A method for screening high-activity macrobrachium rosenbergii nauplii

Abstract

The application discloses a kind of high-activity mysis of macrobrachium rosenbergii screening method, belong to aquaculture technical field.The method includes: pre-treatment of immersion washing, using 100 mesh nylon net to catch I stage mysis, stirring treatment in the first immersion washing container containing 100ppm formaldehyde and 6 ‰ brackish water;First light source induction screening, using 580-595nm, 1500-2000lux LED light source induction above second immersion washing container, and high-activity I stage larvae that float up are collected in batches;Disinfection treatment, after soaking with 20-30ppm povidone iodine, rinse;Again light source induction screening, after the larvae are developed into II stage after constant temperature cultivation at 28-30 DEG C for 24 hours, again light source induction is carried out and high-activity II stage larvae that float up are collected in batches;Finally, concentrated cultivation is carried out.The application realizes the high-efficiency, standardization sorting of high-activity mysis by the combination of specific wavelength light source induction and twice screening before and after key development period, and optimizes immersion washing, disinfection and cultivation parameters, significantly improves the quality of seedling and the survival rate of seedling.

Description

Technical Field

[0001] This invention belongs to the field of aquaculture technology, specifically relating to a method for screening highly active zoea larvae of the giant freshwater prawn. Background Technology

[0002] As an important freshwater aquaculture species, the giant freshwater prawn (Macrobrachium rosenbergii) is valued for its delicious meat, high nutritional value, and short growth cycle. In giant freshwater prawn seedling production, the zoea larval stage is crucial in determining seedling quality—at this stage, the larvae are tiny (only 1-2 mm in length during stage I) and their physiological functions are not yet mature. Their activity directly affects the success rate of metamorphosis into larvae, disease resistance, and overall growth rate.

[0003] However, there are significant technical shortcomings in the current screening process for zoea larvae during the breeding of giant freshwater prawns, mainly in the following three aspects:

[0004] (1) The screening methods lack scientific rigor and accuracy: Current seedling production relies heavily on screening methods based on human experience, such as judging the activity of larvae by observing their swimming speed, body color, and other external characteristics. This method is not only inefficient but also inaccurate, resulting in a large number of low-activity and weak larvae being mixed into the seedling population, which seriously affects the overall quality of subsequent seedling production.

[0005] (2) Lack of dedicated screening equipment: In current operations, ordinary fishing nets with uneven mesh and sharp edges are often used to collect larvae, which can easily cause mechanical damage to the larvae. At the same time, the cultivation containers are mostly ordinary cement pools or transparent plastic buckets, which cannot effectively simulate the dark light environment required for the natural growth of zoea larvae, and can easily cause stress reactions in the larvae. In addition, the selection of light sources is not targeted, and it is impossible to use light of specific wavelengths to effectively induce the separation of highly active larvae, which further increases the screening error.

[0006] (3) Deficiencies in pretreatment and disinfection: After hatching, zoea larvae are prone to being covered by parasites such as vesicanthii and bell-shaped worms. The existing process lacks targeted deworming steps. These parasites compete for nutrients with the larvae and may even block their gills, affecting their respiratory function. At the same time, there is a lack of standardized disinfection procedures, which allows pathogens carried by the larvae to enter the subsequent cultivation stage, significantly increasing the risk of disease outbreaks.

[0007] In view of this, the present invention proposes a screening method for highly active zoea larvae of giant freshwater prawns, which can significantly improve the survival rate and quality of subsequent seedlings, and provide key technical support for seedling optimization in the upstream of the giant freshwater prawn aquaculture industry chain. Summary of the Invention

[0008] In view of the problems existing in the above-mentioned screening methods, such as reliance on manual experience, lack of specialized equipment, and insufficient pretreatment and disinfection, the present invention provides a screening method for highly active zoea larvae of Macrobrachium rosenbergii to solve the above-mentioned technical defects.

[0009] The technical solution adopted by this invention to solve its technical problem is as follows:

[0010] This invention provides a method for screening highly active zoea larvae of the giant freshwater prawn, comprising the following steps:

[0011] S1. Pre-treatment by immersion: Newly hatched stage I zoea larvae were collected from the broodstock rearing pond using a 100-mesh nylon net, counted, and then transferred to the first immersion container. The first immersion container contained a formaldehyde solution with a concentration of 100 ppm and brackish water with a salinity of 6‰. After stirring at 30 rpm for 1 minute, the stage I zoea larvae were collected with a 100-mesh nylon net and rinsed once with brackish water with a salinity of 6‰, and then transferred to the second immersion container.

[0012] S2. Initial Light Source-Induced Screening: An LED light source is placed directly above the second immersion container, with the wavelength adjusted to 580-595nm and the illuminance to 1500-2000 lux. After turning on the light source, the container is left to stand for 2 minutes. A 100-mesh nylon net is used to collect the Stage I zoea larvae floating on the water surface. After 3 minutes, a second collection is performed, and this operation is repeated 2-3 times. The collected Stage I zoea larvae are identified as highly active Stage I zoea larvae, and those that do not float to the surface are discarded.

[0013] S3. Disinfection treatment: Transfer the highly active stage I zoea larvae obtained in step S2 to a disinfection container, add povidone-iodine to make the povidone-iodine concentration in the water reach 20-30 ppm, and soak for 15-20 minutes; stir once every 5 minutes during soaking; after soaking, use a 100-mesh nylon net to remove the highly active stage I zoea larvae, and rinse them 3 times with brackish water with a salinity of 6‰, 2 minutes each time, until there is no povidone-iodine residue;

[0014] S4. Secondary Light Source Induction Screening: Transfer the highly active Stage I zoea larvae treated in step S3 to a constant temperature incubation container and incubate at 28-30℃ for 24 hours to allow them to develop into Stage II zoea larvae. Place an LED light source directly above the constant temperature incubation container and adjust the wavelength of the light source to 580-595nm. After turning on the light source, let it stand for 2 minutes and use an 80-mesh nylon net to collect the Stage II zoea larvae floating on the water surface. After 3 minutes, perform a second collection and repeat this operation 2-3 times. The collected Stage II zoea larvae are identified as highly active Stage II zoea larvae, and those that do not float to the surface are discarded.

[0015] S5. Centralized cultivation: Transfer the highly active stage II zoea larvae obtained in step S4 to a seedling cultivation pond, control the water temperature at 28-30℃, pH at 7.5-8.0, dissolved oxygen at ≥5mg / L and salinity at 12‰, and feed them regularly.

[0016] Preferably, in step S1, both the first immersion container and the second immersion container are 400L PP plastic black buckets with a wall thickness of 5mm, a smooth inner wall without sharp edges, a rounded corner radius of 2cm, and a drain valve at the bottom of the bucket.

[0017] Preferably, in steps S1 and S3, stirring is performed using a soft stirring rod.

[0018] Preferably, in steps S2 and S4, the illuminance of the LED light source is 1800 lux, the installation height of the light source is adjustable within a range of 30-40 cm, and it is equipped with a focusing cover with a focusing angle of 60°.

[0019] Preferably, the sterilization container in step S3 is equipped with an automatic dosing device for automatically injecting povidone-iodine and controlling the concentration error within ±1 ppm.

[0020] Preferably, in step S3, the concentration of povidone-iodine is 25 ppm and the soaking time is 18 minutes.

[0021] Preferably, in step S4, the constant temperature incubation container is a 1000L PP plastic black bucket, which is equipped with a heating wire, a temperature sensor and an intelligent temperature controller.

[0022] Preferably, in step S4, the larval culture density in the constant temperature culture container is 12 million to 15 million larvae per cubic meter.

[0023] Preferably, in step S5, the water temperature in the seedling cultivation pond is controlled at 29℃, the pH value is controlled at 7.8, the dissolved oxygen is controlled at 5.5mg / L, and the salinity is controlled at 12‰.

[0024] Preferably, in step S5, the regular feeding involves feeding Artemia nauplii three times a day, with each feeding amount being 15% of the body weight of the highly active stage II zoea larvae.

[0025] In summary, compared with the prior art, the screening method for highly active zoea larvae of the giant freshwater prawn provided by this invention has the following beneficial effects:

[0026] (1) Significantly improved screening accuracy and efficiency: This invention combines a technical solution of "specific wavelength (580-595nm) light source induction" with "two screenings before and after the critical developmental period (initial screening after stage I, and rescreening after stage II)" to utilize the phototaxis of highly active larvae for physical separation, effectively eliminating weak individuals that floated to the surface due to brief stress during the first screening, and increasing the screening accuracy from about 65% in the traditional method to over 85%. At the same time, this method achieves rapid and batch-based activity sorting, shortening the screening time per batch to less than 2 hours, and solving the problems of "slow, poor, and missed" in traditional empirical screening that relies on visual observation.

[0027] (2) Effectively reduces the risk of damage and disease to larvae: This invention employs solutions specifically designed to protect larvae in several key steps. A 100-mesh or 80-mesh soft nylon net is used in the soaking, collection, and rinsing stages, and a soft stirring rod is used for gentle stirring. These measures control the mechanical damage rate of larvae to below 3%. Furthermore, the combined steps of "soaking to remove insects (100ppm formaldehyde solution)" and "povidone-iodine disinfection (20-30ppm)" effectively kill ectoparasites (removal rate exceeding 90%) and block pathogen transmission, reducing the pathogen-carrying rate of larvae by 40%, thereby significantly reducing the incidence of disease in the subsequent seedling stage.

[0028] (3) Optimizing seedling quality and improving economic benefits: Through the high-precision, low-damage screening process described above, this invention ensures that all seedlings entering the centralized cultivation stage are highly active Stage II zoea larvae. These larvae are robust and uniformly active, laying a good foundation for their subsequent development, thereby significantly improving the success rate of metamorphosis from zoea larvae to shrimp larvae. Ultimately, this invention improves the overall quality of giant freshwater prawn seedlings from the source, bringing farmers higher survival rates and more stable production benefits. Attached Figure Description

[0029] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0030] Figure 1 This is a schematic diagram of the screening device for highly active zoea larvae of the giant freshwater prawn according to the present invention;

[0031] Figure 2 This is a flowchart of the screening method for highly active zoea larvae of the giant freshwater prawn according to the present invention. Detailed Implementation

[0032] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. It should be noted that all parameters involved in this invention (such as disinfectant concentration, temperature, light conditions, etc.) are given within a preferred range. Those skilled in the art, based on the principles disclosed in the specification and the guidance of the following embodiments, can verify and adjust other values ​​within this range using conventional means, and these adjustments all fall within the substantial protection scope of this invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0034] This invention aims to overcome the three core problems of existing screening technologies for zoea larvae of the giant freshwater prawn: low efficiency, poor accuracy, and non-dedicated equipment. By integrating the biological characteristics of zoea larvae (such as phototaxis), precise environmental control technology, and the synergistic design of a dedicated screening device, a standardized and efficient screening method is constructed. This method is particularly suitable for large-scale seed production scenarios. Through the dedicated device and standardized process detailed later, it aims to achieve high-precision screening (accuracy >85%), low damage (damage rate <3%), and low disease risk of highly active larvae, and to ensure the uniformity and stability of subsequent seed quality from the source, providing key technical support for the industry.

[0035] Figure 1 A diagram of the screening device for highly active zoea larvae of the giant freshwater prawn of the present invention is shown. Please refer to it. Figure 1 The core of this invention lies in the synergistic design of a "dedicated screening device + standardized screening method". This dedicated screening device, tailored to the physiological characteristics and screening needs of flea larvae, specifically consists of the following five functional units:

[0036] Specialized collection unit: 100-mesh nylon net ( Figure 1 The diagram shows a 100-mesh net. The net has a mesh density of 100 mesh (0.15mm aperture), is made of soft nylon material, has good resistance to seawater corrosion, and its edges are coated with a 1mm thick rubber layer to effectively avoid scratching juveniles during harvesting, achieving gentle and efficient collection.

[0037] The immersion culture unit consists of the first immersion container and the second immersion container. Figure 1Specifically, this is manifested in two parts: a rinsing tank and a light-induction tank, both of which are 400L PP plastic black tanks. The black tanks are made of food-grade PP plastic (acid and alkali resistant, anti-aging), with a 5mm thick wall and a smooth, rounded inner wall (2cm radius) to prevent larvae from being trapped or scratched. The tanks are 80cm high and 60cm in diameter, with a 5cm drain valve at the bottom and a 100-mesh filter for easy trapping of larvae during water changes. This black tank simulates the dark environment in which flea larvae naturally grow, reducing stress and meeting the needs of both batch rinsing and temporary cultivation.

[0038] The light source induction unit consists of a 580-595nm LED light and a light focusing cover. The LED light has a fixed wavelength of 580-595nm (tested to show this wavelength has the strongest phototactic attraction to larvae), a power of 30W, and an adjustable illuminance range of 1500-2000 lux. It is mounted on a lamp holder with an adjustable height (range 30-40cm). The focusing cover is made of PC material, with a focusing angle of 60° and a diameter of 20cm, which can uniformly focus the light onto the water surface in the tank (covering an area with a diameter of 50cm), avoiding uneven illumination that could lead to missed detections. This unit utilizes the phototaxis of larvae to achieve precise separation of highly active and inactive individuals.

[0039] Disinfection and rinsing unit: includes disinfection container ( Figure 1 Specifically, this is manifested in the disinfection tank and the rinsing tank. The disinfection containers are equipped with an automatic dosing device. The automatic dosing device has a volume of 5L and is equipped with a precision metering pump (error ±1ppm). It can automatically inject disinfectant (such as povidone-iodine), supports timed and quantitative dosing, and realizes precise dosing of disinfectant and standardized rinsing, avoiding dosage errors caused by manual operation.

[0040] Thermostatic incubation unit: consisting of a thermostatic incubation container ( Figure 1 Specifically, this is achieved through a 1000L constant-temperature black tank equipped with a temperature control system. The black tank is made of PP plastic, with a volume of 1000L, and its walls contain a 500W heating wire and a temperature sensor with an accuracy of ±0.5℃. The temperature control system is equipped with an intelligent temperature controller, which can be set within a temperature range of 28-30℃ (the suitable growth temperature for zoea larvae). It automatically heats up when the temperature falls below the set value and automatically shuts off when the temperature rises above it, providing a stable constant-temperature cultivation environment for the zoea larvae.

[0041] Figure 2 The flowchart of the screening method for highly active zoea larvae of the giant freshwater prawn according to the present invention is shown. Based on the above-mentioned dedicated screening device, the present invention provides a screening method for highly active zoea larvae of the giant freshwater prawn, comprising the following steps:

[0042] This invention provides a method for screening highly active zoea larvae of the giant freshwater prawn, comprising the following steps:

[0043] S1. Pre-treatment by Immersion: Newly hatched Stage I zoea larvae are collected from the broodstock rearing tank using a 100-mesh nylon net, counted, and transferred to the first immersion container. The first immersion container contains a 100 ppm formaldehyde solution and brackish water with a salinity of 6‰. The mixture is gently stirred at 30 rpm (using a soft stirring rod to avoid damaging the larvae) for 1 minute. Then, Stage I zoea larvae are collected again with the 100-mesh nylon net and rinsed once with the 6‰ salinity brackish water before being transferred to the second immersion container. Both the first and second immersion containers are 400L PP plastic black buckets with a wall thickness of 5mm, smooth inner walls without sharp edges, and a 2cm radius corner radius. A drain valve is installed at the bottom of each bucket. Each bucket holds 4-5 million larvae; this optimized density effectively avoids overcrowding and oxygen deprivation.

[0044] This step aims to simulate the salinity of the flea larvae's natural habitat using 6‰ brackish water to reduce environmental stress on the larvae; at the same time, it utilizes 100ppm formaldehyde solution to effectively kill parasites (such as twigworms) carried on the larvae's body surface while ensuring their safety, thus providing a healthy larval population for subsequent screening.

[0045] S2. Initial Light Source-Induced Screening: An LED light source is placed 30-40cm directly above the second immersion container, with the wavelength adjusted to 580-595nm and the illuminance to 1500-2000 lux. After turning on the light source, allow it to stand for 2 minutes (highly active larvae will actively rise to within 10cm of the water surface due to phototaxis). Gently collect the floating Stage I zoea larvae using a 100-mesh nylon net and transfer them to a temporary container. After 3 minutes, perform a second collection (to capture highly active larvae that are delayed in rising). Repeat this operation 2-3 times for each black container to ensure no highly active larvae are missed. The collected Stage I zoea larvae are identified as highly active Stage I zoea larvae, and those that do not rise are discarded. Preferably, an LED light source is fixed 35cm directly above the second immersion container, with an illuminance of 1800 lux, ensuring that the light evenly covers the water surface inside the container through a focusing hood.

[0046] This step utilizes the selective phototaxis of highly active larvae to wavelengths of 580-595 nm to achieve rapid and non-destructive separation from less active individuals. This design increases screening efficiency by more than five times compared to traditional visual observation methods.

[0047] S3. Disinfection treatment: Transfer the highly active stage I zoea larvae obtained in step S2 to a disinfection container, add povidone-iodine through an automatic dosing device to achieve a povidone-iodine concentration of 20-30 ppm in the water, and soak for 15-20 minutes; during the soaking period, gently stir once every 5 minutes to ensure uniform contact of the solution; after soaking, use a 100-mesh nylon net to collect the highly active stage I zoea larvae, and rinse the larvae 3 times with brackish water with a salinity of 6‰, rinsing for 2 minutes each time, until there is no disinfectant residue in the water, and verify and confirm by using residual iodine test strips.

[0048] S4. Secondary Light-Induced Screening: Transfer the highly active Stage I zoea larvae treated in step S3 to a constant-temperature incubation container and incubate at 28-30℃ for 24 hours to allow them to develop into Stage II zoea larvae (body length increases to 1.8-2.0 mm, and appendages are more fully developed). Place an LED light source 30-40 cm (preferably 35 cm) directly above the constant-temperature incubation container, adjusting the wavelength to 580-595 nm. After turning on the light, let it stand for 2 minutes, then use an 80-mesh nylon net to collect the Stage II zoea larvae floating on the water surface. Perform a second collection after 3 minutes, repeating this operation 2-3 times. The collected Stage II zoea larvae are identified as highly active Stage II zoea larvae, and those that do not float are discarded to ensure uniform activity of individuals after screening. The constant-temperature incubation container is a 1000L PP plastic black bucket, equipped with a heating wire, temperature sensor, and intelligent temperature controller. The density of larvae in constant temperature culture containers is controlled at 12-15 million larvae per cubic meter.

[0049] This step, through secondary screening, can effectively eliminate "pseudo-high-activity" individuals (such as weak larvae that temporarily float to the surface due to stress) generated during the first light induction, significantly improving the final screening accuracy from 65% in a single screening to over 85%, thus ensuring the uniformity of activity of the larval population after screening.

[0050] S5. Centralized cultivation: The highly active stage II zoea larvae obtained in step S4 are transferred to a seedling cultivation pond. The water temperature is controlled at 28-30℃, pH value at 7.5-8.0, dissolved oxygen at ≥5mg / L and salinity at 12‰. Feed is provided regularly until the seedling cultivation process is completed.

[0051] Example 1

[0052] Based on the aforementioned method and process, the following specific embodiment will further illustrate the implementation of the present invention.

[0053] 1. Implementation Preparation

[0054] Sufficient preparation work needs to be done before starting the screening process:

[0055] Materials preparation: Newly hatched first-stage zoea larvae of giant freshwater prawns, artificial brackish water with a salinity of 6‰ after aeration for 24 hours to remove chlorine and impurities, analytical grade formaldehyde for diluting and preparing a 100ppm solution, aquaculture-specific povidone-iodine for preparing a 20-30ppm solution, and disinfected Artemia nauplii larvae as subsequent rearing feed.

[0056] Equipment debugging: Check that all units of the special screening device are in good working order, including confirming that the 100-mesh and 80-mesh nylon nets are undamaged, the LED light wavelength has been calibrated to 580-595nm, the temperature control system of the constant temperature incubation container (1000L PP plastic black bucket) is operating normally (set temperature 29℃, control accuracy ±0.5℃), and the automatic dosing device is accurate in metering (error ≤1ppm).

[0057] Environmental preparation: Maintain the temperature of the seedling nursery at 28-30℃. Except for the light-induced selection process, avoid direct sunlight on the cultivation area. Ensure that the dissolved oxygen concentration of all cultivation water is ≥5mg / L and the pH value is maintained between 7.5 and 8.0 (adjusted if necessary using aerators and pH adjusters).

[0058] 2. Specific Implementation Steps

[0059] This embodiment uses the processing of 12 million stage I zoea larvae as an example to illustrate the operation process in detail:

[0060] (1) Immersion Pretreatment

[0061] Collection and Counting: Newly hatched Stage I zoea larvae were gently scooped from the broodstock rearing tank using a 100-mesh nylon net with coated edges. The total number was confirmed as 12 million using a counting instrument.

[0062] Immersion Procedure: Divide the collected larvae evenly into three 400L PP plastic black buckets, which will serve as immersion containers. Add the prepared "100ppm formaldehyde solution + 6‰ brackish water" to each bucket until it is full. Then, gently stir the solution with a soft stirring rod at 30 rpm for 1 minute. This process utilizes formaldehyde to effectively kill external parasites (such as Cyclostome and Vorticella), while the 6‰ brackish water environment helps reduce environmental stress on the larvae.

[0063] Transfer and Transition: Immediately after rinsing, the larvae are removed from the rinsing solution using a 100-mesh nylon net and rinsed once with clean 6‰ brackish water to remove residue. The larvae are then transferred to another 400L PP plastic black drum, which serves as a second rinsing container and contains only 6‰ brackish water. The final density is controlled to retain approximately 4 million larvae per drum; this optimized density effectively avoids overcrowding and oxygen deprivation, ready for the next screening step.

[0064] (2) Initial light source-induced screening

[0065] Equipment setup: Install LED lights with a wavelength of 580-595nm at a height of 35cm directly above each of the three 400L black tanks used as the second rinsing containers. Turn on the light source and adjust the illuminance to 1800 lux to ensure that the light can evenly cover the water surface area inside the tank through the focusing hood.

[0066] Collection Procedure: After turning on the light source and allowing the water to settle for 2 minutes, highly active Stage I zoea larvae will cluster and rise to the surface due to phototaxis. Immediately, use a 100-mesh nylon net to gently collect these rising larvae along the surface. After settling for 3 minutes, a second collection is conducted to capture any highly active individuals that may delay rising. This collection procedure is repeated twice. Ultimately, approximately 1.8-2 million larvae were collected per bucket in the first collection, and approximately 150,000-200,000 larvae in the second collection, totaling 2-2.2 million highly active Stage I zoea larvae per bucket. A total of approximately 6.2 million highly active individuals were collected from the three buckets. The remaining approximately 5.8 million larvae that did not rise were deemed low-activity and discarded. This method utilizes specific light waves for induction, significantly improving screening efficiency compared to traditional visual observation methods.

[0067] (3) Disinfection and constant temperature incubation

[0068] Disinfection treatment: Approximately 6.2 million highly active stage I zoea larvae obtained from the screening process were transferred to a dedicated disinfection container. Povidone-iodine was injected into the water using an automatic dosing device to achieve a concentration of 25 ppm, and the larvae were soaked for 18 minutes. During soaking, the larvae were gently stirred every 5 minutes to ensure that the disinfectant solution made full contact with all larvae.

[0069] Rinsing verification: After soaking, use a 100-mesh nylon net to remove the juveniles and rinse them thoroughly with 6‰ brackish water for a total of 3 times, each time for 2 minutes, until the residual iodine test paper verifies that there is no povidone-iodine residue in the water.

[0070] Constant-temperature rearing: After disinfection and rinsing, the larvae were transferred to a 1000L constant-temperature rearing tank. The temperature of the constant-temperature system was set at 29℃, and the rearing density was controlled at approximately 13 million larvae / cubic meter. Under these stable conditions, the larvae were continuously reared for 24 hours. Monitoring was conducted every 8 hours during the rearing period. No larval mortality was observed, and microscopic observation confirmed that all larvae had developed into stage II zoea larvae (body length increased to 1.8-2.0 mm, with more complete appendage development).

[0071] (4) Secondary light source-induced screening

[0072] Secondary screening: An LED light source with a wavelength of 580-595nm was turned on again 35cm directly above the constant-temperature rearing tank. After the light was on and the tank remained still for 2 minutes, an 80-mesh nylon net (suitable for the size of stage II larvae) was used to collect the larvae floating on the surface. After remaining still for 3 minutes, a second collection was performed. This process was repeated twice. Ultimately, approximately 4.5 million larvae were collected in the first collection and approximately 300,000 in the second, for a total of approximately 4.8 million highly active stage II zoea larvae. Approximately 1.4 million low-activity individuals that did not float to the surface were discarded. This secondary screening effectively eliminated "pseudo-high-activity" individuals (such as weak larvae that floated to the surface due to brief stress) that might have been mixed in during the first screening, increasing the overall screening accuracy to over 85%.

[0073] (5) Intensive training

[0074] Environmental setup: Approximately 4.8 million highly active stage II zoea larvae, selected at the final screening stage, were transferred to a 50 m³ nursery pond. The pond water temperature was controlled at 29℃, pH at 7.8, dissolved oxygen concentration at 5.5 mg / L, and salinity at 12‰.

[0075] Feeding Management: Begin standardized feeding management, feeding sterilized Artemia nauplii three times daily at 8:00, 14:00, and 20:00, with each feeding amount being approximately 1.2 kg (calculated as 15% of the total weight of highly active Stage II zoea larvae). Continue cultivation under this optimized environment until the larvae are transferred to the subsequent routine seedling production process.

[0076] 3. Implementation effect verification

[0077] To verify the technical effect of this invention, a comparative experiment was conducted between the juvenile shrimp screened by the method of this invention (the group of this invention) and juvenile shrimp that were not screened by the method of this invention (the unscreened group). Each group was stocked with 100,000 juvenile shrimp, and after 3 months of rearing under the same conditions, the results are compared below:

[0078]

[0079] As can be seen from the comparative data, the seedlings obtained by the screening method of this invention are significantly better than the unscreened group in terms of shrimp survival rate, growth rate (reflected in average body length and culture cycle), and individual weight. This fully verifies the effectiveness and practical value of the technical solution of this invention in improving the quality of giant freshwater prawn seedlings and the economic benefits of aquaculture.

[0080] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A method for screening highly active zoea larvae of the giant freshwater prawn, characterized in that, Includes the following steps: S1. Pre-treatment by immersion: Newly hatched stage I zoea larvae are collected from the broodstock rearing pond using a 100-mesh nylon net, counted, and then transferred to the first immersion container. The first immersion container contains a formaldehyde solution with a concentration of 100 ppm and brackish water with a salinity of 6‰. After stirring at 30 rpm for 1 minute, the stage I zoea larvae are collected with a 100-mesh nylon net and rinsed once with brackish water with a salinity of 6‰, and then transferred to the second immersion container. S2. Initial Light Source-Induced Screening: An LED light source is placed directly above the second immersion container, with the wavelength adjusted to 580-595nm and the illuminance to 1500-2000 lux. After turning on the light source, the container is left to stand for 2 minutes. A 100-mesh nylon net is used to collect the Stage I zoea larvae floating on the water surface. A second collection is performed after 3 minutes, and this operation is repeated 2-3 times. The collected Stage I zoea larvae are identified as highly active Stage I zoea larvae, and those that do not float to the surface are discarded. S3. Disinfection treatment: Transfer the highly active stage I zoea larvae obtained in step S2 to a disinfection container, add povidone-iodine to make the concentration of povidone-iodine in the water reach 20-30 ppm, and soak for 15-20 minutes; stir once every 5 minutes during soaking; after soaking, use a 100-mesh nylon net to pick up the highly active stage I zoea larvae, and rinse with brackish water with a salinity of 6‰ 3 times, 2 minutes each time, until there is no povidone-iodine residue; S4. Secondary Light Source Induction Screening: Transfer the highly active Stage I zoea larvae treated in step S3 to a constant temperature incubation container and incubate at 28-30℃ for 24 hours to allow them to develop into Stage II zoea larvae. Place an LED light source directly above the constant temperature incubation container and adjust the wavelength of the light source to 580-595nm. After turning on the light source, let it stand for 2 minutes and use an 80-mesh nylon net to collect the Stage II zoea larvae floating on the water surface. After 3 minutes, perform a second collection and repeat this operation 2-3 times. The collected Stage II zoea larvae are identified as highly active Stage II zoea larvae, and those Stage II zoea larvae that do not float to the surface are discarded. S5. Centralized cultivation: Transfer the highly active stage II zoea larvae obtained in step S4 to a seedling cultivation pond, control the water temperature at 28-30℃, pH at 7.5-8.0, dissolved oxygen at ≥5mg / L and salinity at 12‰, and feed them regularly.

2. The method for screening highly active zoea larvae of the giant freshwater prawn according to claim 1, characterized in that, In step S1, both the first immersion container and the second immersion container are 400L PP plastic black buckets with a wall thickness of 5mm, smooth inner walls without sharp edges, a rounded corner radius of 2cm, and a drain valve at the bottom of the bucket.

3. The method for screening highly active zoea larvae of the giant freshwater prawn according to claim 1, characterized in that, In steps S1 and S3, the stirring is carried out using a soft stirring rod.

4. The method for screening highly active zoea larvae of the giant freshwater prawn according to claim 1, characterized in that, In steps S2 and S4, the illuminance of the LED light source is 1800 lux, the installation height of the light source is adjustable from 30 to 40 cm, and it is equipped with a focusing cover with a focusing angle of 60°.

5. The method for screening highly active zoea larvae of the giant freshwater prawn according to claim 1, characterized in that, The disinfection container described in step S3 is equipped with an automatic dosing device for automatically injecting povidone-iodine and controlling the concentration error within ±1 ppm.

6. The method for screening highly active zoea larvae of the giant freshwater prawn according to claim 1, characterized in that, In step S3, the concentration of povidone-iodine is 25 ppm, and the soaking time is 18 minutes.

7. The method for screening highly active zoea larvae of the giant freshwater prawn according to claim 1, characterized in that, In step S4, the constant temperature incubation container is a 1000L PP plastic black bucket, which is equipped with a heating wire, a temperature sensor and an intelligent temperature controller.

8. The method for screening highly active zoea larvae of the giant freshwater prawn according to claim 1, characterized in that, In step S4, the larval culture density in the constant temperature culture container is 12 million to 15 million larvae per cubic meter.

9. The method for screening highly active zoea larvae of the giant freshwater prawn according to claim 1, characterized in that, In step S5, the water temperature in the seedling cultivation pond is controlled at 29℃, the pH value is controlled at 7.8, the dissolved oxygen is controlled at 5.5mg / L, and the salinity is controlled at 12‰.

10. The method for screening highly active zoea larvae of the giant freshwater prawn according to claim 1, characterized in that, In step S5, the regular feeding refers to feeding Artemia nauplii three times a day, with each feeding amount being 15% of the body weight of highly active stage II zoea larvae.

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