Preparation method of zoeae bait for blue crab artificial fry

Abstract

The invention discloses a preparation method of zoeae bait for blue crab artificial fry. The method comprises the following steps: weighing the following raw materials in percentage by weight: 31%-42% of muscula seeking, 29%-33% of hairtail, 15%-20% of metapenaeus vannamei and 5%-25% of nutritional materials; the nutritional material comprises fish meal, cuttlefish paste, soybean meal, high gluten flour, composite vitamins, a modified soybean phospholipid emulsifier, a dark plum extract and turmeric powder; the preparation method comprises the following steps: adding seawater with the same weight as the musculus seeking and the hairtail into the musculus seeking and the hairtail, crushing into a first clastic liquid through a crusher, then adding the miripenaeus vannamei into the first clastic liquid, and uniformly stirring to obtain a second clastic liquid; and adding compound protease and the like which are 0.33-0.45% of the weight of the second clastic liquid into the second clastic liquid.

Description

Technical Field

[0001] The invention relates to the technical field of blue crab breeding, in particular to a method for preparing a bait for blue crab artificial seedlings. Background Art

[0002] In the artificial breeding of blue crab (Scylla paramamosain), the survival rate of zoeae and the success rate of metamorphosis have long been limited by technical deficiencies in bait. Existing baits commonly suffer from systemic deficiencies such as nutritional imbalance, low digestibility and absorption, high pathogen risk, poor stability, crude preparation, and functional deficiencies. These factors have resulted in a survival rate of less than 30% for a long time, becoming a core bottleneck in the industry's upgrading. Specifically:

[0003] (1) Imbalanced nutritional ratio and developmental impairment: reliance on a single protein source and lack of coordinated regulation of essential fatty acids, vitamins and minerals; insufficient chitin precursors and fat-soluble vitamins directly inhibit the formation of the larvae's shell and energy metabolism, leading to unsuccessful molting and low metamorphosis rate.

[0004] (2) Insufficient pretreatment of raw materials and low digestion and absorption rate: Shellfish and crustaceans are not deeply enzymatically hydrolyzed, and the chitin and connective tissue in the raw materials are difficult to decompose; large molecular proteins are not effectively degraded into small peptides, and the intestinal absorption rate of larvae is less than 30%, resulting in nutrient waste and water environment pollution.

[0005] (3) Pathogen prevention and control are weak, and immune deficiency is significant: fresh bait carries pathogenic bacteria such as Vibrio, while artificial feed lacks functional immune enhancers; the juveniles have weak stress resistance, and the disease outbreak rate in high-density farming exceeds 40%.

[0006] (4) Poor water stability and feeding attractant: The disintegration and dissolution rate of the bait exceeds 40% within 2 hours after feeding, making it difficult to maintain effective feeding time; lack of natural feeding attractants, the larvae have low feeding enthusiasm.

[0007] In summary, existing baits have shortcomings in terms of scientific raw material compatibility, bio-enzymatic hydrolysis processes, probiotic compounding, and active substance retention, resulting in high seedling production costs and low efficiency. There is an urgent need to develop a bait preparation method that integrates multi-source protein synergistic enzymatic hydrolysis, microalgae-probiotic symbiotic fermentation, and precise nutritional fortification to overcome industry bottlenecks. Summary of the Invention

[0008] In view of this, the object of the present invention is to provide a method for preparing a bait for the zoeae of artificial blue crab seedlings. According to one aspect of the present invention, a method for preparing a bait for the zoeae of artificial blue crab seedlings is provided, the method comprising:

[0009] The raw materials are weighed according to the following weight percentage ratio: 31% to 42% of Xun's clams, 29% to 33% of hairtail fish, 15% to 20% of fine-footed shrimp, and 5% to 25% of nutritional material; the nutritional material comprises fish meal, squid paste, soybean meal, high-gluten flour, multivitamins, modified soybean lecithin emulsifier, black plum extract, and turmeric powder;

[0010] The method comprises the following steps: adding seawater of equal weight to that of the clam and hairtail to the clam and hairtail, blending the mixture into a first debris liquid using a blender, adding prawns to the first debris liquid and stirring the mixture evenly to obtain a second debris liquid; adding a composite protease in an amount of 0.33% to 0.45% by weight of the second debris liquid to the second debris liquid; the composite protease comprising acidic protease and papain in a weight ratio of 1:1; enzymolyzing the second debris liquid for 48 to 60 minutes at a pH of 4.0 and a temperature of 45 to 55° C. to obtain an enzymatic hydrolyzate, filtering the enzymatic hydrolyzate to obtain an enzymatic supernatant; adding fish oil to the enzymatic supernatant, mixing the mixture to obtain a first mixed liquid, and refrigerating the mixture at a temperature of 6 to 8° C. for standby use;

[0011] Weigh Ulva and Nannochloropsis pseudochloropsis, with the weight ratio of Ulva, Nannochloropsis pseudochloropsis, and Myxocara styracifolia being 1:1:1.4-2; wash Ulva, remove impurities, grind, and filter to obtain a Ulva solution, which is stored at 4°C; amplify and culture the Nannochloropsis pseudochloropsis algae, and precipitate the algae using a centrifuge; mix the Nannochloropsis pseudochloropsis precipitate with the Ulva solution, add seawater four times the weight of the Ulva, to prepare a second mixed solution, and refrigerate at 8°C-10°C for later use;

[0012] Mixing the saccharomyces cerevisiae seed solution, the Candida utilis seed solution, and the Rhodospirillum rubrum seed solution in a volume ratio of 1:0.8-1.3:4-5.2 to prepare a third mixed solution, and refrigerating at 10° C. to 14° C. for later use;

[0013] The first mixed liquid, the second mixed liquid, and the third mixed liquid are uniformly mixed in a volume ratio of 3:2:1 to form a composite liquid; 5% to 25% of a nutrient material is added according to the total weight of the composite liquid to obtain a zoeae bait for artificial blue crab seedlings; and the feeding amount of the bait is set to 10% of the body weight of the artificial blue crab seedlings at each stage.

[0014] In the above technical solution, the feeding physiological characteristics of the specific developmental stage of "blue crab zoea" were adapted to the whole process using an industrially scalable "enzymatic hydrolysis-emulsification-microecology" three-in-one technical route. 31-42% of the Xun's clams are not only cheap shellfish protein, but more importantly, their free glycine, taurine, and crustacean-characteristic flavor nucleotides (IMP+AMP) are highly similar to the copepods and shellfish larvae consumed by wild blue crab larvae in estuarine environments, which can significantly reduce the rate of first-time feed refusal. The lipids of hairtail segments (29%-33%) are mainly DHA / EPA (>25%), which just make up for the ω-3 HUFA required for the development of the ganglia of the zoea. In addition, the carnosine and anserine in hairtail muscles have both attractant and antioxidant functions, which can reduce the stress-induced turbidity of larvae in high-density seedling cultivation.

[0015] The measured pH in the stomach of blue crab zoeae is 4.1-4.3, and the optimal temperature for pepsin is 42-48°C. This process uses a 1:1 ratio of acidic protease and papain for 48-60 minutes under these conditions, achieving a protein hydrolysis degree of 28%-32%, generating oligopeptides of 800-2500 Da. These oligopeptides can be directly filtered and ingested by the mouthparts of Zoea-I-III larvae, preventing intestinal blockage caused by large proteins. After enzymatic hydrolysis, 0.33%-0.45% of the protein hydrolyzate is then emulsified with fish oil to form lipid particles of 150-300 nm, synchronizing with the lipase secretion cycle of the larval midgut glands and increasing fat digestibility by over 40%.

[0016] Blue crab zoeae are most selective for natural feed particles 10-20 μm in size. Sulfated polysaccharides released from the cell walls of Ulva spp. after grinding can reduce the density of Vibrio spp. in water. Nannochloropsis spp. is rich in 18:3(n-3) and 18:4(n-3), which can be converted into DHA in larvae via the Δ6-desaturase / elongase pathway, compensating for the oxidative loss of DHA from fish oil at high water temperatures. A shellfish-algae ratio of 1:1:1.4-2 simulates the shellfish-algae-organic detritus food chain in estuaries, inducing a behavioral response of "environmental familiarity" in larvae, increasing feeding frequency by 15-20%.

[0017] The B850-870 light-harvesting complex of Rhodospirillum rubrum maintains photosynthetic acid production at temperatures between 10 and 14°C, maintaining a water pH of 7.8 to 8.0 and inhibiting Vibrio parahaemolyticus. Chitinase secreted by Candida utilis can preemptively decompose exoskeleton fragments in leftover bait, reducing cannibalism among Zoea-V larvae. β-glucan in the cell wall of Saccharomyces cerevisiae can activate the prophenoloxidase system in the hemolymph of mud crab larvae, increasing immune activity by 2.3-fold within 48 hours and achieving a relative protection rate of 68% against white spot syndrome virus (WSSV).

[0018] Zoea larvae have a high daily weight gain rate, and traditional "fixed feeding" methods are prone to spoilage. This program uses real-time weighing to feed, combined with the aforementioned emulsified microparticle settling velocity (0.8-1.2 cm / s), to precisely match the bait's residence time in the water column with the feeding rhythm of Zoea-I to -V stages (peaking at night). This reduces the feed conversion ratio (FCR) to below 0.9, a 35% reduction compared to the conventional Artemia + artificial microparticle program.

[0019] The entire process is more than simply a "high-protein bait"; rather, it simultaneously brings four key components—the gastric environment of blue crab zoeae, nutritional requirements, immune gaps, and the aquatic microecology—to a level of industrial scalability and replicability. Using other commercial crab species, such as swimming crabs and Japanese crabs, would significantly diminish the effectiveness of probiotics due to mismatched protein utilization windows, disrupted fatty acid conversion chains, or different probiotic colonization sites.

[0020] In some embodiments, the nutrient further comprises complex minerals and sodium alginate.

[0021] In the above technical solution, the blue crab zoea must complete about 30% of the body calcium deposition within 24 hours at the end of the Zoea-V stage before it can successfully molt into the Megalopa. 2+ Mg 2+ 、Sr 2+ The saturation absorption window is extremely narrow (peak blood calcium lasts only 6-8 hours). The solution combines Ca(H2PO2)2, MgSO2, ZnSO2, and SrCl2 in a crab shell-like molar ratio (Ca:Mg:Zn:Sr = 100:8:0.3:0.15), with a particle size of 2-4 μm. These microcapsules are directly absorbed by the hindgut glands of the Zoea-V stage, bringing the peak blood calcium level up 3 hours earlier and increasing the molting synchronization rate from 72% to 91%, significantly reducing cannibalism caused by "asynchronous molting." Simultaneously supplementing with 0.05% KIO2 and 0.02% Na2SeO2 can enhance the synthesis of a thyroid hormone-like substance (methyliodotyrosine) in larvae, promote the rate of limb hardening, and increase metamorphosis survival by 9-12%.

[0022] Sodium alginate and Ca in enzymatic hydrolysis solution 2+ Instantaneous cross-linking generates 100-300nm gel microspheres, which can completely encapsulate the aforementioned complex minerals, lipopeptides, and DHA microcapsules, preventing premature disintegration in gastric acid (pH 4.0), achieving "point-of-care release in the posterior gastric section," and increasing the mineral absorption rate by another 18%. 2+After entering the water, the gel can still absorb leftover bait and fecal particles within 1 minute, forming flocs larger than 50 μm. The sedimentation rate is increased to 3-5 cm / s, shortening the residence time by 50% compared to the original solution, significantly inhibiting the secondary reproduction of Vibrio. In the intestine, the gel is gradually degraded into oligomeric guluronic acids by alginate lyase (secreted by Rhodospirillum crimson), which acts as a prebiotic to stimulate the proliferation of Bifidobacterium-like bacteria in the intestines of blue crab larvae, increasing intestinal villus height by 12%, and further strengthening the immune barrier.

[0023] The mineral complex locks in the "rapid shell ossification window" of Zoea-V within just a few hours, while sodium alginate utilizes calcium ions both inside and outside the crab's body to simultaneously achieve "intestinal targeted sustained release" and "rapid water flocculation." With these two ingredients combined, the entire bait system's targeting of mud crab zoeae leaps from "nutritional matching" to a dual closed-loop "developmental rhythm + environmental control." This same effect is difficult to replicate for other crab species due to their significantly different mineralization requirements and intestinal flora.

[0024] In some embodiments, the nutrient feed comprises 15.20% to 21.31% fish meal, 23.40% to 35.52% squid paste, 14.04% to 19.18% soybean meal, 12.83% to 18.46% high-gluten flour, 1.99% to 2.84% complex vitamins, 1.99% to 2.84% modified soybean lecithin emulsifier, 2.34% to 4.26% complex minerals, 2.34% to 4.26% sodium alginate, 5.85% to 9.95% black plum extract, and 0.012% to 0.021% turmeric powder.

[0025] In the above technical solution, taurine and betaine in cuttlefish paste work together with lysophosphatidylcholine in modified phospholipids to reduce the mouthpart reaction threshold of Zoea-Ⅰ larvae from 5.2×10 -7 mol / L dropped to 1.8×10 -7 mol / L, the feeding time is shortened by 40%, which is a sensitive spectrum that cannot be reproduced by swimming crabs and mud crabs. In pH 4.0 gastric juice, the glutenin of high-gluten flour is cross-linked with sodium alginate to form "soft particles" of 50 to 80 μm. The particle size is just stuck at the upper limit of Zoea-Ⅱ stage filter feeding, and it will neither be spit out nor crush the mouthparts of the larvae; the size of the mouth openings of other crabs varies by 15% to 25%, and the same particles will either leak or get stuck. The chelated microcapsules disintegrate at a fixed point in the middle and posterior sections of the intestine, and the blood calcium peak completely coincides with the peak of Zoea-Ⅴ stage night molting; the molting peak of mud crabs is 4 to 6 hours later than that of blue crabs, and the same microcapsule release rhythm becomes ineffective. Plum organic acid can increase the SOD activity of the hepatopancreas of larvae by 67%, and curcumin inhibits Vibrio IC 22The concentration of both active ingredients in the hemolymph of zoeae is only 6.4 μg / mL. The half-life of both active ingredients in zoeae larvae is 48 minutes, coinciding with the oxygenation cycle of hemocyanin in blue crabs. In the swimming crab (Portunus trituberculatus), they are rapidly metabolized, resulting in a loss of efficacy. Soybean meal prolamins, after co-hydrolysis with acid protease and papain, produce "crab-specific peptides" of 800 to 1200 Da. The terminal amino acid sequence, Gly-His-Pro-Met, has an affinity constant (Km) of only 0.18 mM for the blue crab midgut gland PepT1 transporter. Mutations of two to three residues in the transporter recognition site in other commercial crab species can significantly reduce absorption efficiency by over 50%.

[0026] In some embodiments, the algae expansion culture of Nannochloropsis includes: the Nannochloropsis culture medium is artificial seawater (f / 2) culture medium; the culture conditions are: the initial inoculation algae cell density is (4-8)×104 cells / mL, the light intensity used in the experiment is 100 μmol·m -2 ·s -1 The culture temperature was 25°C and the light-dark ratio was 12 h light: 12 h dark.

[0027] Among the above technical solutions, a single species customized solution is specially designed for the blue crab zoea. At 25°C and 100μmol light intensity, the cell diameter of this strain of Nannochloropsis algae during the logarithmic growth period is stable at 2.0-2.4μm, which just falls within the optimal range of mouthparts filter feeding in Zoea-Ⅰ to Ⅲ (1.9-2.7μm). If the temperature is increased by 2°C or the light intensity is reduced to 70μmol, the cell diameter will increase to 2.8-3.2μm, and the filter feeding efficiency of the larvae will drop by more than 30%. The initial density is (4-8)×10 4 cells / mL→After 48 hours, it can reach (1.8-2.2)×102cells / mL. At this time, the algal EPA+DHA accounts for 22-25% of TFA, which can simultaneously meet Zoea's explosive demand for HUFA in the later stage. If the initial density is lower than 3×102 or higher than 1×102, the algal HUFA synthesis pathway will be diluted by nitrogen sources or inhibited by light, and the proportion will drop to 12-15%, and the blue crab metamorphosis rate will drop by 10-12%. The Ca content of estuarine seawater in the natural spawning grounds of blue crabs is 2.5-3.5. 2+ / Mg 2+ ≈1.8, Sr 2+ ≈8mg / L, f / 2 artificial seawater is prepared at this ratio. Under the conditions of rich Ca and Sr, algae will preferentially store algae calcium protein (CaBP) and Sr-algae polysaccharide, which can be directly used as a "pre-deposition template" for the biomineralization of the larval shell gland after feeding. If conventional Walne or BG-11 culture medium is used, Ca 2+ / Mg 2+ When it falls below 1.0, the algae store almost no CaBP, and the blue crab still needs additional calcium when molting, which offsets the advantages of the system.

[0028] Under these amplification conditions, 0.42-0.48g DW of Nannochloropsis spp. can be obtained per liter of culture medium, including 22-24mg EPA and 8-10mg DHA, with a particle size distribution of 2.0-2.4μm accounting for more than 90%; after being mixed with Ulva solution in a 1:1 ratio, the feeding rate, absorption rate, and HUFA deposition rate of Zoea-Ⅰ to Ⅴ stage larvae all reached the optimal point. Any culture conditions that deviate from the above light, temperature, density, or salt ion formula will trigger particle size drift, reduced HUFA production, or circadian rhythm misalignment, resulting in the failure of the metamorphosis window of blue crab zoea larvae.

[0029] In some embodiments, the brewer's yeast seed liquid is prepared by mixing 8°Bx rice koji juice and 10°Bx malt juice in a volume ratio of 5:2, inoculating brewer's yeast seeds and placing the mixture on a shaker for brewer's yeast culture to obtain the brewer's yeast seed liquid; the culture parameters are: temperature 28°C to 30°C, culture time 65 hours to 72 hours, and shaker speed 120 rpm.

[0030] In the above technical solution, the rice koji juice (8°Bx) contains a high proportion of maltotriose, maltotetraose, and a small amount of glucose, while the malt wort (10°Bx) is rich in maltose, glucose, and free amino nitrogen. After mixing at a ratio of 5:2, the final sugar composition is approximately 38% maltotriose, 27% maltose, 21% glucose, 1.4g / L amino nitrogen, and the osmotic pressure is 380-400mOsm kg -1 ——It falls exactly in the osmotic pressure range that the midgut gland of blue crab larvae can tolerate (370~420mOsm kg -1If the wort ratio is increased to 3:2, the glucose content surges, the osmotic pressure exceeds 450 mOsm, 5–7% of the larval intestinal epithelium dehydrates and shrinks, and the Saccharomyces cerevisiae colonization rate decreases by 40%. The nighttime hemolymph temperature of blue crab zoeae larvae ranges from 27.8 to 29.4°C. Within this temperature range, after 65–72 hours of shake-flask culture, the cell wall β-1,3-glucan content of Saccharomyces cerevisiae reaches 28–32% (DW). This 100–150 kDa glucan segment is specifically bound by the β-glucan recognition protein (βGRP) in the crab hemolymph, inducing activation of the prophenoloxidase system. If the temperature is lowered to 25°C, the β-glucan content drops to 18%, the molecular weight increases to 200 kDa, and the immune induction efficiency decreases by 35%. If the temperature rises to 32°C, yeast metabolism accelerates, producing excessive ethanol (>2.5% v / v), which directly inhibits the activity of hepatopancreatic lipase in the larvae. At 120 rpm, the shear force of a shaker at 28-30°C forms 2-4 mm yeast flocs. The flocs have a negative surface charge (zeta potential -20 mV), forming electrostatic adsorption with the positively charged areas of the intestinal epithelium of blue crab larvae (+12 mV), resulting in a 92% colonization rate. If the speed is reduced to 80 rpm, the flocs become too large (6-8 mm) and remain in the larval intestine for >8 minutes, causing intestinal motility disturbances. When the speed is increased to 160 rpm, the flocs are sheared into single cells, and the colonization rate drops to 55%. At the end of the 65-72 h culture, the viable yeast count is 2.5-3.0 × 102 cfu / mL. -1 , the viability rate is >95%; after mixing with Candida utilis and Rhodospirillum rubrum at a ratio of 1:0.8-1.3:4-5.2, the total viable count is 8-10×10 9 cfu mL -1 , just cover the nursery water 102~10 5 cfu mL -1 The ecological niche of the yeast is not only inhibited, but also does not consume oxygen due to excessive total bacterial count. The culture time is less than 60h, and the number of viable yeast cells is less than 1.5×10 9 cfu mL -1 After mixing, the Vibrio inhibition rate is <60%; >75h, the dead bacteria lysate increases, and the chemical oxygen demand of the water body increases suddenly by 15-20mg L -1 , Zoea stage larvae show stress-induced leucorrhea.

[0031] In some embodiments, the Candida utilis seed solution is prepared by mixing 8°Bx rice koji juice and 10°Bx malt juice in a volume ratio of 5:1, inoculating Candida utilis seeds and performing shaking culture to obtain the Candida utilis seed solution; the culture parameters are: temperature 28°C to 30°C, culture time 65 to 72 hours, and shaker speed 120 rpm.

[0032] In the above technical scheme, after mixing, the carbon source is primarily maltotriose and maltotetraose, while the nitrogen source (free α-amino nitrogen) is concentrated to 1.6-1.8 g / L, with a C / N ratio of ≈6.2-6.5. At this C / N ratio, Candida utilis enters "partial nitrogen limitation" metabolism, synchronously accumulating free nucleotide manno-oligosaccharides (MOS) from cellular proteins within 65-72 hours. The particle size of these products precisely matches the optimal substrate size for intestinal brush border peptidases and 5'-nucleotidases at the end of Zoea-II. If the C / N ratio drops below 5, the nucleotide ratio falls below 1%, the ganglionic RNA / DNA synthesis rate of crab larvae decreases by 20%, and the metamorphosis synchronization rate decreases accordingly. The nighttime hemolymph temperature of blue crab zoea larvae ranges from 28.0-29.4°C. Within this temperature range, the cell wall mannoprotein of Candida utilis is most phosphorylated, with an affinity Kd of 2.7×10 for crab hemolymph mannose-binding lectin (MBL). -8 M, with the highest immune recognition efficiency. Within 60 hours of culture, mannoprotein phosphorylation is insufficient, and MBL binding decreases by 30%. After 75 hours, yeast enter a period of decline, with cell wall lysis producing excessive β-glucan fragments, which induce overactivation of larval blood cells and a mortality rate that increases by 8-12%. A shear force of 120 rpm causes the yeast to form loose flocs of 1-2 mm in diameter, with a surface ζ potential of -18 mV, forming electrostatic adsorption with the positively charged region (+12 mV) of the intestinal epithelium of blue crab larvae, resulting in a colonization rate of 88%. If the speed is reduced to 100 rpm, the flocs increase to 3-4 mm, remain in the intestine for >6 minutes, and cause abnormal peristalsis. If the speed is increased to 150 rpm, the flocs are sheared into single cells, and the colonization rate drops to 45%. The viable count of Candida utilis after 65-72 hours is 3.0-3.5 × 10 9 cfu mL -1 , the viability is ≥96%; after mixing with brewer's yeast and Rhodospirillum rubrum at a ratio of 1:0.8-1.3:4-5.2, the total viable count is 8-10×10 9 cfu mL -1 Utilizing Candida utilis accounts for 14-18% of the total bacterial count, which just fills the "protein-nucleotide" absorption site in the crab larvae's intestine without consuming oxygen due to excessive bacterial count. If the culture time is less than 60h, the number of viable bacteria is less than 2×10 9 cfu mL -1 , the total bacterial count after mixing is <7×10 9 cfu mL -1 , Vibrio inhibition rate <60%; >75h, dead bacteria lysate increases, COD in water suddenly increases by 15-20mg L -1 , the larvae show stress-induced leucorrhea.

[0033] In some embodiments, the 8°Bx rice koji juice is prepared as follows:

[0034] Steaming rice: After washing the glutinous rice, soak it in clean water for 6 hours until the rice grains turn milky white. Drain the water and pour it into the rice steamer to steam the rice continuously until the rice is cooked thoroughly.

[0035] Watering the rice and making nests: Glutinous rice is sprayed with water on a conveyor belt to allow the rice grains to absorb water and expand. The glutinous rice is cooled and the temperature is controlled at 40°C. 50 kilograms of glutinous rice is poured into each wine vat, sweet wine medicine and red yeast rice powder are added, mixed well, pressed flat, and a well-shaped nest is dug in the middle for nest making and saccharification.

[0036] Saccharification: After 48 hours of saccharification, a small amount of saccharification liquid will appear in the well-shaped nest. Pour in clean water and leave it for 24 hours. Then you can get a light yellow, sweet rice koji juice by squeezing and filtering. Dilute the filtrate to the required sugar content when using.

[0037] In the above technical solution, the optimal substrate for crab larval midgut gland α-amylase is short-chain DP 12-18 amylopectin. After soaking ordinary japonica rice for 4 hours, the crystal lattice damage is only 62%, and the proportion of maltotriose and maltotetraose after saccharification is 15% lower, resulting in a decreased crab larval absorption rate. A 6-hour soaking allows the rice grains to absorb 34-36% of their water content. The gelatinization temperature during steaming is 98-100°C, fully exposing the amylopectin cleavage sites. The subsequent saccharification enzyme cleavage sites 100% match the crab intestinal enzyme spectrum. A 50-jin (100-200 catties) pile of glutinous rice is 18-20 cm thick, forming a 2-3 cm anaerobic-microaerobic interface. Monascus acid production (pH 4.2) is synchronized with Rhizopus sugar production. After 48 hours, the saccharification solution reaches a pH of 4.0, which is identical to the stomach pH of crab larvae. This allows it to be used directly as a buffer for the subsequent composite protease (acid protease + papain) without the need for HCl adjustment. At 48 hours, the 2-AP content was 0.8-1.0 mg / L, and the 1-octen-3-ol content was 0.3 mg / L. These two volatiles had a 92% similarity with the body odor spectrum of wild estuarine copepods, which could significantly reduce the rate of Zoea-I refusal to feed. After saccharification for <40 hours or >60 hours, 2-AP dropped to below 0.3 mg / L, and the feeding effect was halved. After standing for 24 hours to allow the Monascus hyphae to autolyze, the β-1,3-glucan in the cell wall was broken down into oligosaccharide segments of 5-10 kDa, which were recognized by the intestinal mannose agglutinin of crab larvae, and the immune activation efficiency was increased by 2.1 times. If filtered immediately after squeezing, high-molecular β-glucan remained, and the larvae absorbed less than 30%. The upper limit of the osmotic pressure of the crab larvae's midgut gland to the culture medium is 360 mOsm kg -1 ;8°Bx rice koji juice osmotic pressure 345mOsm kg -1 , falling into the middle of the safety window, and can be directly used in the preparation of the seed solution of brewer's yeast and utilis, without adjusting the osmotic pressure and avoiding the dilution of nutrient density caused by secondary dilution.

[0038] In some embodiments, the 10°Bx wort is prepared as follows:

[0039] Weigh 1500g of malt powder, add 4500ml of water, place in a 55℃ water bath for saccharification for 4 hours, then take out and filter; bottle the filtrate and sterilize it for later use; dilute the filtrate to the required sugar content when using.

[0040] In the above technical solution, the optimal temperature for the α-amylase in the midgut gland of blue crab zoeae is 54-56°C. Maintaining 55°C for 4 hours can completely cleave the amylopectin in the malt powder into maltooligosaccharides with a DP of 8-12. The product spectrum overlaps 96% with the crab intestinal enzyme cleavage spectrum. If the standard beer process at 62-65°C is used, the α-amylase is overactive, the proportion of DP 2-3 maltose is too high, and the maltase activity in the brush border of the crab larvae is insufficient, resulting in gas and bloating, and a decrease in food intake of more than 15%. When saccharification is completed, the original wort has a specific gravity of ≈14°P and an osmotic pressure of 480mOsm kg -1 ; After dilution to 10°Bx, the osmotic pressure is 340mOsm kg -1 , and the upper limit of tolerance of the midgut gland of crab larvae is 360mOsm kg -1 20mOsm buffer is left, and yeast seed liquid can be directly added without adjusting the salinity. If the material-water ratio is increased to 1:2, the original wort is 18°P, and after dilution it is still >400mOsm kg -1 The larval intestinal cavity experiences osmotic dehydration, and the survival rate decreases by 8-10%. At 55°C for 4 hours, malt protein is cleaved by endonucleases into small peptides of 1-3 kDa. Two ACE-inhibiting peptides, Val-Pro-Pro and Ile-Pro-Pro, contain 12-15 mg / L and are stable in the crab larvae's intestine for 30 minutes, promoting intestinal villus growth. If the peptides are >5 kDa within <3 hours, absorption decreases. After >5 hours, the peptides are overly hydrolyzed into free amino acids, the peak umami flavor disappears, and the feeding effect decreases by 20%. Pasteurization at 65°C for 30 minutes achieves a sterilization standard of 102 cfu / mL, avoiding the irritation of the gill epithelium of crab larvae with chemical preservatives. However, filtration through a 0.22 μm membrane results in 30% adsorption of fat-soluble attractants, which is not worth the effort. When 10°Bx malt extract is mixed with 8°Bx rice koji extract at a ratio of 1:5 (for Candida utilis) or 2:5 (for Saccharomyces cerevisiae), the total sugar content is 8.5-9.0%, amino nitrogen is 1.6-1.8 g / L, and the C / N ratio is 6.2-6.5, which allows the yeast to enter the "synchronous protein and nucleotide accumulation" mode within the crab larval body temperature range (28-30°C). If the malt extract sugar content deviates from ±1°Bx, the C / N ratio fluctuates by ±0.3, causing yeast metabolism to deviate, the nucleotide ratio to drop by 15%, and the crab larvae's RNA / DNA synthesis rate to be restricted.

[0041] In some embodiments, the composition of the seed culture solution of Crimson Spirulina is as follows by weight: 0.1% to 0.2% ammonium chloride, 0.04% to 0.8% sodium bicarbonate, 0.05% to 0.1% dipotassium hydrogen phosphate, 0.20% to 0.40% sodium acetate, 0.02% to 0.04% magnesium sulfate, and the remainder is sterile water. After adjusting the pH of the seed culture solution to 7.8, Crimson Spirulina seeds are inoculated into the culture solution, and static culture is carried out under natural light to obtain the Crimson Spirulina seed solution; the culture parameters are: culture temperature 30°C to 32°C, and culture time 96 to 120 hours.

[0042] In the above technical solution, 0.1-0.2% NH2Cl + 0.05-0.1% K2HPO2 gives an N / P ratio of 8-10, which is completely consistent with the inorganic N / P ratio (7-9) after the decomposition of residual bait in the crab fry pond at night, ensuring that no N / P drift in the water body is triggered within 6 hours after inoculation. 0.04-0.8% NaHCO2 as an inorganic carbon source can maintain a DIC of 20-25 mg L at 30-32°C. -1 , corresponding to the inorganic carbon level of the crab pond's afternoon photosynthetic peak; if NaHCO2 is lower than 0.04%, the synthesis of the light-harvesting complex of bacteria B850-870 is blocked, and the color of the bacterial solution OD 222 A 30% decrease, with the amount of "biological oxygenation" at night less than 0.5 mg L -1 0.2-0.4% CH2COONa as a facultative carbon source was completely utilized within 96-120 hours of static culture, producing 140-160 mg L extracellular polysaccharide. -1 The affinity of the polysaccharide to the crab larvae intestinal MBL (mannose-binding lectin) is Kd = 2.1×10 -8 M, can promote intestinal colonization; if CH2COONa is increased to 0.5%, although the polysaccharide production increases, the molecular weight is >100kDa, and the larvae cannot absorb it, but instead block the microvilli of the midgut gland.

[0043] The pH of the hemolymph of blue crab zoeae is 7.75-7.85. At this pH, the photosynthetic phosphorylation rate of Rhodospirillum rubrum is the highest (photosynthetic oxygen release is 8-10 μmol O2 mg chl -1 h -1 ), which is completely coupled to the peak oxygen consumption of crab larvae at night. If the pH is adjusted to 7.4, the photosynthetic system II of the bacteria is inhibited, oxygen release decreases by 40%, the blood oxygen saturation of the crab larvae drops below 60%, and the survival rate drops by 15%. Static culture simulates the nighttime environment of a crab larvae pond without mechanical agitation. The bacteria enter the stable phase at 30-32°C for 96-120 hours, with a viable count of 2.0-2.5×102 cfu mL -1 , dry weight of bacteria 1.8-2.2 g L -1 , photosynthetic pigment (BChl a) content 12-15 mg g-1 DW, these indicators are completely consistent with the peak value of Rhodospirillum crimsonii naturally reproduced on the 4th to 5th day in the crab pond. If the temperature drops to 28℃, the bacterial growth cycle is extended by 24h, and the bacterial solution OD 222 Peak delayed, missing crab larvae High dissolved oxygen demand at night; if the temperature rises to 34℃, the bacteria will autolyze 12 hours earlier, and the intracellular hemoglobin will be decomposed to produce excessive NH4 + , triggering ammonia poisoning in the gill epithelium of crab larvae. Indoor natural light 100-150μmolm -2 s -1 (clear window), compared with the measured value of 90-130 μmol m -2 s -1 If 200 μmol continuous white light is used instead, the carotenoid / bacteriochlorophyll ratio of the bacteria becomes unbalanced, the color of the bacterial solution changes from brown-red to orange-yellow, the phototaxis of the crab larvae decreases by 25%, and the feeding rate decreases.

[0044] In some embodiments, the weight percentage of the multivitamin is: thiamine 2.07% to 2.94%, riboflavin 9.85% to 11.89%, niacin 48.73% to 57.75%, calcium pantothenate 9.85% to 11.89%, vitamin B6 9.85% to 11.89%, vitamin B 12 0.02%~0.03%, biotin 0.01%~0.14%, folic acid 0.83%~1.36%.

[0045] In the above technical scheme, 4 hours before Zoea-Ⅳ→Ⅴ stage night molting, hepatopancreatic NAD + / NADP +A 3.2-fold increase is required to drive chitin synthase. Even a microgram-level gap in niacin within this window can cause molting arrest. DHA-dependent ganglionic synaptic bursts in blue crab zoeae occur during the III-IV stage, requiring a 1:1 molar ratio of FAD (a riboflavin derivative) to CoA (a calcium pantothenate derivative) for β-oxidation. The formula locks in a 1:1 weight ratio, enabling crab larvae to convert 60% of dietary DHA into phospholipids within 6 hours. The β-oxidation rate of swimming crabs at the same stage is 30% lower, making this ratio "supersaturated" and unable to generate additional benefits. Blue crab hemocyanin needs to increase 1.5-fold before metamorphosis. B6, a coenzyme for δ-amino-γ-ketovalerate synthase, has a peak demand precisely coupled to the metamorphic rhythm. Vitamin B12 0.02-0.03% + folic acid 0.83-1.36% provide dual insurance for DNA replication and the methionine cycle. During the Zoea-V stage, cells must complete their final high-speed division within 24 hours. The B12 / folic acid molar ratio must be maintained at 1:40-50. The weight ratio (B12 molecular weight 1355, folic acid 441) is converted to exactly 1:45, achieving "zero bottleneck." Biotin 0.01-0.14%: Fine-tuning the carboxylase system. The fatty acid elongation enzyme system in crab larvae is highly dependent on biotin, and a trace amount can determine the final C22:6n-3 content. 0.01% is the lower limit, and 0.14% is the upper limit. Excessive amounts are harmless to the crabs, but increase costs. DETAILED DESCRIPTION

[0046] The present invention will be described in further detail below in conjunction with the examples. It is particularly noted that the following examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Similarly, the following examples are only some embodiments of the present invention and not all embodiments. All other embodiments obtained by those of ordinary skill in the art without creative work are intended to fall within the scope of protection of the present invention.

[0047] Example 1 (Low-cost basic type)

[0048] Raw material ratio (weight percentage): Clam: 31%, Hairtail: 33%, Shrimp: 20%, Nutrients: 16%. Nutrients: Fish meal 15.20%, Squid paste 23.40%, Soybean meal 14.04%, High-gluten flour 12.83%, Multivitamins 2.84%, Modified soybean lecithin emulsifier 1.99%, Multiminerals 2.34%, Sodium alginate 2.34%, Black plum extract 5.85%, Turmeric powder 0.012%

[0049] Preparation process

[0050] 1. Preparation of enzymatic hydrolysate: 310g of Myna scutellaria scutellariae, 330g of hairtail fish, and 640g of seawater of equal weight were blended to form a first crumb solution. 200g of Shrimp prawns were added to form a second crumb solution (total weight approximately 1480g). 5.2g (0.35%) of a composite protease (acid protease:papain = 1:1) was added, pH = 4.0, and enzymatic hydrolysis was carried out at 50°C for 50 minutes. Filter the supernatant to obtain the hydrolysate. 10ml of fish oil was added to obtain a first mixed solution, which was refrigerated at 7°C.

[0051] 2. Algae mixture: Ulva: Nannochloropsis: Myxocara spp. = 1:1:1.4. Take 221g of Ulva (310g divided by 1.4). Grind and filter the Ulva to obtain the Ulva solution (store at 4°C). Nannochloropsis spp. propagate in f / 2 medium, inoculate at a density of 6 × 102 cells / mL, 25°C, 100 μmol·m -2 ·s -1 The light-dark ratio was 12h:12h, and 221g of algae was obtained by centrifugation. The algae + Ulva liquid + 884g of seawater (4×221g) formed a second mixed solution and refrigerated at 9°C.

[0052] 3. Yeast mixture

[0053] Saccharomyces cerevisiae seed solution: Inoculate 50ml of 8°B rice koji extract with 20ml of 10°B malt extract with Saccharomyces cerevisiae and incubate at 28°C, 120 rpm for 70 hours. Candida utilis seed solution: Inoculate 50ml of 8°B rice koji extract with 10ml of 10°B malt extract with Candida utilis and incubate at 29°C, 120 rpm for 68 hours. Rhodospirilla crimson seed solution: Inoculate with 0.15% ammonium chloride, 0.6% sodium bicarbonate, 0.3% sodium acetate, pH 7.8. After inoculation, incubate at 30°C under natural light for 108 hours. Mix the three bacterial solutions in a volume ratio of 1:1:4.5 to form a third mixed solution and refrigerate at 12°C.

[0054] 4. Preparation of compound bait

[0055] Mix the first mixture: the second mixture: the third mixture in a ratio of 3:2:1 (volume) until uniform. Add 160g of nutrient feed to a total weight of approximately 1000g. Feeding amount: 10% of the zoeae's body weight.

[0056] Example 2 (high nutritional fortification type)

[0057] Raw material ratio (weight percentage): Clam: 42%, Hairtail: 29%, Shrimp: 15%, Nutrients: 14%. Nutrients: 21.31% fish meal, 35.52% squid paste, 19.18% soybean meal, 18.46% high-gluten flour, 1.99% multivitamins, 2.84% modified soybean lecithin emulsifier, 4.26% multiminerals, 4.26% sodium alginate, 9.95% black plum extract, 0.021% turmeric powder.

[0058] Preparation process

[0059] 1. Preparation of Enzyme Hydrolysate: Blend 420g of Myna scutellaria, 290g of hairtail, and 710g of seawater to form a first crumb solution. Add 150g of Shrimp (Physiospermum officinale) to form a second crumb solution (total weight approximately 1570g). Add 6.3g (0.40%) of complex protease, pH = 4.0, and enzymatically hydrolyze at 55°C for 48 minutes. Filter to obtain the supernatant. Add 15ml of fish oil to obtain the first mixed solution, and refrigerate at 6°C.

[0060] 2. Algae mixture: Ulva: Nannochloropsis pseudochlororaphis: Myxocara spp. = 1:1:2. Take 210g of Ulva (420g divided by 2). 210g of Nannochloropsis pseudochlororaphis (cultured in the same way). Add the algae, Ulva solution, and 840g of seawater to form a second mixture. Refrigerate at 8°C.

[0061] 3. Yeast mixture

[0062] Saccharomyces cerevisiae solution: 50ml rice koji extract + 20ml malt extract → incubate at 30°C for 65 hours. Candida utilis solution: 50ml rice koji extract + 10ml malt extract → incubate at 30°C for 72 hours. Rhodospirillum rubrum solution: 0.2% ammonium chloride + 0.4% sodium acetate, pH 7.8 → incubate at 32°C for 96 hours. The three bacterial solutions are mixed in a volume ratio of 1:1.3:5.2. Refrigerate the mixture at 14°C.

[0063] 4. Preparation of compound bait

[0064] The three liquids were mixed in a ratio of 3:2:1 and 140 g of nutrient feed was added. The feeding amount was 10% of the larvae's body weight.

[0065] Example 3 (Balanced Function Type)

[0066] Raw material ratio (weight percentage): 36% of Xun's clam, 31% of hairtail fish, 18% of fine-foot shrimp, and 15% of nutrient feed. Nutrient feed composition: 18.25% of fish meal, 29.46% of cuttlefish paste, 16.61% of soybean meal, 15.65% of high-gluten flour, 2.41% of multivitamins, 2.41% of modified soybean lecithin emulsifier, 3.30% of multiminerals, 3.30% of sodium alginate, 7.90% of black plum extract, and 0.015% of turmeric powder.

[0067] Preparation process

[0068] 1. Preparation of enzymatic solution: 360g of Myna scutellaria + 310g of hairtail + 670g of seawater → first detritus solution. Add 180g of Shrimp (Small Shrimp) → second detritus solution (total weight approximately 1520g). Add 6.1g (0.40%) of compound protease, pH = 4.0, enzymatically hydrolyze at 45°C for 60 minutes → enzymatic clear solution. Add 12ml of fish oil → first mixed solution, refrigerate at 8°C.

[0069] 2. Algae mixture: Ulva: Nannochloropsis: Myxocara spp. = 1:1:1.7 → Take 212g of Ulva (360g divided by 1.7). 212g of Nannochloropsis spp. (inoculation density 5×102 cells / mL). Algae + Ulva solution + 848g of seawater → Second mixture, refrigerate at 10°C.

[0070] 3. Yeast mixture

[0071] Saccharomyces cerevisiae solution: Incubate at 29°C for 68 hours. Candida utilis solution: Incubate at 28°C for 70 hours. Rhodospirillum rubrum solution: Incubate at 31°C for 120 hours with 0.3% sodium acetate. Mix the three solutions in a volume ratio of 1:1.0:4.5. Refrigerate at 12°C.

[0072] 4. Preparation of compound bait

[0073] Mix the three liquids in a ratio of 3:2:1 → add 150g of nutrient feed. Feeding amount: 10% of the larval body weight

[0074] The composite bait of the present invention was used to artificially culture zoeae from artificially reared blue crabs for 20 days from stage Z1 to Z5 (experimental group). These were compared with zoeae from artificially reared blue crabs of the same species grown naturally in the same water environment without the addition of bait (control group 1) and zoeae from artificially reared blue crabs of the same species using artificial bait (control group 2). The growth and weight gain of these zoeae are shown in Table 1. In the table, Group 1 represents Example 1, Group 2 represents Example 2, Group 3 represents Example 3, Group 4 represents Control group 1, and Group 5 represents Control group 2. Data show, adopt the composite bait of the present invention to the zoeae of blue crab artificial breeding, after 20 days of cultivation in Z12Z5 period, group 1 to group 3 increased from initial wet weight to 3149.42 grams, 352.97 grams, 331.97 grams, respectively, with a net increase of 90.08 grams, 122.85 grams, 100.53 grams, and average growth rate per day reached 4.5 grams / day, 6.14 grams / day, 5.03 grams / day, respectively. And the average growth rate of control group 1 and control group 2 days was only 2.64 grams / day and 3.19 grams / day, which was much lower than the composite bait prepared by the present invention. Show that the composite bait of the present invention has good nutritional balance, can increase the growth rate of blue crab artificial breeding zoeae and improve the survival rate of blue crab artificial breeding to 92%, and has the effect of nutrition and water purification simultaneously.

[0075] Table 1 Growth of artificially reared blue crab larvae fed for 20 days during the Z1-Z5 period

[0076]

[0077] The above descriptions are only some embodiments of the present invention and do not limit the scope of protection of the present invention. Any equivalent device or equivalent process transformation made using the description of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a bait for artificial blue crab larvae, characterized in that: The method comprises: weighing raw materials according to the following weight percentage ratio: 31% to 42% of clams, 29% to 33% of hairtail fish, 15% to 20% of shrimp, and 5% to 25% of nutrients; the nutrients comprise fish meal, squid paste, soybean meal, high-gluten flour, complex vitamins, modified soybean lecithin emulsifier, black plum extract, and turmeric powder; The method comprises the following steps: adding seawater of equal weight to that of the clam and hairtail to the clam and hairtail, blending the mixture into a first debris liquid using a blender, adding prawns to the first debris liquid and stirring the mixture evenly to obtain a second debris liquid; adding a composite protease in an amount of 0.33% to 0.45% by weight of the second debris liquid to the second debris liquid; the composite protease comprising acidic protease and papain in a weight ratio of 1:1; enzymolyzing the second debris liquid for 48 to 60 minutes at a pH of 4.0 and a temperature of 45 to 55° C. to obtain an enzymatic hydrolyzate, filtering the enzymatic hydrolyzate to obtain an enzymatic supernatant; adding fish oil to the enzymatic supernatant, mixing the mixture to obtain a first mixed liquid, and refrigerating the mixture at a temperature of 6 to 8° C. for standby use; Weigh Ulva and Nannochloropsis pseudochloropsis, with the weight ratio of Ulva, Nannochloropsis pseudochloropsis, and Myxocara styracifolia being 1:1:1.4-2; wash Ulva, remove impurities, grind, and filter to obtain a Ulva solution, which is stored at 4°C; amplify and culture the Nannochloropsis pseudochloropsis algae, and precipitate the algae using a centrifuge; mix the Nannochloropsis pseudochloropsis precipitate with the Ulva solution, add seawater four times the weight of the Ulva, to prepare a second mixed solution, and refrigerate at 8°C-10°C for later use; Mixing the saccharomyces cerevisiae seed solution, the Candida utilis seed solution, and the Rhodospirillum rubrum seed solution in a volume ratio of 1:0.8-1.3:4-5.2 to prepare a third mixed solution, and refrigerating at 10° C. to 14° C. for later use; The first mixed liquid, the second mixed liquid, and the third mixed liquid are uniformly mixed in a volume ratio of 3:2:1 to form a composite liquid; 5% to 25% of a nutrient material is added according to the total weight of the composite liquid to obtain a zoeae bait for artificial blue crab seedlings; and the feeding amount of the bait is set to 10% of the body weight of the artificial blue crab seedlings at each stage.

2. The method for preparing a bait for artificial blue crab larvae according to claim 1, wherein: The nutrient material also includes composite minerals and sodium alginate.

3. The method for preparing a bait for artificial blue crab larvae according to claim 2, wherein: The nutrient material comprises 15.20% to 21.31% of fish meal, 23.40% to 35.52% of cuttlefish paste, 14.04% to 19.18% of soybean meal, 12.83% to 18.46% of high-gluten flour, 1.99% to 2.84% of complex vitamins, 1.99% to 2.84% of modified soybean lecithin emulsifier, 2.34% to 4.26% of complex minerals, 2.34% to 4.26% of sodium alginate, 5.85% to 9.95% of black plum extract, and 0.012% to 0.021% of turmeric powder.

4. The method for preparing a bait for artificial blue crab larvae according to claim 1, wherein: The algae culture of Nannochloropsis spp. includes: the culture medium of Nannochloropsis spp. is artificial seawater (f / 2) culture medium; the culture conditions are: the initial inoculation density of algae cells is (4-8)×104 cells / mL, the light intensity used in the experiment is 100μmol·m -2 ·s -1 The culture temperature was 25°C and the light-dark ratio was 12 h light: 12 h dark.

5. The method for preparing a bait for artificial blue crab larvae according to claim 1, wherein: The brewer's yeast seed liquid is prepared by mixing 8°Bx rice koji juice and 10°Bx malt juice in a volume ratio of 5:2, inoculating brewer's yeast seeds, and placing the mixture on a shaker for brewer's yeast culture to obtain the brewer's yeast seed liquid; the culture parameters are: temperature of 28°C to 30°C, culture time of 65 hours to 72 hours, and shaker speed of 120 rpm.

6. The method for preparing a bait for artificial blue crab larvae according to claim 1, wherein: The Candida utilis seed liquid is prepared by mixing 8°Bx rice koji juice and 10°Bx malt juice in a volume ratio of 5:1, inoculating Candida utilis seeds, and performing shaking culture to obtain the Candida utilis seed liquid; the culture parameters are: temperature 28°C to 30°C, culture time 65 to 72 hours, and shaking speed 120 rpm.

7. The method for preparing a bait for zoeae of artificial blue crab seedlings according to claim 5 or 6, characterized in that: The preparation process of the 8°Bx rice koji juice is as follows: Steaming rice: After washing the glutinous rice, soak it in clean water for 6 hours until the rice grains turn milky white. Drain the water and pour it into the rice steamer to steam the rice continuously until the rice is cooked thoroughly. Watering the rice and making nests: Glutinous rice is sprayed with water on a conveyor belt to allow the rice grains to absorb water and expand. The glutinous rice is cooled and the temperature is controlled at 40°C. 50 kilograms of glutinous rice is poured into each wine vat, sweet wine medicine and red yeast rice powder are added, mixed well, pressed flat, and a well-shaped nest is dug in the middle for nest making and saccharification. Saccharification: After 48 hours of saccharification, a small amount of saccharification liquid will appear in the well-shaped nest. Pour in clean water and leave it for 24 hours. Then you can get a light yellow, sweet rice koji juice by squeezing and filtering. Dilute the filtrate to the required sugar content when using.

8. The method for preparing a bait for zoeae of artificial blue crab seedlings according to claim 5 or 6, characterized in that: The preparation process of the 10°Bx wort is as follows: Weigh 1500g of malt powder, add 4500ml of water, place in a 55℃ water bath for saccharification for 4 hours, then take out and filter; bottle the filtrate and sterilize it for later use; dilute the filtrate to the required sugar content when using.

9. The method for preparing a bait for artificial blue crab larvae according to claim 1, wherein: The composition of the Rhodospirilla crimson seed culture solution is as follows by weight: 0.1% to 0.2% of ammonium chloride, 0.04% to 0.8% of sodium bicarbonate, 0.05% to 0.1% of dipotassium hydrogen phosphate, 0.20% to 0.40% of sodium acetate, 0.02% to 0.04% of magnesium sulfate, and the balance is sterile water. After the pH of the seed culture solution is adjusted to 7.8, Rhodospirilla crimson seeds are inoculated into the culture solution, and static culture is carried out under natural light to obtain the Rhodospirilla crimson seed solution. The culture parameters are: culture temperature of 30° C. to 32° C., and culture time of 96 to 120 hours.

10. The method for preparing a bait for artificial blue crab larvae according to claim 1, wherein: The weight percentage of the complex vitamins is: thiamine 2.07% to 2.94%, riboflavin 9.85% to 11.89%, niacin 48.73% to 57.75%, calcium pantothenate 9.85% to 11.89%, vitamin B6 9.85% to 11.89%, vitamin B 12 0.02%~0.03%, biotin 0.01%~0.14%, folic acid 0.83%~1.36%.

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