WO2019146410A1

WO2019146410A1 - Method for feeding anguilliformes larvae

Info

Publication number: WO2019146410A1
Application number: PCT/JP2019/000466
Authority: WO
Inventors: 永田　良一; 優川上
Original assignee: 株式会社新日本科学
Priority date: 2018-01-26
Filing date: 2019-01-10
Publication date: 2019-08-01
Also published as: CN111526715B; JPWO2019146410A1; JP7248596B2; KR102505201B1; CN111526715A; TW201932002A; KR20200103767A

Abstract

[Problem] To provide a method for feeding Anguilliformes larvae (a method for producing Anguilliformes larvae or Anguilliformes fish) at a high survival rate. [Solution] A method for feeding Anguilliformes larvae in an environment at a salt concentration of 10-38‰ inclusive, wherein: when the period of time from hatching of Anguilliformes eggs to mouth opening of the Anguilliformes larvae is referred to as a first stage and the time period, following the first stage, until the Anguilliformes larvae grow to a full body length of 10 mm is referred to as a second stage, the Anguilliformes larvae are reared in an environment at a salt concentration of 34-36‰ inclusive for at least a half of the first stage; and the Anguilliformes larvae are reared in an environment at a salt concentration of 10-28‰ inclusive for at least a half of the second stage.

Description

How to raise eel fish larvae

The present invention relates to a method for rearing eel-order fish larvae. More specifically, the present invention relates to a method for rearing eel-order fish larvae which effectively changes the concentration of components in the culture system.

Japanese Patent Application Laid-Open No. 2013-236598 describes a breeding method of eel-order fish, which adjusts the concentration of dissolved oxygen in breeding water.

JP, 2013-236598, A

On the other hand, it is extremely difficult for eelfish fish to hatch and grow to larval fish, and eel fish larvae can not be effectively reared only by adjusting the dissolved oxygen concentration (DO) of the culture system. For this reason, the breeding method (production method of eel-order fish larva or eel-order fish) of the eel-order fish larva with high survival rate was desired.

The present invention is basically based on the findings from the example that an eel-order fish larva can be effectively reared by setting the salt concentration of the culture system to a low state after opening the eel-order fish larva.

The present invention relates to a method for rearing eel-order fish larvae. This method is basically a method of rearing eel-order fish larvae in an environment with a salinity concentration of 10 to 38.
The first stage is from the hatching of the eel-order fish larvae to the opening of the eel-order fish larvae. And, after the first stage, the second stage is to reach 10 mm in total length of eel fish larvae.
In that case, we raise eel-order fish larvae in an environment with a salinity of 34 or more and 36 or less for at least half of the first phase. And we raise eel eyes fish larva in environment of salinity more than 10 and 28 or less period for at least half period of the second period.

In this method, it is preferable to grow eel larvae and larvae in an environment with a salinity of 16 to 25 for at least half of the second phase.

In this method, it is preferable to gradually reduce the salinity concentration from the last day or two days before the first term to the first day or second day of the second term.

Next, the third phase is from the second phase until the total length of the eel fish larvae becomes 20 mm.
In this case, it is preferable to cultivate eel-order fish larvae in an environment with a salinity of 21 to 36, for at least half of the third period. It is more preferable to cultivate eel-order fish larvae in an environment where the salt concentration is at least 23% and not more than 25% during at least half of the third period. Furthermore, it is preferable to gradually change the salinity from the last day or two days before the second term to the first day or the second day of the third term.

As demonstrated by the examples, according to the present invention, eel-order fish larvae can be effectively reared.

FIG. 1 is a graph in place of a drawing showing the appearance rate of normal individuals of 5-day-old larvae after rearing hatchery eel fish using artificial seawater adjusted to 30 and 35 vessels. FIG. 2 is a graph in place of a drawing showing the total length and body height of the Japanese sea urchin fish larvae reared in the normal concentration group (33-35 と) and the low concentration group (16-18 ‰). FIG. 3 is a graph as a substitute for a drawing showing the transition of the survival rate of Japanese eel-like fish larvae reared in the normal concentration group (33-35 ‰) and the low concentration group (16-18 ‰). FIG. 4 is a graph replaced with a drawing showing the total length of 124-day-old larvae obtained by the breeding method using low and medium concentrations in combination. FIG. 5 is a graph in place of a drawing showing the total length and body height of the Japanese sea urchin fish larvae reared in the normal concentration group (33-35 と) and the medium concentration group (23-25 ‰). FIG. 6 is a graph as a substitute for a drawing showing the transition of the survival rate of Japanese eel-like fish larvae reared in the normal concentration group (33-35 ‰) and the medium concentration group (23-25 ‰).

The present invention relates to a method for rearing eel-order fish larvae. This method is basically a method of rearing eel-order fish larvae in an environment with a salinity concentration of 10 to 38.

Growth Stage Classification of Eels Fish Larvae In this specification, the growth season classification of eel fish larvae is defined as follows.
The first stage is from the hatching of the eel-order fish larvae to the opening of the eel-order fish larvae (before feeding). And it will be called the second phase from the first phase until the total length of the eel fish larvae becomes 10 mm. The third phase is from the second phase until the total length of the eel-order fish larvae reaches 20 mm.
In addition, when there are multiple eel-order fish larvae, the first phase may be a period until half of them open. The same applies to the second and third term. For example, the second term may be taken when the full length of half of eel fish larvae becomes 10 mm or more, and the third term may be taken when half length of eel fish larvae becomes 20 mm or more .

The first phase is usually from 5 to 8 days of age after hatching.
The second phase is usually up to about 40 days old (eg, 20 to 50 days old, 35 to 45 days old depending on the environment).
The third phase is usually up to about 100 days old (eg, 50 to 120 days old, 90 to 110 days old depending on the environment).

Eels Fish Examples of eels fish are eel, anago, duck and moray eel. Among these, eel is preferred. Examples of eels are Japanese eels (Anguilla japonica), European eels (Anguilla anguilla), Eel (Anguilla marmorata), and American eels (Anguilla rostrata). In addition, since an eel-like fish grows through a leptocephalus larva, although it demonstrates focusing on an eel below, it can be made to grow similarly about other eel-like fish. The juveniles of the eels are called leptokefals larvae. In the natural world, for example, it is considered that the number of days required from the hatching of Japanese eel (Anguilla japonica) to Shirasu eel is about 160 to 180 days. Since the total length of Shirasu eels that are naturally collected is about 60 mm, it is considered that the body size that can reach the maximum elongation period, that is, the transformable body size is 60 mm or more. On the other hand, in the case of artificially produced Leptocephalus larvae, the transformable size is 50 to 60 mm in total length, and in order to grow up to that body size, long-term rearing usually longer than 200 days using shark egg feed Are required, and some individuals require more than 400 days. It is feared that such a long seedling production period leads to a decrease in survival rate and an increase in production costs.

Breeding system of eel order fish In order to raise the eel order fish, a usual container (for example, an acrylic container) used for raising the eel order fish may be used. For breeding systems of eel-like fish, reference may be made to known literatures as appropriate. In the present invention, known feeds may be used appropriately.

Thyroid hormone, vitamins and their derivatives may be added to the breeding water. Examples of vitamins are vitamin A, retinoic acid and vitamin C. In particular, retinoic acid was effective because it forms a heterodimer with thyroid hormone. When these were actually administered, the breeding of eel-order fish larvae (especially eel larvae) increased.

The method of the present invention can be carried out in a water stop condition or in a flowing environment. It is desirable to use the water temperature in the range of 20 ° C to 28 ° C. Furthermore, it is desirable to use in the range of 22 ° C to 26 ° C. During induction, it is desirable to breed while performing aeration such as oxygen.

The water contained in the breeding water used in the method of the present invention is not particularly limited. Tap water, ground water, hot spring water, natural seawater, distilled water, deionized water, etc. may be used, or commercially available artificial seawater based on the above water may be used.

It is preferable that rearing of eel fish is performed in a dark room. The following describes the breeding plan after hatching.

At least half of the first period, we raise eel-order fish larvae in an environment with a salinity of 34 or more and 36 or less. The salinity concentration may be 34 to 35, may be 35 to 36, or may be 34.5 to 35.5. The “at least half period” may be the whole, 50% to 95%, 60% to 90%, or 70% to 85%. In addition, it is preferable that the fluctuation (difference from the average) of the salinity concentration in the first term (particularly, from the beginning of the first term to 3 days or 4 days) is 20% or less (or 10% or less). The salinity may be gradually reduced from the last day or two days before the first phase.

In the second period, it is preferable to make the salt concentration lower than in the first period. The salinity may be lowered gradually at the beginning of the second phase (eg, until the first day or until the second day). At least half the period of the second phase, we raise eel-order fish larvae in an environment with a salinity of 10 to 28. It is preferable to cultivate eel-order fish larvae in an environment with a salinity of 16 to 25 for at least half of the second period. The salinity concentration may be 16 ‰ 23 ‰, 17 ‰ 23 ‰ or less, 17 ‰ 20 ‰ or less, 20 ‰ 25 ‰ or less, or 20 塩 23 ‰ or less. The “at least half period” may be the whole, 50% to 95%, 60% to 90%, or 70% to 85%. The variation (difference from the mean) of the salinity concentration during the second phase (period from the third day of the second phase to the third day before the last day) is preferably 20% or less (or 10% or less).

It is preferable to reduce the salt concentration from the last day or two days before the first transition phase to the first or second day of the second phase.

The third stage salt concentration is preferably higher than the second stage salt concentration. At the beginning of the third trimester (eg, until the first day or until the second day), the salinity may be lowered gradually. It is preferable to cultivate eel-order fish larvae in an environment with a salinity of 21 or more and 36 or less for at least half of the third period. It is more preferable to cultivate eel-order fish larvae in an environment where the salt concentration is at least 23% and not more than 25% during at least half of the third period. The salinity concentration may be from 23 to 24%, from 24 to 25%, or from 23.5 to 24.5%. The “at least half period” may be the whole, 50% to 95%, 60% to 90%, or 70% to 85%. The variation (difference from the mean) of the salinity concentration during the third term (period from the third day of the third term to the third day before the last day) is preferably 20% or less (or 10% or less). Furthermore, it is preferable to gradually change the salinity from the last day or two days before the second term to the first day or the second day of the third term.

Hereinafter, the present invention will be specifically described using examples. The present invention also includes those modified by the person skilled in the art from the following examples as appropriate and combinations of known techniques.

(Preparation of hatchling larva)
Artificial insemination of Japanese eel eggs and sperm obtained by artificial ripening. After fertilization, eggs in which cleavage was observed were used as fertilized eggs. The fertilized eggs were reared in a 100 L panlight aquarium using artificial seawater at a temperature of 34 ° to 35 ° C. at 25 ° C. After about 1.5 days, several eel hatched. Thus, eel larvae were obtained.

(Test method: first-phase optimization)
Artificial seawater adjusted to 30 and 35 vessels was prepared in two types of 500 mL beakers, to which 50 tails of eel larvae were placed, and kept in a 25 ° C. incubator.

(Seed and seedling evaluation)
Normal and malformed individuals of 5-day-old larvae were counted.
1) The tail is broken,
2) The lower jaw was not closed, or 3) the head defected larva was judged as a malformed larva.

Results FIG. 1 shows the appearance rate of normal individuals of 5-day-old larvae after breeding eels after hatching using artificial seawater adjusted to 30 and 35 vessels. As shown in FIG. 1, the larval fish reared in 30 artificial seawater had a normal rate of 8.0%, while the larva reared in 35 artificial seawater had a high normal rate of 96.0%. The results are shown. From this, it was thought that it is suitable to use high concentration seawater of about 35 fish for larval breeding from hatchling larva to feeding start.

(Preparation of hatchling larva)
Artificial insemination of Japanese eel eggs and sperm obtained by artificial ripening. After fertilization, fertilized eggs were reared in a 100 L panlite water tank using artificial sea water with a salt concentration of 34-35 as the fertilized eggs as cleavage eggs. About 1.5 days later, hatched larvae were obtained.

(Preparation of feeding start larva)
The hatched eel larvae were transferred to a 20 L lyzel water tank, and reared at 25 ° C., 34-35 saltwater with artificial seawater. The normal larvae, 6 days old after hatching, were transferred 200 to a 5 L ball tank.

(Test method: Optimization of the second phase after optimizing the first phase)
Artificial seawater was injected into the water tank, and the volume was 5 liters. Two test plots were prepared: a normal concentration group with a salinity of 33-35% and a low concentration group with a salinity of 16-18%. The Japanese eel leptocephalus larvae were adapted to two aquariums. After that, a feed equivalent to 3 mL of a diet based on a nutlnut egg was pipetted into the bottom of the water tank to start feeding. During the feeding period, water was shut off for 15 minutes. After 15 minutes, the food remaining on the bottom was washed away at a flow rate of 0.4 to 0.5 L per minute. The above operation was repeated 5 times in total every 2 hours. Feeding time was 7 o'clock, 9 o'clock, 11 o'clock, 13 o'clock and 15 o'clock. After feeding five times, the larvae of Japanese eel leptocephalus were transferred to the same type water tank. During the non-feeding time period, water was kept supplied at a flow rate of 0.4 to 0.5 L per minute. During the feeding period, breeding was continued while circulating and filtering artificial seawater at 25 ° C.

(Seed and seedling evaluation)
The animals were fed and raised for 30 days, the number of deaths was measured, and the total length and body height at 35 days of age were measured under a stereomicroscope. The experiment was performed three times for the normal concentration group.

result:
Figure 2 shows the full length and body height of Japanese eel larvae reared in the normal concentration group (33-35 ‰) and low concentration group (16-18 ‰). The graph is shown as mean ± standard deviation. In the figure, the initials indicate the start of feeding, and n indicates the number of individuals. Figure 3 shows the change in the survival rate of Japanese eel larvae reared in the normal concentration group (33-35 ‰) and low concentration group (16-18 ‰). For the normal concentration group, the results of each experiment performed three times are shown. As shown in FIG. 2, no significant difference was observed between the normal concentration group (33-35) and the low concentration group (16-18) at the end of 30 days rearing The On the other hand, as shown in Fig. 3, the low concentration group always had lower wear rate than the normal concentration group, and at the end of the test, the survival rate of the normal concentration group was 22-29%, while the low concentration was low. The survival rate of the ward was about 69%. For this reason, it was found that the survival rate is dramatically increased by significantly reducing the salt concentration of the culture system for a predetermined period after feeding.

(Preparation of larva)
Using the individuals bred in the above low concentration area (16-18), the optimum conditions for the next growth stage were sought.

(Test method: Optimization of the third phase after optimizing the first and second phases)
Approximately 50 tails of 35-day-old eel larvae were bred in a 5 L ball-type water tank. A feed equivalent to 3 mL of a diet based on a capris egg was pipetted into the bottom of the water tank to start feeding. Water was shut off for 15 minutes during the feeding period. After 15 minutes, the food remaining on the bottom was washed away at a flow rate of 0.4 to 0.5 L per minute. The above operation was repeated 5 times in total every 2 hours. Feeding time was 7 o'clock, 9 o'clock, 11 o'clock, 13 o'clock and 15 o'clock. After feeding five times, the larvae of Japanese eel leptocephalus were transferred to the same type water tank. During the non-feeding time period, water was kept supplied at a flow rate of 0.4 to 0.5 L per minute. During the feeding period, breeding was continued while circulating and filtering 25.degree. C. low concentration artificial seawater (16 to 18). From the low concentration (16-18%), the concentration was shifted over one week so that the artificial seawater concentration was about 25% when the age of 80 days was reached. Thereafter, breeding was continued using the same feeding environment as described above. The artificial seawater during that time was 25 ° C, and it was changed at 23-25 ‰ concentration (medium concentration artificial seawater).

result:
From 50 to 60 days of age, low concentration artificial seawater (16-18 fish) showed a clear growth delay as seen relatively in comparison to the normal concentration of larva co-fed. Therefore, the culture system was changed from low concentration artificial seawater to medium concentration artificial seawater (23-25). Subsequent growth showed a tendency to recover, and at 124 days of age, Leptoke fars larvae with a maximum length of 36.2 mm were produced. FIG. 4 shows the total length of 124-day-old larvae obtained by the breeding method using low and medium concentrations. As shown in FIG. 4, the average total length of eel larvae grew to about 30 mm by the breeding method using low and medium concentrations in combination.

(Preparation of hatchling larva)
Artificial insemination of Japanese eel eggs and sperm obtained by artificial ripening. After fertilization, eggs in which cleavage was observed were used as fertilized eggs. Fertilized eggs were bred in a 100 L panlite water tank using artificial seawater with a salt concentration of 34 to 35 at 25 ° C. About 1.5 days later, hatched larvae were obtained.

(Preparation of feeding start larva)
The hatched larva was transferred to a 20 L Klysel water tank and kept at 25 ° C., artificial seawater with a salinity concentration of 34 to 35 ‰. It became 6 days old after hatching, and it was confirmed that the appearance frequency of the malformed juvenile fish is low or there is no malformed juvenile fish. Then, 200 eel larvae were transferred to a 5 L ball tank.

(Test method: Optimization of the second phase after optimizing the first phase)
Artificial seawater was injected into a lyselle type water tank, and the volume was 5 liters. Two types of test plots were prepared: a normal concentration group with a salinity concentration of 33 to 35% and a medium concentration region with a salinity concentration of 23 to 25%. In the middle concentration group, two similar experiments were conducted. The Japanese eel leptocephalus larvae were adapted to two aquariums. After that, a feed equivalent to 3 mL of a diet based on a nutlnut egg was pipetted into the bottom of the water tank to start feeding. Water was shut off for 15 minutes during the feeding period. After 15 minutes, the food remaining on the bottom was washed away at a flow rate of 0.6 to 0.8 L per minute. The above operation was repeated 5 times in total every 2 hours. Feeding time was 7 o'clock, 9 o'clock, 11 o'clock, 13 o'clock and 15 o'clock. After feeding five times, the larvae of Japanese eel leptocephalus were transferred to the same type water tank. During the non-feeding time period, water injection continued at a flow rate of 0.6 to 0.8 L per minute. During the feeding period, breeding was continued while circulating and filtering artificial seawater at 25 ° C.

(Seed and seedling evaluation)
The animals were fed and raised for 30 days, the number of deaths was measured, and the total length and body height at 35 days of age were measured under a stereomicroscope.

result:
FIG. 5 shows the total length and body height of Japanese eel larvae reared in the normal concentration group (33-35 ‰) and the medium concentration group (23-25 ‰). The graph is the mean value ± standard deviation value. FIG. 6 shows the change in the survival rate of Japanese eel larvae reared in the normal concentration group (33-35 ‰) and the medium concentration group (23-25 ‰). As shown in FIG. 5, the total length and body height at the end of 30 days of breeding were not significantly different between the normal concentration group (33-35) and the medium concentration group (23-25). As shown in FIG. 6, the medium concentration group always had a lower wear rate than the normal concentration group, and at the end of the test, the survival rate of the normal concentration group was 1.5%, while The survival rates were 27% and 39%. Thus, in the rearing by medium concentration group, survival rate higher than normal concentration group was recognized.

The present invention can be utilized in the marine industry.

Claims

A method for rearing fish eel larvae in an environment with a salinity concentration of 10 to 38, and
The period from the hatching of the eels to the opening of the eels fish is the first phase,
When after the first stage until the total length of the eel fish larvae reaches 10 mm is the second stage,
Rearing said eel fish larvae in an environment with a salinity of 34 to 36, for at least half of the first period;
Rearing said eel larvae in an environment with a salinity of 10 to 28 and at least half of the second period,
Method.
A method of rearing an eel-order fish larva according to claim 1;
Rearing said eel larvae in an environment with a salinity of 16 to 25 and at least half of the second period,
Method.
A method of rearing eel-order fish larvae according to claim 1, wherein the salinity concentration is gradually reduced from the last day or two days before the first term to the first day or the second day of the second term.
The method of rearing eel-order fish larvae according to claim 1, wherein after the second period, the length of the eel-order fish larvae is 20 mm until the third period,
Rearing said eel fish larvae in an environment with a salinity of 21 to 36, for at least half of the third period,
Method.
A method of rearing eel-order fish larvae according to claim 4;
Rearing said eel fish larvae in an environment with a salinity of at least 23 and not more than 25 for at least half of the third period,
Method.
A method of rearing eel-order fish larvae according to claim 4, wherein the salt concentration is gradually changed from the last day or two days before the second term to the first day or the second day of the third term.