First, the significance of the proliferation of directional transplanted fish in lakes and reservoirs China's freshwater aquaculture mainly includes small-surface pond culture and large-surface lakes and reservoirs.
Pond cultivation, in the past 30 years, especially since 1978, has undergone institutional reforms, through the transformation of old fish ponds, the development of swamps, low-lying wasteland, saline-alkali land, the development of suburban fish farming, the construction of commercial fish bases, and the establishment of standardized supporting facilities for fish ponds. Improve the technical level of fish farming, apply aerators, feeds, and promote effective varieties, and so on, so both in the expansion of aquaculture area, increase the aquaculture yield, increase the total aquaculture production, improve the proportion of high-quality fish and economic benefits, have achieved With great development, in 1978 China's pond aquaculture area was 10,823,300 mu, and the aquaculture output was 497,000 tons, with an average yield of 48 kilograms per mu, and the highest was 300 to 500 kilograms. In 2000, China's pond aquaculture area was expanded to 33.3 million mu and the output reached 10.87 million tons. The average yield per mu was 326.6 kg, and the highest was more than 1,000 kg. In 2000, compared with 1978, the pond aquaculture area expanded 2.1 times, the aquaculture production increased by 20.8 times, the average yield per mu increased by 5.8 times, and the aquaculture production accounted for 65 percent of the total freshwater aquaculture production. 2% increased to 71.7% in 2000, an increase of 6.5 percentage points, and the number of farmed species increased from 10 to tens.
In the past 30 years, especially since 1978, large-scale breeding of lakes and reservoirs has seen great development. After system reforms, the introduction of small-surface pond aquaculture technology, the development of lakes and reservoirs, reservoirs of lakes and lakes, and “three networks "Farming and strengthening of supporting facilities for large-scale fingerlings and fish-prevention facilities have resulted in the rapid development of directional transplanted proliferation of fish, crab, and other fine varieties. In 1978, the aquaculture area of ​​lakes and reservoirs in China was With 26,093,000 mu, the output is 184,000 tons, and the average yield per mu is 7 kg. In 2000, the aquaculture area was expanded to 37.738 million mu, and the aquaculture production reached 243,000 tons. The average yield per mu was 64.3 kg. In 2000, compared with 1978, the aquaculture area increased by 44.6%, the aquaculture production increased by 12.1 times, and the average yield per mu increased by 8.2 times. However, due to rapid development of pond aquaculture and rapid increase in production, the proportion of lake and reservoir aquaculture production to the total freshwater aquaculture production in the same period decreased from 24.2% in 1978 to 16%, a drop of 8.2%.
Lakes and reservoirs were cultured on a large surface. Compared with ponds with small water surfaces, the development was still at a low level. The speed of development was still very slow, and 52.3% of the large water surface was exploitable without utilisation. The water surface of the breeding area was developed. The average yield is still very low. At present, the average yield per mu is only 1/5 of the pond's yield. Pond aquaculture accounts for 42% of total freshwater aquaculture, while aquaculture production accounts for 78%, while lakes and reservoirs account for 48% of the country's total freshwater aquaculture area, while aquaculture production only accounts for 16%.
It can be seen from the above that pond culture is better than economically developed areas on the southeast coast, while lakes and reservoirs are better than western development areas.
To develop freshwater aquaculture, we must also work with both hands, and both hands must be hard. While grasping the pond culture, we must also pay close attention to the development and utilization of lakes and reservoirs. Because there are many advantages in the development and utilization of lakes and reservoirs, one is abundant in resources. At present, there are still 35.56 million mu of water that can be exploited but not yet exploited. Even if the water surface has been farmed, the average yield per unit area is very low. Therefore, there is great potential for development. The second is the development of large water surface, which does not compete with agriculture for arable land, and can increase the utilization of land and resources. Third, the investment is small, the effect is quick and the benefits are high. Varieties, such as transplanting whitebait, can achieve very good economic, social, and ecological benefits in a relatively short period of time. Fourth, products that are concentrated and are mostly exported through foreign exchange. Therefore, the development of large-surface lakes and reservoir breeding, especially the development of targeted migration of fish and large-surface fishes in lakes and reservoirs, has great potential for development and broad prospects for development. It is one of the key development directions for developing freshwater aquaculture in the future.
Second, the main varieties of fish and reservoirs for targeted transplantation of fish proliferation China has a vast territory, and lakes and reservoirs are distributed throughout the country. Therefore, according to the environmental conditions such as the location of lakes, reservoirs, climate, water quality, food organisms, and composition of fish species, transplant breeding technology requirements, sources of transplanted seeds, economic strength, and economic benefits should be investigated. Research, through adequate argumentation, selected transplanted varieties according to local conditions. At present, from the national point of view, the main breeds for transplantation and proliferation include whitebait, ichinobumin, high whitefish, squid, and river crabs.
Third, the main technical points of the directional transplanted fish in lakes and reservoirs 1. A background survey is conducted on the lakes and reservoirs to be transplanted, and the climate, hydrology, water quality, composition and structure of the biological populations in the waters, the status of the biomass and biofeeds, and the human influence on the waters are to be ascertained.
2. Through in-depth investigation and study of the waters to be transplanted, a full demonstration will be made to determine the suitable varieties for transplantation and proliferation.
3. According to the characteristics of transplanted varieties to be transplanted and the technical requirements for transplantation and proliferation, different methods for selecting and transplanting proliferation should be determined to adapt to the different methods of transplantation for proliferating broodstock, larvae and fertilized eggs.
4. According to the reproductive ability of the transplanted species, the reasonable load of the water to be transplanted, and the economic strength, the total amount of transplanted fish and the number and number of batch transplants are determined.
5. We will conduct follow-up investigations on the changes in the amount of resources and resources that have been released, and master the dynamic laws to determine the start time of arrests, reasonable catches, and retention, so as to ensure the regeneration of resources and sustainable development.
6. Strengthen the management of fishery administrations, formulate prohibited fishing areas, prohibit fishing seasons, provide fishing gear and fishery laws, strengthen protection, and prevent the occurrence of vicious accidents such as stealing, stealing, poisoning, and fish frying.
7. To carry out institutional reforms, it is best to optimize the combination of technology holders, users of water rights, and investors to give full play to their respective advantages so as to give full play to the enthusiasm of all investors, ensure the legitimate rights and interests of all investors, and continuously improve operating efficiency. .
Fourth, the proliferation of silverfish transplantation technology (A) the theoretical basis for the proliferation of silverfish transplantation to increase the lakes, reservoirs, large areas of water surface productivity of important factors, is that the economic fish in the water area can maximize, fully and effectively use its natural For bait resources, species with higher biological benefits are selected as members of fisheries fauna. During its lifetime, the whitebait has the zooplankton as the main food, and it is in the third trophic level. The food chain is short, the life cycle is only one year, and the generations alternate rapidly and adapt well. From the point of view of large silverfish, its rapid growth, rapid sexual maturity and high production coefficient not only can increase the catch, but also can greatly improve the quality of catches.
(II) Selection of transplanted silverfish species When selecting the type of silverfish to be transplanted, it must be based on the specific environmental conditions of each place and based on the characteristics of the biology and ecological habits of different types of whitebait, especially the breeding habits. Choose to determine the appropriate category. There are 20 species of silverfish in the world, of which 15 species are in China. In our country, under the natural conditions have formed a dominant population, and in the north and south of China through the transplantation of proliferation has shown that the species with greater fishery value are the new species of Taihu silverfish and silverbait. After they moved into new waters, they were able to grow and reproduce, complete the life cycle, and proved to be successful in transplanting. They could produce higher fishery yields. Currently, they are the first choice for the proliferation of silverfish transplantation. Because of its short life cycle, rapid change of generations, ability to adapt to the environment, and short food chain, it can reproduce itself in lakes, reservoirs and other large and medium-sized waters. Its strong vitality is conducive to the expansion of the number of populations and does not require annual seedlings. At the same time, it has a high economic value and is one of the products that China is currently exporting through foreign exchange. It is praised as “small gold†and “water ginsengâ€. It is convenient to eat and nutritious. It is a kind of high-protein, low-fat, rich A variety of trace elements of aquatic food, fishing, processing, sales and more easily. Therefore, it has promoted the success of transplantation in various places and has its inherent necessity.
(III) Selection of the conditions for the proliferation of silverfish transplantation breeding water The new silverfish and silverbait of Taihu Lake are open-water fish and are suitable for living in waters with a closed or semi-enclosed ecological environment with a certain coast and open water. Therefore, moving into the water area requires relatively stable water level, fresh water, and no pollution. It is best to be between the medium and rich nutrition types. Various physical and chemical factors are suitable. In the ecosystem, especially in the middle and upper layers of water, there must be a space ecological environment, and bait There are abundant biological resources and there are fewer fierce fish in the upper and middle layers. This is an ideal breeding, growing, and developing water area.
1. Water area: The area moved into the water area can be large or small, large and medium-sized reservoirs, lakes and small water bodies can all be. However, practice in recent years has proved that the water surface is 2350 to 4500 acres, and all have achieved biological effects. Therefore, it is generally considered that the transplanted water surface is suitable for about 0.3 to 10,000 mu.
2. Water level and water depth: The required water level is relatively stable, with an average water depth of about 2 meters.
3. Substratum: Grafted and hard bottom grafting has a good effect of proliferation. It is better that the sediment does not exceed 1 cm.
4. Water quality (1) Water temperature: The growth water temperature is 0.5～32°C, the suitable water temperature is 25～30°C, and the appropriate temperature for spawning period: the new whitebait in Taihu Lake is 9.2～22.2°C, the big whitebait is 3 .8 to 6°C. The accumulated temperature of the life cycle is 3982 to 6430 degrees.
(2) Dissolved oxygen: Dissolved oxygen is required to be maintained at 5 to 10 mg/l.
(3) PH value: 6.5-9.2
(4) Salinity: 0 to 12.5 inches
(5) Total alkalinity: 0.93 to 13.73 mmol/L (6) Total hardness: 1.78 to 6.29 mmol/L (7) Nitrate: 0.075 to 1.92 mg/L l (8) Phosphate: 0.033 to 0.16 mg/L (9) Silicate: 1.22 to 6.85 mg/L (10) Transparency: Generally 30 to 500 cm. Composition of fish fauna (1) The composition of fishes in the waters that are required to be moved into is relatively simple, and it is better to have a relatively small ecological environment, especially for the fish in the upper and middle layers.
(2) Attention should be paid to the food structure of the dominant populations moved into the waters. To control the population of foods competing with the whitebait, it is necessary to control the stocking numbers of cockroaches, squid and chlamydna, particularly after moving into the whitebait. Fish, which compete with each other in food, kill each other during breeding.
(3) In fertile waters, feral fish should be controlled within 5% to 15%, preferably below 5%, and up to 15%.
6. Food composition (1) Plankton: To have abundant plankton resources, the quantity of phytoplankton should not be less than 1,150,000 per litre, and plankton biomass should be above 3.45 mg/l.
(2) Small wild fish and shrimp: It is the main bait for the adult stage of large silverfish. It is required to move into small and medium wild fish and shrimps in the water area.
(D) Silverfish transplantation method and operation process Silverfish transplantation methods are divided into three kinds of transplantation methods: broodstock, larvae and fertilized eggs.
A, broodstock transplantation method should pay attention to the climate and water temperature, the silverfish is generally from late November to early December, before the waters in the frozen, the water temperature at 6 ~ 8 °C when the best transplant.
1. The choice of broodstock: Choose individuals with good physique, good plumpness, body length of 12 cm or more, male to female ratio of 1:3, male fish can be more appropriate, which is conducive to natural spawning and artificial insemination.
2. Broodstock fishing and transport: Can be seized with purse seine, trawls and larvae. After being caught, they are picked up in a plastic bucket with a dip net, then transported in a canvas bucket, or transported by a plastic bag. The general canvas bucket volume is 1 meter 1 meter 1 meter, first joins 1/2 water, installs the silver fish 10 to 15 kilograms, uses the oxygen bottle to continuously oxygenate; Fills the oxygen with the plastic bag, 10 kilograms of water, may install the kin fish 2 kilograms . The transport time is best in the morning or evening, after 2 to 5 hours of transport, no problem. If the water temperature is higher, cool the ice in the canvas bucket or plastic bag.
3. Bring the broodstock into operation: After arriving at the destination, adjust the water temperature first so that the temperature of the water in the transporting canvas bucket or plastic bag and the water temperature in the cage to be placed gradually approach.
The cage can be made of 8 mesh mesh and has a size of 1 meter 2 meters and 1.5 meters. Two hours after the broodstock enters the box, the upper part of the cage is submerged into the water by 5 to 10 cm so that the broodstock can swim freely. After 8 to 12 hours, the cage is lifted to see if there are silver fish in the cage, if there is dead fish, and if there is dead fish, count the number to calculate the survival rate of transport.
B, Tsai, and Juvenile Transplantation A method of transplanting hatchery or larvae harvested in lakes or reservoirs into transplanted breeding waters.
1. A juvenile, juvenile fish choice: Choose healthy, disease-free, non-destructive individuals. The larvae should be selected after artificial hatching for 5 days after the unopened Pingyou seedlings. After 2 to 3 days of moving into the waters, it is possible to eat and feed outside food organisms.
Juveniles should choose a strong physique and a body length of 3 to 4 centimeters, which is more adaptable to the environment.
2. Aberdeen and juvenile transport: Water is added in plastic bags and transported with oxygen. After 10 kg of water is added, 50,000 to 100,000 larvae are loaded, or 0.5 to 10,000 juveniles are loaded.
3. Feeding juvenile fish and young fish: Before putting it on, test the water first, then remove 10 to 20 juvenile fish and put it into a 1000 ml beaker filled with water that has moved into the water. After 2 to 4 hours, if no abnormalities are found , You can put the larvae into a 40-mesh sieve to sew a mesh sieve of 0.5m, 1m, and 1m, so that the larvae can swim freely. The juveniles can be placed in 8 to 20 meshes and the size is 0.8. In a cage of 1.5 meters and 1 meter, after 2 hours, the cage is immersed 5 to 10 cm below the surface of the water, allowing juveniles to swim freely. After 8 hours, the cage is checked for dead. Fish, if not found, indicates that the survival rate of transportation is high. If dead fish is found, the number of points is used to calculate the survival rate of transport.
C, fertilized egg transplantation method Fertilized egg quality check: due to the development of the fertilized egg to the mid-late period of the original intestine, can normal development to the larvae ruptured membrane. Therefore, whether the egg is fertilized should be calculated from the late period of the original intestine. The development period can only be determined by microscopic observation. It is also inaccurate to visually distinguish fertilized eggs by naked eyes.
2. Fertilized egg counting method: According to the observed results of artificial hatching of fertilized eggs, when the water temperature is 12 to 14.5°C, the time for the development of silverfish embryos to the late intestine is about 38 to 40 hours after fertilization. Calculate the fertilization rate is randomly sampled, randomly picked a certain number of fertilized eggs, placed under a microscope or dissection microscope observation, respectively, the normal embryonic development of the fertilized eggs and the number of white, moldy dead eggs, and then calculated according to the following formula :
Fertility rate = 100%
The counting method of fertilized eggs adopts the concentrated volume sampling method. That is, with a 10 ml measuring cylinder, 10 ml of fertilized eggs are randomly selected, and then the 10 ml eggs are counted to obtain the number of particles per ml of fertilized eggs (grain). After several random samplings, count the number of eggs per milliliter, and then multiply the total volume of the fertilized eggs to find the total number of fertilized eggs. The formula is as follows:
Total egg count (grain) = grain/ml total ml Counted by production practice, the total number of fertilized eggs in silverfish is approximately 1200 to 1600 grains per ml.
3. Fertilized egg transportation The choice of fertilized egg transport for the new whitebait in Taihu Lake depends on the temperature of the hatching water. When the water temperature is low and the water temperature is below 14°C, it is transported after 2 to 3 days of temporary conservation; when the water temperature is above 15°C, it can be transported after being raised for 1 day. If the transportation is too late or the transportation distance is too long, the fertilized egg may break the membrane during transportation and the mortality rate is high.
During the reproduction period of the giant whitebait, the water temperature is low, and the incubation period is longer. At this time, there is no problem of early emergence due to high water temperature. Its transportation time is mainly based on embryonic development and various preparations. It is better to avoid the sensitive period after 5 to 6 days of fertilization and transport it after the late stage of the upper intestine, which is more conducive to the development of fertilized eggs.
Fertilized eggs can be oxygenated or not oxygenated by air, water or land.
(1) Oxygenation transport of plastic bags: This method is applicable to long-distance, high-volume transportation.
Made of polyethylene strong plastic bags, size 40 cm 80 cm. Ovulation density depends on the time of transportation and the temperature of the water. In general, 12 to 15 kilograms of the original reservoir water filtered by a 120 mesh sieve is added to each bag, and 50,000 to 150,000 fertilized eggs can be shipped and then oxygenated. The suitable water temperature in the bag is 0-10°C, and the most suitable water temperature is 2-8°C.
If you are transporting to the area south of the Yellow River in late January, you will need to put an ice pack in the bottom of the foam plastic box to reduce the water temperature and keep the water temperature no higher than 10°C. If you transport to the northeast and northwest regions, you should put it around the foam box. Plus cotton insulation, especially train transportation, to prevent the water in the plastic bag at the bottom of the foam box freezing, so as not to affect the survival rate of fertilized eggs. Under the above conditions, the transportation rate is generally not affected after 48 hours of transportation.
(2) open large containers with water transport: This method is generally suitable for a short distance transport.
Large plastic boxes, plastic cylinders, and plastic vats can be used for transportation. The ovulation density should be determined according to the specific circumstances. Generally every cubic meter of water can contain 100,000 to 600,000 eggs. The water temperature in the container is maintained at 2-8°C. During the journey, we must pay attention to turning the eggs, adding fresh water, and maintaining good water quality. The conditional oxygenation effect will be better.
(3) Wet and low-temperature transport 1 Strong polyethylene plastic bag: Count the eggs according to the volume method and put them in a single or double plastic bag, drain the gas in the bag, and quickly oxygenate, bundle and then pack the foam plastic box or Can be transported after the carton. Pay attention to the temperature during transportation, and keep the temperature in the box at 2 to 8°C.
2 large mouth thermos: The fertilized eggs directly into the thermos flask covered with a moist gauze pad, so that the egg and the bottom of the bottle to maintain a certain space to accommodate the ice in the way due to water after melting. On the top of the egg, cover it with moist gauze, and then add an appropriate amount of ice to the top of the egg, seal it and transport it. The temperature inside the bottle is kept at 2-8°C.
3 wooden boxes: wooden boxes filled with eggs, can be designed for different sizes of specifications, generally divided into two types of wooden boxes and boxes.
Lamellar wooden box: Put the eggs in the egg trays of each layer, or wrap them in the wet gauze cloth that holds the egg tray, and put some crushed ice pieces on the top layer to keep the fertilized eggs moist and cool. At the bottom of the lowest wooden box, there are several drainage holes drilled. When air is transported, the lowest floor does not contain eggs, and it does not drill drainage holes.
Box-type wooden box: When transporting the fertilized eggs, the egg is placed in a porous polyethylene plastic bag with a hole diameter of less than 0.8 mm, and then the plastic bag is placed in a box. In order to ensure the humidity and low temperature, the bag should be protected between plastic bags. Fill some sponge pieces.
(4) The thermos carries water at a low temperature: During transport, add ice, keep the temperature at 2~8°C, stir the fertilized eggs properly, and change the water.
(5) The thermos bottle is mixed with plastic bags and wet gauze. Transportation: Use a square, 15 cm 15 cm strong plastic bag, fill with water 250 ml, and the density of fertilized eggs is 140-300 capsules/ml, ie, 3 eggs per bag. 50,000 to 40,000 tablets, folded in large-bore thermos of 8 pound capacity, each layer of fertilized eggs, plus a layer of broken ice, filled with caps, placed in the box to be shipped . Each bottle can contain 200,000 to 500,000 fertilized eggs.
The above several transport methods, the strong plastic bag oxygenation plus packaging foam plastic boxes or cartons, the best transport, its large volume of transport, can be transported over long distances, the environment is easy to control. If you transport to cold areas, you can add insulation; if you transport to warm areas, you can add ice to cool down, and you can do it as you like. The temperature is kept at 2~8°C.
4. Placement of fertilized eggs (1) The direct placement of fertilized eggs into the bottom of the transplanted waters has proven that the hatching rate is more than 80% when the sediment is 1 centimeter; the hatching rate is 56% when the sediment is 1.5 centimeters; At a centimetre, the hatching rate is 14%; when the sediment is 3 centimeters, no larva hatches. Therefore, it is best to choose the delivery point in the leeward sunny, stable water quality, no pollution, depth of 1.5 to 2 meters, the bottom is flat, hard, sandy, silt does not exceed 1 cm in the area as well.
Transplanting large silverbaiers in the northern area is at an ice-sealing time. At this time, we must first open the ice eyes at the feed point and slowly dip the eggs in plastic bags into the water under the ice eyes. When the water temperature inside and outside the bags is basically the same, open the plastic bags. Spread the eggs evenly in the water. When you launch, plan to select more points for delivery.
Through practical experience over the past few years, it has been proved that transplants have a good effect on well-margined waters. The "latency period" is short and the population effect quickly forms. Therefore, prior to the launch of some waters, they should first select the feeding points and clean up and reform the sediments; some still lay a layer of sand within a certain range; some also lay a straw mat; Make an egg-laying station and place the eggs on square or rectangular countertops made of cement.
(2) The eggs are placed in cages suspended in water and hatched into larvae, and freely swim into the water. The shape of the cage can be square or rectangular, but it is preferably circular. The size of the cage depends on the size of the transplanted water and the number of transplanted silver fish eggs. Large lakes and reservoirs have large water surfaces and can carry tens of millions of eggs. It is best to make a large cage with a diameter of 1 meter, and can make 2 to 3 layers. The underlying mesh is 40-60 mesh to prevent leakage of eggs. Around the 20 to 40 mesh clothing, so that larvae can swim freely after hatching. The top layer is made of 8 to 10 mesh mesh, and the eggs can be poured directly. There is a zipper between the layers, mainly for laying eggs. The distance between the layers is 15-20 cm, and they are supported by steel bars. The round cage of the cage is reinforced with No. 6 steel. In this multi-layered cage, one can lay 300,000 to 500,000 eggs. When you are under the net, set 3 points in the lower layer to hang the net pendant and sink the net. Three points are set on the top of the net, which is a nylon rope tied with a polyethylene plastic block as a float, or a bamboo raft on the water. The cage is suspended in water 1.5 to 2 meters below the surface of the water. After the fertilized eggs are placed in cages, they can be lifted in parallel with the surface of the water for 7 to 10 days if conditions permit. The eggs are moved a few times to allow the overlapping eggs to move, which is more conducive to hatching. If it is in a small water area, or a plain type reservoir, when there is a lot of silt in the water area, the cage can be washed to facilitate the flow of water, and dozens of eggs can be taken out at any time to observe the progress of embryonic development.
(5) Proliferative incubation period and population formation of silverfish transplantation In theory, the greater the number of transplants, the greater the density and the quicker the effect. Generally speaking, the success of silverfish transplantation is great and the effect is good. However, if the number of disposable transplants is too large and the cost is too high, the transplant unit will be economically unaffordable. Therefore, depending on the specific circumstances, it is necessary to put them in batches and at different times. Therefore, the size of transplantation should be based on the ecological environment conditions of the transplanted waters and local conditions. Generally transplanted into the body, no less than 2 to 3 tails per hectare of water, male to female ratio of 1:2 to 3; transplanted fertilized eggs, according to the hatching rate of 70% to 80% of the calculation, each hectare is about 500 to 1500.
After the whitebait has moved into the waters, follow-up investigations are conducted. It is necessary to carry out multi-point trials from time to time with small trawls, especially during the breeding season to catch broodstock and check the growth of the whitebait and gonadal development. If gonads are found to mature and can normally spawn, fertilize, and hatch larvae, then it is suggested that the whitefish can develop normally and reproduce in the waters, which has already formed a biological effect. Generally, in the second year after the occurrence of biological effects, it is possible to track trials based on different months of age, and estimate the resource reserves according to the relative relationship between the trials and arrests and decide whether to carry out productive fishing. The so-called "latency period" refers to the stage in which the transplanted subject has begun to breed and form a population in the newly moved waters. According to the practical experience of transplanting silverfish around the country, the population effect (ie, incubation period) of the new whitebait in Taihu Lake is generally 3 to 4 years, and individual is 2 years; the population effect period of the giant whitebait is generally 2 years, and individual 1 Years, but there are also 3 years to form a population.
(Six) Evaluation of proliferation of silverfish transplantation After evaluation of silverfish transplantation, whether it is in fertilized eggs, larvae, or broodstock, monthly or fixed spots are required to monitor whether or not silvery fish are present, especially in spring season. During the breeding season, more trials and inspections were conducted. If there is silver fish, no matter how much, it is necessary to conduct biological assays and check the development of gonadal. If the gonad matures, it shows that it can grow and develop normally in the water moved into the area and has biological effects. It can continue as planned. If no silverfish are caught for two consecutive years, a comprehensive analysis will be conducted to study every aspect of the transplantation process to see which part is out of order. It may also be a matter of physical, chemical and biological factors that move into the waters. A certain factor has limited the normal growth and development of whitebait, summed up the reasons for not succeeding, and then targeted effective measures. The length of the incubation period is closely related to the number of launches, the number of launches, and the conditions of the water environment. Practice has proved that, under normal circumstances, the incubation period is 1 to 3 years, and the fishery population is formed. It is usually 3 years, and individual ones are 1 or 4 years old.
The silverfish was found in the waters after its introduction, but it does not mean that the transplantation has been successful. It must go through several stages and finally produce a stable fishery population effect, so as to show that the transplant proliferation has been truly successful.
The main assessment methods are the following five points:
1. Biological effects: Transplanted fertilized eggs can migrate to water to hatch larvae, grow, develop and reproduce. Adults can grow into broodstock in the same year. The gonads develop well and they can lay eggs. Learn effect.
2. Formation of population: The generation of biological effects marks the transfer of fertilized eggs or adult fish from whitebait, which can reproduce in offspring and form populations and join supplementary groups.
3. Forming a fishery effect: The continuous increase of supplemental groups is the result of increasing population after transplantation, making population supplemented groups produce yields and produce fishery effects.
4. Intense competition in environmental and ecological factors: At the same time as the rapid increase in the number of populations, there are fierce contradictions with the eco-environmental factors in the waters, such as competition in food, space, and spawning grounds, and mutual food, resulting in this period of population. The drastic changes may be reduced to varying degrees, and sometimes there will be a substantial decline or increase.
5. The stability of dominant populations: After fierce competition among various factors in the ecological environment of waters, the population gradually emerged a natural ecological balance in competition. The ecological factors in the waters balance each other, and the whitebait has become a dominant species. The population has begun to show a stable situation and the transplantation and proliferation have been successful. If eager to harvest a large number of populations in the fierce struggle between populations and the ecological environment, it will inevitably weaken the competitiveness of the whitebait population in the ecological environment, making it unable to form dominant populations, which will inevitably lead to the failure of transplantation.
Therefore, in order to make rational use of resources, it is necessary to estimate the amount of resources before fishing; in addition, monitoring the changes in the growth, population density, and dietary biomass of different stages of silverfish in the waters, and analyzing the feeding ability and ecology of the water body. The potential to conduct a more rational assessment of the effect of transplantation and to develop a scientific and reasonable fishery fishing plan to ensure the stability of the whitebait resources.
(7) Strengthen the proliferation and protection of whitebait resources and increase the proliferation of silverfish transplantation. Protecting the ecological environment of reservoirs and maintaining and improving water productivity: Reservoirs are water conservancy systems for flood prevention, flood irrigation, power generation and fish farming, and the comprehensive use of surface water resources. Establishing ecological projects centered on natural or artificial ecosystems such as water bodies, forest lands, and grasslands in its runoff areas, with the aim of rational development and utilization of major biological and non-biological resources, to maximize the potential of reservoir resources. Improving the ecological and economic benefits of reservoirs is an important task of the reservoir management department. Fish is the main product of the reservoir. The pros and cons of the ecological environment of the reservoir directly affect the fishery production. Therefore, it is very important to protect the water body from contamination, maintain the content of some nutrient salts in the water body, and increase the primary productivity in the water body. Therefore, according to the different requirements of reservoir water supply for water quality, measures such as fertilization and water quality adjustment can be taken to create a good ecological environment for the growth of whitebait. In the control and development and utilization of reservoirs, the water level requirements of fish breeding season should be taken into account as much as possible. When discharging floodwater, it is necessary to take care of fish escape prevention work and provide conditions for deploying blocking facilities so as to minimize the loss of water from whitebait resources.
2. The selection and delineation of the Silverbait Resource Conservation Area: The structure of the whitebait population is simple, and the number of cultured fish is 100%. The decrease in the number of supplementary groups directly affects the fishery output of the year. Therefore, if the fishery is carried out within the entire water area during the breeding season, it will inevitably destroy the breeding process, reduce the number of broodstock, destroy, kill and infer fertilized eggs, and reduce the number of supplementary groups, resulting in a decline in fishery production. Therefore, according to the breeding habits of the whitebait, selecting and demarcating resource reproduction protection zones in the transplanted waters is conducive to the conservation of resources of the whitebait. Silverfish is a kind of open-water fish, suitable for living in the middle and upper layers of a relatively wide range of coastal waters. By the breeding season, it migrates to the shallow sandy bottom with relatively hard sediments and less silt, and shelters the sunny side of the bay. The library maggot breeds eggs. Therefore, according to the breeding habits of whitebait, 5% to 10% of the suitable water area can be demarcated on the surface of the water, delineated as a resource reproduction protection zone, and all fishing vessels are prohibited from entering. In this way, during the breeding season, a part of the whitebait can be bred in the protected area, ensuring the number of supplementary groups and increasing the benefits of population proliferation.
3. Determine the no-fishing area and the closed fishing season: Delineate 5% to 10% of the water area or larger water area within the fishery water area as a year-round imprisonment area, as a safe place for the growth of the silverfish to thrive, in order to protect a part of the whitebait Provide supplementary groups and breeding resources for the whitebait population.
At the same time, to determine the banned period of silverfish, according to the different types of silverfish, different spawning period, respectively, to determine. The spring group of the new whitebait in Taihu Lake should be from March to May, and the autumn group should be from October to November; while the whitebait should be from the late December to the end of March the following year as a captive period. In this way, consistent with the ecological habits of the whitebait, it ensures the breeding population of the egg-laying broodstock and a large number of proliferating supplementary populations to ensure its proliferation potential and obtain greater efficiency.
4. Adjust the fish population structure in the transplanted whitebaill waters. In the waters where the silverfish are transplanted, reduce the amount of squid feeding and increase some herbivorous fish that do not compete with the whitebait; at the same time, remove and suppress Ono. Miscellaneous fish and ferocious fish. Although the small wild fish are small in size, they compete for space and food with the whitebait, especially the fish in the pond. They will be able to eat each other. Therefore, it is best not to transplant the fish in the area of ​​transplanted whitebait fish. The ferocious fish, mainly fish and white, and horse and fish, have strong fertility. The active space is upper and middle, and the staple food of small wild fish and shrimp is in conflict with the migration of silverfish. Therefore, it is necessary to strengthen the clearance.
5. Determine a reasonable stock of silverfish resources: After successfully transferring silverfish into the waters, follow up investigations on the distribution, growth, food habits and breeding habits of the whitebait in the waters, and conduct breeding assessments to determine their reasonableness. Fishing volume and its retention. Since the history of transplanting whitebait is not long, the exact determination of the catch of silverfish in different types of waters has yet to be further studied. As far as the current situation is concerned, in the waters of normal cod rearing areas, about 2 kilograms of whitebait can be produced per acre of water in the case of natural multiplication of resources; for the shortage of stocked eels, there is no stock of cod. In the waters, about 5 to 7 kg of whitebait can be produced per acre. In some water areas, such as the Tianjin Beitang Reservoir, the production of fish such as squid is maintained at a relatively high level, with an average of about 38 kg/mu, 1992 The annual production of large silverfish is still 2.5 kg; the Baiguishan Reservoir in Henan has yielded 1.4 kg of fresh whitebait per mu for many years. The provision of catches is mainly to ensure that there are enough stocks and that there are enough spawning brooders and at the same time higher fish yields. In view of the fact that the current history of silverfish transplantation is not long, the retention of whitebait still refers to the practical experience of fish stocks in the lake, leaving a certain number of species, and the remaining amount in Taihu Lake is 27% of the estimated total resources, and Dianchi in Yunnan is about 10%.
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Pond cultivation, in the past 30 years, especially since 1978, has undergone institutional reforms, through the transformation of old fish ponds, the development of swamps, low-lying wasteland, saline-alkali land, the development of suburban fish farming, the construction of commercial fish bases, and the establishment of standardized supporting facilities for fish ponds. Improve the technical level of fish farming, apply aerators, feeds, and promote effective varieties, and so on, so both in the expansion of aquaculture area, increase the aquaculture yield, increase the total aquaculture production, improve the proportion of high-quality fish and economic benefits, have achieved With great development, in 1978 China's pond aquaculture area was 10,823,300 mu, and the aquaculture output was 497,000 tons, with an average yield of 48 kilograms per mu, and the highest was 300 to 500 kilograms. In 2000, China's pond aquaculture area was expanded to 33.3 million mu and the output reached 10.87 million tons. The average yield per mu was 326.6 kg, and the highest was more than 1,000 kg. In 2000, compared with 1978, the pond aquaculture area expanded 2.1 times, the aquaculture production increased by 20.8 times, the average yield per mu increased by 5.8 times, and the aquaculture production accounted for 65 percent of the total freshwater aquaculture production. 2% increased to 71.7% in 2000, an increase of 6.5 percentage points, and the number of farmed species increased from 10 to tens.
In the past 30 years, especially since 1978, large-scale breeding of lakes and reservoirs has seen great development. After system reforms, the introduction of small-surface pond aquaculture technology, the development of lakes and reservoirs, reservoirs of lakes and lakes, and “three networks "Farming and strengthening of supporting facilities for large-scale fingerlings and fish-prevention facilities have resulted in the rapid development of directional transplanted proliferation of fish, crab, and other fine varieties. In 1978, the aquaculture area of ​​lakes and reservoirs in China was With 26,093,000 mu, the output is 184,000 tons, and the average yield per mu is 7 kg. In 2000, the aquaculture area was expanded to 37.738 million mu, and the aquaculture production reached 243,000 tons. The average yield per mu was 64.3 kg. In 2000, compared with 1978, the aquaculture area increased by 44.6%, the aquaculture production increased by 12.1 times, and the average yield per mu increased by 8.2 times. However, due to rapid development of pond aquaculture and rapid increase in production, the proportion of lake and reservoir aquaculture production to the total freshwater aquaculture production in the same period decreased from 24.2% in 1978 to 16%, a drop of 8.2%.
Lakes and reservoirs were cultured on a large surface. Compared with ponds with small water surfaces, the development was still at a low level. The speed of development was still very slow, and 52.3% of the large water surface was exploitable without utilisation. The water surface of the breeding area was developed. The average yield is still very low. At present, the average yield per mu is only 1/5 of the pond's yield. Pond aquaculture accounts for 42% of total freshwater aquaculture, while aquaculture production accounts for 78%, while lakes and reservoirs account for 48% of the country's total freshwater aquaculture area, while aquaculture production only accounts for 16%.
It can be seen from the above that pond culture is better than economically developed areas on the southeast coast, while lakes and reservoirs are better than western development areas.
To develop freshwater aquaculture, we must also work with both hands, and both hands must be hard. While grasping the pond culture, we must also pay close attention to the development and utilization of lakes and reservoirs. Because there are many advantages in the development and utilization of lakes and reservoirs, one is abundant in resources. At present, there are still 35.56 million mu of water that can be exploited but not yet exploited. Even if the water surface has been farmed, the average yield per unit area is very low. Therefore, there is great potential for development. The second is the development of large water surface, which does not compete with agriculture for arable land, and can increase the utilization of land and resources. Third, the investment is small, the effect is quick and the benefits are high. Varieties, such as transplanting whitebait, can achieve very good economic, social, and ecological benefits in a relatively short period of time. Fourth, products that are concentrated and are mostly exported through foreign exchange. Therefore, the development of large-surface lakes and reservoir breeding, especially the development of targeted migration of fish and large-surface fishes in lakes and reservoirs, has great potential for development and broad prospects for development. It is one of the key development directions for developing freshwater aquaculture in the future.
Second, the main varieties of fish and reservoirs for targeted transplantation of fish proliferation China has a vast territory, and lakes and reservoirs are distributed throughout the country. Therefore, according to the environmental conditions such as the location of lakes, reservoirs, climate, water quality, food organisms, and composition of fish species, transplant breeding technology requirements, sources of transplanted seeds, economic strength, and economic benefits should be investigated. Research, through adequate argumentation, selected transplanted varieties according to local conditions. At present, from the national point of view, the main breeds for transplantation and proliferation include whitebait, ichinobumin, high whitefish, squid, and river crabs.
Third, the main technical points of the directional transplanted fish in lakes and reservoirs 1. A background survey is conducted on the lakes and reservoirs to be transplanted, and the climate, hydrology, water quality, composition and structure of the biological populations in the waters, the status of the biomass and biofeeds, and the human influence on the waters are to be ascertained.
2. Through in-depth investigation and study of the waters to be transplanted, a full demonstration will be made to determine the suitable varieties for transplantation and proliferation.
3. According to the characteristics of transplanted varieties to be transplanted and the technical requirements for transplantation and proliferation, different methods for selecting and transplanting proliferation should be determined to adapt to the different methods of transplantation for proliferating broodstock, larvae and fertilized eggs.
4. According to the reproductive ability of the transplanted species, the reasonable load of the water to be transplanted, and the economic strength, the total amount of transplanted fish and the number and number of batch transplants are determined.
5. We will conduct follow-up investigations on the changes in the amount of resources and resources that have been released, and master the dynamic laws to determine the start time of arrests, reasonable catches, and retention, so as to ensure the regeneration of resources and sustainable development.
6. Strengthen the management of fishery administrations, formulate prohibited fishing areas, prohibit fishing seasons, provide fishing gear and fishery laws, strengthen protection, and prevent the occurrence of vicious accidents such as stealing, stealing, poisoning, and fish frying.
7. To carry out institutional reforms, it is best to optimize the combination of technology holders, users of water rights, and investors to give full play to their respective advantages so as to give full play to the enthusiasm of all investors, ensure the legitimate rights and interests of all investors, and continuously improve operating efficiency. .
Fourth, the proliferation of silverfish transplantation technology (A) the theoretical basis for the proliferation of silverfish transplantation to increase the lakes, reservoirs, large areas of water surface productivity of important factors, is that the economic fish in the water area can maximize, fully and effectively use its natural For bait resources, species with higher biological benefits are selected as members of fisheries fauna. During its lifetime, the whitebait has the zooplankton as the main food, and it is in the third trophic level. The food chain is short, the life cycle is only one year, and the generations alternate rapidly and adapt well. From the point of view of large silverfish, its rapid growth, rapid sexual maturity and high production coefficient not only can increase the catch, but also can greatly improve the quality of catches.
(II) Selection of transplanted silverfish species When selecting the type of silverfish to be transplanted, it must be based on the specific environmental conditions of each place and based on the characteristics of the biology and ecological habits of different types of whitebait, especially the breeding habits. Choose to determine the appropriate category. There are 20 species of silverfish in the world, of which 15 species are in China. In our country, under the natural conditions have formed a dominant population, and in the north and south of China through the transplantation of proliferation has shown that the species with greater fishery value are the new species of Taihu silverfish and silverbait. After they moved into new waters, they were able to grow and reproduce, complete the life cycle, and proved to be successful in transplanting. They could produce higher fishery yields. Currently, they are the first choice for the proliferation of silverfish transplantation. Because of its short life cycle, rapid change of generations, ability to adapt to the environment, and short food chain, it can reproduce itself in lakes, reservoirs and other large and medium-sized waters. Its strong vitality is conducive to the expansion of the number of populations and does not require annual seedlings. At the same time, it has a high economic value and is one of the products that China is currently exporting through foreign exchange. It is praised as “small gold†and “water ginsengâ€. It is convenient to eat and nutritious. It is a kind of high-protein, low-fat, rich A variety of trace elements of aquatic food, fishing, processing, sales and more easily. Therefore, it has promoted the success of transplantation in various places and has its inherent necessity.
(III) Selection of the conditions for the proliferation of silverfish transplantation breeding water The new silverfish and silverbait of Taihu Lake are open-water fish and are suitable for living in waters with a closed or semi-enclosed ecological environment with a certain coast and open water. Therefore, moving into the water area requires relatively stable water level, fresh water, and no pollution. It is best to be between the medium and rich nutrition types. Various physical and chemical factors are suitable. In the ecosystem, especially in the middle and upper layers of water, there must be a space ecological environment, and bait There are abundant biological resources and there are fewer fierce fish in the upper and middle layers. This is an ideal breeding, growing, and developing water area.
1. Water area: The area moved into the water area can be large or small, large and medium-sized reservoirs, lakes and small water bodies can all be. However, practice in recent years has proved that the water surface is 2350 to 4500 acres, and all have achieved biological effects. Therefore, it is generally considered that the transplanted water surface is suitable for about 0.3 to 10,000 mu.
2. Water level and water depth: The required water level is relatively stable, with an average water depth of about 2 meters.
3. Substratum: Grafted and hard bottom grafting has a good effect of proliferation. It is better that the sediment does not exceed 1 cm.
4. Water quality (1) Water temperature: The growth water temperature is 0.5～32°C, the suitable water temperature is 25～30°C, and the appropriate temperature for spawning period: the new whitebait in Taihu Lake is 9.2～22.2°C, the big whitebait is 3 .8 to 6°C. The accumulated temperature of the life cycle is 3982 to 6430 degrees.
(2) Dissolved oxygen: Dissolved oxygen is required to be maintained at 5 to 10 mg/l.
(3) PH value: 6.5-9.2
(4) Salinity: 0 to 12.5 inches
(5) Total alkalinity: 0.93 to 13.73 mmol/L (6) Total hardness: 1.78 to 6.29 mmol/L (7) Nitrate: 0.075 to 1.92 mg/L l (8) Phosphate: 0.033 to 0.16 mg/L (9) Silicate: 1.22 to 6.85 mg/L (10) Transparency: Generally 30 to 500 cm. Composition of fish fauna (1) The composition of fishes in the waters that are required to be moved into is relatively simple, and it is better to have a relatively small ecological environment, especially for the fish in the upper and middle layers.
(2) Attention should be paid to the food structure of the dominant populations moved into the waters. To control the population of foods competing with the whitebait, it is necessary to control the stocking numbers of cockroaches, squid and chlamydna, particularly after moving into the whitebait. Fish, which compete with each other in food, kill each other during breeding.
(3) In fertile waters, feral fish should be controlled within 5% to 15%, preferably below 5%, and up to 15%.
6. Food composition (1) Plankton: To have abundant plankton resources, the quantity of phytoplankton should not be less than 1,150,000 per litre, and plankton biomass should be above 3.45 mg/l.
(2) Small wild fish and shrimp: It is the main bait for the adult stage of large silverfish. It is required to move into small and medium wild fish and shrimps in the water area.
(D) Silverfish transplantation method and operation process Silverfish transplantation methods are divided into three kinds of transplantation methods: broodstock, larvae and fertilized eggs.
A, broodstock transplantation method should pay attention to the climate and water temperature, the silverfish is generally from late November to early December, before the waters in the frozen, the water temperature at 6 ~ 8 °C when the best transplant.
1. The choice of broodstock: Choose individuals with good physique, good plumpness, body length of 12 cm or more, male to female ratio of 1:3, male fish can be more appropriate, which is conducive to natural spawning and artificial insemination.
2. Broodstock fishing and transport: Can be seized with purse seine, trawls and larvae. After being caught, they are picked up in a plastic bucket with a dip net, then transported in a canvas bucket, or transported by a plastic bag. The general canvas bucket volume is 1 meter 1 meter 1 meter, first joins 1/2 water, installs the silver fish 10 to 15 kilograms, uses the oxygen bottle to continuously oxygenate; Fills the oxygen with the plastic bag, 10 kilograms of water, may install the kin fish 2 kilograms . The transport time is best in the morning or evening, after 2 to 5 hours of transport, no problem. If the water temperature is higher, cool the ice in the canvas bucket or plastic bag.
3. Bring the broodstock into operation: After arriving at the destination, adjust the water temperature first so that the temperature of the water in the transporting canvas bucket or plastic bag and the water temperature in the cage to be placed gradually approach.
The cage can be made of 8 mesh mesh and has a size of 1 meter 2 meters and 1.5 meters. Two hours after the broodstock enters the box, the upper part of the cage is submerged into the water by 5 to 10 cm so that the broodstock can swim freely. After 8 to 12 hours, the cage is lifted to see if there are silver fish in the cage, if there is dead fish, and if there is dead fish, count the number to calculate the survival rate of transport.
B, Tsai, and Juvenile Transplantation A method of transplanting hatchery or larvae harvested in lakes or reservoirs into transplanted breeding waters.
1. A juvenile, juvenile fish choice: Choose healthy, disease-free, non-destructive individuals. The larvae should be selected after artificial hatching for 5 days after the unopened Pingyou seedlings. After 2 to 3 days of moving into the waters, it is possible to eat and feed outside food organisms.
Juveniles should choose a strong physique and a body length of 3 to 4 centimeters, which is more adaptable to the environment.
2. Aberdeen and juvenile transport: Water is added in plastic bags and transported with oxygen. After 10 kg of water is added, 50,000 to 100,000 larvae are loaded, or 0.5 to 10,000 juveniles are loaded.
3. Feeding juvenile fish and young fish: Before putting it on, test the water first, then remove 10 to 20 juvenile fish and put it into a 1000 ml beaker filled with water that has moved into the water. After 2 to 4 hours, if no abnormalities are found , You can put the larvae into a 40-mesh sieve to sew a mesh sieve of 0.5m, 1m, and 1m, so that the larvae can swim freely. The juveniles can be placed in 8 to 20 meshes and the size is 0.8. In a cage of 1.5 meters and 1 meter, after 2 hours, the cage is immersed 5 to 10 cm below the surface of the water, allowing juveniles to swim freely. After 8 hours, the cage is checked for dead. Fish, if not found, indicates that the survival rate of transportation is high. If dead fish is found, the number of points is used to calculate the survival rate of transport.
C, fertilized egg transplantation method Fertilized egg quality check: due to the development of the fertilized egg to the mid-late period of the original intestine, can normal development to the larvae ruptured membrane. Therefore, whether the egg is fertilized should be calculated from the late period of the original intestine. The development period can only be determined by microscopic observation. It is also inaccurate to visually distinguish fertilized eggs by naked eyes.
2. Fertilized egg counting method: According to the observed results of artificial hatching of fertilized eggs, when the water temperature is 12 to 14.5°C, the time for the development of silverfish embryos to the late intestine is about 38 to 40 hours after fertilization. Calculate the fertilization rate is randomly sampled, randomly picked a certain number of fertilized eggs, placed under a microscope or dissection microscope observation, respectively, the normal embryonic development of the fertilized eggs and the number of white, moldy dead eggs, and then calculated according to the following formula :
Fertility rate = 100%
The counting method of fertilized eggs adopts the concentrated volume sampling method. That is, with a 10 ml measuring cylinder, 10 ml of fertilized eggs are randomly selected, and then the 10 ml eggs are counted to obtain the number of particles per ml of fertilized eggs (grain). After several random samplings, count the number of eggs per milliliter, and then multiply the total volume of the fertilized eggs to find the total number of fertilized eggs. The formula is as follows:
Total egg count (grain) = grain/ml total ml Counted by production practice, the total number of fertilized eggs in silverfish is approximately 1200 to 1600 grains per ml.
3. Fertilized egg transportation The choice of fertilized egg transport for the new whitebait in Taihu Lake depends on the temperature of the hatching water. When the water temperature is low and the water temperature is below 14°C, it is transported after 2 to 3 days of temporary conservation; when the water temperature is above 15°C, it can be transported after being raised for 1 day. If the transportation is too late or the transportation distance is too long, the fertilized egg may break the membrane during transportation and the mortality rate is high.
During the reproduction period of the giant whitebait, the water temperature is low, and the incubation period is longer. At this time, there is no problem of early emergence due to high water temperature. Its transportation time is mainly based on embryonic development and various preparations. It is better to avoid the sensitive period after 5 to 6 days of fertilization and transport it after the late stage of the upper intestine, which is more conducive to the development of fertilized eggs.
Fertilized eggs can be oxygenated or not oxygenated by air, water or land.
(1) Oxygenation transport of plastic bags: This method is applicable to long-distance, high-volume transportation.
Made of polyethylene strong plastic bags, size 40 cm 80 cm. Ovulation density depends on the time of transportation and the temperature of the water. In general, 12 to 15 kilograms of the original reservoir water filtered by a 120 mesh sieve is added to each bag, and 50,000 to 150,000 fertilized eggs can be shipped and then oxygenated. The suitable water temperature in the bag is 0-10°C, and the most suitable water temperature is 2-8°C.
If you are transporting to the area south of the Yellow River in late January, you will need to put an ice pack in the bottom of the foam plastic box to reduce the water temperature and keep the water temperature no higher than 10°C. If you transport to the northeast and northwest regions, you should put it around the foam box. Plus cotton insulation, especially train transportation, to prevent the water in the plastic bag at the bottom of the foam box freezing, so as not to affect the survival rate of fertilized eggs. Under the above conditions, the transportation rate is generally not affected after 48 hours of transportation.
(2) open large containers with water transport: This method is generally suitable for a short distance transport.
Large plastic boxes, plastic cylinders, and plastic vats can be used for transportation. The ovulation density should be determined according to the specific circumstances. Generally every cubic meter of water can contain 100,000 to 600,000 eggs. The water temperature in the container is maintained at 2-8°C. During the journey, we must pay attention to turning the eggs, adding fresh water, and maintaining good water quality. The conditional oxygenation effect will be better.
(3) Wet and low-temperature transport 1 Strong polyethylene plastic bag: Count the eggs according to the volume method and put them in a single or double plastic bag, drain the gas in the bag, and quickly oxygenate, bundle and then pack the foam plastic box or Can be transported after the carton. Pay attention to the temperature during transportation, and keep the temperature in the box at 2 to 8°C.
2 large mouth thermos: The fertilized eggs directly into the thermos flask covered with a moist gauze pad, so that the egg and the bottom of the bottle to maintain a certain space to accommodate the ice in the way due to water after melting. On the top of the egg, cover it with moist gauze, and then add an appropriate amount of ice to the top of the egg, seal it and transport it. The temperature inside the bottle is kept at 2-8°C.
3 wooden boxes: wooden boxes filled with eggs, can be designed for different sizes of specifications, generally divided into two types of wooden boxes and boxes.
Lamellar wooden box: Put the eggs in the egg trays of each layer, or wrap them in the wet gauze cloth that holds the egg tray, and put some crushed ice pieces on the top layer to keep the fertilized eggs moist and cool. At the bottom of the lowest wooden box, there are several drainage holes drilled. When air is transported, the lowest floor does not contain eggs, and it does not drill drainage holes.
Box-type wooden box: When transporting the fertilized eggs, the egg is placed in a porous polyethylene plastic bag with a hole diameter of less than 0.8 mm, and then the plastic bag is placed in a box. In order to ensure the humidity and low temperature, the bag should be protected between plastic bags. Fill some sponge pieces.
(4) The thermos carries water at a low temperature: During transport, add ice, keep the temperature at 2~8°C, stir the fertilized eggs properly, and change the water.
(5) The thermos bottle is mixed with plastic bags and wet gauze. Transportation: Use a square, 15 cm 15 cm strong plastic bag, fill with water 250 ml, and the density of fertilized eggs is 140-300 capsules/ml, ie, 3 eggs per bag. 50,000 to 40,000 tablets, folded in large-bore thermos of 8 pound capacity, each layer of fertilized eggs, plus a layer of broken ice, filled with caps, placed in the box to be shipped . Each bottle can contain 200,000 to 500,000 fertilized eggs.
The above several transport methods, the strong plastic bag oxygenation plus packaging foam plastic boxes or cartons, the best transport, its large volume of transport, can be transported over long distances, the environment is easy to control. If you transport to cold areas, you can add insulation; if you transport to warm areas, you can add ice to cool down, and you can do it as you like. The temperature is kept at 2~8°C.
4. Placement of fertilized eggs (1) The direct placement of fertilized eggs into the bottom of the transplanted waters has proven that the hatching rate is more than 80% when the sediment is 1 centimeter; the hatching rate is 56% when the sediment is 1.5 centimeters; At a centimetre, the hatching rate is 14%; when the sediment is 3 centimeters, no larva hatches. Therefore, it is best to choose the delivery point in the leeward sunny, stable water quality, no pollution, depth of 1.5 to 2 meters, the bottom is flat, hard, sandy, silt does not exceed 1 cm in the area as well.
Transplanting large silverbaiers in the northern area is at an ice-sealing time. At this time, we must first open the ice eyes at the feed point and slowly dip the eggs in plastic bags into the water under the ice eyes. When the water temperature inside and outside the bags is basically the same, open the plastic bags. Spread the eggs evenly in the water. When you launch, plan to select more points for delivery.
Through practical experience over the past few years, it has been proved that transplants have a good effect on well-margined waters. The "latency period" is short and the population effect quickly forms. Therefore, prior to the launch of some waters, they should first select the feeding points and clean up and reform the sediments; some still lay a layer of sand within a certain range; some also lay a straw mat; Make an egg-laying station and place the eggs on square or rectangular countertops made of cement.
(2) The eggs are placed in cages suspended in water and hatched into larvae, and freely swim into the water. The shape of the cage can be square or rectangular, but it is preferably circular. The size of the cage depends on the size of the transplanted water and the number of transplanted silver fish eggs. Large lakes and reservoirs have large water surfaces and can carry tens of millions of eggs. It is best to make a large cage with a diameter of 1 meter, and can make 2 to 3 layers. The underlying mesh is 40-60 mesh to prevent leakage of eggs. Around the 20 to 40 mesh clothing, so that larvae can swim freely after hatching. The top layer is made of 8 to 10 mesh mesh, and the eggs can be poured directly. There is a zipper between the layers, mainly for laying eggs. The distance between the layers is 15-20 cm, and they are supported by steel bars. The round cage of the cage is reinforced with No. 6 steel. In this multi-layered cage, one can lay 300,000 to 500,000 eggs. When you are under the net, set 3 points in the lower layer to hang the net pendant and sink the net. Three points are set on the top of the net, which is a nylon rope tied with a polyethylene plastic block as a float, or a bamboo raft on the water. The cage is suspended in water 1.5 to 2 meters below the surface of the water. After the fertilized eggs are placed in cages, they can be lifted in parallel with the surface of the water for 7 to 10 days if conditions permit. The eggs are moved a few times to allow the overlapping eggs to move, which is more conducive to hatching. If it is in a small water area, or a plain type reservoir, when there is a lot of silt in the water area, the cage can be washed to facilitate the flow of water, and dozens of eggs can be taken out at any time to observe the progress of embryonic development.
(5) Proliferative incubation period and population formation of silverfish transplantation In theory, the greater the number of transplants, the greater the density and the quicker the effect. Generally speaking, the success of silverfish transplantation is great and the effect is good. However, if the number of disposable transplants is too large and the cost is too high, the transplant unit will be economically unaffordable. Therefore, depending on the specific circumstances, it is necessary to put them in batches and at different times. Therefore, the size of transplantation should be based on the ecological environment conditions of the transplanted waters and local conditions. Generally transplanted into the body, no less than 2 to 3 tails per hectare of water, male to female ratio of 1:2 to 3; transplanted fertilized eggs, according to the hatching rate of 70% to 80% of the calculation, each hectare is about 500 to 1500.
After the whitebait has moved into the waters, follow-up investigations are conducted. It is necessary to carry out multi-point trials from time to time with small trawls, especially during the breeding season to catch broodstock and check the growth of the whitebait and gonadal development. If gonads are found to mature and can normally spawn, fertilize, and hatch larvae, then it is suggested that the whitefish can develop normally and reproduce in the waters, which has already formed a biological effect. Generally, in the second year after the occurrence of biological effects, it is possible to track trials based on different months of age, and estimate the resource reserves according to the relative relationship between the trials and arrests and decide whether to carry out productive fishing. The so-called "latency period" refers to the stage in which the transplanted subject has begun to breed and form a population in the newly moved waters. According to the practical experience of transplanting silverfish around the country, the population effect (ie, incubation period) of the new whitebait in Taihu Lake is generally 3 to 4 years, and individual is 2 years; the population effect period of the giant whitebait is generally 2 years, and individual 1 Years, but there are also 3 years to form a population.
(Six) Evaluation of proliferation of silverfish transplantation After evaluation of silverfish transplantation, whether it is in fertilized eggs, larvae, or broodstock, monthly or fixed spots are required to monitor whether or not silvery fish are present, especially in spring season. During the breeding season, more trials and inspections were conducted. If there is silver fish, no matter how much, it is necessary to conduct biological assays and check the development of gonadal. If the gonad matures, it shows that it can grow and develop normally in the water moved into the area and has biological effects. It can continue as planned. If no silverfish are caught for two consecutive years, a comprehensive analysis will be conducted to study every aspect of the transplantation process to see which part is out of order. It may also be a matter of physical, chemical and biological factors that move into the waters. A certain factor has limited the normal growth and development of whitebait, summed up the reasons for not succeeding, and then targeted effective measures. The length of the incubation period is closely related to the number of launches, the number of launches, and the conditions of the water environment. Practice has proved that, under normal circumstances, the incubation period is 1 to 3 years, and the fishery population is formed. It is usually 3 years, and individual ones are 1 or 4 years old.
The silverfish was found in the waters after its introduction, but it does not mean that the transplantation has been successful. It must go through several stages and finally produce a stable fishery population effect, so as to show that the transplant proliferation has been truly successful.
The main assessment methods are the following five points:
1. Biological effects: Transplanted fertilized eggs can migrate to water to hatch larvae, grow, develop and reproduce. Adults can grow into broodstock in the same year. The gonads develop well and they can lay eggs. Learn effect.
2. Formation of population: The generation of biological effects marks the transfer of fertilized eggs or adult fish from whitebait, which can reproduce in offspring and form populations and join supplementary groups.
3. Forming a fishery effect: The continuous increase of supplemental groups is the result of increasing population after transplantation, making population supplemented groups produce yields and produce fishery effects.
4. Intense competition in environmental and ecological factors: At the same time as the rapid increase in the number of populations, there are fierce contradictions with the eco-environmental factors in the waters, such as competition in food, space, and spawning grounds, and mutual food, resulting in this period of population. The drastic changes may be reduced to varying degrees, and sometimes there will be a substantial decline or increase.
5. The stability of dominant populations: After fierce competition among various factors in the ecological environment of waters, the population gradually emerged a natural ecological balance in competition. The ecological factors in the waters balance each other, and the whitebait has become a dominant species. The population has begun to show a stable situation and the transplantation and proliferation have been successful. If eager to harvest a large number of populations in the fierce struggle between populations and the ecological environment, it will inevitably weaken the competitiveness of the whitebait population in the ecological environment, making it unable to form dominant populations, which will inevitably lead to the failure of transplantation.
Therefore, in order to make rational use of resources, it is necessary to estimate the amount of resources before fishing; in addition, monitoring the changes in the growth, population density, and dietary biomass of different stages of silverfish in the waters, and analyzing the feeding ability and ecology of the water body. The potential to conduct a more rational assessment of the effect of transplantation and to develop a scientific and reasonable fishery fishing plan to ensure the stability of the whitebait resources.
(7) Strengthen the proliferation and protection of whitebait resources and increase the proliferation of silverfish transplantation. Protecting the ecological environment of reservoirs and maintaining and improving water productivity: Reservoirs are water conservancy systems for flood prevention, flood irrigation, power generation and fish farming, and the comprehensive use of surface water resources. Establishing ecological projects centered on natural or artificial ecosystems such as water bodies, forest lands, and grasslands in its runoff areas, with the aim of rational development and utilization of major biological and non-biological resources, to maximize the potential of reservoir resources. Improving the ecological and economic benefits of reservoirs is an important task of the reservoir management department. Fish is the main product of the reservoir. The pros and cons of the ecological environment of the reservoir directly affect the fishery production. Therefore, it is very important to protect the water body from contamination, maintain the content of some nutrient salts in the water body, and increase the primary productivity in the water body. Therefore, according to the different requirements of reservoir water supply for water quality, measures such as fertilization and water quality adjustment can be taken to create a good ecological environment for the growth of whitebait. In the control and development and utilization of reservoirs, the water level requirements of fish breeding season should be taken into account as much as possible. When discharging floodwater, it is necessary to take care of fish escape prevention work and provide conditions for deploying blocking facilities so as to minimize the loss of water from whitebait resources.
2. The selection and delineation of the Silverbait Resource Conservation Area: The structure of the whitebait population is simple, and the number of cultured fish is 100%. The decrease in the number of supplementary groups directly affects the fishery output of the year. Therefore, if the fishery is carried out within the entire water area during the breeding season, it will inevitably destroy the breeding process, reduce the number of broodstock, destroy, kill and infer fertilized eggs, and reduce the number of supplementary groups, resulting in a decline in fishery production. Therefore, according to the breeding habits of the whitebait, selecting and demarcating resource reproduction protection zones in the transplanted waters is conducive to the conservation of resources of the whitebait. Silverfish is a kind of open-water fish, suitable for living in the middle and upper layers of a relatively wide range of coastal waters. By the breeding season, it migrates to the shallow sandy bottom with relatively hard sediments and less silt, and shelters the sunny side of the bay. The library maggot breeds eggs. Therefore, according to the breeding habits of whitebait, 5% to 10% of the suitable water area can be demarcated on the surface of the water, delineated as a resource reproduction protection zone, and all fishing vessels are prohibited from entering. In this way, during the breeding season, a part of the whitebait can be bred in the protected area, ensuring the number of supplementary groups and increasing the benefits of population proliferation.
3. Determine the no-fishing area and the closed fishing season: Delineate 5% to 10% of the water area or larger water area within the fishery water area as a year-round imprisonment area, as a safe place for the growth of the silverfish to thrive, in order to protect a part of the whitebait Provide supplementary groups and breeding resources for the whitebait population.
At the same time, to determine the banned period of silverfish, according to the different types of silverfish, different spawning period, respectively, to determine. The spring group of the new whitebait in Taihu Lake should be from March to May, and the autumn group should be from October to November; while the whitebait should be from the late December to the end of March the following year as a captive period. In this way, consistent with the ecological habits of the whitebait, it ensures the breeding population of the egg-laying broodstock and a large number of proliferating supplementary populations to ensure its proliferation potential and obtain greater efficiency.
4. Adjust the fish population structure in the transplanted whitebaill waters. In the waters where the silverfish are transplanted, reduce the amount of squid feeding and increase some herbivorous fish that do not compete with the whitebait; at the same time, remove and suppress Ono. Miscellaneous fish and ferocious fish. Although the small wild fish are small in size, they compete for space and food with the whitebait, especially the fish in the pond. They will be able to eat each other. Therefore, it is best not to transplant the fish in the area of ​​transplanted whitebait fish. The ferocious fish, mainly fish and white, and horse and fish, have strong fertility. The active space is upper and middle, and the staple food of small wild fish and shrimp is in conflict with the migration of silverfish. Therefore, it is necessary to strengthen the clearance.
5. Determine a reasonable stock of silverfish resources: After successfully transferring silverfish into the waters, follow up investigations on the distribution, growth, food habits and breeding habits of the whitebait in the waters, and conduct breeding assessments to determine their reasonableness. Fishing volume and its retention. Since the history of transplanting whitebait is not long, the exact determination of the catch of silverfish in different types of waters has yet to be further studied. As far as the current situation is concerned, in the waters of normal cod rearing areas, about 2 kilograms of whitebait can be produced per acre of water in the case of natural multiplication of resources; for the shortage of stocked eels, there is no stock of cod. In the waters, about 5 to 7 kg of whitebait can be produced per acre. In some water areas, such as the Tianjin Beitang Reservoir, the production of fish such as squid is maintained at a relatively high level, with an average of about 38 kg/mu, 1992 The annual production of large silverfish is still 2.5 kg; the Baiguishan Reservoir in Henan has yielded 1.4 kg of fresh whitebait per mu for many years. The provision of catches is mainly to ensure that there are enough stocks and that there are enough spawning brooders and at the same time higher fish yields. In view of the fact that the current history of silverfish transplantation is not long, the retention of whitebait still refers to the practical experience of fish stocks in the lake, leaving a certain number of species, and the remaining amount in Taihu Lake is 27% of the estimated total resources, and Dianchi in Yunnan is about 10%.
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