A method for regulating late autumn breeding of mandarin fish in aquaculture

Abstract

This invention relates to a method for regulating the late autumn breeding of mandarin fish, belonging to the field of artificial fish breeding in aquaculture technology. The operation of this invention is as follows: (1) Inducing spawning in spring by injecting a high dose of a single oxytocin into the mandarin fish parent stock; (2) Under the action of the high dose of the single oxytocin, partial spawning is completed, achieving an average spawning volume per female fish of 20%-30% of the theoretical spawning volume in spring; (3) After spawning until the end of June, controlled feeding management is carried out to reduce the amount of feed, so that the fish are in a nutritional state of maintenance or slow growth; (4) In July and August, nutritional enhancement cultivation is carried out, and sufficient feeding is restored for a period of time before formal spawning to promote the rapid secondary development of the gonads of the parent mandarin fish; oxytocin is injected at a conventional effective dose to induce artificial insemination of the parent mandarin fish, resulting in concentrated spawning, achieving an average spawning volume per female fish of 80%-90% of the spawning volume in autumn. This invention can achieve the dual use of mandarin fish parent stock in one year through conventional hormone injection and feed management.

Description

Technical Field

[0001] This invention belongs to the field of artificial fish breeding in aquaculture technology, specifically involving an artificial breeding control method that combines hormone intervention and nutritional regulation to enable mandarin fish to reproduce twice a year, especially to achieve late autumn breeding. Background Technology

[0002] Mandarin fish ( Siniperca chuatsi Mandarin fish (Siniperca chuatsi) is a valuable freshwater economic fish species in my country. While its artificial breeding technology is quite mature, its reproductive activities are still strictly controlled by the natural light and temperature cycle, with the breeding season highly concentrated from late April to May each year. This concentrated seedling production model leads to an oversupply and low prices in spring, while seedlings are scarce and expensive in autumn, severely restricting the flexibility and year-round production of mandarin fish farming. To solve the problem of off-season seedling supply, some attempts have been made by those skilled in the art. For example, temperature and light control can alter the physiological rhythms of broodstock, but this method requires large-scale investment and high operating costs, making it difficult to promote and apply on a large scale. Some studies have also attempted to directly intensively cultivate broodstock that have already bred in the spring for reuse in the autumn. However, broodstock that have bred in the spring are usually weak, and their gonads enter a long period of degeneration and absorption (Phase II). To make them mature again in the autumn of the same year requires an extremely long recovery period and extremely high nutritional input, resulting in low and unstable success rates, asynchronous ovarian development, and poor spawning induction effects. Therefore, existing technologies lack a simple, low-cost, and highly successful method to effectively regulate the large-scale reproduction of mandarin fish in autumn. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for regulating the late autumn breeding of mandarin fish that can effectively induce large-scale spawning of mandarin fish in autumn (July-August).

[0004] The method of this invention is based on a deep understanding of the reproductive physiology of mandarin fish. Through the strategy of "inducing first, then controlling, and then inducing spawning", the core is to break the natural law that the gonads of mandarin fish directly enter a long period of rest after spring reproduction, and achieve precise intervention in the reproductive cycle.

[0005] The following are the steps for controlling the late autumn breeding of mandarin fish in aquaculture:

[0006] (1) Spring preparation for labor induction

[0007] In mid-April, mandarin fish broodstock with gonads developed to stage IV were selected and injected with a single oxytocin; the injection dose for females was 100 µg / fish, and the injection dose for males was halved.

[0008] (2) Inducing partial spawning

[0009] Under the action of a single oxytocin, the parent mandarin fish will release mature eggs from their ovaries within 28-32 hours, completing incomplete spawning, i.e. partial spawning, and achieving an average egg production of 20%-30% of the theoretical carrying capacity per female in spring.

[0010] (3) Controlled feeding aquaculture

[0011] From the time of spawning until the end of June, feed control management is implemented for the mandarin fish broodstock that have completed some spawning. The amount of prey fish is reduced, that is, the daily amount of prey fish is controlled at 5%-8% of the body weight of the mandarin fish broodstock, and the feeding frequency is once every 2-3 days, so that the mandarin fish broodstock are in a nutritional state of maintaining growth or slow growth.

[0012] (4) Formal labor induction in autumn

[0013] From July to August, the mandarin fish broodstock under controlled feeding management were nutritionally enhanced. 20-30 days before the formal spawning induction in autumn, the feeding was resumed in full, with the daily feed amount of bait fish being 15%-20% of the body weight of the mandarin fish broodstock, fed twice a day, morning and evening, to promote the rapid secondary development of the gonads of the mandarin fish broodstock. At the conventional effective dose, spawning hormones were injected and artificial insemination was performed to induce the mandarin fish broodstock to spawn in a concentrated manner, completing the late autumn breeding and achieving an average egg production of 80%-90% of the total number of eggs carried in autumn per female.

[0014] Further technical solutions are as follows:

[0015] In step (1), the single oxytocin is a luteinizing hormone-releasing hormone analog (LHRH-A2).

[0016] In step (4), the injection of oxytocin at a conventional effective dose is as follows:

[0017] For female fish, inject luteinizing hormone-releasing hormone analog (LHRH-A2) at a dose of 4 µg / kg, dioxone maleate (DOM) at a dose of 6 mg / kg, and human chorionic gonadotropin (HCG) at a dose of 1000 IU / kg.

[0018] For male fish, the doses of luteinizing hormone-releasing hormone analogue (LHRH-A2), dioxone maleate (DOM), and human chorionic gonadotropin (HCG) were all halved.

[0019] The beneficial technical effects of this invention are reflected in the following aspects:

[0020] 1. This study pioneered a combined approach of "high-dose single hormone pre-induction of spawning + controlled feeding management" to artificially intervene in the annual reproductive cycle of mandarin fish, a clever concept that breaks through traditional thinking. High-dose single hormone pre-induction of spawning: The key operation is the injection of a high dose of a single oxytocin (LHRH-A2 100 µg / fish). The purpose of this dose is not to empty the ovaries completely, but to stimulate the release of some eggs that have entered IV (approximately 20%-30% of the gestational age). Physiologically, this operation has the effect of "clearing part of the space" and "resetting the developmental process," preventing over-matured and degenerated eggs, and keeping the ovaries in an active but not empty "standby state." Controlled feeding management: The amount of prey fish fed is strictly controlled at a low level necessary for survival and basic metabolism, such as 5% of the broodstock's body weight, fed every other day. This stage involves simulating a special "physiological signal" through nutritional stress, causing the fish to prioritize the slow accumulation of basic nutrition for immature eggs in the gonads rather than body growth. This prepares the fish for potential redevelopment in the autumn, prevents the parent fish from rapidly accumulating fat due to overnutrition, inhibits the redevelopment of the gonads, controls their growth rate, and synchronizes their physiological rhythm with the target autumn breeding season.

[0021] In early July, the controlled feeding management was ended, and the fish were switched to intensive nutrition cultivation, being fed a sufficient amount of live prey fish to promote rapid development of the gonads to the end of stage IV or stage V within 20-30 days. At this time, due to the partial emptying of the ovaries in spring and the physiological regulation in summer, the oocytes of the parent fish developed with high synchronicity. Subsequently, injection of a conventional effective dose of oxytocin (LHRH-A2 4 µg / kg + DOM 6 mg / kg + HCG 1000 IU / kg) successfully achieved concentrated spawning and fertilization with a high rate of synchronization.

[0022] By partially spawning in the spring, the gonads of the parent fish are prevented from naturally degenerating and remain in an active state. This results in good synchronization of secondary development in the autumn, and the spawning rate, fertilization rate, and hatching rate can all reach the excellent levels of spring breeding.

[0023] 2. The operation method of the present invention does not require expensive temperature and light control equipment, and can be achieved through conventional hormone injection and feed management, making it very suitable for large-scale application in ordinary farms.

[0024] 3. The present invention offers significant economic benefits. The autumn seedlings produced can be sold as "late-season mandarin fish" or "winter-season mandarin fish" seedlings in autumn and winter, avoiding the peak season for spring seedlings. The price is much higher than that of spring seedlings, greatly improving the economic benefits of mandarin fish seedling cultivation. At the same time, it enables the broodstock to be used twice a year, improving the utilization efficiency of the broodstock. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to specific embodiments. Example 1

[0026] On April 17, 2024, at Anhui Dawei Aquaculture Co., Ltd., six female and three male mandarin fish (female-to-male ratio of 2:1) aged 2 winters were selected as parent fish. The females weighed 1.5-2.0 kg and the males weighed 1.0-1.5 kg.

[0027] The steps for controlling the late autumn breeding of mandarin fish are as follows:

[0028] (1) Spring preparation for labor induction

[0029] Female fish were injected with a luteinizing hormone-releasing hormone analog (LHRH-A2) at the base of their pectoral fins. The injection dose for female fish was 100 µg / fish, and the injection dose for male fish was halved.

[0030] (2) Inducing partial spawning

[0031] After injection, the fish were placed in a spawning pond at a water temperature of 24°C with gentle water flow stimulation. Approximately 28 hours after exposure to a high dose of oxytocin, the parent mandarin fish were observed to begin spawning, but the spawning process was short-lived. Egg collection revealed that the average number of eggs laid per female was about 25% of her estimated gestation weight in the spring. This indicates that "partial spawning" was achieved.

[0032] (3) Controlled feeding aquaculture

[0033] Some of the spawning mandarin fish broodstock were transferred to a broodstock rearing pond for controlled feeding management. From spawning until the end of June, live bait fish were fed daily at 5% of the total weight of the broodstock, once every 3 days. During this period, the water quality was kept clean and the dissolved oxygen was sufficient.

[0034] (4) Formal labor induction in autumn

[0035] Starting July 1st, the broodstock mandarin fish under controlled feeding management underwent nutritional enhancement. Live silver carp fry were fed daily at a rate of 20% of the broodstock's total weight, twice a day (morning and evening), to promote rapid secondary development of the broodstock's gonads. By July 25th, examination revealed that most female fish had swollen and softened abdomens again, with plump eggs, and a small number of mature eggs could be squeezed out. Male fish could expel thick sperm.

[0036] At 10:00 AM on July 28th, autumn spawning was formally induced in mature mandarin fish parent stock. Female fish were injected with a luteinizing hormone-releasing hormone analogue (LHRH-A2) at a dose of 4 µg / kg, dioxin maleate (DOM) at a dose of 6 mg / kg, and human chorionic gonadotropin (HCG) at a dose of 1000 IU / kg.

[0037] For male fish, the doses of luteinizing hormone-releasing hormone analogue (LHRH-A2), dioxone maleate (DOM), and human chorionic gonadotropin (HCG) were all halved.

[0038] After injection, the male and female fish were placed in two separate parent rearing ponds at a water temperature of 28°C. Approximately 22 hours later, the parent fish began to swim rapidly and frequently, indicating the onset of estrus. The male and female parent fish were then removed from the parent ponds for artificial insemination. The spawning rate reached 100%, and the fertilization rate reached 92%, resulting in the hatching of 280,000 mandarin fish fry. By August 20th, 220,000 mandarin fish fry with a body length of 3 cm had been raised. Example 2

[0039] On April 10, 2025, at Anhui Dawei Aquaculture Co., Ltd., 10 female and 5 male mandarin fish (female-to-male ratio 2:1) of two-year-old age were selected as broodstock. The females weighed 1.8-2.0 kg and the males weighed 1.2-1.5 kg.

[0040] The steps for regulating the late autumn breeding of mandarin fish are as follows:

[0041] (1) Spring preparation for labor induction

[0042] Female fish were injected with a luteinizing hormone-releasing hormone analog (LHRH-A2) at the base of their pectoral fins. The injection dose for female fish was 100 µg / fish, and the injection dose for male fish was halved.

[0043] (2) Inducing partial spawning

[0044] After injection, the fish were placed in a spawning pond at a water temperature of 22°C with gentle water flow stimulation. After 30 hours of treatment with a single oxytocin, the mandarin fish broodstock were observed to begin estrus and spawning. However, the spawning process was short-lived. Egg collection revealed that the average number of eggs laid per female was approximately 22% of her estimated gestation weight in the spring. This indicates that "partial spawning" was achieved.

[0045] (3) Controlled feeding aquaculture

[0046] Some of the spawning mandarin fish broodstock were transferred to a broodstock rearing pond for controlled feeding management. From spawning until the end of June, live bait fish were fed daily at 6% of the total weight of the broodstock, once every 3 days. During this period, the water quality was kept clean and the dissolved oxygen was sufficient.

[0047] (4) Formal labor induction in autumn

[0048] Starting July 10th, the mandarin fish broodstock, which had undergone controlled feeding, began intensive nutritional cultivation. Live silver carp fry were fed daily at a rate of 20% of the broodstock's total weight, twice a day, morning and evening, to promote rapid secondary gonadal development. By August 5th, examination revealed that most females had swollen and softened abdomens again, with plump eggs that could be expressed as mature eggs, while males could express thick sperm.

[0049] At 9:00 AM on August 6th, autumn spawning was formally induced in parent mandarin fish with mature gonads.

[0050] For female fish, inject luteinizing hormone-releasing hormone analog (LHRH-A2) at a dose of 4 µg / kg, dioxone maleate (DOM) at a dose of 6 mg / kg, and human chorionic gonadotropin (HCG) at a dose of 1000 IU / kg.

[0051] For male fish, the doses of luteinizing hormone-releasing hormone analogue (LHRH-A2), dioxone maleate (DOM), and human chorionic gonadotropin (HCG) were all halved.

[0052] After injection, the male and female fish were placed in two separate parent rearing ponds at a water temperature of 26°C. Approximately 24 hours later, the parent fish began to swim rapidly and frequently, indicating the onset of estrus. The male and female parent fish were then removed from the parent ponds for artificial insemination. The spawning rate reached 100%, and the fertilization rate reached 95%, resulting in the hatching of 500,000 mandarin fish fry. By September 3rd, 350,000 mandarin fish fry with a body length of 3 cm had been raised.

[0053] Those skilled in the art will readily understand that the above embodiments 1-2 are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for regulating the late autumn breeding of mandarin fish, characterized in that, The operation steps are as follows: (1) Spring preparation for labor induction In mid-April, select mandarin fish broodstock that have reached stage IV of gonadal development and inject them with a single oxytocin; the injection dose for female fish is 100-150 µg / fish, and the injection dose for male fish is halved. (2) Inducing partial spawning Under the action of a single oxytocin, the parent mandarin fish will release mature eggs from their ovaries within 28-32 hours, completing incomplete spawning, i.e. partial spawning, and achieving an average egg production of 20%-30% of the theoretical carrying capacity per female in spring. (3) Controlled feeding aquaculture From the time of spawning until the end of June, feed control management is implemented for the mandarin fish broodstock that have completed some spawning. The amount of prey fish is reduced, that is, the daily amount of prey fish is controlled at 5%-8% of the body weight of the mandarin fish broodstock, and the feeding frequency is once every 2-3 days, so that the broodstock mandarin fish are in a nutritional state of maintaining growth or slow growth. (4) Formal labor induction in autumn From July to August, the mandarin fish broodstock under controlled feeding management were nutritionally enhanced. 20-30 days before the formal spawning induction in autumn, the feeding was resumed in full, with the daily feed amount of bait fish being 15%-20% of the body weight of the mandarin fish broodstock, fed twice a day, morning and evening, to promote the rapid secondary development of the gonads of the mandarin fish broodstock. At the conventional effective dose, spawning hormones were injected and artificial insemination was performed to induce the mandarin fish broodstock to spawn in a concentrated manner, completing the late autumn breeding and achieving an average egg production of 80%-90% of the total number of eggs carried in autumn per female.

2. The method for regulating late autumn breeding of mandarin fish according to claim 1, characterized in that: In step (1), the single oxytocin is a luteinizing hormone-releasing hormone analog (LHRH-A2).

3. The method for regulating late autumn breeding of mandarin fish according to claim 1, characterized in that: In step (4), the injection of oxytocin at a conventional effective dose is as follows: For female fish, inject luteinizing hormone-releasing hormone analog (LHRH-A2) at a dose of 4 µg / kg, dioxone maleate (DOM) at a dose of 6 mg / kg, and human chorionic gonadotropin (HCG) at a dose of 1000 IU / kg. For male fish, the doses of luteinizing hormone-releasing hormone analogue (LHRH-A2), dioxone maleate (DOM), and human chorionic gonadotropin (HCG) were all halved.