A high-efficiency feeding mode for northern long oyster spat

Abstract

The present application relates to a kind of bait feeding mode suitable for northern oyster larva breeding work, at the D type larva period of northern oyster, feed mixed bait of chrysomonad and chlorella.The present application significantly improves the growth rate and survival rate of long oyster larvae by feeding mixed bait of chrysomonad and chlorella, and shortens the breeding cycle.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aquaculture, and particularly relates to a high-efficiency feed feeding mode suitable for northern Crassostrea gigas larvae. BACKGROUND

[0002] Crassostrea gigas is one of the important economic species in China, which belongs to filter-feeding bivalves and mainly distributes in the Yellow Sea, Bohai Sea and East China Sea. Larvae cultivation is the key to the sustainable development of Crassostrea gigas aquaculture industry, and stable production and supply of high-quality feed algae are crucial to ensure the healthy and efficient growth of larvae. In recent years, the seed production enterprises of Crassostrea gigas are concentrated in southern regions such as Guangdong, Fujian and Zhejiang, which are suitable for the breeding and seed production of Crassostrea gigas due to the suitable water temperature. However, the significant difference in breeding environment, especially temperature, between the north and south limits the healthy development of Crassostrea gigas aquaculture industry in the north, and has a significant impact on the feed demand and growth status of Crassostrea gigas larvae.

[0003] In southern regions, Chlorella is mainly fed during the cultivation of Crassostrea gigas larvae, while in northern regions, Chrysophyta is mainly fed. Chrysophyta, with its characteristics of no cell wall and rich in polyunsaturated fatty acids, helps the growth and development of Crassostrea gigas larvae. However, the growth rate of Chrysophyta is slow, especially during the peak demand period, which may not be able to provide sufficient feed. In addition, the optimal growth temperature of Chrysophyta is 15-20℃, and when the water temperature exceeds this range, its growth rate and stability will be adversely affected. The larviculture work in the North Yellow Sea is usually carried out in mid-June, when the water temperature in the natural sea area is often above 20℃, which leads to a decrease in the reproduction rate of Chrysophyta, thereby affecting the stability of feed supply. In contrast, Chlorella has a wider temperature range, especially at 25℃, it grows rapidly, which can ensure a stable supply of feed. In addition, Chlorella has a thin cell wall, which is easy for larvae to digest and absorb, improving the utilization efficiency of feed. Chlorella is also rich in protein, vitamins and other nutrients, which can meet the high nutritional needs of Crassostrea gigas larvae and promote their healthy development.

[0004] Therefore, in view of the problems of unstable feed supply and high cost in the process of Crassostrea gigas larviculture in northern regions, there is an urgent need for an improved feed feeding mode to reduce the cost in the process of breeding and improve the efficiency and yield of breeding. This demand provides important technical background and practical significance for the present application. SUMMARY

[0005] The present application aims to provide a feed feeding mode suitable for the breeding of northern Crassostrea gigas larvae.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is: a bait feeding mode suitable for the breeding work of northern oyster larvae, during the D-type larva period of the northern oyster, mixed bait of chlorella and chlorella is fed, the growth rate and survival rate of the larvae are improved, and the breeding cycle is shortened.

[0007] The D-type larvae are continuously fed with the mixed bait of chlorella and chlorella, and only chlorella is fed from the middle of the shell top larvae.

[0008] In the present application, when initially feeding, the mixed bait of chlorella and chlorella has a quantity ratio of chlorella: chlorella = 1:5-10. With the growth of the larvae, the feeding proportion of chlorella is gradually reduced.

[0009] The D-type larvae, that is, the shape of the larvae appears obvious "D" type after fertilization for 1 day.

[0010] The water temperature is 22-25℃, the salinity is 25-35‰, and the pH value is 7.0-8.5 when the mixed bait is fed.

[0011] The density of the larvae is 5-10 / mL when the mixed bait is fed.

[0012] The feeding process is that the bait is fed three times a day, and the water is changed every 4 days.

[0013] The advantages of the present application are:

[0014] 1. Effectiveness: By feeding the mixed bait of chlorella and chlorella, the growth rate and survival rate of the long oyster larvae are significantly improved, and the breeding cycle is shortened.

[0015] 2. Economy: By feeding the mixed bait, it is helpful to reduce the production cost of the long oyster breeding industry.

[0016] 3. Simple operation: The method of the present application is simple and easy to operate, and is suitable for application in actual production.

[0017] 4. Scientific research value: The present application provides new technical support for the development of the long oyster breeding industry. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The survival rates of oyster larvae after feeding in three ways are provided for the embodiments of the present application. Among them, the mixed feeding group of chlorella and chlorella (1:10) is marked as "A", the mixed feeding group of chlorella and chlorella (1:5) is marked as "B", the chlorella feeding group is marked as "C", and the chlorella feeding group is marked as "D".

[0019] Figure 2The shell length data of the embodiments of the present application after feeding in three ways is provided. Among them, the mixed feeding group of chlorella and small ball algae (1:10) is marked as "A", the mixed feeding group of chlorella and small ball algae (1:5) is marked as "B", the feeding group of small ball algae is marked as "C", and the feeding group of chlorella is marked as "D". The vertical coordinate represents the shell length, and the unit is μm. The significant difference is marked by letters when p value < 0.05.

[0020] Figure 3 The proportion of the H. variegatus larvae appearing after feeding in three ways is provided for the embodiments of the present application. Among them, the mixed feeding group of chlorella and small ball algae (1:10) is marked as "A", the mixed feeding group of chlorella and small ball algae (1:5) is marked as "B", the feeding group of small ball algae is marked as "C", and the feeding group of chlorella is marked as "D".

[0021] Figure 4 The average number of attachment on the attachment base after feeding in three ways is provided for the embodiments of the present application. Among them, the mixed feeding group of chlorella and small ball algae (1:10) is marked as "A", the mixed feeding group of chlorella and small ball algae (1:5) is marked as "B", the feeding group of small ball algae is marked as "C", and the feeding group of chlorella is marked as "D". DETAILED DESCRIPTION

[0022] The specific embodiments of the present application are further described below in conjunction with examples. It should be pointed out that the specific embodiments described here are only for the purpose of illustration and explanation of the present application, and are not limited to the present application.

[0023] Example 1 Survival rate of Pinctada martensii larvae under different feeding modes

[0024] 1. Experimental materials: D-type larvae were taken from Liaoning Dalian Zhuzidao Group Seed Farm, and chlorella and small ball algae were provided by Zhuzidao Seed Farm.

[0025] 2. Experimental method: Collect D-type larvae and randomly divide them into A, B, C, and D groups, and measure the mortality rate of each group of larvae during 0-15 days. Group A: mixed feeding of golden algae and chlorella, continuous feeding of golden algae and chlorella, initial feeding concentration of 500 cells / mL golden algae and 5000 cells / mL chlorella. As the larvae grow, gradually reduce the feeding proportion of golden algae, reduce 50 cells / mL per day. After 11 days, only feed chlorella, 4L each time. Group B: mixed feeding of golden algae and chlorella, continuous feeding of golden algae and chlorella, initial feeding concentration of 500 cells / mL golden algae and 2500 cells / mL chlorella. As the larvae grow, gradually reduce the feeding proportion of golden algae, reduce 50 cells / mL per day. After 11 days, only feed chlorella, 4L each time. Group C: only feed chlorella, 4L each time. Group D: only feed golden algae, 200ml each time. Each breeding tank contains 150L of seawater, the density of larvae is 5-10 per mL, the seawater temperature is 23-25℃, the salinity is 25-35‰, and the pH value is 7.0-8.5. Change the water every 4 days and feed twice a day. Five-point counting method is adopted, 2ml water body is taken at each position, and counting is carried out under a microscope, and the water body is mixed before sampling.

[0026] 3. Experimental results: After 15 days of experiment, the survival rate of larvae in group A is 50.1%; the survival rate of group B is 54%; the survival rate of group C is 37%; and the survival rate of group D is 16%. The experimental results show that in the case of reducing the number of water changes, as shown in Figure 1 , the mixed feeding mode of golden algae and chlorella can significantly improve the survival rate of long oyster larvae.

[0027] Example 2 Growth status of long oyster larvae under different feeding modes

[0028] 1. Experimental materials: D-type larvae were taken from Liaoning Dalian Zhuzidao Group Breeding Farm, and golden algae and chlorella were provided by Zhuzidao Breeding Farm.

[0029] 2. Experimental method: At 0 days, 2 days, 4 days, 10 days and 15 days, long oyster larvae cultured under different feeding modes were sampled. When sampling, 500 mesh filter screen was used to collect larvae from 50 mL water body, and then observation and photography were carried out under a microscope. Shell length measurement was analyzed by ImageJ software. The breeding conditions and methods used in the experiment were consistent with those of Example 1.

[0030] 3. Experimental results: At 15 days, the average shell length of group A was 248μm, the average shell length of group B was 218μm, the average shell length of group C was 210μm, and the average shell length of group D was 190μm. As shown in Figure 2As shown, the mixed feeding mode of golden algae and chlorella can significantly improve the growth rate of oyster larvae.

[0031] Example 3: Eyespot occurrence rate of oyster larvae under different feeding modes

[0032] 1. Experimental materials: Type D larvae were obtained from the Zhangzidao Group Seed Farm in Dalian, Liaoning Province, while Chlorella and Chlorella were provided by the Zhangzidao Seed Farm.

[0033] 2. Experimental Methods: Groups A and B were fed a mixture of golden algae and chlorella during days 0-10, 4L of chlorella per feeding from days 11-15, and 6L of chlorella per feeding from days 15-20. Group C was fed only 4L of chlorella from days 0-15, and 6L of chlorella per feeding from days 15-20. Group D was fed only golden algae, 200mL of golden algae per feeding from days 0-15, and 400mL of golden algae per feeding from days 11-20. Groups A, B, C, and D were all fed twice daily. Each rearing tank contained 150L of seawater, with a larval density of 1-3 larvae / mL, a seawater temperature of 23-25℃, a salinity of 25-35‰, and a pH of 7.0-8.5. The water was changed every 4 days, and feeding was done twice daily. Oyster larvae fed for 20 days under different farming methods were collected. 50 ml of water was collected from the larvae using a 300-mesh filter. The appearance of eye spots was observed under a 10× objective lens. The number of eye spots was counted and the eye spot rate was calculated.

[0034] 3. Experimental results: such as Figure 3 As shown, the mixed feeding mode of Chlorella and Golden Algae significantly increased the rate of eyespot emergence. During the growth of the Pacific oyster, once eyespots form, the larvae begin to seek attachment sites. The earlier the eyespots appear, the lower the likelihood of larval loss.

[0035] Example 4: Attachment rate of oyster larvae under different feeding modes

[0036] 1. Experimental materials: Type D larvae were obtained from the Zhangzidao Group Seed Farm in Dalian, Liaoning Province, while Chlorella and Chlorella were provided by the Zhangzidao Seed Farm.

[0037] 2. Experimental Methods: After feeding the larvae under different rearing models for 20 days, 50 uniform attachment substrates were placed in each of the four groups (A, B, C, and D). Five days after larvae attachment, the number of juvenile shellfish on each attachment substrate was counted, and the attachment metamorphosis rate was calculated using the formula: Attachment Metamorphosis Rate = Total Number of Juvenile Shellfish on Attachment Substrate / Total Number of Larvae. The rearing conditions and methods were consistent with those in Example 3.

[0038] 3. Experimental Results: The experimental results show that, as Figure 4 As shown, under the same cultivation time and using the same type of attachment substrate, the larval attachment metamorphosis rate of the mixed feeding group of Chlorella and Chlorella was significantly better than that of the other two groups.

[0039] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above embodiments, and any changes, modifications, substitutions, combinations, simplifications, etc. made without departing from the spirit and principles of the present application should be equivalent replacement manners and should be included in the protection scope of the present application.

Claims

1. A feeding method suitable for breeding oyster larvae in northern China, characterized in that... During the D-type larval stage of the northern oyster, a mixture of golden algae and chlorella was continuously fed. As the larvae grew, the proportion of golden algae was gradually reduced, and by the middle stage of the apical larvae, only chlorella was fed.

2. The feeding method for oyster larvae breeding in northern China according to claim 1, characterized in that, In the mixed feed of golden algae and chlorella, the ratio of golden algae to chlorella is 1:5~10.

3. The feeding method for larvae of northern oysters as described in claim 1, characterized in that, The D-type larvae are those that exhibit a distinct "D" shape one day after fertilization.

4. The feeding method for oyster larvae breeding in northern China according to claim 1, characterized in that, The mixed feed is fed in water with a temperature of 22-25℃, a salinity of 25-35‰, and a pH of 7.0-8.

5.

5. The feeding method for oyster larvae breeding in northern China according to claim 1, characterized in that, When feeding the mixed feed, the density of larvae is 5 to 10 per mL.

6. The feeding method for larvae of northern oysters according to any one of claims 1-5, characterized in that, The feeding process involves feeding the animals three times a day and changing the water every four days.

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