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    Home > Biochemistry News > Plant Extracts News > Extensive fish farming in lakes and reservoirs

    Extensive fish farming in lakes and reservoirs

    • Last Update: 2021-01-08
    • Source: Internet
    • Author: User
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    Fish farming is carried out on large surfaces such as lakes, reservoirs and ditches by releasing fish species into these bodies of water, and when they grow to the size of edible fish, in order to obtain fish products, which is called extensive fish farming in lakes and reservoirs. It is characterized by the growth of fish and the production of their populations, which depend entirely (or mainly) on natural bait resources in the water. This characteristic determines that people must choose the appropriate release object according to the natural conditions of the water body, determine the reasonable proportion between the breeds, the appropriate number of stocks (density) and good fish species specifications (quality), and combine the measures of preventing the escape of fish, controlling ferocious fish, rational fishing and so on, so that the fish population in lakes and reservoirs in the species, The quantity, age and other structures are suitable for the bait resources of the water body, so that the biological products (i.e. all kinds of bait resources) at all nutrition levels in the water ecosystem are fully, rationally and efficiently
    listed
    as economic fish, and make full use of the space and time of the water body in order to give full play to the fish production potential of the water body. In other words, comprehensive measures are taken to enable the energy and material transformation of such fish-farming ecosystems to take place in the direction and manner required, so that energy flows are fully integrated into the orbit of producing economic fish, in order to achieve sustained high-yield and efficient objectives.。 Directory . Meaning of Rational Release
    . Reasonable Release Technology for Lakes and Reservoirs
    .
    . . . Production Management for Extensive Farming

    . . . Impact of Breeding Fisheries on Lake EcosystemsThe fish yield of a cultured water body is the result of a combination of many factors, but the key technologies to achieve high yield and high efficiency are concentrated in "reasonable stocking". It includes reasonable release objects, determining a reasonable proportion between breeds, reasonable discharge quantity (density) and good species specifications (quality). Although the conditions of various water bodies vary widely, the principle of rational release is generally applicable, except that the technical focus varies depending on the conditions of the water bodies.The vast number of fishery workers in China have carried out a large number of production practices and experimental studies, and systematically summarized the theory and comprehensive technical measures of "reasonable stocking" suitable for China's national conditions, so that the lake and reservoir fish production has achieved high and stable production. Such as Qingshan Reservoir in Zhejiang Province (8500 mu) l966-1982 17-year average yield of 43 kg per mu, Baitan Lake in Hubei Province (6000 mu) l966-1975 10-year average yield per mu 43kg, Wuhan Donghu Fishery (22,000 mu) in the lake to carry out the production of technology test period, so that fish production from l971 mu yield 8.8 kg year by year to l978 36.5 kg, an average annual increase of 23.5%. These facts eloquently prove the correctness and strong vitality of the theory and practice of "reasonable breeding". The forms of extensive breeding can be divided into periodic regular release and timely supplementary release. The former refers to some species that cannot reproduce naturally in lake reservoirs, while the latter refers to some species that can reproduce in lake reservoirs, but often have insufficient populations and need to be replenished in time.。 Lake, reservoir reasonable stocking technology Edit this paragraph back catalogue (1) suitable for fish area calculation method China's fish-breeding lakes are generally small and medium-sized shallow water lakes, water depth often does not exceed 5m, the bottom of the lake is relatively flat and small tilt, the water level is relatively stable and small, caused by fluctuations in the water level of the area change is very small, so the lake fish area is relatively stable.is different from the reservoir, the water level is constantly changing during the operation of the reservoir. The change is related to the characteristics of the flood stage, the runoff size and the operational requirements of the reservoir when it plays the functions of flood control, irrigation, power generation and water supply. With the rise and fall of the water level, the corresponding reservoir area expands or shrinks, making it difficult to determine the fish area of the reservoir reasonably. However, it is necessary to correctly determine the reservoir fishing area to make the reservoir fishery utilization plan, make rational use of resources, implement various fishery management measures, correctly
    stattation
    and analyze the production effectiveness, so it is necessary to find a more correct and reasonable calculation method of fish culture area according to the characteristics of the reservoir. At present, there are two methods used in China: l, according to hydration observation data, statistics of 5 years to l0 years or more reservoir water level of the multi-year average, and the average water level of the reservoir area corresponding to the multi-year can be used as the reservoir fish area. When the average water level of each year is counted, it can be based on the average water level of each month of the year, or the average water level of each month of the main growth of fish from May to l0.2, according to the main function of reservoir design, determine a most frequent water level as the approved fish level, then the reservoir area corresponding to the approved fish level is the approved fish area.there are two more ways to determine the approved fish level:fish level s (normal water level one dead water level) ×2/3 s dead water level or fish water level s (normal water level one dead water level) ×1/2 plus dead water level the difference between the two is that the multiplication coefficient is different (2/3 or 1/2), which coefficient should be used, should be determined according to different reservoirs, it is best to test before checking. The first method is based on the actual operation of reservoirs and is therefore more correct, but requires systematic hydroen observatories. The second method is generally close to the actual situation, but there may be large errors. This requires appropriate amendments in the light of the actual situation.It must be pointed out that the so-called "reservoir fish area" should refer to the most frequently maintained surface area during the growth of fish, and the size of the reservoir area during the peak fish growth season and when the reservoir load reaches its peak, the impact on the reservoir fish production is large. Therefore, the above should be taken into account in calculating the area of fish in the reservoir.(ii) The first problem encountered by the selection of farmed fishthe rational release of lakes and reservoirs is which species are selected as the target of release? Lakes, reservoirs and other aquatic ecosystems have a variety of ecological small habitats, from the space, there are surface, middle, bottom, coastal zones and open water areas are different; Therefore, in order to give full play to the production potential of water bodies, it is necessary for a variety of different living habits and eating economic fish to occupy their own ecological habitats, in order to make full and rational use of water space and bait resources, which requires a variety of fish for "mixed breeding". The selection of stocking objects must take into account the chemical and chemical nature of stocking waters, the composition of natural baits and the structure of natural fish systems. The reasonable discharge objects of lakes and reservoirs should meet the following conditions: 1, rapid growth and high economic value.2, natural bait rich and easy to get.3, seedlings easy to obtain a large number.4, do not prey on other economic fish in the waters.present, China's lakes, reservoirs stocked species, mainly mackerel, herring, herring , herring, herring, carp, mackerel,and other mild economic fish. They differentiate in terms of food and habitat, so that they basically eat their own food in the same body of water, each with its own own small ecological habitat. Their use of water bodies' space and bait resources, as well as the interrelations between species, can tend to be complementary rather than directly competitive. In addition, in some saline lakes in the interior, the environmental conditions are harsh, where slugs, slugs, grass fish, fish, etc. either grow very slowly or are difficult to survive, the development of such inland saline waters, Vassyaro fish and Qinghai Lake naked carp are available for selection. it should be emphasized that mortality from stocks, mainly in waters dominated by artificial stocks, should be minimized. Therefore, ferocious fish must not be the object of lake and reservoir release. Some reservoirs in our country once fish production to very low levels because of the fish disaster, so the lesson deserves attention. Therefore, it is necessary to take all kinds of measures to curb the development of ferocious fish stocks, which is an important part of the fishery management of lakes and reservoirs, and also an important measure to ensure rational breeding. (iii) Mixed fish mixing ratiol, to slugs, slugs as the main breeding objects due to China's lakes, reservoirs are generally more fertile, plankton species, high biomass, rapid turnover, proliferation, humus and bacteria also have a wealth of sources and quantities, very suitable for filter-eating mackerel, mackerel culture. Moreover, the short food chain of mackerel and mackerel, with them as the main breeding object, can reduce the energy conversion series, improve the efficiency of energy conversion, so that high yield can be obtained. The herring and herring are large in size and growing fast, the seed source is easy to solve, the fishing is easy, and the excellent cultured fish that is passed around our country. Therefore, the vast majority of lakes and reservoirs in China are mainly stocked with mackerel and mackerel. Generally can account for 60% to 80% or more of the total release. These two fish also dominate the total catch (Table 6-1-2). It is shown that the practice of mixing and breeding a variety of fish is correct, mainly in the form of slugs and slugs. 2, to the degree of water quality fertility, to determine the ratio of the two general mackerel should be more than the herring in different degrees. A large number of production practices have proved that, in general, lakes and reservoirs in the breeding effect of slugs is often less than slugs. For example, the Qingshan Reservoir in Zhejiang Province produces more mackerel than mackerel under conditions where the herring is more released than the mackerel (Table 6-2). A similar phenomenon occurs in Wuhan East Lake. l Between 973 and l976, a total of 400.l fish species were launched in East Lake, 3.759 million mackerel species, and 240,000 more mackerel than slugs. But in four years, the number of catch tails of mackerel was 284.28 million fewer than that of mackerel. Judging from the growth rate, the same age mackerel in the East Lake is faster than the herring. For example, two-year-old mackerel weighs 0.7kg, while three-year-old mackerel weighs 1.1kg, three-year-old mackerel weighs 1.55kg and herring weighs 2.4kg. Compared with catches, the catch of two- and three-year-old mackerel in four years was 1.74 times that of mackerel. The above facts show that increasing the ratio of herring species to fish production is very valuable. Therefore, in most lakes and reservoirs, the ratio of slugs should exceed the proportion of slugs to varying degrees, and the specific ratio of release between the two should be mastered and adjusted according to the degree of water quality and thinness and the effect of release. Such as Qingshan reservoir from the initial accounted for 85%, 15%, adjusted to 30% year by year, when the effect is most satisfactory. Generally speaking, the water body is in the medium nutrition, medium-rich nutrition or transition to the full nutritional level, the ratio of the ratio of the two nutrients is about 3:7 or 4:6 is more appropriate, so that the two kinds of fish can have a better growth rate and fertility, fish production is also relatively high. However, local production experience has also shown that with the improvement of the level of nutrient-rich water, algae productivity and biomass increase, it is more beneficial to the growth of mackerel, it should be correspondingly increased the proportion of herring stocks in order to achieve high yield. Such as the Suzhou suburb of Jinji Lake (10768 mu) since the mid-1970s began to accept urban sewage, with the flow of nutrients outside the lake area increased, water quality fertilizer, greatly accelerated the process of water nutrients, algae population surge. According to l977-l98l testing, the average annual number of phytophytes reached 3.6958 million / L, April - July peak number of 52.223 million / L - 60.508 million / L, the species of diatom door, algae gate and green algae door in the small algae advantage. In 1977, the number of zoozos reached 66,429/L. Take the advantage of wheelworms. Due to the change of water quality to fertilizer, the water body baiting force increased, so that the fishing output of Jinji Lake increased significantly. According to statistics, in 198l the total lake fish production increased by 527.4t (0.94 times) compared to 1978, of which the total increase in the production of mackerel and mackerel increased by 445.0t (0.88 times), but with the The increase was particularly significant, with an increase of 388.6 tons (1.68 times), accounting for 73.68 per cent of the total increase, while mackerel increased by only 56.4t (0.21 times), accounting for 10.69 per cent of the increase. During this period, the existing amount of plankton increased by 7l, the release of mackerel and mackerel species increased by 91%, and the growth rate and fertility index of mackerel were still normal and stable compared with previous years, but the growth rate and catch rate of mackerel decreased. Therefore, in this case, the appropriate compression of the ratio of herring to increase the proportion of herring, is a necessary step to further capture high yield. 3, the proportion of other fish stocking "algae lake (library)" in stocking to slugs, slugs-based at the same time, should also be put , , grass fish, carp, mackerel and other fish, in order to play other types of bait resources to produce fish potential and make full use of water space. The proportion of these kinds of fish in the total stocking is about 20%, the specific stocking of each fish, should be based on the water body of the corresponding bait resources, proliferation capacity, as well as the corresponding species after stocking growth rate and other indicators to determine and adjust. It should be pointed out that some units pay more attention to the main breeding of mackerel and mackerel, and often ignore other breeding species, in fact, the potential and economic benefits of these species can not be ignored. the "grass-shaped lake" and the peaceful prototype reservoir, with abundant aquatic vegetation and abundant benthics, while plankton are relatively few. In this category of water, the proportion of herbivorous fish, benthic predatory fish and omnivorous fish stocks, which can account for about 40 per cent of total stocks, should be increased. However, the proliferation capacity of aquatic grasses and benthic animals is low, and if grass fish and herring are over-breeded, aquatic plant resources will be severely damaged or even destroyed, and musals such as screws will be reduced or extremely poor accordingly. At this time, the "grass-type lake" will be "algae-type lake" transformation, in the breeding can only be from grass fish, herring-based mixed breeding type to slug-based mixed breeding type, most of the middle and lower reaches of the Yangtze River fish lakes have a similar experience. According to the experience of the masses, such as 250g per acre of grass fish 30 tails, l years to 2 years can be basically eaten up. In the case of few aquatic plants in the lake, such as grass fish per acre at 1.5
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