Sea bass breeding method

Abstract

The invention provides a sea bass breeding method which comprises the following steps: parent fish selection and intensive cultivation: selecting 3-5-year-old healthy parent fish, domesticating in a circulating water system with illumination, water temperature and salinity, and feeding intensive feed to promote gonad development; step-by-step spawning induction: injecting the female fish twice, and injecting the male fish once to improve spawning induction synchronism; the semen and the eggs are mixed and activated through ultraviolet irradiation, and the fertilization efficiency is improved; pulse-type water flow hatching: inhibiting water mildew by combining with sound wave oscillation, wherein the hatching rate reaches 85% or above; staged fry breeding: phage-probiotic enhanced rotifers are fed in the fry stage, and microcapsule feed coated with sodium alginate-chitosan is used in the juvenile stage, so that the survival rate and the growth speed of the fry are remarkably increased. The method solves the problems of low fertilization rate, weak seedling disease resistance and the like in traditional breeding through methods of environment simulation, nutrient enrichment, biological prevention and control and the like, and is suitable for large-scale seedling breeding and deep-sea breeding.

Description

Technical Field

[0001] The invention relates to the technical field of aquatic breeding, and in particular to a sea bass breeding method. Background Art

[0002] Sea Bass ( Lateolabrax maculatus The genus Perciformes belongs to the family Euperciformes, also known as Qingzhai, Huazhai, Huayu, Yuban, and Yuzhaizi. It has an elongated, laterally flattened body covered with small ctenoid scales. Its mouth is large, with a prominent lower jaw that is longer than the upper. It is silvery-gray with scattered small black spots on its back and dorsal fin. Its dorsal fin is bimodal, with the front dorsal fin bearing multiple spines. The inner margin of its mouth is lined with fine teeth. The white perch has a bluish-gray back, a pale belly, and irregular black spots on its sides. The black perch is a darker black-gray overall.

[0003] As an important commercial marine fish species in my country, sea bass farming requires high-quality seedlings for large-scale cultivation. However, current sea bass breeding technology faces multiple bottlenecks, hindering the efficient development of the industry.

[0004] At the germplasm resource level, long-term self-propagation and overfishing of wild broodstock have led to germplasm degradation, with significant declines in traits such as slower growth and decreased disease resistance. Traditional breeding methods are difficult to meet the needs of rapid renewal of improved varieties due to their long cycles and low efficiency. The application of modern molecular breeding technology in the sea bass field has lagged behind, and a targeted improvement technology system has not yet been formed.

[0005] In the process of broodstock cultivation and artificial breeding, gonad development is sensitive to environmental factors. Traditional cultivation methods rely on experience-based regulation, which can easily lead to asynchronous gonad maturation of broodstock and low response rate to induced spawning. The fertilization process is greatly affected by operating techniques and the environment, and there are problems such as unstable fertilization rate and high deformity rate. The fertilization rate of natural spawning is only 40-70%, the egg membrane is fragile and easy to break, and it is susceptible to water mold disease during the incubation period; resulting in low hatching efficiency and serious impact on seedling production.

[0006] In terms of seedling cultivation, fry and juvenile fish have stringent nutritional requirements for live bait. If natural bait is not effectively fortified, live bait can carry pathogens that can easily lead to nutritional deficiencies and deformities in the fry, resulting in large-scale mortality. Diseases such as vibriosis and nocardiosis are frequent, with the incidence of vibriosis exceeding 70% during the seedling cultivation period. Traditional chemical control methods are prone to drug resistance and residue problems, making it difficult to improve seedling survival rates. In addition, existing technologies lack in-depth analysis of the sea bass's reproductive cycle and environmental adaptability. This is particularly true in the specific climate and marine environments of Zhuhai, where natural reproduction patterns are mismatched with artificial control techniques, hindering the implementation of localized seedling cultivation technology. Summary of the Invention

[0007] In view of this, the present invention proposes a sea bass breeding method to solve the above problems.

[0008] The technical scheme of the present application is implemented as follows: a sea perch breeding method, comprising the following steps: (1) selection of parent fish: select healthy sea perch of 3-5 years old and 1.5-3 kg in weight, the female fish has red and swollen genital aperture, and the male fish has narrow genital aperture and sperm flows out when the abdomen is slightly pressed; (2) intensive cultivation of parent fish: domestication in light and circulating water for 28-32 days, and daily feeding of intensive feed with a daily feeding amount of 3-5% of the fish weight; (3) gradient induced spawning: when the egg diameter of the female fish is greater than or equal to 0.6 mm, the female fish is injected twice in the abdominal cavity, and the male fish is injected once; (4) fertilization: collect the eggs and sperm, the sperm and egg ratio is 1:1.2-1.8 mL / 10,000 particles, add 4-8 times the volume of physiological saline to the sperm to stir, and activate the fertilization by ultraviolet irradiation; (5) hatching of fertilized eggs: transfer the fertilized eggs to a hatching barrel, the hatching density is 40-60 million particles / barrel, and pulse water flow stimulation is adopted; (6) breeding: the fry is bred in sections and fed with different period feeds.

[0009] Further, the intensive feed in step (2) comprises the following raw materials in parts by weight: fish meal 40-60 parts, phosphorus shrimp powder 10-12 parts, fish oil 1-3 parts, seaweed polysaccharide 8-15 parts, yeast β-glucan 15-18 parts, bile acid 0.3-0.5 parts, and vitamin D 0.3-0.5 parts.

[0010] Further, the light cycle in step (2) is 8L:16D, the water temperature is 18±0.5℃, the salinity is 28±1‰, and the dissolved oxygen is greater than or equal to 5 mg / L.

[0011] Further, the gradient induced spawning in step (3) is first injection of luteinizing hormone-releasing hormone analogue (LHRH-a) 1-3 μg / kg+ diosgenin (DOM) 0.5-1.2 mg / kg, and 24 hours later, second injection of human chorionic gonadotropin (HCG) 400-600 IU / kg+luteinizing hormone-releasing hormone analogue (LHRH-a) 4-6 μg / kg.

[0012] Further, the activation of fertilization in step (4) is irradiation by 254 nm ultraviolet light at an intensity of 20-30 μW / cm 2 for 30-60 s.

[0013] Further, the hatching barrel in step (5) has a diameter of 1.0-1.5 m and a water depth of 1.0-2.0 m, the water temperature is controlled at 19-21℃, the salinity is 22-28‰, and the dissolved oxygen is greater than or equal to 6 mg / L, the pulse water flow stimulation has a water flow rate of 0.15-0.25 m / s and a pulse frequency of 5-8 times / min.

[0014] Further, the pulse water flow incubation barrel bottom in step (5) is provided with a sound wave oscillator, generating ultrasonic waves with a frequency of 25-30 kHz and a sound intensity of 0.3-0.6 W / cm 2 , and starting for 1-3 s in each pulse water flow cycle.

[0015] Further, the segmented cultivation in step (6) comprises: ① Larval fish period (0-20 days old): from the third day after opening, the enhanced rotifer filtered through a 50-70 mesh sieve is fed, and the feeding density is 5-8 pieces / mL; ② Juvenile fish period (20-50 days old): microcapsule feed is fed, the core is enhanced rotifer powder, the shell is sodium alginate-chitosan composite membrane, the mass-volume ratio of the core and the composite membrane is (2-5):1 g / mL, and the daily feeding amount accounts for 12-18% of the body weight.

[0016] Further, the enhanced rotifer is soaked and cultured for 12-24 hours by a bacteriophage-probiotic synergistic preparation, the bacteriophage has a preparation titer of ≥1×10 8 PFU / mL, and the number of live probiotic bacteria is ≥1×10 7 CFU / mL.

[0017] Further, the microcapsule feed is mixed by the enhanced rotifer powder, lactoferrin and DHA algal oil according to a mass-volume ratio of (90-95):(0.5-0.8):(4.5-5.5) g / mL, granulated into a core through a sharp hole plate with a pore size of 0.2-0.4 mm, immersed in a mixed solution of 0.5-1.2%wt sodium alginate and 0.2-0.4%wt chitosan, cross-linked and solidified by a 1-3% CaCl2 solution, and freeze-dried to obtain the microcapsule feed with a particle size of 50-80 μm.

[0018] Compared with the prior art, the present application has the following advantages: The breeding method of the present application significantly improves the breeding efficiency and seedling quality, the parent fish breeding stage adopts precise environmental regulation and nutrition strengthening, optimizes the quality of gonadal development, and provides high-quality germplasm for subsequent breeding; the gradient induced production technology combined with ultraviolet radiation activation fertilization method improves the synchronization of induced production and fertilization efficiency, and reduces the risk of embryonic malformation; in the incubation link, the natural tidal environment is simulated by pulse water flow, and the sound wave oscillation technology is used to inhibit disease infection, to create suitable conditions for embryonic development; in the process of seedling cultivation, phage-probiotic synergistic strengthening and microcapsule coated feed technology are used to improve the disease resistance and nutrient absorption efficiency of juvenile fish in stages, to speed up the growth rate and improve the survival rate; the whole process technology effectively solves the problems of low fertilization rate and weak disease resistance of seedlings in traditional breeding, adapts to large-scale breeding and deep-sea breeding and other adverse environments, improves the environmental adaptability of seedlings, reduces the breeding cost and disease incidence, and provides core technical support for the independent controllability and sustainable development of the sea bass seed industry. DETAILED DESCRIPTION

[0019] In order to better understand the technical content of the present application, specific examples are provided below to further illustrate the present application.

[0020] The experimental methods used in the embodiments of the present application are conventional methods unless otherwise specified.

[0021] The materials, reagents, etc. used in the embodiments of the present application can be obtained from commercial channels unless otherwise specified.

[0022] The phage in the embodiments of the present application is Halorubrumicosahedral phage, which is purchased from China Typical Culture Collection Center, and the strain preservation number is CCTCC PV2021070; the probiotic is Lactobacillus plantarum, which is purchased from China Typical Culture Collection Center, and the strain preservation number is CCTCC AB2010210.

[0023] Example 1: A sea bass breeding method Step (1) parent fish selection: Select 3-5 year-old healthy sea bass from sea area breeding population, female fish weight 2.0-2.5 kg (reproductive pore red, soft and swollen abdomen), male fish weight 1.8-2.2 kg (reproductive pore narrow, light pressure abdomen with milky white semen flow), a total of 50 female fish and 20 male fish.

[0024] Step (2) parent fish intensive cultivation: Environmental conditions: acclimated in circulating water for 28 days, water temperature 17.5℃, salinity 28‰, dissolved oxygen≥5mg / L, light cycle 8L:16D, light intensity 500lux.

[0025] The formula of the fortified feed (weight parts): fish meal 40 parts, krill meal 10 parts, fish oil 1 part, algal polysaccharide 8 parts, yeast β-glucan 15 parts, bile acid 0.3 parts, vitamin D 0.3 parts.

[0026] Preparation method: the raw materials are ground through a 70-mesh sieve, mixed uniformly, and granulated (particle size 2.0 mm), and fed 3 times a day at 08:00, 14:00 and 20:00, with a daily feeding amount of 3% of the fish body weight.

[0027] Step (3) Staged production promotion: Female fish: First injection (10:00): LHRH-a 1 μg / kg + DOM 0.5 mg / kg fish weight.

[0028] Second injection (24 hours later, 10:00): HCG 400 IU / kg + LHRH-a 4 μg / kg fish weight.

[0029] Male fish: Synchronous injection of HCG 400 IU / kg + LHRH-a 4 μg / kg fish weight at the time of the second injection of female fish.

[0030] Step (4) Fertilization: After 36 hours of effect, the female fish eggs (egg diameter 0.65 mm, viability 95%) are collected, mixed according to the ratio of semen: egg grains = 1 mL: 12,000 grains (semen density 1.2×10 9 / mL) Add 4 times the volume of physiological saline (0.9% NaCl, 25℃) to the semen, gently stir for 30 seconds, transfer to the ultraviolet operating table, and activate fertilization under 254 nm ultraviolet light at an intensity of 20 μW / cm 2 for 30 seconds.

[0031] Step (5) Hatching of fertilized eggs: Hatching barrel: diameter 1.0 m, water depth 1.0 m, water temperature 19℃, salinity 22‰, dissolved oxygen ≥6 mg / L, pulse type water flow rate 0.15 m / s, pulse frequency 5 times / min, hatching density 400,000 grains / barrel.

[0032] A sound wave oscillator is installed at the bottom of the hatching barrel, which is started for 1 second per pulse cycle, generating ultrasonic waves with a frequency of 25 kHz and a sound intensity of 0.3 W / cm 2 , to inhibit the attachment of Saprolegnia.

[0033] (6) Larval rearing: Larval stage (0-20 days old): On the 3rd day after opening (body length 3.5 mm), the enriched rotifer filtered through a 50-mesh sieve was fed, with a feeding density of 5 per mL, and fed at 8:00, 14:00, and 20:00 each time.

[0034] The enriched rotifer was soaked in advance with the phage-probiotic synergistic preparation (phage titer 1x10 8 PFU / mL, and the number of live probiotic bacteria 1x10 7 CFU / mL) for 12 hours.

[0035] Juvenile stage (20-50 days old): Feeding of microcapsule feed: Preparation of the core: the enriched rotifer powder was mixed with lactoferrin and DHA algal oil at a mass-volume ratio g / mL of 90:0.5:4.5, and granulated through a sharp hole plate with a pore size of 0.2 mm.

[0036] Preparation of the shell: immersed in a mixed solution of 0.5% wt sodium alginate and 0.2% wt chitosan, cross-linked and solidified in a 1% CaCl2 solution for 10 minutes, and then freeze-dried to obtain microcapsules with a particle size of 50 μm (core: composite membrane = 2g:1mL).

[0037] The daily feeding amount accounted for 12% of the body weight of the juvenile fish, and was fed in four times (07:00, 11:00, 15:00, and 19:00).

[0038] Example 2 Step (1) selection of broodstock: Healthy 3-5 year old sea bass were selected from the sea area breeding population, with female fish weighing 2.0-2.5 kg (reproductive orifice red, soft and swollen abdomen), and male fish weighing 1.8-2.2 kg (reproductive orifice narrow, milky white semen flowing out when gently pressing the abdomen), a total of 50 female fish and 20 male fish.

[0039] Step (2) intensive cultivation of broodstock: Environmental conditions: acclimated in circulating water for 32 days, water temperature 18.5℃, salinity 29‰, dissolved oxygen ≥5 mg / L, light cycle 8L:16D, light intensity 500 lux.

[0040] Formulation of the intensive feed (weight parts): fish meal 60 parts, krill meal 12 parts, fish oil 3 parts, algal polysaccharide 15 parts, yeast β-glucan 18 parts, bile acid 0.5 parts, vitamin D 0.5 parts.

[0041] Preparation method: the raw materials were ground through a 90-mesh sieve, mixed uniformly, and granulated (particle size 2.0 mm), and fed in three times at 08:00, 14:00, and 20:00 each day, with a daily feeding amount of 5% of the body weight.

[0042] Step (3) stepwise induction of spawning: Female fish: First injection (10:00): LHRH-a 3 pg / kg + DOM 1.2 mg / kg fish weight.

[0043] Second injection (24 hours later, 10:00): HCG 600 IU / kg + LHRH-a 6 pg / kg fish weight.

[0044] Male fish: Synchronous injection of HCG 600 IU / kg + LHRH-a 6 pg / kg fish weight at the second injection of female fish.

[0045] Step (4) Fertilization: After 36 hours of effect, collect female fish eggs (egg diameter 0.65 mm, viability 95%), mix according to sperm: egg ratio = 1 mL: 1.8 million particles (sperm density 1.2 x 10 9 particles / mL) Add 8 times the volume of physiological saline (0.9% NaCl, 25°C) to the sperm, gently stir for 30 seconds, transfer to the ultraviolet operation table, and irradiate with 254 nm ultraviolet light at an intensity of 30 pW / cm 2 for 60 s to activate fertilization.

[0046] Step (5) Hatching of fertilized eggs: Hatching barrel: diameter 1.5 m, water depth 2.0 m, water temperature 21°C, salinity 28‰, dissolved oxygen ≥ 6 mg / L, pulse water flow rate 0.25 m / s, pulse frequency 8 times / min, hatching density 600,000 particles / barrel.

[0047] Install a sound wave oscillator at the bottom of the hatching barrel, start for 3 s every pulse cycle, generate ultrasonic waves with a frequency of 30 kHz and a sound intensity of 0.6 W / cm 2 , and inhibit the attachment of Saprolegnia.

[0048] (6) Rearing: Larval stage (0-20 days old): On the 3rd day after hatching (body length 3.5 mm), feed the enhanced rotifer filtered through a 70-mesh sieve, with a feeding density of 8 / mL, feeding at 8:00, 14:00, and 20:00 each day.

[0049] Soak the enhanced rotifer in a bacteriophage-probiotic synergistic preparation (bacteriophage titer 1 x 10 8 PFU / mL, probiotic viable count 1 x 10 7 CFU / mL) in advance, for 24 hours.

[0050] Juvenile stage (20-50 days old): Feed microencapsulated feed: Core preparation: Reinforced rotifer powder was mixed with lactoferrin and DHA algal oil at a mass-volume ratio of 95:0.8:5.5 g / mL, and granulated through a sharp hole plate with a pore size of 0.4 mm.

[0051] Shell preparation: Immerse in a mixture of 0.5-1.2% wt sodium alginate and 0.4% wt chitosan, cross-link and solidify in a 3% CaCl2 solution for 10 minutes, and then freeze-dry to obtain microcapsules with a particle size of 80 μm (core: composite membrane = 5 g: 1 mL).

[0052] The daily feeding amount was 18% of the body weight of the juvenile fish, and was fed in four times (07:00, 11:00, 15:00, 19:00).

[0053] Example 3 Step (1) Selection of brood fish: Select 3-5 year-old healthy sea bass from the marine breeding population, with female fish weighing 2.0-2.5 kg (genital pore red, soft and swollen abdomen), and male fish weighing 1.8-2.2 kg (genital pore narrow, milky white semen flowing out when gently pressing the abdomen), a total of 50 female fish and 20 male fish.

[0054] Step (2) Intensive cultivation of brood fish: Environmental conditions: acclimatize in a circulating water for 30 days, water temperature 18℃, salinity 28‰, dissolved oxygen ≥5 mg / L, light cycle 8L:16D, light intensity 500 lux.

[0055] Intensive feed formula (weight parts): fish meal 50 parts, krill meal 11 parts, fish oil 2 parts, algal polysaccharide 12 parts, yeast β-glucan 17 parts, bile acid 0.4 parts, vitamin D 0.4 parts.

[0056] Preparation method: grind the raw materials through an 80-mesh sieve, mix uniformly, and granulate (particle size 2.0 mm), feed 3 times a day at 08:00, 14:00 and 20:00, with a daily feeding amount of 4% of the fish body weight.

[0057] Step (3) Graded induction of spawning: Female: First injection (10:00): LHRH-a 2 μg / kg + DOM 0.8 mg / kg fish weight.

[0058] Second injection (24 hours later, 10:00): HCG 500 IU / kg + LHRH-a 5 μg / kg fish weight.

[0059] Male: Synchronous injection of HCG 500 IU / kg + LHRH-a 5 μg / kg fish weight at the same time as the second injection of female fish.

[0060] Step (4) Fertilization: 36 hours after the effect, the female fish eggs (0.65 mm in diameter, 95% motility) were collected and mixed according to the formula of semen:egg = 1 mL:15,000 eggs (semen density 1.2×10 9 pcs / mL) Add 6 times the volume of semen with physiological saline (0.9% NaCl, 25℃), stir gently for 30 seconds, transfer to the UV operating table, and irradiate with 254nm ultraviolet light at an intensity of 25μW / cm 2 , irradiate for 40s to activate fertilization.

[0061] Step (5) Fertilized egg hatching: Hatching bucket: diameter 1.2m, water depth 1.5m, water temperature 20℃, salinity 25‰, dissolved oxygen ≥6mg / L, pulse water flow rate 0.20m / s, pulse frequency 7 times / min, hatching density 500,000 grains / bucket.

[0062] The acoustic oscillator is installed at the bottom of the incubator, and each pulse cycle is activated for 2 seconds, generating a frequency of 28kHz and a sound intensity of 0.5W / cm 2 Ultrasonic waves can inhibit the adhesion of water mold.

[0063] (6) Seedling cultivation: Larvae (0-20 days old): On the third day after hatching (body length 3.5 mm), the fish were fed with fortified rotifers filtered through a 60-mesh sieve at a feeding density of 7 per mL, once at 8:00, 14:00, and 20:00 daily.

[0064] The enhanced rotifers were soaked in a phage-probiotic synergistic preparation in advance (phage titer 1×10 8 PFU / mL, viable probiotic count 1×10 7 CFU / mL), immersion time 18 hours.

[0065] Juvenile stage (20-50 days old): Feeding microcapsule feed: Kernel preparation: Fortified rotifer powder was mixed with lactoferrin and DHA algae oil at a mass volume ratio of 93:0.7:5 g / mL and pelletized through a 0.3 mm aperture orifice plate.

[0066] Shell preparation: Immerse in a mixture of 0.8%wt sodium alginate and 0.3%wt chitosan, cross-link and solidify with 2% mass concentration CaCl2 solution for 10 minutes, and freeze-dry to obtain microcapsules with a particle size of 60μm (core: composite membrane = 3g:1mL).

[0067] The daily feeding amount is 16% of the juvenile fish body weight, and is fed in 4 times (07:00, 11:00, 15:00, and 19:00).

[0068] Comparative Example 1 The difference between this comparative example and Example 3 is that the step (4) fertilization process uses ultraviolet light activation; other operations are carried out according to Example 3.

[0069] Comparative Example 2 The difference between this comparative example and Example 3 is that the step (5) fertilized egg hatching is not stimulated by pulsed water flow; other operations are carried out according to Example 3.

[0070] Comparative Example 3 The difference between this comparative example and Example 3 is that the step (5) fertilized egg hatching does not use acoustic oscillation; other operations are carried out according to Example 3.

[0071] Comparative Example 4 The difference between this comparative example and Example 3 is that the step (6) fry period of the fry feeding routine rotifer, no phage-probiotic enhanced treatment.

[0072] Comparative Example 5 The difference between this comparative example and Example 3 is that the step (6) juvenile period of the fry feeding microcapsule feed does not contain DHA algal oil.

[0073] Test Example 1: Effect of ultraviolet irradiation on fertilization rate Test index: Fertilization rate: Observe cleavage after 6h of fertilization, calculate the proportion of fertilized eggs (cleavage stage cells ≥ 2 cells are considered fertilized eggs).

[0074] Malformation rate: 24h after hatching, count the proportion of malformed fry (spinal curvature, tail loss, etc.).

[0075] Results:

[0076] Ultraviolet activated fertilization can significantly improve the fertilization rate by 15.3% and reduce the malformation rate by 9.6%, proving the key role of this step in improving the efficiency of reproduction.

[0077] Test Example 2: Effect of pulsed water flow stimulation on hatching rate Test index: Hatching rate: 48h after fertilization, count the proportion of broken membrane fry to fertilized eggs.

[0078] Hatching time: Record the time required for 50% of fertilized eggs to break membrane.

[0079] Results:

[0080] The hatching rate is increased by 15.1%, and the hatching time is shortened by 8h, which shows that the water flow simulates the natural tidal environment, and promotes the synchronism of embryo development.

[0081] Test example 3: inhibitory effect of sound wave oscillation on water mold Detection index: Water mold infection rate: the proportion of water mold mycelium attached to the surface of the fertilized egg observed 24h after fertilization.

[0082] Survival egg rate: the proportion of fertilized eggs not infected with water mold after hatching is over.

[0083] Results:

[0084] The application uses sound wave oscillation to destroy the water mold mycelium structure through mechanical vibration, so that the water mold infection rate is reduced by 17.8%, the survival egg rate is increased by 17.8%, and the hatching environment is significantly improved.

[0085] Test example 4: test of fry survival rate Detection index: Fry survival rate: the proportion of survival fry to initial hatching fry at 20 days old.

[0086] Vibrio infection rate: take the intestinal tissue of fry, and culture and count the number of Vibrio harveyi.

[0087] Results:

[0088] Rotifer intensive treatment cracks pathogenic bacteria through phage, and probiotics colonize the intestinal tract, so that the survival rate of fry is increased by 15.3%, and the Vibrio infection rate is reduced by 23.3%, which shows that rotifer intensive treatment plays a key role in early disease resistance of seedlings.

[0089] Test example 5: influence of DHA algal oil on juvenile fish growth Detection index: Average body length: the total length (nose end to tail fin end) of juvenile fish is measured at 50 days old.

[0090] Specific growth rate (SGR): the calculation formula is SGR (% / d)=(ln final body weight-ln initial body weight) / days*100.

[0091] Results:

[0092] DHA algal oil promotes lipid metabolism and cell membrane development, so that the body length of juvenile fish is increased by 32.4%, and the specific growth rate is increased by 34.4%, which proves that DHA algal oil has a key influence on the growth of seedlings.

[0093] The above merely provides the preferred embodiment of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method of breeding and propagating sea bass, characterized by: The following steps are involved: (1) Broodstock selection: Select healthy sea bass aged 3-5 years and weighing 1.5-3 kg. The female fish should have a red genital pore and a swollen abdomen, while the male fish should have a narrow genital pore and semen will flow out when the abdomen is lightly pressed. (2) Broodstock intensive cultivation: 28-32 days of acclimatization in light and circulating water, daily feeding of enriched feed, the daily feeding amount is 3-5% of the fish body weight; (3) Stepped induced spawning: When the diameter of the eggs of female fish is ≥0.6 mm, female fish are injected intraperitoneally twice, while male fish are injected once; (4) Fertilization: Collect eggs and semen, with a semen to egg ratio of 1:1.2-1.8 mL / 10,000 eggs, add 4-8 times the volume of semen in normal saline, stir, and activate fertilization by ultraviolet irradiation; (5) Fertilized egg hatching: transfer the above fertilized eggs to the hatching bucket, with a hatching density of 400,000 to 600,000 eggs per bucket, and use pulsed water flow stimulation; (6) Seedling cultivation: Cultivate the seedlings in sections and feed them at different times.

2. The method for breeding sea bass according to claim 1, wherein: The fortified feed in step (2) comprises the following raw materials in parts by weight: 40-60 parts of fish meal, 10-12 parts of krill meal, 1-3 parts of fish oil, 8-15 parts of seaweed polysaccharide, 15-18 parts of yeast β-glucan, 0.3-0.5 parts of bile acid, and 0.3-0.5 parts of vitamin D.

3. The method of claim 1, wherein the sea bass is selected from the group consisting of Striped bass (Morone saxatilis), White bass (Morone chrysops), Yellow bass (Morone mississippiensis), and their hybrids. The light cycle in step (2) is 8L:16D, the water temperature is 18±0.5°C, the salinity is 28±1‰, and the dissolved oxygen is ≥5mg / L.

4. The sea bass breeding method according to claim 1, wherein: The stepwise induction of labor in step (3) is a first injection of luteinizing hormone-releasing hormone analogue (LHRH-a) 1-3 μg / kg + dioxinone (DOM) 0.5-1.2 mg / kg, and a second injection of human chorionic gonadotropin (HCG) 400-600 IU / kg + luteinizing hormone-releasing hormone analogue (LHRH-a) 4-6 μg / kg 24 hours later.

5. The sea bass breeding method according to claim 1, wherein: Step (4) the activation of fertilization is by 254 nm ultraviolet light, at an intensity of 20-30 μW / cm 2 for 30-60 s.

6. The method of claim 1, wherein the sea bass is selected from the group consisting of Striped bass (Morone saxatilis), White bass (Morone chrysops), Yellow bass (Morone mississippiensis), and their hybrids. In step (5), the hatching bucket has a diameter of 1.0-1.5 m, a water depth of 1.0-2.0 m, a water temperature controlled at 19-21° C., a salinity of 22-28‰, and dissolved oxygen ≥6 mg / L. The water flow rate of the pulsed water flow stimulation is 0.15-0.25 m / s, and the pulse frequency is 5-8 times / min.

7. A sea bass breeding method according to claim 6, characterized in that: The bottom of the pulse water flow hatching barrel in step (5) is provided with a sound wave oscillator, which produces ultrasonic waves with a frequency of 25-30 kHz and a sound intensity of 0.3-0.6 W / cm 2 , and is started for 1-3 s in each pulse water flow cycle.

8. The sea bass breeding method according to claim 1, wherein: The segmented cultivation in step (6) includes: ① Larval stage (0-20 days old): From the third day after hatching, feed the fish with fortified rotifers filtered through a 50-70 mesh sieve at a feeding density of 5-8 rotifers / mL; ② Juvenile stage (20-50 days old): Feed microcapsule feed, the core of which is reinforced rotifer powder and the shell of which is sodium alginate-chitosan composite film. The mass volume ratio of the core and the composite film is (2-5):1 g / mL, and the daily feeding amount accounts for 12-18% of body weight.

9. A method of breeding and propagating sea bass as claimed in claim 8 wherein: The said reinforced rotifer is soaked and cultured for 12-24 hours by phage-probiotic synergistic preparation, the phage is preparation titer ≥1×10 8 PFU / mL, and the viable count of probiotic bacteria is ≥1×10 7 CFU / mL.

10. The sea bass breeding method according to claim 8, characterized in that: The microcapsule feed is prepared by mixing fortified rotifer powder with lactoferrin and DHA algae oil at a mass-to-volume ratio of (90-95) g / mL: (0.5-0.8) g / mL: (4.5-5.5), granulating the mixture into an inner core through a 0.2-0.4 mm aperture sharp hole plate, immersing the mixture in a 0.5-1.2% wt sodium alginate and 0.2-0.4% wt chitosan mixture, cross-linking and solidifying the mixture with a 1-3% mass concentration CaCl2 solution, and freeze-drying to obtain a microcapsule feed with a particle size of 50-80 μm.

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