Grass carp culture method and system capable of shortening sexual maturity time

Abstract

The invention belongs to the technical field of culture, and discloses a grass carp culture method capable of shortening sexual maturity time, which comprises the following steps: 1, parent screening; feeding with feed; managing water temperature. By systematically analyzing the synergistic effect of antioxidant regulation of tocopherol (vitamin E), feed nutrition optimization and water temperature accurate management, the sexual maturity period of large-scale cultured grass carp is successfully and stably controlled within 3 years. The breakthrough has important practical significance on reduction of breeding cost and guarantee of offspring seed supply.

Description

Technical Field

[0001] This invention belongs to, but is not limited to, the field of aquaculture technology, and particularly relates to a method and system for cultivating grass carp that shortens the time to sexual maturity. Background Technology

[0003] The current integrated maturation system of "constant temperature gradual increase + high protein intensive feeding" is widely used for the rapid breeding of grass carp broodstock: farmers first overwinter the broodstock in a constant temperature pond at 20–22℃, and then feed them at 1–2℃ per week in the spring. -1 The temperature was gradually increased to 28℃, and the animals were fed an extruded diet rich in n-3LC-PUFAs with a crude protein content of over 40% throughout the feeding process. The aim was to activate the HPG axis earlier through the parallel stimulation of temperature and nutrition, enabling the ovaries to complete the transition from stage III to stage V within 18–20 months. This approach has shortened the cycle of the first batch of usable oocytes by nearly one year in laboratory settings and some factory-scale production facilities, and it has practical value in solving the problem of off-season seedling shortages in seedling farms in southern factories.

[0004] However, practice has also revealed three types of technical bottlenecks: ① High-protein feed significantly increases ammonia nitrogen and nitrite loads under high temperature conditions, causing fatty liver and mild ovarian inflammation in the parent fish, and the actual maturity rate often drops below 60%; ② Uniform heating curves ignore individual differences in aromatase activation thresholds, resulting in poor ovarian synchronicity and forcing an increase in the number of induced spawning times and hormone dosages; ③ Prolonged constant temperature weakens the parent fish's sensitivity to environmental signals such as light and water flow, leading to increased hormone dependence and management costs, which is in obvious conflict with the current sustainable demands of zero-discharge recirculating aquaculture systems. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for cultivating grass carp that shortens the time to sexual maturity.

[0006] This invention is implemented as follows: a method for cultivating grass carp that shortens the time to sexual maturity, the method comprising:

[0007] S1: Parental screening;

[0008] S2: Feeding;

[0009] S3: Water temperature management.

[0010] Furthermore, S1 specifically includes:

[0011] (1) Genetic selection and breeding:

[0012] Select superior breeds from F3 generation and above, and select parent fish with sexual maturity age ≤4 years and weight ≥4.5kg. The female fish body length / body height ratio should be 3.2-3.5. Prioritize individuals that are free from disease and have a growth rate 20% higher than the population average.

[0013] (2) Gonadal development assessment:

[0014] The diameter of oocytes was detected using 7.5MHz high-frequency ultrasound imaging technology. Oocytes ≥0.6mm were classified as stage III ovaries. The number of scale rings ≥3 rings was used to determine the sexual maturity potential.

[0015] Furthermore, S2 specifically includes:

[0016] (1) Formula composition:

[0017] The diet maintains 32% crude protein, 6% total fat, and 200 mg / kg vitamin E, while significantly reducing soybean meal and increasing marine-based ingredients: per 100 kg of formula, only 12 kg of 46% crude protein soybean meal is retained; fishmeal is increased to 18 kg (approximately 18%), supplemented with 5 kg of fish oil and 1 kg of soybean lecithin; the remainder is filled with grains (35 kg of wheat or corn), 10 kg of wheat bran, 5 kg of corn gluten meal, and conventional minerals, trace elements, choline (1500 mg / kg), DL-methionine (1200 mg / kg), phytase + compound NSP enzyme, etc. This provides 1.9% lysine, 1.0% sulfur-containing amino acids, approximately 13 MJ / kg of metabolizable energy, and maintains the ω-6 / ω-3 ratio at approximately 1.2:1.

[0018] This program employs a three-pronged approach of "reducing soybean meal and increasing fishmeal, fish oil, and phospholipids" to significantly reduce plant anti-nutritional factors and high ω-6 load. It leverages calcium-phosphorus balance and the choline-methionine-phospholipid combination to promote VLDL assembly and the export of intrahepatic fat. Combined with high doses of vitamin E and antioxidants such as Zn and Se, it can reduce triglyceride deposition in hepatocytes, inhibit lipid peroxidation, and improve bile flow within 4-6 weeks. This effectively alleviates or even reverses feed-induced fatty liver while maintaining growth performance and controllable costs.

[0019] (2) Feeding Management:

[0020] Gonadal development period: Water temperature ≥ 20℃

[0021] The daily feeding rate is 3.5%, divided into 4 feedings at 05:00, 11:00, 17:00 and 21:00. Slow-release pelleted feed containing 0.5% DHA is added at night.

[0022] Furthermore, S3 specifically includes:

[0023] (1) Basic temperature zone:

[0024] Maintain the water temperature at 25-28℃. Grass carp are warm-water fish and their suitable temperature range is 25-30 degrees Celsius. The daily fluctuation is ±3℃. Through the circulating water system, the daily water exchange rate is 15%, simulating the natural day-night temperature difference.

[0025] (2) Gonadal induction period, 6 months before reproduction:

[0026] Implement a gradient stimulation of "daytime warming-nighttime cooling", raising the temperature to 30℃ from 08:00 to 18:00 and lowering it to 25℃ at night to promote sex hormone synthesis;

[0027] (3) Critical period control:

[0028] Overwintering period (December-February): Maintain stable water temperature of 20-22℃ and dissolved oxygen ≥7mg / L to prevent gonadal degeneration; Breeding initiation period (March-May): Gradually raise the temperature to 26℃ within 3 weeks.

[0029] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows:

[0030] First, (1) Increase accumulated temperature. Taking advantage of the high accumulated temperature in Guangxi, grass carp are raised and cultivated in Guangxi. At the same time, plastic greenhouses are built in winter to keep the water temperature above 15℃, which promotes the sexual maturity of grass carp.

[0031] (2) Enhance nutrition by feeding green fodder throughout the breeding period and feeding lettuce leaves 1-2 times a week or adding vitamin E (200mg / kg) to promote the sexual maturity of grass carp.

[0032] (3) Increase dissolved oxygen in aquaculture water, appropriately reduce stocking density, monitor dissolved oxygen in aquaculture ponds in real time, and maintain dissolved oxygen in aquaculture ponds (≥7mg / L).

[0033] Using the above methods can effectively promote the sexual maturity of grass carp at three years old.

[0034] This invention establishes dynamic models of photoperiod (10L:12D), water temperature gradient (fluctuating between 20-28℃), and dissolved oxygen (≥7mg / L), and combines these with a vitamin E (200mg / kg) formulation in the feed. Under large-scale aquaculture conditions, this invention successfully and stably shortens the sexual maturity cycle of grass carp to three years. This was confirmed through experiments using fish scales and gonad sections. This provides quantifiable operational standards for constructing a freshwater fish maturation-promoting technology system and offers a theoretical basis for efficient freshwater fish aquaculture, possessing significant economic and ecological value.

[0035] This invention, through systematic analysis of the synergistic effects of tocopherol (vitamin E) antioxidant regulation, feed nutrition optimization, and precise water temperature management, successfully stabilized the sexual maturity cycle of grass carp in large-scale farming within three years. This breakthrough has significant practical implications for reducing farming costs and ensuring the supply of seedlings.

[0036] Secondly, this invention can significantly shorten the sexual maturity time of grass carp. For grass carp fry production enterprises and related units, it can effectively increase the average annual fry yield per broodstock, thereby significantly improving fry production efficiency and economic benefits. For grass carp breeding institutions, this invention can shorten the cycle of each breeding generation by more than one year, greatly accelerating the breeding process, improving breeding efficiency, and effectively reducing the long-term cost investment in broodstock rearing.

[0037] The technical solution proposed in this invention fills the technical gap in the field of grass carp reproduction regulation at home and abroad. It is the first time that a systematic intervention and significant advance of the sexual maturity time of grass carp has been achieved, and it has broad application prospects and industrial promotion value.

[0038] This invention represents a breakthrough in solving the long-standing technical problem of the excessively long reproductive cycle of grass carp. This issue has always been a core concern in the fields of aquaculture and genetic breeding, but previously there had been no truly effective technical means to significantly shorten the maturation time.

[0039] The technical solution of this invention breaks through the traditional understanding and technical prejudice that "grass carp need to be raised for more than four years before they can reach sexual maturity and reproduce." It proposes and verifies an innovative path that can significantly shorten the breeding cycle without affecting the quality of reproduction, demonstrating important technical foresight and theoretical guiding value. Attached Figure Description

[0040] Figure 1 This is a flowchart of a grass carp cultivation method for shortening the sexual maturity time provided in an embodiment of the present invention;

[0041] Figure 2 This is a flowchart of water temperature management provided in an embodiment of the present invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0043] Grass carp, a major freshwater aquaculture species in my country, typically takes more than four years to reach sexual maturity, severely restricting the efficiency of seedling renewal and the breeding process. While existing technologies have attempted single-point interventions such as temperature-controlled breeding or high-protein feed, a systematic and highly controllable system for regulating maturity has not been established, making it difficult to substantially shorten the reproductive cycle or achieve a substantial acceleration of the breeding generation pace. This invention addresses this bottleneck by developing a systematic design.

[0044] In terms of parental selection, this method establishes a phenotypic-physiological composite screening mechanism that is highly correlated with sexual maturity potential by screening the genetic basis of superior populations from the F3 generation and above, combined with the body size index (body length / body height ratio) and growth advantage indicators of individual growth deviation from the mean. In particular, the introduction of 7.5MHz high-frequency ultrasound imaging technology to assess the diameter of stage III ovarian oocytes in real time, combined with squamous cell ring interpretation, enables precise prediction and visual control of gonadal development in the early stages of breeding.

[0045] Regarding nutritional intervention, this invention breaks through the traditional approach of nutritional fortification centered on high protein. Based on optimized protein-fat ratios, it introduces functional components DHA, L-carnitine, and β-glucan to enhance reproductive system development efficiency from three directions: gonadal membrane structure formation, energy metabolism activation, and immune homeostasis regulation. More importantly, in terms of feeding management, a four-segment timed feeding model based on the coupling of diurnal rhythm and metabolic window is adopted. Furthermore, slow-release pelleted feed at night maintains a stable endocrine activation state, enhancing the exogenous induction effect of gonadal physiological rhythms.

[0046] In terms of temperature control strategy, this invention avoids the risk of endocrine feedback disorder caused by long-term constant temperature in existing technologies, and instead adopts a dynamic temperature control system that combines diurnal temperature gradient stimulation with a segmented temperature increase mechanism during the critical period. Six months before breeding, an "alternating heat stimulation" method is implemented, in which the water temperature is gradually increased to 30°C between 08:00 and 18:00, and then naturally cooled to 25°C at night, to simulate the diurnal temperature variation of natural water systems and induce the gradual activation of the hypothalamus-pituitary-gonadal axis (HPGaxis).

[0047] Hibernation management is crucial in determining whether gonadal atrophy occurs. This invention sets the overwintering temperature control window at 20–22°C while maintaining dissolved oxygen levels above 7 mg / L, creating a low-metabolic, low-stress physiological environment that does not induce gonadal atrophy—a "non-hibernating" state. Compared to traditional static overwintering models, this strategy essentially preserves the basic conditions for gonadal endocrine activation, laying a physiological foundation for subsequent sexual maturation.

[0048] Regarding the initiation stage of reproduction, this method designed a gradual process of uniformly raising the water temperature to 26°C over three weeks, forming a continuous and gentle gonadotropin release curve. This natural induction mechanism under "non-hormone injection" conditions achieves relatively concentrated synchronous maturation of gonads with lower physiological burden, marking a substantial step forward for this invention in a non-drug-based, eco-friendly aquaculture approach.

[0049] like Figure 1 As shown in the figure, an embodiment of the present invention provides a method for cultivating grass carp to shorten the time to sexual maturity, the method comprising:

[0050] S1: Parental screening;

[0051] S2: Feeding;

[0052] S3: Water temperature management.

[0053] S1 specifically includes:

[0054] (1) Genetic selection and breeding:

[0055] Select superior breeds from F3 generation and above, and select parent fish with sexual maturity age ≤4 years and weight ≥4.5kg. The female fish body length / body height ratio should be 3.2-3.5. Prioritize individuals that are free from disease and have a growth rate 20% higher than the population average.

[0056] (2) Gonadal development assessment:

[0057] The diameter of oocytes was detected using 7.5MHz high-frequency ultrasound imaging technology. Oocytes ≥0.6mm were classified as stage III ovaries. The number of scale rings ≥3 rings was used to determine the sexual maturity potential.

[0058] S2 specifically includes:

[0059] (1) Formula composition: 32% crude protein soybean meal + fish meal, 6% fat fish oil + phospholipids, 200mg / kg vitamin E;

[0060] (2) Feeding Management:

[0061] Gonadal development period: Water temperature ≥ 20℃

[0062] The daily feeding rate is 3.5%, divided into 4 feedings at 05:00, 11:00, 17:00 and 21:00. Slow-release pelleted feed containing 0.5% DHA is added at night.

[0063] Breeding season enhancement:

[0064] L-carnitine (500 mg / kg) and 0.1% β-glucan were added, and a pulsed feeding pattern of "2 days of feeding + 1 day of fasting" was adopted to stimulate GtH gonadotropin.

[0065] like Figure 2 As shown, S3 specifically includes:

[0066] (1) Basic temperature zone:

[0067] Maintain the water temperature at 25-28℃. Grass carp are warm-water fish and their suitable temperature range is 25-30 degrees Celsius. The daily fluctuation is ±3℃. Through the circulating water system, the daily water exchange rate is 15%, simulating the natural day-night temperature difference.

[0068] (2) Gonadal induction period, 6 months before reproduction:

[0069] Implement a gradient stimulation of "daytime warming-nighttime cooling", raising the temperature to 30℃ from 08:00 to 18:00 and lowering it to 25℃ at night to promote sex hormone synthesis;

[0070] (3) Critical period control:

[0071] Overwintering period (December-February): Maintain stable water temperature of 20-22℃ and dissolved oxygen ≥7mg / L to prevent gonadal degeneration; Breeding initiation period (March-May): Gradually raise the temperature to 26℃ within 3 weeks.

[0072] From 2021 to 2023, grass carp raised using the above-mentioned aquaculture methods at the Guangxi Zhuang Autonomous Region Characteristic Freshwater Fish Comprehensive Experimental Base were able to reach sexual maturity with over 30% males and about 10% females.

[0073] Existing commercial breeding systems for grass carp (Ctenopharyngodonidella) primarily utilize a natural light-water temperature model, requiring the gonads to undergo a complete vernalization-summerization process to reach maturity, typically lasting 28-32 months. The fundamental reasons for delayed maturity are: ① The parent population has a diverse genetic background and significant body size variations, resulting in uneven reserves of lipids and steroids required to activate the hypothalamus-pituitary-gonadal (HPG) axis; ② The protein-to-fat ratio in conventional feeds is unbalanced, failing to continuously supply the n-3 long-chain polyunsaturated fatty acids (LC-PUFAs) needed for gonadal lipid synthesis; ③ Fluctuations in water temperature are misaligned with the optimal activation window of the grass carp ovarian cytoplasmic membrane enzyme system, causing oocyte development to arrest at stage II.

[0074] This scheme first uses a weighted multi-index broodstock selection model (WMI-BAS, Weight-Matrix Integrated Broodstock Assessment Scheme) to screen candidate broodstock: actual age at sexual maturity (in months) < 24 months, body weight 2.5 ± 0.3 kg, body length-to-body height ratio 4.8-5.1, and total daily weight gain (SGR) ≥ 2.1%·d. -1 A threshold of ≥1.35 was used, and the alleles of microsatellite markers CId-E10 and CId-G14 were combined to construct a closed population from families enriched with early-maturity alleles. This screening directly improved the homogeneity of the population's mean Gonadosomatic Index (GSI), providing a predictable gonadal response window for subsequent nutrition-temperature control interventions.

[0075] This feed formula targets the key rate-limiting substrates for ovarian steroid synthesis in grass carp, providing 45% crude protein (highly digestible fishmeal + fermented soybean meal 3:1), 10% crude fat, and 14 MJ·kg digestible energy. -1Based on this formula, the ratio of DHA to EPA in the fatty phase is 2.2, and it is supplemented with 2% phospholipids to promote the absorption of yolk precursors in oocytes. Micronutrient fortification includes: Vitamin E 300 mg / kg. -1 Enhance ovarian antioxidant capacity; Vitamin C-phosphate 600mg / kg -1 Maintaining the balance of corticosterone reduction and oxidation; additionally adding 0.06% β-glucan-selenium yeast complex immune booster to improve the integrity of the parent liver-gut barrier and avoid the inhibition of the HPG axis by disease-stress.

[0076] Based on the diurnal feeding-metabolic rhythm of grass carp, this program sets four feeding ratios: 15%-35%-35%-15%; before dawn, the supply of basal steroidal raw materials is increased; the main meal in the morning covers the peak of vitellogenin synthesis; in the afternoon, plasma triglyceride levels are maintained stable; and a small supplement is given at dusk to avoid a sudden drop in blood glucose at night. This is combined with a sub-dose gonadotropin-releasing peptide analog (LRH-A, 2 μg / kg). -1 Feed-based pulse coating enhances GnRH-I pulse amplitude through a feed-endocrine synergistic approach, significantly shortening the transition time between follicular phase III and IV.

[0077] A segmented temperature accumulation strategy was adopted in the closed-loop circulating water system: the temperature was maintained at 20±1℃ for 120 days before spawning to accumulate basic nutrients; then, the temperature was increased by 1.5℃ every 10 days until it reached 28℃, which was maintained for 40 days. Dissolved oxygen and ammonia nitrogen were monitored in real time during this period, with DO ≥ 6 mg·L⁻¹. -1 NH3-N≤0.02mg·L -1 The temperature rise curve is related to the activity of grass carp ovarian aromatase (P450-arom) with temperature Q. 10 Relationship matching can simultaneously increase the secretion rate of estradiol-17β (E2) and 17-α-hydroxyprogesterone (17-OHP), accelerating the secondary maturation of oocyte nuclei.

[0078] By integrating genetically homogenized parents, targeted nutrient filling, and precise temperature control, this method reduced the overall median time to sexual maturity from 29.4±1.1 months to 18.2±0.8 months; the ovarian maturity rate (percentage of stage IV + stage V) increased by 31%. Closed-loop parameter tuning was achieved by continuously measuring GSI, plasma E2, and testicular 11-ketotestosterone (11-KT) levels: when GSI ≥ 10% and E2 ≥ 3 ng·mL... -1 The temperature rise is stopped and the spawning process begins in still water. This process replaces empirical judgment with precise metabolic-endocrine indicators, providing a replicable, data-driven operational paradigm for large-scale commercial breeding.

[0079] Evidence related to the technical effects obtained by the embodiments of the present invention.

[0080] 1.1 Scale Age Determination Experiment

[0081] 1.1.1 Experimental Principle

[0082] In 1898, scale rings were first used as an age determination mechanism for carp, and have since been widely applied in age determination work (51). The principle of this method is that fish development is uneven due to various factors such as season and gonadal development, and this unevenness is periodic, thus forming growth rings on the scales (52). Generally speaking, fish develop vigorously in summer when nutrients are abundant, and slow down in winter when nutrients are scarce, which corresponds to the appearance of sparse and dense bands on the scales (53). Therefore, the scales will show alternating sparse and dense rings, and the boundary between the two is generally used as an age marker.

[0083] 1.1.2 Experimental Procedure

[0084] (1) Scale collection

[0085] Take scales from the posterior region of the same batch of fish, and ensure that the measurement sites are consistent (54). Take 3-5 scales from each fish for cross-verification. When collecting the scales, ensure their integrity.

[0086] (2) Scale cleaning

[0087] Place the scales in a petri dish containing 75% alcohol, gently brush them with a soft brush to remove mucus and dirt, rinse the scales with distilled water, and place them on absorbent paper to dry.

[0088] (3) Transparency processing

[0089] Soak the scales in xylene for 5-10 minutes (in a well-ventilated environment), then transfer them to a glass slide and seal with glycerin.

[0090] (4) Microscopic observation

[0091] When observed with a stereomicroscope, the rings of the grass carp's scales are U-shaped, and the annual rings are formed by the oblique cuts created when the tightly packed rings of the previous year are cut by the loosely packed rings of the following year.

[0092] Example 1: At a parent fish farm, 120 healthy male and 120 healthy grass carp were selected each year in mid-March as the initial population. After 24 hours of dark rearing, the ovaries of each fish were examined using 10MHz high-frequency ultrasound to record the average diameter of the oocytes. Microscopic observation of the ring patterns on the sixth scale row was also performed. 47 females and 52 males were selected from those with oocyte diameter ≥0.6mm and ≥3 annual rings. Within 48 hours of selection, the fish were fed the feed formula of claim 4 at a daily feeding rate of 2.0% of body weight, fed once at 8:00 AM.

[0093] Following this, during the rapid gonadal development period at the end of April, the fish were additionally fed slow-release granules containing 0.5% DHA (20% of the daily diet) at 21:00 every night for 30 consecutive days. At the end of May, tests showed that the average GSI in females was 12.8%, serum E2 increased by 34%, and the sperm density in males reached 2.3 × 10⁻⁶. 9 mL -1 The fertilization rate after artificial induction of spawning was 93.6% and the hatching rate was 88.4%, which were 7.5 and 9.2 percentage points higher than the control group of the same batch in the previous year that did not use this method, respectively.

[0094] Example 2: In a contiguous pond covering tens of thousands of acres, 200 overwintering broodstock grass carp were selected in late September. After being placed in a 6‰ saline bath for 10 minutes, high-frequency ultrasound combined with scale ring analysis of the same model was used to screen out 60 females and 65 males, all of which met the standards for oocyte diameter and scale rings. From October onwards, they were fed the same high-fishmeal fermented soybean meal compound feed at a daily feeding rate of 1.5%, with half the amount in the morning and half in the afternoon. At the same time, DHA slow-release pellets were supplemented at 22:00 in the evening, accounting for 25% of the total daily feed, for 45 days.

[0095] In January of the following year, when the water temperature reached 18℃, ultrasound examination was performed. The ovaries of the female fish were concentrated in stages IV–V, with an average oocyte diameter of 0.82 mm. The plasma testosterone content of the male fish increased by 41%. In early February, the broodstock reached their natural breeding peak. 62.3 kg of eggs were successfully collected without hormone induction, with an average fertilization rate of 91.2%, which could produce 580 million fry. The survival rate of the broodstock was 100%, which fully verified the reliability of this method in regulating the reproductive performance of the broodstock and improving reproductive efficiency during the overwintering period.

[0096] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for cultivating grass carp to shorten the time to sexual maturity, characterized in that, In order, they include: S1 parent selection: Select grass carp parents with a sexual maturity age of no more than 48 months, a body weight of 2.5–5.0 kg, a body length to body height ratio of 4.8–5.1, a daily weight gain coefficient of no less than 2.1%·d-1, and a body condition coefficient of no less than 1.35; S2 Feeding: Feed the parent animals a compound feed containing 45% crude protein, 10% crude fat, 14 MJ·kg-1 digestible energy, and a DHA to EPA mass ratio of 2.2, and feed them in segments at four times: 05:00, 11:00, 17:00, and 21:

00. S3 water temperature management: Maintain the water temperature at 20±1℃ in the closed-loop circulating water system for 120 consecutive days, then increase the temperature by 1.5℃ every 10 days to 28℃ and maintain it for 40 days.

2. The method according to claim 1, characterized in that, The parental screening further includes the identification of microsatellite markers CId-E10 and CId-G14 alleles to establish a closed population containing the precocious allele.

3. The method according to claim 1, characterized in that, The selected parent lines were evaluated by high-frequency ultrasound imaging to detect the oocyte diameter and by combining it with the number of scale rings. The oocytes with a diameter of not less than 0.6 mm and a number of scale rings of not less than 3 were confirmed to be retained.

4. A compound feed for grass carp broodstock, characterized in that, It consists of the following components by weight percentage: 30% highly digestible fishmeal, 10% fermented soybean meal, 15% corn flour, 5% fish oil, 2% phospholipids, 35% wheat bran, and contains 300 mg / kg of vitamin E. -1 Vitamin C-phosphate 600 mg / kg -1 β-glucan-selenium yeast complex 0.06%.

5. The method according to claim 1, characterized in that, During gonadal development, feed the animals at night with slow-release pelleted feed containing 0.5% docosahexaenoic acid.

6. The method according to claim 1, characterized in that, Add 500 mg / kg of L-carnitine to the feed during the breeding preparation period. -1 It contains 0.1% β-glucan and is fed in a pulse feeding pattern of two days of feeding and one day of fasting.

7. The method according to claim 1, characterized in that, The base water temperature is maintained at 25–28℃ with a daily fluctuation of no more than 3℃, and a daily water exchange of 15% is implemented through a circulating water system.

8. The method according to claim 1, characterized in that, Six months before breeding, a gradient temperature increase / decrease was applied, with daytime temperatures at 30°C and nighttime temperatures at 25°C.

9. The method according to claim 1, characterized in that, During the overwintering period, maintain the water temperature at 20–22℃ and the dissolved oxygen at no less than 7 mg·L⁻¹, and raise the water temperature to 26℃ at a constant rate within 3 weeks during the breeding start period.

10. An intelligent aquaculture breeding system, comprising a high-frequency ultrasonic detection module, an automatic feeding device, a temperature-controlled water circulation management unit, and a central control module, wherein the high-frequency ultrasonic detection module, the automatic feeding device, and the temperature-controlled water circulation management unit are respectively communicatively connected to the central control module, and the central control module sets aquaculture parameters and issues instructions to each module to execute the method described in claim 1.

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