JP5357829B2 - Eel larvae feed - Google Patents

Description

  The present invention relates to an eel larvae feed.

  Eels are important aquaculture species with high production, but all seedlings depend on natural white eels. For this reason, not only does the aquaculture cost fluctuate significantly depending on the catch of glass eel, but in recent years there has been a risk of depletion of natural resources. In order to solve this problem, attempts have been made for complete aquaculture of eel, where egg collection, hatching, and breeding are all carried out under artificial breeding. So far, we have succeeded in raising eel parent fish, artificial spawning, and artificial hatching, from naturally collected glass eels, but since the larvae after artificial hatching have reached the juvenile stage, they have died, so commercialization Was a big hindrance.

  The eel hatches from the egg and then goes through the pre-leptocefal until the yolk is absorbed and becomes a transparent gelatinous leptocephalus with a flat plate. Later, the leptocephalus grown to the willow leaf shape undergoes transformation and changes its shape from gelatinous to hard glass eel. Usually, the Leptocephalus period from hatching to metamorphosis is called the larval stage, and the glass eel period after the metamorphosis is called the fry stage. In particular, the period from hatching to pre-leptokephalus is called hatching larvae.

  Preleptocephalus has not yet darkened the eyes, and therefore it is thought that there is probably little visual acuity, and the needle-like teeth are still underdeveloped, so they cannot prey actively. On the other hand, in the Leptocephalus stage, the eyes turn black, swimming begins, and active predation is observed. Leptocephalus and preleptocephalus are usually distinguished by the position of the anus and the number of sarcomas from the head to the anus as one indicator, and the leptocephalus phase is relative to the anus compared to the preleptocephalus phase. Located behind. Under artificial breeding, preleptocephalus is usually about 3 to 10 mm in size, which corresponds to the period from hatching to the 14th day. Leptocephalus is about 10-60mm in size, and corresponds to the period from the pre-leptokephalus period to about 7-9 months after hatching. Leptocephalus grown to a size of about 60 mm slowly transforms into glass eel over a period of about 20 days.

  So far, many of the ecology of natural eel larvae has been encapsulated in mystery, and it has been difficult to find a good food to feed after artificial hatching. First, a feed mainly composed of freeze-dried powder of shark eggs was developed, which confirmed growth for about 30 days (Patent Document 1). After that, when the fish egg or chicken egg is fed with a diet containing soybean and krill enzyme digests from which phytic acid has been removed, leptocephalus that grows for more than 30 days appears, especially freeze-dried powder of shark eggs and phytic acid. Leptocephalus which grows for more than 250 days by giving a feed containing an enzyme-degraded product of soybean and krill, from which sucrose has been removed, appears to be transformed into glass eel (Patent Document 2). However, the frequency is very low and it has not been put to practical use (Non-patent Document 1).

  In addition, the number of sharks is very small. In recent years, the Washington Convention has proposed the regulation of shark catch, and it has become necessary to develop a feed that can replace the freeze-dried powder of shark eggs.

Japanese Patent Laid-Open No. 11-253111 JP 2005-013116 A

Tanaka H, Aquaculture 201 p51-60 (2001)

  An object of the present invention is to provide a feed for eel larvae that can replace the freeze-dried powder of shark eggs.

As a result of intensive studies to solve the above problems, the present inventors have used the contents of red sea cucumber fish eggs in eel larvae feed, without using a freeze-dried shark egg powder, We found the growth of eel larvae and a high survival rate, and completed this study.
The gist of the present invention is the following (1) to (3) eel larvae feed and a method for breeding eel larvae using them.
(1) An eel larvae feed containing red sea cucumber egg content.
(2) The eel larvae feed of (1), wherein the red sea bream fish eggs are from the yolk formation period to the ovulation period.
(3) A method for raising eel larvae using the eel larvae feed of (1) or (2) above.

  INDUSTRIAL APPLICABILITY The present invention can provide a feed exhibiting the same growth and survival rate as an eel larvae feed using a freeze-dried shark egg powder and a breeding method using the same.

FIG. 1 shows the body length of eel larvae when fed with the red sea cucumber feed described in Example 2. FIG. 2 shows the height of the eel larvae when fed with the red sea cucumber feed described in Example 2. FIG. 3 shows the survival rate of eel larvae when fed with the red sea cucumber feed described in Example 2.

  The present invention relates to the growth of eel larvae. Examples of the eel larvae to be the subject of the present invention include eel larvae to be cultured such as Japanese eel (Anguilla japonica) and European eel (Anguilla anguilla). The eel larvae referred to in the present invention refers to eel larvae at a stage prior to transformation into a glass eel such as preleptocephalus and leptocephalus.

The red squirrel of the present invention refers to the fish of the order of the red squirrel among the vertebrate phylum Lepidoptera. The red-eyed kingfishes include the horse mackerel family, the red-headed family, the sturolesaceae, the acanada family, the radiquesaceae, the frisodeo family, and the Ryugnotokidae family. All of these are considered to have the property of being easily used as the initial feed for eel larvae because they inhabit the deep sea from the middle of the area where natural eel larvae inhabit and lay eggs of prolific floating eggs.
Among these, the red squirrel family includes the red squirrel (Lampris guttatus), also known as Mandai or Chrysanthemum, and the Southern Opa (Lampris immaculatus), also known as Moonfish, which is mainly found in the southern hemisphere. Since it is caught alive and easily circulated for food, eggs are also readily available, which is particularly preferable.
A fish egg consists of an egg membrane and the contents wrapped in the egg membrane. A fish egg becomes an oocyte after completing the growth phase of the oocyte, and enters a maturation phase after a growth phase in which egg membrane formation and accumulation of oil balls and egg yolk are started. It is then released outside the body by ovulation, but until then it accumulates in the ovary of the fish. Among these, for use in feed, it is preferable to use fish egg contents that are rich in nutritional components and are in the stage from egg maturation to pre-laying. In particular, in view of the accumulation of egg yolk, which is a nutrient component such as protein, those at least after the yolk formation period in which the yolk formation has already started are preferable.

The red and red fish eggs used in the present invention can be obtained by catching natural or farmed red sea cucumbers and removing the ovaries. The red sea bream fish eggs may be raw, salted, frozen, liquid, or powdered. When preparing the feed, red sea bream fish eggs may be mixed with other feed ingredients as they are, but in order to maintain the uniformity of the ingredients and always produce the feed, feed preparation It is preferable to crush the fish eggs before to take out the contents of the red sea cucumber fish eggs and mix them with other feed ingredients to produce a feed.
In order to give sufficient growth as a feed ingredient, it is desirable that the fish egg content of the red sea bream used in the present invention is mixed with the feed without deteriorating the nutritional components of the red sea bream fish eggs. In order to mix the nutrient components of red squirrel eggs into the feed without deterioration, it is preferable to use the raw red squirrel eggs in raw or salted or frozen form within one year.

  The feed of the present invention can be prepared by adding water to the fish egg contents of the red sea cucumbers or appropriate water. In addition, the feed of the present invention may be prepared by adding any material that can be used as a feed for eel larvae, but it is possible to add ingredients that inhibit the growth of eel larvae. It is not preferable. Known ingredients that inhibit the growth of eel larvae include phytic acid, lectins, and egg poisons such as dinognerin.

In the feed of the present invention, the above-described fish egg content may be used alone, or other known components such as vitamin mixtures, ascorbic acid, and krill decomposition products may be mixed and used.
In order to make the feed of the present invention easy to feed eel larvae in the breeding aquarium, the content of the egg and other known ingredients are 3 to 50% by weight of the feed weight, more preferably 10%. It is preferable to use it mixed with water so that it is in the range of ˜40% by weight, more preferably 20-30% by weight.

  When raising eel larvae using the feed of the present invention, the feed may be directly put into a water tank where eel larvae are raised, and eaten in a state of being sedimented or applied. When the water in the breeding aquarium is circulated, it is preferable to stop the water while feeding in order to efficiently settle and apply the food. It is preferable to feed the feed in such a way that it always remains in a settled state so as not to be deficient, and divided into five times a day. In order to prevent deterioration of water quality due to the residual feed, it is preferable to wash the residual feed by pouring water between 10 minutes and 60 minutes after feeding.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited by these examples.

<Comparison of survival rate and growth when ovary egg of each fish type is used as feed source>
The growth and survival of eel larvae were compared with each feed using ovarian eggs of each fish species as feed materials. About 300 7-day-old larvae obtained by the method described in Non-Patent Document 1 were housed in a 10 L round bottom aquarium and used as test fish. The method for raising larvae was performed according to Non-Patent Document 1. Five tanks were installed, and feed corresponding to each tank was fed from the age of 8 days. The frequency of feeding was 3 times a day, and the breeding water temperature was 24 ° C. At the time of breeding until 20 and 30 days of age, the number of survivors, body length and height were measured, and the growth and survival were evaluated. In this example, the eel is Japanese eel (Anguilla japonica), the tuna is bluefin tuna (Thunnus orientalis), the dolphin is Coryphaena hippurus, the red sunfish is Lampris guttatus, and the madara is madara (Gadus). macrocephalus).

  Equivalent amounts of distilled water were added to the ovarian eggs of each fish species. After crushing, the contents were filtered through a mesh of 400 μm and further filtered through a 100 μm mesh to recover the contents from which egg membranes and the like were removed. A series of operations were performed under ice cooling. Furthermore, after freezing this component, it was pulverized by freeze-drying to obtain ovary egg powder of each fish species as feed material.

  The amount of distilled water shown in Table 1 was added to the ovarian egg powder of each fish species, and the liquid components obtained by stirring were used as feeds 1-5. The numbers in the table indicate g. The larvae group fed with these feeds 1 to 5 were designated as “Feed 1 ward” to “Feed 5 ward”, respectively.

  In evaluating the performance of these feeds, a feed containing shark eggs as a main raw material was prepared as an index of growth and survival of the test fish, and rearing with this feed was used as a comparative control. The krill decomposition product described in Patent Document 2 was used as an additive. When this feed is used, up to glass eel can be reared. Table 2 shows the composition of this feed. The numbers in the table indicate g. This feed was designated as feed 6. A group of larvae reared on feed 6 was designated “feed 6 ward”. In this example, the shark refers to Squalus acanthias.

  Each feed was given immediately after hatching, and the survival rate at 20 and 30 days of age after hatching, and the average and standard deviation (SD) of the total length and height of the surviving individuals were measured. The results are shown in Tables 3 and 4. The feed 4 had a higher survival rate than the known feed 6 and showed almost the same growth as the feed 6 (dunn, 0.05 <P).

<Growth and growth of red squirrel eggs during long-term breeding>
Using feed 4 and feed 6 used in Example 1, growth and survival until 51 days after hatching were compared. The body length, height, and survival rate were measured on the 20th, 30th, 40th, and 51st days after the hatching, starting from the day when the feed was started. A graph comparing the body length is shown in FIG. 1, a graph comparing the body height is shown in FIG. 2, and a graph comparing the survival rate is shown in FIG.

  As shown in FIG. 1 and FIG. 2, the body length and height throughout the breeding period showed almost the same growth as when a feed containing conventional shark eggs was given.

  As shown in FIG. 3, the survival rate was higher throughout the breeding period than when a conventional diet containing shark eggs was given.

  According to the present invention, it is possible to efficiently raise eels.

Claims (3)

  An eel larvae feed containing red sea cucumber egg content.   2. The eel larvae feed according to claim 1, wherein the red sea bream fish has an egg yolk formation period to an ovulation period.   An eel larva rearing method using the eel larvae feed according to claim 1 or 2.

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