JPS6156029A - Artificial mature promotion of eel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for artificially ripening eels, more specifically, a method for artificially ripening eels by hormone injection, in which the eels are brought to maturity in a state that approximates their natural environment. Put it in a pressure tank for further ripening.
This invention relates to a method for ripening eels that induces ovulation.

(Prior art) Artificial ripening of eels has been practiced for a long time in Japan, and transparent eggs were obtained at the Chiba Fisheries Experiment Station in 1971. In addition, in 1947, the Faculty of Fisheries, Hokkaido University
Natural spawning through artificial ripening has been successful. Furthermore,
The University of Tokyo and the Shizuoka Prefectural Fisheries Research Institute have also obtained transparent eggs through artificial ripening.

(Problems to be Solved by the Invention) However, in all of the experiments described above, the spawning of ripened eels, ψ? I could not successfully carry out milling. This is because the environment for ripening and spawning is different from the natural one, and therefore the eel's normal maturation, spawning, fertilization, and 4R
This is thought to be due to the fact that f. In other words, in the conventional method, fruit jtl: artificial ripening is performed only by hormone injection, so the MrJl of the broodstock may be impaired, eggs may be released but are immature, or the broodstock may die while still being overripe. As a result, satisfactory spawning and subsequent breeding were not possible. Thus, under anthropogenic conditions that differ markedly from natural boundaries,
Because the eggs are forcibly ripened and released, even if eggs are released, only immature eggs are obtained, and most qt larvae are not qt.
? They died within about a week after becoming wild.

(Means for solving the problems) In order to solve these problems and obtain good mature eggs, sufficient consideration must be given to the natural environmental factors of the eel. In other words, physical factors such as pressure and water temperature, biological factors such as plankton,
Although other geographical factors can be mentioned, the present inventors focused on physical factors among these factors, and using an appropriate hormone agent (11. This invention was completed by learning that if the eel is placed in a pressure tank that creates an environment similar to the deep sea to further promote ripening, it is possible to cause eel ovulation to occur A and obtain good mature eggs. This is what we have come to.

Therefore, the object of the present invention is to obtain iI of broodstock fish! To provide an artificial ripening method capable of inducing ovulation and obtaining well-matured eggs without sacrificing health.

The artificial ripening method of eel according to the present invention includes the first step of artificially ripening eel broodstock by administering a germline stimulating hormone, and the ripening eel broodstock is fully ripened in pressurized seawater. 27S2 steps.

Eel eggs float 1 minute apart, and spawn at a depth of approximately 300 meters.
It is said to be carried out in seawater areas ranging from 500 meters to 500 meters, with high temperatures and relatively high salinity.

Deep sea spawning at a depth of 300 to 500 m includes eel eggs and qr.
It is thought that this is to protect the hatched young fish from being eaten by other small fish, and to allow them to encounter a thick plankton layer of 30 to 50 m during the feeding period immediately after they separate and float to 1r%. Furthermore, since the rapid shedding is thin, there is a risk of damaging the egg membrane if the egg emerges from the sea surface, but deep-sea spawning is thought to have a protective layer of 11'm that prevents such damage.

From the above points, water depth, that is, water pressure, is considered to have the most important effect on eel ripening and ovulation.

In the present invention, paying attention to this point, the eel is ripened by injecting or administering a germ line stimulating hormone such as the pituitary gland of a fish such as Nijima to the eel parent fish, and the hormone is imparted to the eel at around the i & 2nd month. That is, when the increase in body weight begins to become noticeable, transfer the seawater to a pressurized seawater tank device as shown in the figure, and gradually increase the pressure with air or oxygen to a final pressure of 5 atm or more, preferably 30 to 50 In the figure, reference number 1 is a pressure tank, which can be made of any suitable material such as metal. Appropriate temperature measuring means 2 are arranged in the tank l. The tank l is also connected via a safety valve and a valve 3 to a pressurized gas source 4, such as a compressor or a high pressure oxygen gas cylinder. In the illustrated apparatus, a high pressure oxygen gas cylinder is used. tank 1
Seawater is introduced from population 5 onwards. After introducing seawater, a pressure-resistant neck member 6 that is 5% tight and watertight is attached to the inlet 5 of the tank. The temperature of the seawater in the tank 1 can be set to a desired temperature, for example, by housing the tank 1 in a constant temperature bath (not shown).

In the present invention, it has been found that it is preferable to maintain the temperature of the seawater in the tank at around 24°C. When a pressure-resistant tank containing eels is maintained at a nearly constant pressure within the specified range, the eels ripen and reach ovulation. nnm in the tank
If you put it in and allow it to ovulate, it will be possible to obtain fertilized eggs, and if it becomes @, it will become a 9r larva.

(Effects of the Invention) As described above, the method of artificially (i:t) eel according to the present invention does not rely solely on the role of hormones as in the past, but rather achieves a certain degree of 0-degree ripening by administering hormones. Since the eel is further ripened under pressure to a state where normal ovulation occurs, it has the excellent effect of being able to obtain mature eggs with considerable repeatability.

(Example) The present invention will be further explained below with reference to Examples.

A fully matured 1it that has been ripened in seawater since early autumn! Using five healthy eel broodstock, we injected into the dorsal muscle of each eel,
Pituitary-like 20mg1i without bleeding! : Injection was administered once a week for 8 weeks. The Pituitary Gland from Nijima was ingested from Nijima, preserved in 7 seton, ground in a mortar, and dissolved in physiological saline. 9
Place each solid into the pressurized seawater tank device shown in the figure through the opening.
The pressure was slowly increased to 30 atm, and the water temperature was brought to 24°C.

The results were as shown in the fjSI table.

1st table Week 1° 12345 [i78!3 3 0322015G24 上當' 10 II 12 +31415181
(Egg laying) 2 (Death) 3 (Egg release) 4 (Death) 5 (Egg release) *Numbers indicate weight gain rate (%).

The experiment was repeated four times with similar results.

Next, for comparison, a conventional ripening method was carried out. That is,
Five broodstock eel fish were given the pituitary gland of rainbow trout prepared in the same manner at a rate of 1 lq once until the eel died or ovulation occurred. The results were as shown in Table ■.

fftJII table week'4 1 2 3 4 5 8 7 8 910
2-1-! -2211129 50-3-2-2-3-2-1? 7 weeks” 10 11 12 13 14 15 181
39 39 45 4951 6051 (
Egg release) 25047 (dead) 3 5258 (dead) 4 -5-11-12-15 (dead) 5 19
24 31 30 27 18 (hey death) *Numbers are weight gain rate (%) - (IIll body weight at 1 hour) /
(Starting body 11) indicates xlOO.

As can be seen from the above results, the ones that were ripened using the conventional ripening method had 1 ovulated, 3 died due to weight gain, and
One individual died and the ovulation rate was 20%,
According to the method of the present invention.

Three ovulated, one died due to weight gain, and one died.The ovulation rate was significantly improved to 60%, and on average 2/3 of the ovulated animals produced mature eggs that formed a perivitelline cavity. Ta.

[Brief explanation of the drawing]

The figure is a schematic diagram showing an example of a pressurized seawater tank device suitable for carrying out the method for artificially ripening eel according to the fourth invention. 1...Pressure tank, 2φ...Temperature measurement means, 3...Safety valve and valve, 4Φ...Pressurized gas source, 5...
・Tank inlet, 6. Lid member, -

Claims (5)

[Claims] (1) A first step in which eel broodstock is artificially ripened by administering a germ line stimulating hormone, and a second step in which the ripened eel broodstock is fully ripened in pressurized seawater. Artificial ripening method for eel. (2) The method according to claim 1, wherein the second step is performed under a pressure of 5 atmospheres or more. (3) The method according to claim 1, wherein the eel broodstock is transferred to the second step when the weight increase becomes noticeable in the first step. (4) The method according to claim 1, wherein the second step is performed in a pressurized atmosphere using oxygen gas. (5) The method according to claim 1, wherein the second step is performed in an atmosphere of pressurized air.