The northern Jiangsu region, especially Yancheng, is the country's major silver cockroach breeding area. It is characterized by large Tangkou (more than 100 mu), medium density (1600/mu), no aerators, or insufficient aerators ( Every 30 kilograms of aerobic machine load is more than 30 acres. It is inconvenient to change the water. Feed the feed with the bait feeder (50-100 mu for each feeder). In this mode of cultivation, dissolved oxygen in water mainly comes from natural conditions, mainly due to the photosynthesis of algae and dissolved oxygen brought about by wind waves. The aerator only plays a role of mixing water and saving urgency.
In this paper, experiments were conducted to understand the influence of wind direction, climate, pond environment and other factors on the level of dissolved oxygen in fish ponds, and the effect of dissolved oxygen on the feeding and growth status of carps. A corresponding solution was proposed.
First, the experimental method using dissolved oxygen instrument, combined with the current wind direction, climate, fish feeding conditions and environment, detect fish ponds in different locations, different depths of dissolved oxygen content.
Second, the experimental equipment Beijing Tianjian Innovation Instrument Co., Ltd. Portable fluorescence dissolved oxygen meter. This dissolved oxygen meter does not require calibration and maintenance, and is not affected by water flow and other factors, and is accurate and rapid.
Location: Haifeng Farm, Dafeng City, Yancheng City.
Third, the experimental results
1, August 21, 3 pm. A 100-acre pond is sunny and there is a southerly wind. The bait feeder is located to the south. About 15 meters from the shore, the dissolved oxygen was 3.8 at the bottom 50cm, and the dissolved oxygen was 4.75 at 10cm from the water surface. In the pond next to the pond, the area of ​​the pond is 150 mu. The feeder is in the middle of the east, 20 meters from the shore, and the dissolved oxygen is 13.1 at a distance of 50cm from the water surface.
2. August 22, 2 pm, southeast wind. In 90 acres of ponds, the dissolved oxygen at the east of the material platform is 3 (30cm from the water surface), and the surface water at the downwind (northwest corner) is 12.9, and the bottom water is 11. Next to 200 acres of square pond, feeding machine in the north, three. The easternmost bait feeder dissolved oxygen between 4-5, the westernmost feeders dissolved oxygen at 13-15, and dissolved oxygen dropped 2-3 points when feeding.
3, August 23, 4 pm, southeast wind. The two 250-ton ponds, together with cyanobacteria at the northwestern corner of the east side of the pond, measured up to 23 supersaturated dissolved oxygen values. The feeder has 3 points and is evenly distributed to the west. The most north of dissolved oxygen is 7-8, the middle is about 11 and the south is about 13 dissolved oxygen. It is related to measured values ​​of dissolved oxygen, and eating conditions are also better from south to north. When the dissolved oxygen was higher than 11 hours, the fish that had eaten at the feed table were swimming quickly and kept spraying. The captain of the feeding bait opened and there was no decrease in fish.
4, August 24, 10:00 am, cloudy, southeast wind. A 200-mu pond measured dissolved oxygen in the north at 3.1, and the fish fed less.
5, August 25, 10:00 am, cloudy, northeast winds. A 1000-mu fish pond was measured at the feeding station on the south side. The dissolved oxygen was 2.0 and the water surface was 3.4 at the westernmost point 50 cm above the water surface. Under the wind at the shore dissolved oxygen is 5.8. The dissolved oxygen is 3.75 at 30 meters offshore, and the dissolved oxygen is 4.2-5.0 on the water surface. It is worth noting that due to the large size of the pond and the relatively large waves at the downwind, it was thought that the dissolved oxygen must not be too low, but the results were unexpected.
6, September 17, 9 am, light rain, Dongfeng. Two 250-acre fish ponds, feeding machine one east, one west. The dissolved oxygen was measured below 40 cm away from the surface of the feeder and was below 2.2. The fish did not eat well and the fish could not be seen on the water surface.
When measuring dissolved oxygen, the author consciously chose to measure the dissolved oxygen near the feeding table during the feeding period in order to observe the correlation between the feeding conditions and dissolved oxygen values. The results showed that when the dissolved oxygen was around 2.0, only a small number of fish in the material table consumed under the water. At 3.0-4.0, only a small amount of fish was swimming on the water, swimming slowly, and easily frightened. Until the dissolved oxygen reached 12, it was clearly observed that with the increase of dissolved oxygen, the fish swimd more quickly during the feeding process, and the fish caught more fiercely. More fish caught food on the water surface and often jumped and sprayed.
It is also worth noting that when feeding feeds, a large number of fish gather around the feeder to catch food, which will obviously cause a decrease in local dissolved oxygen. Usually when dissolved for 30 minutes, dissolved oxygen will drop by about 3 o'clock. Therefore, it is often found that the fish eats better when the feed is started. After a while, the fish is significantly reduced and even scattered. But it will come back after some time. The reason is that the initial dissolved oxygen is generally around 5-7. When the fish overtakes the food and causes the local dissolved oxygen to drop below 3, it will dissipate due to lack of oxygen. Therefore, we believe that for fish to eat well, the dissolved oxygen at the feed point should reach 6 or more. And the bait feeder spreads out, so that each feeder feeds less fish.
IV. Discussion
1. Why does the wind direction have such a big impact on dissolved oxygen?
After analysis, the following reasons are given. (1) Effect of algae density. The algae were blown downwind, the algae density was higher in the downwind and the photosynthesis was stronger. It was observed that when there is buoyant blue algae in a 250-mu pond, the density of blue-green algae at the downwind is very high, and the measured supersaturated dissolved oxygen is as high as 22 or more. (2) The wind blows the dissolved oxygen from the surface to the downwind at a relatively high level of dissolved oxygen, making the dissolved oxygen at the lower end of the wind higher. (3) The wind blowing in the air can also directly dissolve oxygen in the air.
However, the wind and waves make the amount of oxygen in the air directly soluble in water very small, and the proportion is very low. In the data of the dissolved oxygen in 1,000 acres of ponds measured on August 25th, even in large ponds, in the case of large winds and waves, there was no cloudy day for the sun, and the dissolved oxygen at the downwind was only between 2-5. Only dissolved oxygen at the side of the border is higher. Dissolved oxygen in water mainly depends on the photosynthesis of algae. According to statistics, more than 90% of dissolved oxygen in water comes from algae photosynthesis. Our data also confirms this.
Layered phenomenon of dissolved oxygen in water. Regardless of whether it is an upwind or a downwind, in the presence of the sun, the dissolved oxygen in the surface layer is much higher than the bottom layer, but the vertical dissolving oxygen difference between the upwinds is greater. Obviously, the wind plays a decisive role in the agitation and stratification of the water body. However, the degree of non-uniformity in the longitudinal distribution of this dissolved oxygen is much less before cloudy or in the morning before the sun.
Other related factors: (1) The size and shape of the Tangkou, the larger the pond, the easier it is to fluctuate, the better the effect of the wind; (2) The factors that hinder the wind source at the pond, such as the height of the Tanggu, and the Tanggu Plants, reeds, etc. In one measurement, the two feeders were located on the southern side of the leeward, but the pond had a high water level, there was no obstruction on the dam, and there were reeds on the side of the pond. The measured dissolved oxygen value was 8 and B was 3.8.
2. The significance of the experimental results In the actual production, we often find strange phenomena. Adjacent to the pond, only the orientation of the feeding machine is different. One fish pond feeds actively, one feeds slowly and less. The final growth rate and feed coefficient vary greatly. Or in the same pond, some bait-feeding fishes are under pressure and some feed baits have almost no fish. Through this experiment, it is shown that the problem of poor feeding of most fish is directly related to dissolved oxygen. The level of dissolved oxygen at the feed point determines the size of the feed rate. Feeding a low amount of feed not only directly affects the growth of the fish, but also can affect the feed conversion rate and the fish's body resistance if it is eaten under long-term hypoxia. Perhaps it is just a wrong position of a feeding machine that can determine the benefits of the entire fish pond for one year.
3. Improve the effective measures for dissolved oxygen at the feeding point (1) Grasp the position of the feeding bait and try to use the high dissolved oxygen area in the fish pond to allow the fish to feed in the high dissolved oxygen area, so that the bait-feeder spends most of its time Downwind. In Northern Jiangsu, the feeder is in the northwest position and is in a windy position most of the time. In other regions, it can be adjusted according to local conditions.
(2) Clear the adverse effects of the wind source around the fish pond, such as raising the water level, lowering the dam, removing the surrounding weeds, reeds, trees, etc.
(3) Extend the length of the feeder to the middle of the pond to eliminate the adverse effects of the lee.
V. Summary
1. The squid usually starts to eat when it is dissolved in oxygen 3-4. Considering that fish clusters consume oxygen, we recommend that the dissolved oxygen should be above 6 before feeding the feed.
2. By changing the position of the bait feeder, the bait feeder should try to be in the high dissolved oxygen zone in the pond, which can effectively increase the bait rate, reduce the bait coefficient, increase the growth rate, and reduce the fish disease.
3. Although salmon farming is basically fed by a domesticated bait feeder, due to various reasons, there is sometimes a case where the puffer fish no longer floats and concentrates on feeding. In order to grow squid, it is sometimes hard to feed. In the case of adequate dissolved oxygen in the feed point, the feeding amount can be calculated based on the size of the carp, the water temperature, etc., by feeding rate, or by adding artificial feeding materials.
4, through a number of fish pond measurement data summary, cloudy, rainy days, foggy days and other weather, even if the wind, dissolved oxygen is very low. Dissolved oxygen in the upwind was significantly lower than dissolved oxygen in the downwind. The dissolved oxygen in the bottom layer of water is obviously lower than that in the top layer. Fish feeding in the clusters will reduce local dissolved oxygen. Algae photosynthesis is the main source of dissolved oxygen in water bodies.
5. We have found that it is difficult to accurately determine the level of dissolved oxygen in the pond based on feelings and experiences. Using a dissolved oxygen meter is a very good approach. Advanced instruments such as dissolved oxygen meters should be vigorously promoted so that oxygen abatement measures can be taken purposely, especially for ponds with aerators.
In this paper, experiments were conducted to understand the influence of wind direction, climate, pond environment and other factors on the level of dissolved oxygen in fish ponds, and the effect of dissolved oxygen on the feeding and growth status of carps. A corresponding solution was proposed.
First, the experimental method using dissolved oxygen instrument, combined with the current wind direction, climate, fish feeding conditions and environment, detect fish ponds in different locations, different depths of dissolved oxygen content.
Second, the experimental equipment Beijing Tianjian Innovation Instrument Co., Ltd. Portable fluorescence dissolved oxygen meter. This dissolved oxygen meter does not require calibration and maintenance, and is not affected by water flow and other factors, and is accurate and rapid.
Location: Haifeng Farm, Dafeng City, Yancheng City.
Third, the experimental results
1, August 21, 3 pm. A 100-acre pond is sunny and there is a southerly wind. The bait feeder is located to the south. About 15 meters from the shore, the dissolved oxygen was 3.8 at the bottom 50cm, and the dissolved oxygen was 4.75 at 10cm from the water surface. In the pond next to the pond, the area of ​​the pond is 150 mu. The feeder is in the middle of the east, 20 meters from the shore, and the dissolved oxygen is 13.1 at a distance of 50cm from the water surface.
2. August 22, 2 pm, southeast wind. In 90 acres of ponds, the dissolved oxygen at the east of the material platform is 3 (30cm from the water surface), and the surface water at the downwind (northwest corner) is 12.9, and the bottom water is 11. Next to 200 acres of square pond, feeding machine in the north, three. The easternmost bait feeder dissolved oxygen between 4-5, the westernmost feeders dissolved oxygen at 13-15, and dissolved oxygen dropped 2-3 points when feeding.
3, August 23, 4 pm, southeast wind. The two 250-ton ponds, together with cyanobacteria at the northwestern corner of the east side of the pond, measured up to 23 supersaturated dissolved oxygen values. The feeder has 3 points and is evenly distributed to the west. The most north of dissolved oxygen is 7-8, the middle is about 11 and the south is about 13 dissolved oxygen. It is related to measured values ​​of dissolved oxygen, and eating conditions are also better from south to north. When the dissolved oxygen was higher than 11 hours, the fish that had eaten at the feed table were swimming quickly and kept spraying. The captain of the feeding bait opened and there was no decrease in fish.
4, August 24, 10:00 am, cloudy, southeast wind. A 200-mu pond measured dissolved oxygen in the north at 3.1, and the fish fed less.
5, August 25, 10:00 am, cloudy, northeast winds. A 1000-mu fish pond was measured at the feeding station on the south side. The dissolved oxygen was 2.0 and the water surface was 3.4 at the westernmost point 50 cm above the water surface. Under the wind at the shore dissolved oxygen is 5.8. The dissolved oxygen is 3.75 at 30 meters offshore, and the dissolved oxygen is 4.2-5.0 on the water surface. It is worth noting that due to the large size of the pond and the relatively large waves at the downwind, it was thought that the dissolved oxygen must not be too low, but the results were unexpected.
6, September 17, 9 am, light rain, Dongfeng. Two 250-acre fish ponds, feeding machine one east, one west. The dissolved oxygen was measured below 40 cm away from the surface of the feeder and was below 2.2. The fish did not eat well and the fish could not be seen on the water surface.
When measuring dissolved oxygen, the author consciously chose to measure the dissolved oxygen near the feeding table during the feeding period in order to observe the correlation between the feeding conditions and dissolved oxygen values. The results showed that when the dissolved oxygen was around 2.0, only a small number of fish in the material table consumed under the water. At 3.0-4.0, only a small amount of fish was swimming on the water, swimming slowly, and easily frightened. Until the dissolved oxygen reached 12, it was clearly observed that with the increase of dissolved oxygen, the fish swimd more quickly during the feeding process, and the fish caught more fiercely. More fish caught food on the water surface and often jumped and sprayed.
It is also worth noting that when feeding feeds, a large number of fish gather around the feeder to catch food, which will obviously cause a decrease in local dissolved oxygen. Usually when dissolved for 30 minutes, dissolved oxygen will drop by about 3 o'clock. Therefore, it is often found that the fish eats better when the feed is started. After a while, the fish is significantly reduced and even scattered. But it will come back after some time. The reason is that the initial dissolved oxygen is generally around 5-7. When the fish overtakes the food and causes the local dissolved oxygen to drop below 3, it will dissipate due to lack of oxygen. Therefore, we believe that for fish to eat well, the dissolved oxygen at the feed point should reach 6 or more. And the bait feeder spreads out, so that each feeder feeds less fish.
IV. Discussion
1. Why does the wind direction have such a big impact on dissolved oxygen?
After analysis, the following reasons are given. (1) Effect of algae density. The algae were blown downwind, the algae density was higher in the downwind and the photosynthesis was stronger. It was observed that when there is buoyant blue algae in a 250-mu pond, the density of blue-green algae at the downwind is very high, and the measured supersaturated dissolved oxygen is as high as 22 or more. (2) The wind blows the dissolved oxygen from the surface to the downwind at a relatively high level of dissolved oxygen, making the dissolved oxygen at the lower end of the wind higher. (3) The wind blowing in the air can also directly dissolve oxygen in the air.
However, the wind and waves make the amount of oxygen in the air directly soluble in water very small, and the proportion is very low. In the data of the dissolved oxygen in 1,000 acres of ponds measured on August 25th, even in large ponds, in the case of large winds and waves, there was no cloudy day for the sun, and the dissolved oxygen at the downwind was only between 2-5. Only dissolved oxygen at the side of the border is higher. Dissolved oxygen in water mainly depends on the photosynthesis of algae. According to statistics, more than 90% of dissolved oxygen in water comes from algae photosynthesis. Our data also confirms this.
Layered phenomenon of dissolved oxygen in water. Regardless of whether it is an upwind or a downwind, in the presence of the sun, the dissolved oxygen in the surface layer is much higher than the bottom layer, but the vertical dissolving oxygen difference between the upwinds is greater. Obviously, the wind plays a decisive role in the agitation and stratification of the water body. However, the degree of non-uniformity in the longitudinal distribution of this dissolved oxygen is much less before cloudy or in the morning before the sun.
Other related factors: (1) The size and shape of the Tangkou, the larger the pond, the easier it is to fluctuate, the better the effect of the wind; (2) The factors that hinder the wind source at the pond, such as the height of the Tanggu, and the Tanggu Plants, reeds, etc. In one measurement, the two feeders were located on the southern side of the leeward, but the pond had a high water level, there was no obstruction on the dam, and there were reeds on the side of the pond. The measured dissolved oxygen value was 8 and B was 3.8.
2. The significance of the experimental results In the actual production, we often find strange phenomena. Adjacent to the pond, only the orientation of the feeding machine is different. One fish pond feeds actively, one feeds slowly and less. The final growth rate and feed coefficient vary greatly. Or in the same pond, some bait-feeding fishes are under pressure and some feed baits have almost no fish. Through this experiment, it is shown that the problem of poor feeding of most fish is directly related to dissolved oxygen. The level of dissolved oxygen at the feed point determines the size of the feed rate. Feeding a low amount of feed not only directly affects the growth of the fish, but also can affect the feed conversion rate and the fish's body resistance if it is eaten under long-term hypoxia. Perhaps it is just a wrong position of a feeding machine that can determine the benefits of the entire fish pond for one year.
3. Improve the effective measures for dissolved oxygen at the feeding point (1) Grasp the position of the feeding bait and try to use the high dissolved oxygen area in the fish pond to allow the fish to feed in the high dissolved oxygen area, so that the bait-feeder spends most of its time Downwind. In Northern Jiangsu, the feeder is in the northwest position and is in a windy position most of the time. In other regions, it can be adjusted according to local conditions.
(2) Clear the adverse effects of the wind source around the fish pond, such as raising the water level, lowering the dam, removing the surrounding weeds, reeds, trees, etc.
(3) Extend the length of the feeder to the middle of the pond to eliminate the adverse effects of the lee.
V. Summary
1. The squid usually starts to eat when it is dissolved in oxygen 3-4. Considering that fish clusters consume oxygen, we recommend that the dissolved oxygen should be above 6 before feeding the feed.
2. By changing the position of the bait feeder, the bait feeder should try to be in the high dissolved oxygen zone in the pond, which can effectively increase the bait rate, reduce the bait coefficient, increase the growth rate, and reduce the fish disease.
3. Although salmon farming is basically fed by a domesticated bait feeder, due to various reasons, there is sometimes a case where the puffer fish no longer floats and concentrates on feeding. In order to grow squid, it is sometimes hard to feed. In the case of adequate dissolved oxygen in the feed point, the feeding amount can be calculated based on the size of the carp, the water temperature, etc., by feeding rate, or by adding artificial feeding materials.
4, through a number of fish pond measurement data summary, cloudy, rainy days, foggy days and other weather, even if the wind, dissolved oxygen is very low. Dissolved oxygen in the upwind was significantly lower than dissolved oxygen in the downwind. The dissolved oxygen in the bottom layer of water is obviously lower than that in the top layer. Fish feeding in the clusters will reduce local dissolved oxygen. Algae photosynthesis is the main source of dissolved oxygen in water bodies.
5. We have found that it is difficult to accurately determine the level of dissolved oxygen in the pond based on feelings and experiences. Using a dissolved oxygen meter is a very good approach. Advanced instruments such as dissolved oxygen meters should be vigorously promoted so that oxygen abatement measures can be taken purposely, especially for ponds with aerators.
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