, the introduction of deep-water wind and wave net boxes from abroad and domestication, but many technologies are still in the exploration stage. With the development of science and technology, China's traditional net box culture gradually deep-water wind-resistant wave net box breeding development, but deep-water wind-resistant net box price is expensive, high technical requirements, supporting facilities requirements are more complete, China is in the introduction of its technology, digestion and absorption transformation stage, so the traditional net box in China also occupies a larger proportion.
. The continuous exchange of water bodies, so that the tank of dissolved oxygen, ammonia nitrogen and other water quality indicators and the vast waters outside the tank in a "dynamic balance" state, because the amount of water in the tank and the water volume of the entire water is very small, so in the water exchange of good net box, the water quality indicators are basically consistent with the large waters outside the tank, which makes the fish in the tank can also "enjoy" the whole large water good ecological conditions, so that the fish in the tank always maintain the ecological conditions needed to grow. Oxygen is sufficient, natural bait can be continuously replenished, fish metabolic activities of waste, waste, waste and feces can be timely with the flow of water around the spread, dilution, decomposition.
, high-density farming and high yields can be obtained by ensuring sufficient natural or artificial bait in the net box. It can be learned that the good ecological conditions in the net box depend on the good ecological conditions and water body exchange of the large water itself, so when selecting the waters where the tank fish are raised, the water conditions should be examined and understood;
small-volume net box can be several times higher than conventional net-box fish load, without affecting the normal growth of fish, the reason is that small-volume net box has a higher water exchange rate. The smaller the net box, the higher the ratio of surface water change area to volume, and the higher the water body exchange rate caused by natural water flow and fish swimming. For example, compared with a small 1m3 net case and a regular carp net box (5m×5m×2m), the ratio of side area to volume is 4:1, while the latter is only 0.8:1. Moreover, small-volume boxes have smaller sizes of length and width, and under the same flow rate, it takes less time for water to pass through small-scale nets. As a result, the water in the small net box is updated quickly.
2, Physiological Principles
the tank limits the activity of fish to a smaller extent, avoids the harm of ferocious fish and the attack of wind and waves, reduces their activity, reduces energy consumption, increases nutrient accumulation, is conducive to growth and fattening. Hu Chuanlin and others (1980) carried out a comparative study of the creatinate content of creatinate, hemolybin (Hb), blood cell ratio (Ht) and other physiological indicators in the muscles of the inside and outside of the net box, and the composition of
national and biochemistry
in the musculars of the mackerel species. Creatic acid phosphate is a high-energy phosphoric acid compound, which plays a great role in the physiological process of muscle exercise, and when the movement is agile or the amount of exercise increases, the muscle work increases and more phosphate creaic acid is needed to provide energy.
results showed that the content of creatic acid phosphate in the muscles of the mackerel species outside the net box was 37.5% higher than that in the net box, while the content of the mackerel species was 43.2% higher, and if the mackerel and mackerel species were put into the sink (flow rate was 0.414m/s to 0.591m/s), Let it struggle to top the water 60min to 120min, the phosphate crea acid content of mackerel than in the net box increased by 67.9%, mackerel increased by 53.5%; The above results show that the net box of mackerel and mackerel are less disturbed, the intensity of activity is reduced, and the energy consumption is less. The study showed that the Hb and Ht species of mackerel and mackerel in the net box were lower than the same species of fish outside the net box, and also proved that the activity of the fish in the net box was lower than that of the fish outside the tank. The fish in the tank is limited by the spatial structure, which reduces the amount of exercise, energy consumption decreases, increases the accumulation of
and fat, which is reflected in the composition of the muscle composition, the same specification of the herring, mackerel muscle moisture content in the net box is less than outside the net box, and the protein and fat percentage content in the tank is higher than outside the net box.
。 Net box structure and materials Edit this paragraph back to the catalog
net box is generally composed of box, shelf, float, sink and fixture, etc.
1, the box is the main part of the net box. The mesh wire is woven into a mesh piece, sewn into boxes of different shapes and sizes. Usually the surrounding wall, bottom and cover nets are stitched together into a closed enclosed box, as well as an open mesh box without a net. Network wire materials have nylon wire (nylon), polyethylene wire (acetylene), polypropylene wire (acrylic) and other synthetic fibers or wire mesh. At present, the most widely used is the low-pressure polyethylene line, made from a diameter of 0.21mm or 0.25mm single wire. Net line specifications are commonly used as follows digital, such as 0.21/2×3, indicating a single wire diameter of 0.21mm, 2 single wire for 1 share, with 3 shares combined, a total of 6 single wire. Polyethylene wire strength, corrosion resistance, low temperature resistance, less water absorption, no oil dyeing, cheap (for nylon wire 30% to 40%), well received by the masses. Nylon wire knotted mesh strength, soft, but higher cost, but also easy to attach dirt and parasites, not easy to wash.
2, the box frame is mounted on the upper outline of the box, supporting the soft box, so that it opens with a certain spatial shape; Materials are often made of bamboo, wood or seamless steel pipes. If the buoyant force of the box holder is insufficient, floats or buckets can be tied to the four corners of the box.
3, float and sink floats are mounted on the upper outline of the wall net, and the suns are mounted on the lower outline of the wall net. Its role is to enable the net box in the water to fully expand, to maintain the design space of the net box. In order to ensure that the cover and bottom mesh can be tiled, a small number of floats and sinks should be installed in the appropriate position to maintain the effective volume of the cage. There are many kinds of floats, the most common application is plastic floats. Plastic floats are between foam floats and hard blow-molded plastic floats. Foam floats with diameters of 8cm to l3cm are generally used. Sinks generally use porcelain protons, weight of 50g to 250g / piece, requiring a smooth surface. Lead, concrete blocks, pebbles, steel pipes, etc. can all be used as sinks. Steel pipe as a sink, but also the bottom net open, so that the cage to maintain a good shape and effective space.
4, anchors and anchor ropes Anchors have iron anchors (10kg/25kg/piece) or concrete blocks (30kg/40kg/piece). Anchor rope with polyethylene rope or steel rope and other cables can be, the length should be more than 3 times the depth of water.
。 Net box production Edit this paragraph back to directory
1, the shape and size of the box flat shape of the box has rectangles, squares, polygons, circles and so on, to rectangles and squares are the most common. The size of the net box can be divided into three categories: large net box, area 60 m2 to l00m2;
the same water conditions, the production capacity of smaller net boxes is larger than that of large nets. This is because as the net box increases, the ratio of the volume of the net box to the area on the side of the net box decreases, i.e. the water body exchange area occupied by the unit volume of the net box decreases; Therefore, the water conditions in smaller nets are better than those in larger ones. Rectangular net box, if the box is long and narrow, the greater the effect of wind and water flow, the greater the ability of water to update. However, the unit cost of small net boxes is high and requires more investment. Each place shall select the specifications of the net box used according to the specific circumstances.
2, the height of the net box feeding filter fish, the height of the wall net should be determined according to the depth of the water, plankton vertical distribution. Generally in the reservoir wall network height of 2m to 4m, lakes take l.5m to 2.0m, shallow sea take 3 to 5m is appropriate. The wall net of the open-air mesh box should be 70cm above the surface of the water when raising fish.
3, mesh size, to do not escape fish, save materials, the tank inside and outside the water body exchange rate is high as a principle for example: net box breeding mackerel, mackerel, fish fry into summer flowers of the net box material should be used 100 mesh / cm2 polyethylene mesh cloth;
production process should be with the growth of fish species specifications, timely switch to a larger mesh. Do graded matching, in order to give full play to the effectiveness of the net box and conducive to the growth of fish. The size of the fish species out of the box is large and neat.
4, net box assembly is generally worn, wound, and three methods of sewing. Such as a covered rectangular mesh box, sewing methods can be
l) with six pieces of mesh and sewing molding; Here is an example × 8m×4m×2m closed soft floating fish mesh box, which shows that the assembly method is as follows: the mesh by 0.21 /
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