A method for constructing an indoor high-efficiency ecological algal phase for blue crab breeding

Abstract

This invention provides a method for constructing an efficient ecological algal community for indoor breeding of mud crabs. Based on the growth characteristics of mud crab zoea larvae and their requirements for water quality and nutrition at each stage, a method for constructing a superior microalgal community and a balanced bacterial-algal community in the mud crab breeding pond is proposed. Six novel algal combinations not previously used in mud crab breeding are used to replace native algae, supplemented with probiotics. A daily combination of algae, bacteria, and biological feed for each developmental stage of the larvae (Z1-C1) is designed, significantly improving the survival rate and efficiency of indoor mud crab breeding. Compared to traditional breeding methods that rely entirely on native algae, this artificially constructed algae is more efficient and reproducible, facilitating the standardization of indoor breeding. This invention promotes a refined management model, achieving a balanced bacterial-algal community, stable and controllable water environment, and avoiding the instability caused by complex and variable native algae. This is more conducive to the promotion of mud crab breeding in areas with poor natural water quality.

Description

Technical Field

[0001] This invention belongs to the field of mud crab farming technology, and relates to an indoor seedling raising technology for mud crabs. Specifically, it relates to a method for constructing an ecological algal community for indoor seedling raising of mud crabs, thereby improving the survival rate and efficiency of indoor seedling raising of mud crabs. Background Technology

[0002] The mud crab (Scylla paramamosain), commonly known as the blue crab, is a euryhaline marine crustacean and an important aquaculture species in southeastern coastal my country. In 2022, my country's mud crab farming output reached 154,700 tons, with a farming area of ​​3.6255 million mu (approximately 248,667 hectares), showing slow growth and a shortage of artificially bred seedlings. Traditional seedling cultivation relies on native algae, but the types and quantities of native algae are highly unstable, fluctuating greatly and uncontrollably with changes in climate and water quality. This instability can lead to over-proliferation or mass extinction of individual species at certain stages, causing problems such as mutation, aging, over-fertilization, and deterioration of the aquatic environment, severely impacting seedling survival rates. Furthermore, unreasonable feed input, disinfection, and excessive medication can disrupt the stability of the aquaculture ecosystem, causing significant stress on crab seedlings and leading to the growth of drug-resistant harmful bacteria and chemical residues, posing safety hazards. Therefore, exploring efficient, controllable, and environmentally friendly mud crab seedling cultivation models is of great significance for achieving green and high-quality development of my country's mud crab farming industry.

[0003] The ecological environment for seedling cultivation must be maintained in a dynamic balance. As primary productive forces, the species and quantity of microalgae directly determine the quality of the aquaculture ecosystem: algal photosynthesis increases water oxygen levels, leading to enhanced seedling activity, improved immunity, and reduced mortality. Simultaneously, algae possess extremely high nutritional value, serving as substitutes for fish oil and fishmeal, and are major producers of highly unsaturated fatty acids (HUFA). Therefore, using algae to fortify rotifers and artichokes can further meet the nutritional needs of rapidly growing seedlings. Compared to single microalgae, the combined use of different algal species can more effectively achieve nutritional fortification of biological feed. Furthermore, the combination of microalgae and probiotics has the advantage of purifying water quality, promptly decomposing and utilizing dead rotifers, artichokes, and larvae, preventing the decay of remains and water pollution, absorbing harmful substances such as ammonia nitrogen and nitrite, maintaining a healthy microecological environment in the seedling pond, and effectively reducing the use of antibiotics. However, there are currently no research reports on the combined application of multiple algae species in conjunction with probiotics. Summary of the Invention

[0004] This invention addresses the aforementioned technical problems by proposing a controllable, efficient, and green ecological seedling cultivation model. Specifically, it provides a method for constructing an ecological algal community for high-efficiency indoor seedling cultivation of mud crabs: seedling cultivation does not rely on native algae, but uses artificially cultivated novel algae to construct the algal community throughout the entire process. Six artificially cultivated novel algae are used in combination to replace native algae, along with the use of probiotics. No antibiotics are used, resulting in a stable and controllable process that significantly improves the survival rate and efficiency of indoor seedling cultivation of mud crabs.

[0005] The six artificial novel algae used in this invention include Isochrysis galbana, Pavlova viridis, Chlorella vulgaris, Nitzschia closterium f. minutissima, Platymonas subcordiformis, and Phaeodactylum tricornutum Bohlin.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for constructing an efficient indoor seedling ecological algal community for mud crabs, characterized by comprising the following steps:

[0008] A. Pre-treatment and seedling introduction

[0009] Seawater is initially filtered using a microfiltration membrane and then disinfected a second time with sodium hypochlorite. The mixture is then fully aerated in a dark room for 3-4 days without fertilization to eliminate native algae. Newly hatched zoea larvae are then introduced into the nursery pond at a concentration of 10,000-50,000 larvae / m³. 3 ;

[0010] B. Larval Culture

[0011] The developmental stages of the larvae are divided into Z1, Z2, Z3, Z4, Z5, M, and C1 stages. Z1-Z5 stages correspond to zoea larvae stages 1-5, M stage corresponds to megalopa larvae, and C1 stage corresponds to juvenile crab stage 1.

[0012] Based on the changing needs of larval development and the results of previous experiments, different algal combinations should be used at different larval development stages (Z1-C1), as follows:

[0013] On the first day of hatching for Z1, directly add 1×10 to the water. 5 -5×10 5 Add *Isorrhiza globulus* solution at an ind / L concentration, using a daily feeding concentration of 1×10⁻⁶. 6 -5×10 6Live rotifers were enhanced with green Pavlova at a concentration of 1 ind / ml for 2-4 hours at a density of 2.4 × 10⁻⁶. 4 -3.6×10 4 pcs / m 3 ;

[0014] During the Z2 period, administer 1×10 mg of the drug directly in the water daily. 6 -5×10 6 Add seawater Chlorella solution at a concentration of 1×10⁻⁶ / L for daily feeding. 6 -5×10 6 The concentration of *Rhizoctonia solani* solution (ind / ml) is 1×10⁻⁶. 8 -5×10 8 Live rotifers were inoculated with a CFU / mL lactic acid bacteria and photosynthetic bacteria compound culture solution for 2-4 hours, and the release density was 2.4 × 10⁻⁶. 4 -3.6×10 4 pcs / m 3 ;

[0015] The daily feeding concentration for stage Z3 is 1×10⁻⁶. 6 -5×10 6 The concentration of *Rhizoctonia solani* solution (ind / ml) is 1×10⁻⁶. 8 -5×10 8 Live brine shrimp were inoculated with a CFU / ml lactic acid bacteria and photosynthetic bacteria complex culture solution for 2-4 hours, and the stocking density was 8×10⁶. 3 -1.2×10 4 pcs / m 3 ;

[0016] During the Z4 period, administer 1×10 mg of the solution directly in the water daily. 6 -5×10 6 Add seawater Chlorella solution at ind / L, and feed daily at 1×10 6 -5×10 6 ind / ml Small Crescent Rhizoidea solution and 1×10 6 -5×10 6 The combined algae formed by ind / ml *Isophyta globulus* solution and 1×10 8 -5×10 8 Live brine shrimp were inoculated with a CFU / mL lactic acid bacteria and photosynthetic bacteria complex culture solution for 2-4 hours, and the stocking density was 8×10⁶. 3 -1.2×10 4 pcs / m 3 ;

[0017] In Z5, administer 1×10 mg of the solution directly in the water daily. 6 -5×10 6 Add seawater Chlorella solution at ind / L, and feed daily using 1 ind / L solution.

[0018] ×10 6 -5×10 6 ind / ml of subcoria syringae solution and 1×10 6 -5×10 6 The combined algae formed by ind / ml of *Phaeodactylum tricornutum* solution were combined with 1×10 8 -5×10 8 Live brine shrimp were inoculated with a CFU / mL lactic acid bacteria and photosynthetic bacteria complex culture solution for 2-4 hours, and the stocking density was 8×10⁶. 3 -1.2×10 4 pcs / m 3 ;

[0019] During the M phase, administer 1×10 mg of the solution directly in the water daily. 5 -5×10 5 Add *Rhizoctonia solani* solution at ind / L, and feed 8×100 mg / day. 3 -1.2×10 4 pcs / m 3 Live brine shrimp;

[0020] Crab seedlings are harvested when the larvae have completely metamorphosed from the M stage to the C1 stage.

[0021] Preferably, the methods for introducing different algae during the larval stage are divided into two types based on their different mechanisms of action: if the main function is ecological regulation, the algal solution is directly poured into the seedling pond; if the main function is feed disinfection and nutritional enhancement, rotifers and brine shrimp that have been soaked and enhanced with bacteria and algae are introduced into the seedling pond.

[0022] The aforementioned larval development stages Z2-Z5 require the supplementation of compound probiotics to achieve optimal benefits. Probiotics competitively inhibit harmful bacteria, and the combination of bacteria and algae can replace antibiotics without leading to the development of drug-resistant strains. They are more beneficial than antibiotics in maintaining the microecological balance of the breeding environment and the animals' bodies, purifying water quality, promoting nutrient absorption in larvae, and enhancing larval immunity. The compound probiotic strain consists of lactic acid bacteria and photosynthetic bacteria. The compound probiotic strain is used in conjunction with algae by mixing the expanded bacterial culture solution with the algae solution, and then using this mixture to soak and strengthen the rotifers and artichokes used for feeding.

[0023] Further optimization involved using pure algal cultures cultured to 10... 5 Algal solution with a concentration of ind / L or higher should be poured into the seedling tank according to the required amount. The microalgae culture medium contains 5-10% ferric citrate, 5-10% ammonium chloride, 5-10% sodium silicate and 5-10% potassium dihydrogen phosphate. The culture time is 5-7 days at 25-30℃, and the incandescent lamp is irradiated for 24 hours at 6000-7000lx.

[0024] The cultivation method for the combined lactic acid bacteria and photosynthetic bacteria strain is as follows: Anaerobic culture of the pure strain at 25-30℃ on sterile medium for 5-7 days, followed by isolation and collection of the precipitated bacteria. Each liter of the sterile medium contains 1g NH4Cl, 0.2g MgCl2, 0.1g yeast extract, 0.5g K2HPO4, 2g NaCl, 15-20g agar, and 5-10g glucose.

[0025] Further optimization was performed, with rotifers and artichokes cultured at 26-30℃ and salinity of 25-33, with full aeration, and fed daily with special compound feed for rotifers and artichokes;

[0026] The method for nutritional fortification of rotifers is as follows: filter live rotifers through a 250-mesh screen, soak them in the fortification solution of bacteria and algae for 2-4 hours, then filter the fortified rotifers through a 250-mesh screen and feed them;

[0027] The method for nutritional fortification of brine shrimp is as follows: Select live brine shrimp larvae from the bottom by letting them settle, remove the shells, filter out the brine shrimp larvae and soak them in the mixed liquid of bacteria and algae for 2-4 hours, then filter out the fortified brine shrimp through a 250-mesh screen and feed them.

[0028] In addition, the management methods for water, temperature, salinity, and light during the seedling cultivation process in step B are as follows:

[0029] (1) Water bodies:

[0030] The water transparency in the seedling rearing pond is between 25-40cm, and the water color is yellowish-green (Z1-Z5) and brownish-brown (M-C1). The total biomass of microalgae at each stage is strictly controlled to be 10 by daily algae introduction. 5 -10 8 ind / L, microalgal biodiversity index greater than 1.12;

[0031] Do not change the water during Z1-Z2. During Z3-Z5, change 25-30% of the water volume in the culture tank every 3 days. On the first day of M, change 40-50% of the water volume in the culture tank, and then do not change the water.

[0032] The ammonia nitrogen level is less than 0.02 mg / L, and the dissolved oxygen level in the water is above 5 mg / L. During the Z1-Z2 period, a small amount of aeration is carried out to make the water appear slightly wavy, while during the Z3-C1 period, the aeration is increased to make the water appear boiling.

[0033] (2) Temperature and salinity

[0034] The water temperature in the seedling pond should be controlled at 23-26℃, the pH value at 7-8, and the salinity at 26-33 for the Z1-Z5 period and 20-25 for the Z5-C1 period.

[0035] (3) Light

[0036] Regarding lighting control, indoor artificial lighting is adjusted to 3000-5000 lx, with lighting time from 6:00 AM to 6:00 PM daily.

[0037] Beneficial protections and effects of the present invention

[0038] Based on the growth characteristics of zoea larvae of the mud crab and their requirements for water quality and nutrition at each stage, this invention proposes a method for constructing a superior microalgal and bacterial-algal balance in mud crab nursery ponds. It uses six novel algal combinations not previously used in mud crab nursery to replace native algae, supplemented with probiotics, and designs daily combinations of algae, bacteria, and biological feed for each larval developmental stage (Z1-C1). The invention demonstrates significant technical advantages.

[0039] (1) The survival rate of mud crab zoea larvae metamorphosing into megalopa larvae and then from megalopa larvae into stage 1 larvae can reach more than 31.13%; the overall time from zoea larvae to stage 1 larvae is shortened by an average of 2-3 days, thus shortening the seedling time; the molting and metamorphosis process of zoea larvae Z1-Z5 is completed within 1 day, reducing cannibalism and ensuring uniform development; the size of stage 1 larvae C1 seedlings obtained is more than 11mg per seedling, which is more than 2.5mg per seedling compared with traditional seedlings; the larvae's ability to withstand hunger is significantly improved, and the average half-lethal time of hunger resistance in the megalopa larvae stage can reach 3.5-4 days.

[0040] (2) No illegal or potentially accumulating chemicals were used during the seedling stage, achieving green, environmentally friendly, and pollution-free seedling cultivation. Throughout the entire seedling cycle, water quality remained stable and controllable, effectively preventing the growth of drug-resistant harmful bacteria, reducing stress responses in larvae, and saving on drug application costs.

[0041] (3) Compared with traditional seedling cultivation using native algae and antibiotics, this method increases the survival rate of Z1-Z2 metamorphosis by more than 15%, Z2-Z3 metamorphosis by more than 14%, Z3-Z4 metamorphosis by more than 18%, Z4-Z5 metamorphosis by more than 15%, Z5-M metamorphosis by more than 14%, and M-C1 metamorphosis by more than 6%. The overall seedling survival rate can be increased by more than 20%. Each female crab can produce 2-4 million Z1 seedlings and obtain 580,000-1,240,000 C1 seedlings, increasing economic benefits by more than 25%.

[0042] (4) Artificially constructed algae are more reproducible than traditional seedling cultivation that relies entirely on native algae, which is conducive to the standardization of indoor seedling cultivation.

[0043] In summary, the method of this invention achieves a balance between bacteria and algae, resulting in a stable and controllable aquatic environment. It avoids the instability caused by complex and variable native algae, which is conducive to the development of a refined management model. It also improves the survival rate and efficiency of indoor seedling cultivation of mud crabs and is more conducive to the promotion of mud crab seedling cultivation in areas with poor natural water quality. Attached Figure Description

[0044] Figure 1 A technical roadmap for indoor seedling cultivation of mud crabs;

[0045] Figure 2 A comparison of the larval development processes of novel algae seedling cultivation, native algae seedling cultivation, and antibiotic-treated seedling cultivation;

[0046] Figure 3 To compare the starvation resistance of megalopa larvae under different seedling raising methods. Detailed Implementation

[0047] The implementation of the present invention will be described in detail below with reference to the embodiments of the present invention. The following embodiments are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0048] 1. Technical route

[0049] Indoor seedling cultivation technology route for mud crabs, as follows Figure 1 As shown, the seedling workshop is divided into four areas: seedling pond 1, algae culture pond 2, microbial culture pond 3, and rotifer and artichoke culture pond 4. Seedling pond 1 is used for the cultivation of mud crab seedlings, algae culture pond 2 is used for the cultivation of different algae species, microbial culture pond 3 is used for the cultivation of compound probiotics formed by the combination of lactic acid bacteria and photosynthetic bacteria, and rotifer and artichoke culture pond 4 is used for nutritional fortification treatment before feeding rotifers or artichokes.

[0050] Figure 1 The arrows in the diagram indicate the specific operating procedures: if the main function is ecological regulation, the algal solution is poured directly into the seedling pond; if the main function is feed disinfection and nutritional enhancement, the algae and bacteria-enhanced rotifers are introduced into the seedling pond by feeding them.

[0051] Among them, the algal solutions of microalgae were all pure algal strains cultured to 10 5 Algal solution with a concentration of ind / L or higher should be poured into the seedling tank according to the required amount. The microalgae culture medium contains 5-10% ferric citrate, 5-10% ammonium chloride, 5-10% sodium silicate and 5-10% potassium dihydrogen phosphate. The culture time is 5-7 days at 25-30℃, and the incandescent lamp is irradiated for 24 hours at 6000-7000lx.

[0052] The cultivation method for the combined lactic acid bacteria and photosynthetic bacteria strain is as follows: Anaerobic culture of the pure strain at 25-30℃ on sterile medium for 5-7 days, followed by isolation and collection of the precipitated bacteria. Each liter of the sterile medium contains 1g NH4Cl, 0.2g MgCl2, 0.1g yeast extract, 0.5g K2HPO4, 2g NaCl, 15-20g agar, and 5-10g glucose.

[0053] Rotifers and Artemia should be cultured at 26-30℃ with a salinity of 25-33, with adequate aeration, and fed daily with a special formulated feed for rotifers and Artemia.

[0054] The method for nutritional fortification of rotifers is as follows: filter live rotifers through a 250-mesh screen, soak them in the fortification solution of bacteria and algae for 2-4 hours, then filter the fortified rotifers through a 250-mesh screen and feed them.

[0055] The method for nutritional fortification of brine shrimp is as follows: Select live brine shrimp larvae from the bottom by letting them settle, remove the shells, filter out the brine shrimp larvae and soak them in the mixed liquid of bacteria and algae for 2-4 hours, then filter out the fortified brine shrimp through a 250-mesh screen and feed them.

[0056] 2. Cultivation Methods

[0057] A. Pre-treatment and seedling introduction

[0058] Seawater is initially filtered using a microfiltration membrane and then disinfected a second time with sodium hypochlorite. The mixture is then fully aerated in a dark room for 3-4 days without fertilization to eliminate native algae. Newly hatched zoea larvae are then introduced into the nursery pond at a concentration of 10,000-50,000 larvae / m³. 3 ;

[0059] B. Larval Culture

[0060] The developmental stages of the larvae are divided into Z1, Z2, Z3, Z4, Z5, M, and C1 stages. Z1-Z5 stages correspond to zoea larvae stages 1-5, M stage corresponds to megalopa larvae, and C1 stage corresponds to juvenile crab stage 1.

[0061] Based on the changing needs of larval development and the results of previous experiments, different algal combinations should be used at different larval development stages (Z1-C1), as follows:

[0062] On the first day of hatching for Z1, directly add 1×10 to the water. 5 -5×10 5 Add *Isorrhiza globulus* solution at an ind / L concentration, using a daily feeding concentration of 1×10⁻⁶. 6 -5×10 6 Live rotifers were enhanced with green Pavlova at a concentration of 1 ind / ml for 2-4 hours at a density of 2.4 × 10⁻⁶. 4 -3.6×104 pcs / m 3 ;

[0063] During the Z2 period, administer 1×10 mg of the drug directly in the water daily. 6 -5×10 6 Add seawater Chlorella solution at a concentration of 1×10⁻⁶ / L for daily feeding. 6 -5×10 6 The concentration of *Rhizoctonia solani* solution (ind / ml) is 1×10⁻⁶. 8 -5×10 8 Live rotifers were inoculated with a CFU / mL lactic acid bacteria and photosynthetic bacteria compound culture solution for 2-4 hours, and the release density was 2.4 × 10⁻⁶. 4 -3.6×10 4 pcs / m 3 ;

[0064] The daily feeding concentration for stage Z3 is 1×10⁻⁶. 6 -5×10 6 The concentration of *Rhizoctonia solani* solution (ind / ml) is 1×10⁻⁶. 8 -5×10 8 Live brine shrimp were inoculated with a CFU / ml lactic acid bacteria and photosynthetic bacteria complex culture solution for 2-4 hours, and the stocking density was 8×10⁶. 3 -1.2×10 4 pcs / m 3 ;

[0065] During the Z4 period, administer 1×10 mg of the solution directly in the water daily. 6 -5×10 6 Add seawater Chlorella solution at ind / L, and feed daily at 1×10 6 -5×10 6 ind / ml Small Crescent Rhizoidea solution and 1×10 6 -5×10 6 The combined algae formed by ind / ml *Isophyta globulus* solution and 1×10 8 -5×10 8 Live brine shrimp were inoculated with a CFU / mL lactic acid bacteria and photosynthetic bacteria complex culture solution for 2-4 hours, and the stocking density was 8×10⁶. 3 -1.2×10 4 pcs / m 3 ;

[0066] In Z5, administer 1×10 mg of the solution directly in the water daily. 6 -5×10 6 Add seawater Chlorella solution at ind / L, and feed daily using 1 ind / L solution.

[0067] ×10 6 -5×10 6ind / ml of subcoria syringae solution and 1×10 6 -5×10 6 The combined algae formed by ind / ml of *Phaeodactylum tricornutum* solution were combined with 1×10 8 -5×10 8 Live brine shrimp were inoculated with a CFU / mL lactic acid bacteria and photosynthetic bacteria complex culture solution for 2-4 hours, and the stocking density was 8×10⁶. 3 -1.2×10 4 pcs / m 3 ;

[0068] During the M phase, administer 1×10 mg of the solution directly in the water daily. 5 -5×10 5 Add *Rhizoctonia solani* solution at ind / L, and feed 8×100 mg / day. 3 -1.2×10 4 pcs / m 3 Live brine shrimp;

[0069] Crab seedlings are harvested when the larvae have completely metamorphosed from the M stage to the C1 stage.

[0070] In addition, the management methods for water, temperature, salinity, and light during the seedling cultivation process in step B are as follows:

[0071] (1) Water bodies:

[0072] The water transparency in the seedling rearing pond is between 25-40cm, and the water color is yellowish-green (Z1-Z5) and brownish-brown (M-C1). The total biomass of microalgae at each stage is strictly controlled to be 10 by daily algae introduction. 5 -10 8 ind / L, microalgal biodiversity index greater than 1.12;

[0073] Do not change the water during Z1-Z2. During Z3-Z5, change 25-30% of the water volume in the culture tank every 3 days. On the first day of M, change 40-50% of the water volume in the culture tank, and then do not change the water.

[0074] The ammonia nitrogen level is less than 0.02 mg / L, and the dissolved oxygen level in the water is above 5 mg / L. During the Z1-Z2 period, a small amount of aeration is carried out to make the water appear slightly wavy, while during the Z3-C1 period, the aeration is increased to make the water appear boiling.

[0075] (2) Temperature and salinity

[0076] The water temperature in the seedling pond should be controlled at 23-26℃, the pH value at 7-8, and the salinity at 26-33 for the Z1-Z5 period and 20-25 for the Z5-C1 period.

[0077] (3) Light

[0078] Regarding lighting control, indoor artificial lighting is adjusted to 3000-5000 lx, with lighting time from 6:00 AM to 6:00 PM daily.

[0079] 3. Technical Effects

[0080] 3.1 Survival rate and specifications

[0081] The ecological algal community constructed using six novel algae significantly improved the survival rate and seedling size of mud crab seedlings compared to traditional native algae and antibiotic-based seedling cultivation. The survival rate of C1 seedlings from the novel algae cultivation reached over 31.13%, representing an absolute increase of over 20% and 24% compared to native algae and antibiotic-based seedling cultivation, respectively. Specifically, the survival rate at each larval developmental stage was increased by an average of over 15% for Z1-Z2 metamorphosis, over 14% for Z2-Z3, over 18% for Z3-Z4, over 15% for Z4-Z5, over 14% for Z5-M, and over 6% for M-C1. The average seedling size of first-stage mud crab larvae obtained from the novel algae cultivation was over 11 mg per larva, an increase of over 2.5 mg per larva. Detailed data are shown in Table 1.

[0082] Table 1 Comparison of survival rate and seedling specifications between novel algae seedling cultivation, native algae seedling cultivation, and antibiotic seedling cultivation.

[0083]

[0084] 3.2 Larval Development Process

[0085] The ecological algal community constructed using six novel algae significantly improved seedling cultivation efficiency compared to traditional native algal cultivation and antibiotic-based seedling cultivation. The metamorphosis time to C1 in the novel algal seedlings was shortened by an average of 2-3 days. Development was more uniform, with the Z1-Z5 molting and metamorphosis processes all completed within one day, reducing cannibalism caused by asynchronous developmental stages. In contrast, the traditional seedling cultivation process, with the Z1-Z5 metamorphosis process taking up to three days, is more complex. (See details...) Figure 2 .

[0086] 3.3 Starvation tolerance of megalopa larvae

[0087] The ecological algal community constructed using six novel algae species significantly improved the starvation resistance of larvae compared to traditional native algal seedling cultivation and antibiotic-based seedling cultivation. The average half-lethal time for 50% starvation mortality in megalopa larvae cultivated using the novel algal species was 3.5-4 days, while the half-lethal time for starvation in traditional seedling cultivation was only 1-2.5 days. (See details...) Figure 3 .

[0088] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A method for constructing an ecological algal phase for efficient indoor breeding of Scylla serrata, characterized in that, It comprises the following steps: A. Pre-treatment and seedling The seawater for seedling is filtered by microfiltration membrane, disinfected twice, fully aerated in dark room, and then the initial hatched copepodid is put into the seedling pond without fertilization; B. Larvae culture The development stages of larvae are divided into Z1, Z2, Z3, Z4, Z5, M and C1 stages, Z1-Z5 stages correspond to copepodid 1-5 stages, M stage corresponds to large-eyed larva, and C1 stage corresponds to 1st stage of crab, The transparency of the water body in the seedling pond is between 25-40 cm, the water color is yellow-green in Z1-Z5 stages, and the water color is brown in M-C1 stages, Z1 Initial hatching on the first day directly in water at 1 x 10 5 -5 x 10 5 ind / L of liquid of the golden alga, daily feeding using a concentration of 1 x 10 6 -5 x 10 6 ind / ml of green baffle algae, 2-4 hours of intensive live rotifer, the density of the ball is 2.4 x 10 4 -3.6 x 10 4 / m 3 ; Z2 phase daily directly in water according to 1 x 10 6 -5 x 10 6 ind / L of seawater Chlorella liquid, daily feeding using a concentration of 1 x 10 6 -5 x 10 6 ind / ml of small new moon-shaped algae liquid with a concentration of 1 x 10 8 -5 x 10 8 CFU / mL of lactic acid bacteria photosynthetic bacteria complex strain liquid to strengthen 2-4 hours of live rotifer, with a density of 2.4 x 10 4 -3.6 x 10 4 ind / m 3 L Z3 stage daily feeding using concentration of 1 x 10 6 -5 x 10 6 ind / ml small new moon rhombus shape algae liquid with concentration of 1 x 10 8 -5 x 10 8 CFU / ml lactic acid bacteria photosynthetic bacteria complex strain liquid to strengthen 2-4 hours of live Artemia, the density of 8 x 10 3 -1.2 x 10 4 / m 3 ; Z4 stage daily directly in water 1 x 10 6 -5 x 10 6 ind / L of seawater Chlorella liquid, daily feeding using 1 x 10 6 -5 x 10 6 ind / ml of small new moon-shaped algae liquid and 1 x 10 6 -5 x 10 6 ind / ml of spherical isogold algae liquid to form a combination of algae with 1 x 10 8 -5 x 10 8 CFU / mL of lactic acid bacteria photosynthetic bacteria complex strain liquid to strengthen 2-4 hours of live Artemia, the density is 8 x 10 3 -1.2 x 10 4 individuals / m 3 ; Z5 daily directly in water at 1 x 10 6 -5 x 10 6 ind / L of seawater Chlorella liquid, daily feeding with 1 x 10 6 -5 x 10 6 ind / ml of Parietochloris incisa liquid with 1 x 10 6 -5 x 10 6 ind / ml of Phaeodactylum tricornutum liquid to form a combined algae to 1 x 10 8 -5 x 10 8 CFU / mL of lactic acid bacteria photosynthetic bacteria complex strain liquid to strengthen 2-4 hours of live Artemia, with a density of 8 x 10 3 -1.2 x 10 4 individuals / m 3 ; During the M phase, administer 1×10 mg of the solution directly in the water daily. 5 -5×10 5 Add *Rhizoctonia solani* solution at ind / L, and feed 8×100 mg / day. 3 -1.2×10 4 pcs / m 3 Live brine shrimp are harvested as crab larvae when they have fully metamorphosed from the M stage to the C1 stage. During the seedling process, the water is not changed in Z1-Z2 stages, 25-30% of the water volume in the culture pond is changed every 3 days in Z3-Z5 stages, 40-50% of the water volume in the culture pond is changed on the first day of M stage, and then the water is not changed; the ammonia nitrogen is less than 0.02 mg / L, and the dissolved oxygen in the water body is more than 5 mg / L, wherein a small amount of air is supplied in Z1-Z2 stages to make the water body show a slight wave, and the air supply amount is increased in Z3-C1 stages to make the water body show boiling state; The water temperature in the seedling pond is controlled to be 23-26℃, the pH value is controlled to be 7-8, the salinity in Z1-Z5 stages is controlled to be 26-33, and the salinity in Z5-C1 stages is controlled to be 20-25; In terms of light control, the indoor artificial light is adjusted to be 3000-5000 lx, and the light time is from 6 am to 18 pm every day.

2. The method according to claim 1, wherein: wherein In step A, the seawater is filtered by microfiltration membrane, disinfected twice by sodium hypochlorite, and fully aerated in dark room to eliminate primary algae in 3-4 days; 3. The method according to claim 1, wherein: The release concentration of the newly hatched Chydorus phaeros is 10000-50000 / m 3 .

4. The method according to claim 1, wherein: wherein In step B, the total microalgae biomass was strictly controlled at 10 5 -10 8 ind / L, and the microalgae biodiversity index was greater than 1.

12.

5. The method according to claim 1, wherein: wherein The algal liquid of the microalgae is pure algal species culture to 10 5 The microalgae culture solution contains 5-10% of ferric citrate, 5-10% of ammonium chloride, 5-10% of sodium silicate and 5-10% of potassium dihydrogen phosphate, and is cultured at 25-30°C for 5-7 days, and is irradiated by 6000-7000 lx incandescent lamp for 24 hours. The culture method of the compound bacterial species of lactic acid bacteria and photosynthetic bacteria used in combination is as follows: the pure bacterial species is anaerobically cultured in sterile culture medium at 25-30℃ for 5-7 days, and the precipitated bacteria are collected and separated, wherein, Each liter of the sterile culture medium contains 1g of NH4Cl, 0.2g of MgCl2, 0.1g of yeast extract, 0.5g of K2HPO4, 2g of NaCl, 15-20g of agar, and 5-10g of glucose.

6. The method according to claim 1, wherein: The culture temperature of rotifers and Artemia is 26-30℃, the salinity is 25-33, and the rotifers and Artemia are fully aerated and fed with special compound feed every day; wherein, The nutrition enhancement method of rotifers is as follows: the active rotifers are filtered by 250 mesh screen, soaked in the mixed liquid of bacteria and algae for 2-4 hours, then filtered by 250 mesh screen after enhancement, and fed; ​ The method for nutritionally enhancing brine shrimp is as follows: live brine shrimp larvae at the bottom are picked up by means of static precipitation, the shells are removed, the larvae are soaked in the mixed liquid of bacteria and algae for 2-4 hours, and then the enhanced brine shrimp is filtered with a 250-mesh screen for feeding.

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