Text: Bread Clip Knowledge
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«——【Preamble】】 ——»
Scallops are one of the important cultured shellfish species in China, and the scallop culture area in China reached 3.8×105hm2 in 2022, accounting for 31% of the total shellfish culture area in China.
As a filter-feeding organism, scallops mainly feed on microalgae in nature, and microalgae are widely used as the main bait for scallop seedlings in the seedling breeding process of scallop culture.
In the traditional scallop artificial seedling process, a special bait workshop is required to provide microalgae, and technicians can judge whether the concentration of microalgae in the microalgae culture tank meets the feeding standard by observing the color of the water body or observing it with a microscope.
The amount of microalgae feeding was determined according to the degree of bait consumption in the scallop nursery pond, and the amount of bait in the process of scallop seedling rearing determined the growth state of scallop seedlings.
Too little feed will cause scallop seedlings to grow stunted, delay the production cycle, and too much feed will pollute the water quality.
The manual feeding method depends on the experience of technicians, and the amount of bait is difficult to standardize, and the amount of microalgae in microalgae culture ponds and scallop nursery ponds is generally used by technicians to detect the amount of microalgae in microalgae culture ponds and scallop nursery ponds.
It causes problems such as inaccurate feeding amount and difficult control of scallop seedling cycle in the process of scallop seedling, and increases the production cost of scallop seedlings.
In order to solve the above-mentioned problems existing in the prior art, it is necessary to design a microalgae concentration with simple structure and reasonable layout, which can detect the concentration of microalgae in the bait workshop and nursery pond in real time.
According to the detection results, the configuration of microalgae of different species and different concentrations can be realized, and the equipment for automatic and accurate feeding of scallop seedlings can be realized.
At the same time, in order to accurately detect the concentration of microalgae and ensure the accuracy of the amount of feed, it is important to find a method that can automatically detect the concentration of microalgae (i.e., microalgae biomass) online.
At present, there are many methods to detect microalgae biomass, for example, a breeding center in Shanghai, the blood plate counting method, optical density method, as well as chlorophyll fluorescence method, hyperspectral imaging method, turbidity method, etc.
Hemocytometry is one of the most commonly used methods, hemocytometry is simple and reliable, but it cannot be directly used for microalgae biomass detection, if machine vision is used instead of manual counting, the counting is difficult, reliable and costly.
Both chlorophyll fluorescence and spectrophotometry are used to estimate microalgal biomass based on the chlorophyll content in microalgal cells.
For example, as early as 2000, some people in Qingdao used the content of chlorophyll a to label the content of phytoplankton, but this method, using ethanol and other chemical reagents, extracted chlorophyll in plant cells to detect its biomass, cannot be used for online detection of microalgae biomass.
Based on the derivative model of optical densitometry, the chlorophyll fit degree of microalgae in the whole growth cycle of microalgae such as golden algae and flat algae was higher than 98%.
However, this method is costly, cumbersome to process, and cannot achieve rapid on-line detection of microalgal biomass.
In a fishery base in Beijing, researchers designed a new chlorophyll fluorescence detector with an accuracy of 99.83% for the detection of microalgae biomass, but external factors such as temperature and salinity in the algae will affect the chlorophyll content of microalgae.
Therefore, the accurate measurement of microalgae biomass cannot be achieved by chlorophyll fluorescence detection.
Hyperspectral imaging technology is often used for early warning and detection of eutrophication in lakes and rivers, and this technology is often used on satellites to detect microalgal biomass in large areas, such as oceans, lakes, rivers, etc.
After combining and comparing seven spectral pretreatment methods, the spectral treatment methods suitable for different algae species were more accurate, but they were only suitable for long-distance and large-area microalgae biomass detection, and were not suitable for Ezo scallop seedling production.
However, the current methods for the detection of microalgal biomass are inefficient, cumbersome to process, and cannot guarantee the detection accuracy.
Therefore, a turbidity measurement method is now used to achieve rapid, accurate and on-line detection of microalgae content in Ezo scallop seedling production.
Based on this method, the feeding equipment for Ezo scallop seedlings was designed to realize the online automatic feeding in the production process and improve the production efficiency and economic benefits of Ezo scallop seedlings.
As shown in Figure 1, an automatic feeding equipment for scallop seedling bait was designed, which was composed of a bait culture tank, a scallop nursery pond, a feeding system and a control platform.
The feeding system connects the bait culture pond with the scallop nursery pond through the pipeline, and realizes the feeding function through the control of the pump and valve through the control platform.
The bait culture tank is connected to the control platform, and the bait culture tank is used to cultivate microalgae, monitor the microalgae culture status, and feed back the microalgae culture status to the control platform.
The scallop nursery pond is connected to the control platform, which is used for scallop seedling, monitors the microalgae consumption in the scallop nursery pond, and feeds back the microalgae consumption to the control platform.
The control platform is connected with the feeding system, and the control platform controls the feeding amount of the automatic feeding component according to the growth of microalgae in the bait culture tank and the bait consumption in the scallop nursery pond.
Scallop larvae had different algae feeding ratios at different growth stages, and when scallop larvae were in the D larval stage, the bait feeding was mainly goldenrod, supplemented by Rhombocystis microcrescent. When the scallop larvae have developed to the middle stage of the shell top larval stage, the algae should be added to the bait.
Therefore, there are three bait culture tanks, which are respectively cultivated for goldenrod, small crescent rhomboids and flat algae. The three bait ponds are equipped with microalgae growth monitoring sensors and continuous micro-aeration devices.
The microalgae growth monitoring sensor is connected to the control platform, and the feeding system is connected to the three bait culture tanks.
The microalgae growth monitoring system uses a microalgae concentration sensor and a water quality detector to complete the monitoring, and the microalgae concentration sensor is set up with different detection ranges according to different types of microalgae.
The principle of the microalgae concentration sensor is that the absorption of light by the microalgae particles in the algae solution causes the change of the turbidity value of the algae liquid, and the detection of the change of microalgae concentration by turbidity has the advantages of convenience, rapidity, and strong anti-interference ability.
It can quickly and timely feedback the culture status of microalgae, which is conducive to calculating the volume of extracted algae liquid and other data according to the required feeding amount.
In a production base in Shandong, some researchers found that in the process of microalgae culture, nutrient salts will be added to the bait culture pond to provide nutrients for the growth of microalgae.
If the microalgae fail to fully absorb the nutrients, the nutrients contained in the nutrients will adversely affect the development of scallop seedlings.
Therefore, some researchers have set up water quality detectors in the bait culture tank to detect the content of residual ammonia, nitrogen, phosphorus and nitrite in the bait culture tank.
The scallop nursery nursery monitoring system consists of a microalgae concentration sensor, a water quality sensor and a continuous micro-aeration device. The scallop nursery condition monitoring system uses a microalgae concentration sensor and communicates with the control platform.
The concentration of microalgae in the scallop nursery pond is much smaller than that in the bait culture pond, in order to ensure the detection accuracy, the microalgae concentration sensor in the nursery pond has a smaller range and more accurate measurement.
Because water temperature has an important impact on the development and feeding of scallop seedlings, water quality detectors were used to monitor ammonia nitrogen content, nitrite content and temperature.
«——【Microalgae biomass and turbidity calibration·】——»
Guangdong, as a major aquaculture province, carried out microalgal biomass and turbidity calibration experiments in order to establish an accurate relationship between microalgae biomass and turbidity.
Aquatic scientists in Guangdong Province selected four commonly used bait microalgae as experimental subjects, including golden algae, flat algae, chlorella and small crescent rhomboids, and used hemocytometry and turbidity meter to corroborate each other.
The experimental material was the algae liquid of four kinds of bait microalgae when they were grown to different densities, and the algae liquid was taken from the bait pond in the scallop seedling production base.
The experimental reagent is Lugo iodine solution, and the experimental instruments are absorbent paper, beaker, washing bottle, hemocytometer, coverslip, pipette, optical microscope, and hash 2100Q portable turbidity meter.
Scoop about 50mL of algae liquid with a small beaker, shake the algae liquid in the small beaker and pour it into the turbidity meter measuring bottle, tighten the cap and drop a drop of silicone oil on the bottle body.
Apply evenly with a linen cloth, shake the bottle again to make the algae liquid even, put it in a portable turbidity meter to read, take out the measuring bottle after measuring once, shake it well, change the direction and measure it again, measure it four times, and take the average value after reading.
After shaking the remaining algae liquid in a small beaker, take about 2 mL of algae liquid with a pipette, drop it onto a hemocytometer, and press it with a coverslip. Take another drop of Rugo-type iodine solution to the left side of the coverslip, and use absorbent paper to suck the iodine solution to the right side of the coverslip to make the staining uniform.
Adjust the light microscopy readings and then estimate the microalgal biomass based on the readings.
The experimental results are shown in Fig. 2, Fig. 3, Fig. 4 and Fig. 5, and the algal biomass and turbidity of Algae algae are positively correlated.
Through this experiment, linear regression equations for the biomass and turbidity of four common bait microalgae were established, and the fitting degree was greater than 0.98, indicating that the regression equation could better reflect the relationship between microalgal biomass and turbidity, and provided a theoretical basis for the on-line detection of microalgae biomass.
«——【·Conclusion·】——»
In order to track and monitor the microalgae culture status in the bait culture pond and the microalgae consumption in the scallop nursery pond in real time during the scallop seedling production process, the feeding scheme was formulated according to the monitoring value to achieve accurate feeding.
Based on the relationship between microalgae biomass and turbidity, the biomass and turbidity of four common bait microalgae were calibrated through experimental studies.
Linear regression equations for turbidity and biomass of four common bait microalgae were established, and the fitting degree was greater than 0.98, which could better reflect the relationship between microalgae biomass and turbidity.
The equipment can accurately monitor the feeding status of Ezo scallop seedlings, and detect the water quality parameters of bait culture ponds and scallop nursery ponds.
Reduce the dependence on manpower in the feeding process of Ezo scallop seedlings, improve the production efficiency of Ezo scallops, and provide a reference for the design of automatic equipment for Ezo scallop seedlings.
In the modern Ezo scallop nursery base, feeding is an important part of the Ezo scallop seedling process. The feeding of Ezo scallop seedlings mainly depends on manual feeding, which is labor-intensive and inefficient, and the detection of scallop feeding and microalgae culture is cumbersome.
Compared with Hubei, Henan currently has no bait equipment dedicated to Ezo scallop seedlings on the market, but many farmers still consult the literature and field research methods.
The specific requirements of Ezo scallop seedling feeding were clarified, and an automatic feeding equipment for Ezo scallop seedling feeding was designed.
The simulation results show that the structural design of the automatic feeding equipment for Ezo scallop seedling and the calibration of microalgae biomass and turbidity are studied.
Now, whether it is some southern cities such as Hunan or Hubei, and coastal cities such as Qingdao and Yantai in the north of the mainland, it can realize automatic and accurate feeding of Ezo scallop seedlings and efficient detection of residual bait.
To improve the production efficiency and economic benefits of Ezo scallop seedlings, and to provide new ideas for the automation and intelligent development of Ezo scallop seedling industry.