JP7320043B2 - Breeding method of Seriola farmed fish - Google Patents

Description

The present disclosure relates to a method for raising Seriola farmed fish.

Yellowtail is generally known as a fish that is in season in winter, and not only wild yellowtail but also cultured yellowtail are distributed from the viewpoint of maintenance of natural resources, quality control, and the like.
It is generally known that when yellowtail reaches maturity and enters the egg-laying period, nutrients are taken up by the egg before and after that, causing the yellowtail to lose weight. For this reason, in the case of wild yellowtail, the spawning period from February to April or after that, and in the case of farmed yellowtail, growth stagnation occurs during or after the spawning period from May to June, or after that. It gets worse and the value of the product goes down. For this reason, various techniques for reducing the effects of growth stagnation, leanness, and the like in farmed yellowtail have been investigated.

Patent Document 1 provides an aquaculture method that does not cause stagnation or decline in the growth of fish caused by the maturation of reproductive organs, spawning, and ejaculation organs, and that allows fish to steadily mature and does not delay shipping. It is Specifically, it discloses an aquaculture method of rearing yellowtail and the like while irradiating electric lights with a constant illuminance from the evening to the next morning from October to May of the following year at the latest. According to this method, the growth of the reproductive organs of the fish is largely suppressed, spawning and sperm release into the water are not occurred, and the fish continue to grow during this period.

Patent Document 2 describes fish feed having a vitamin E content of 90 mg or less per 1 kg and containing at least one antioxidant selected from the group consisting of coenzyme Q10, sesaminol, α-riboic acid and astaxanthin. It is described that stagnation of fish growth due to reproductive activity can be suppressed by using this fish feed.

In addition, in Non-Patent Document 1, by restricting feed intake from winter to spring until just before the breeding season, body weight increases compared to the non-restricted group, and the development of gonads in yellowtail during the breeding season. is suppressed.

JP-A-2003-333953 JP 2013-188207 A

Aquaculture, 424-425 (2014) 10-17

However, the commercial value of yellowtail depends on its size. , it cannot be said that it is sufficient as a commercial value.
In addition, maturation of the reproductive organs is essential for the purpose of continuous aquaculture while maintaining good traits as farmed fish. persistence is lost.

Accordingly, an object of the present disclosure is to obtain Seriola farmed fish that are difficult to lose weight after the reproductive organ maturity stage and that are excellent in persistence.

This disclosure includes:
<1> After breeding Seriola fish for at least two months in a controlled breeding environment, breeding is started using larvae of Seriola fish obtained by artificial egg collection, and the Seriola fish is grown. matter,
A male individual with a gonadal index (GSI) of 0.5% or more and 10.0% or less, or a female individual with a GSI of 0.5% or more and 4.5% or less at the reproductive organ maturity stage, and the degree of obesity Obtaining adult Seriola farmed fish of 18 or more and 3.5 kg or more in weight,
From the obtained adult Seriola cultured fish, after the reproductive organ maturity, the degree of obesity is 17 or more and the weight is 3.5 kg or more, and the gonadal body index (GSI) is lower than the value at the reproductive organ maturity. A method for raising Seriola farmed fish, comprising obtaining Seriola farmed fish.
<2> The breeding method according to <1> above, wherein the GSI of the Seriola cultured fish after reproductive organ maturity is 2.5% or less for male individuals and 1.0% or less for female individuals.
<3> The breeding method according to the above <1> or <2>, wherein the water temperature in the environment for breeding Seriola fish is adjusted to 15° C. to 28° C. from the start of breeding of larvae of Seriola fish.
<4> Any one of <1> to <3> above, including removing individuals with morphological abnormalities and/or poor growth during breeding and selecting individuals of the genus Seriola fish. breeding method.
<5> The breeding method according to any one of the above <1> to <4>, wherein the breeding in the growth includes aquaculture at 10 m to 18 m below the water surface for at least 5 months, and is carried out for 15 months or longer.
<6> The breeding method according to any one of <1> to <5>, wherein weight management of Seriola fish is carried out during breeding for the growth.
<7> Feeding the Seriola fish with a feed containing 0.1 to 0.3 parts by weight of hot pepper per 100 parts by weight of the feed for at least one month during breeding in the growth. The breeding method according to any one of <1> to <6>.
<8> In the reproductive organ maturity stage, the degree of obesity is 18 or more and the body weight is 3.5 kg or more, and the gonadal body index (GSI) is 0.5% or more and 10.0% or less for males, and 0 for females. .5% or more and 4.5% or less,
After reproductive organ maturity, the degree of obesity is 17 or more, the body weight is 3.5 kg or more, and the gonadal body index (GSI) is lower than the value at the reproductive organ maturity.
Seriola farmed fish.
<9> The Seriola farmed fish according to <8>, wherein the GSI of the Seriola farmed fish after reproductive organ maturity is 2.5% or less for male individuals and 1.0% or less for female individuals.
<10> Individuals in the reproductive organ maturity stage, with a degree of obesity of 18 or more and a body weight of 3.5 kg or more, and a gonadal body index (GSI) of 0.5% or more and 10.0% or less for males and 10.0% or less for females. Seriola farmed fish that is 0.5% or more and 4.5% or less in some cases.
<11> Individuals after reproductive organ maturity, with a degree of obesity of 17 or more and a body weight of 3.5 kg or more, and a gonadal body index (GSI) of less than 0.5% for males and 0.5% for females. Seriola farmed fish that is less than 5%.
<12> The Seriola farmed fish according to <8> or <10> above, wherein the male individual Seriola cultured fish at reproductive organ maturity satisfies at least one of the following (1) to (3):
(1) blood concentration of 11-ketotestosterone (11-KT) is 1800 pg/mL to 4500 pg/mL,
(2) 17α,20β-dihydroxy-4-pregnen-3-one (DHP) blood concentration is 100 pg/mL to 450 pg/mL, and
(3) Blood concentration of estradiol (E2) is 130 pg/mL to 400 pg/mL.
<13> The Seriola farmed fish according to <8> or <10> above, wherein the female Seriola farmed fish in the reproductive organ maturity stage satisfies at least one of the following (4) to (6):
(4) blood concentration of 11-ketotestosterone (11-KT) is 20 pg / mL ~ 175 pg / mL,
(5) 17α,20β-dihydroxy-4-pregnen-3-one (DHP) blood concentration is 100 pg/mL to 350 pg/mL, and
(6) Blood concentration of estradiol (E2) is 300 pg/mL to 10000 pg/mL.
<14> The Seriola farmed fish according to any one of <8> to <13>, wherein the fork length is 50 cm or more.
<15> The farmed fish of the genus Seriola according to any one of <8> to <14>, which is yellowtail, amberjack, greater amberjack, or greater amberjack.
<16> Seriola farmed fish obtained by the breeding method according to any one of <1> to <7>.
<17> After breeding Seriola fish for at least two months in a controlled breeding environment, breeding is started using larvae of Seriola fish obtained by artificial egg collection, and the Seriola fish is grown. matter,
A male individual with a gonadal index (GSI) of 0.5% or more and 10.0% or less, or a female individual with a GSI of 0.5% or more and 4.5% or less at the reproductive organ maturity stage, and the degree of obesity Obtaining adult Seriola farmed fish weighing 18 or more and 3.5 kg or more;
A method for rearing mature-stage aquaculture fish of the genus Seriola, comprising:

According to the present disclosure, it is possible to obtain Seriola farmed fish that are less likely to lose weight after the maturity stage of the reproductive organs and that are excellent in persistence.

A method for raising Seriola farmed fish according to an aspect of the present disclosure uses Seriola fish larvae obtained by artificially collecting Seriola fish after breeding Seriola fish for at least two months in a controlled breeding environment. A male individual with a gonadal index (GSI) of 0.5% or more and 10.0% or less, or a GSI of 0.5% or more at the reproductive organ maturation stage. Obtaining a mature stage Seriola cultured fish with a female individual of 4.5% or less, a degree of obesity of 18 or more and a body weight of 3.5 kg or more, from the obtained mature stage Seriola cultured fish, after reproductive organ maturity, A breeding method comprising obtaining Seriola cultured fish having a degree of obesity of 17 or more, a body weight of 3.5 kg or more, and a gonadal index (GSI) lower than the value at the reproductive organ maturity stage.

A Seriola farmed fish according to another aspect of the present disclosure is a Seriola farmed fish obtained by the method for raising Seriola farmed fish according to the above aspect.
In addition, the Seriola farmed fish according to another aspect of the present disclosure has a degree of obesity of 18 or more and a body weight of 3.5 kg or more in the reproductive organ maturity stage, and a gonadal body index (GSI) of 0.5 for males. % or more and 10.0% or less, or 0.5% or more and 4.5% or less for females, and after reproductive organ maturity, with a degree of obesity of 17 or more and a body weight of 3.5 kg or more, and a gonadal body index (GSI) is a Seriola farmed fish that is lower than the figure for reproductive organ maturity.

According to the method for raising Seriola farmed fish in one aspect of the present disclosure, it is possible to obtain Seriola farmed fish that are less likely to lose weight after the maturity stage of the reproductive organs and that are excellent in sustainability.

To further explain this, in the breeding method of the Seriola farmed fish of the present disclosure, Seriola fish are grown from Seriola fish larvae obtained through artificial egg collection, and in the reproductive organ maturity stage, the body weight is 3. A mature-stage Seriola cultured fish having a predetermined GSI with a weight of 5 kg or more and a degree of obesity of 18 or more can be obtained. From such mature-stage Seriola farmed fish with a body weight of 3.5 kg or more and a degree of obesity of 18 or more and a predetermined GSI, although the GSI is reduced, yellowtail that maintains a body weight of 3.5 kg or more and has a degree of obesity of 17 or more. genus farmed fish can be obtained. Such farmed Seriola fish with a body weight of 3.5 kg or more and a degree of obesity of 17 or more has a sufficient commercial value even after the reproductive organ matures, and is a so-called "individual that has become lean after the maturity period". is not equivalent.
Therefore, according to the method for breeding Seriola farmed fish of the present disclosure, even after the reproductive organ maturity period, Seriola farmed fish with a body weight of 3.5 kg or more and a degree of obesity of 17 or more that are not "thin individuals after the maturity period" you can get fish.

The Seriola farmed fish according to one aspect of the present disclosure has a body weight of 3.5 kg or more and obesity of 18 or more in the reproductive organ maturity stage even if the GSI is lower than the reproductive organ maturity stage after the reproductive organ maturity stage GSI in the range not too low, weight ≥3.5 kg and obesity index ≥17 even after reproductive organ maturity.
Therefore, it can provide functional sperm or eggs in the reproductive organ maturation period, is excellent in the sustainability of culture, and is an individual with a sufficiently high degree of obesity and a weight of 3.5 kg or more after the reproductive organ maturation period. It also has the advantage of high commercial value because it has a high content and a sufficiently high proportion of edible parts.

The Seriola farmed fish according to another aspect of the present disclosure is an individual in the reproductive organ maturity stage, has a degree of obesity of 18 or more and a body weight of 3.5 kg or more, and has a gonadal body index (GSI) of 0.00 in the case of males. Seriola farmed fish containing 5% or more and 10.0% or less, and 0.5% or more and 4.5% or less for females.
Seriola farmed fish at reproductive organ maturity stage according to other aspects of the present disclosure are individuals that have a high degree of obesity and sufficient body weight and a GSI that is not too low compared to wild amberjack. This Seriola cultured fish in the reproductive organ maturation period can efficiently provide the Seriola cultured fish after the reproductive organ maturity period according to the above-described aspect.

According to another aspect of the present disclosure, a method for rearing reproductive-stage Seriola farmed fish includes rearing Seriola fish for at least two months in a controlled rearing environment, and then artificially collecting eggs to obtain larvae of Seriola fish. Obtaining, starting breeding from the obtained larvae of the genus Seriola and growing them into genus Seriola, male individuals having a GSI of 0.5% or more and 10.0% or less at the reproductive organ maturity stage, or GSI A method for raising adult Seriola farmed fish, comprising obtaining a mature Seriola farmed fish that is a female individual with a weight of 0.5% or more and 4.5% or less, and has a degree of obesity of 18 or more and a body weight of 3.5 kg or more. be.
According to the breeding method for reproductive stage Seriola cultured fish according to this aspect, it is possible to provide the above-mentioned useful Seriola cultured fish in reproductive organ maturity stage.

In this specification, the term "process" is not only an independent process, but even if it cannot be clearly distinguished from other processes, it is included in this term as long as the intended purpose of the process is achieved. .
In this specification, the numerical range indicated using "-" shall indicate the range including the numerical values described before and after it as the minimum and maximum values, respectively.

As used herein, the amount of each component in the mixture means the total amount of the multiple substances present in the mixture unless otherwise specified when there are multiple substances corresponding to each component in the mixture. . As used herein, the content of each component in a mixture refers to the total content of the multiple substances present in the mixture when there are multiple substances corresponding to each component in the mixture, unless otherwise specified. means.
As used herein, the term "less than" or "less than" with respect to percentage includes 0%, i.e., "does not contain," unless the lower limit is specifically stated, or includes a value that cannot be detected by current means. means range.
The present disclosure will be described below.

The Seriola farmed fish according to one aspect of the present disclosure has a degree of obesity of 18 or more and a body weight of 3.5 kg or more in the reproductive organ maturity stage, and a gonadal body index (GSI) of 0.5% or more and 10 for males. 0.0% or less, 0.5% or more and 4.5% or less for females, after the reproductive organ maturity, with a degree of obesity of 17 or more and a body weight of 3.5 kg or more, and a gonadal body index (GSI) is lower than the value of reproductive organ maturity in Seriola farmed fish.

Seriola Cuvier, which is a farmed fish of the Seriola genus, includes Seriola dumerili, Seriola lalandi Valenciennes, Seriola quinqueradiata, Seriola rivoliana Valenciennes, Seriola carpenteri, Seriola fasciata, Seriola hippos Mention may be made of Gunther, Seriola peruana Steindachner and Seriola zonata. The low GSI Seriola farmed fish may be yellowtail, amberjack, greater amberjack, or greater amberjack, particularly yellowtail.

The Seriola farmed fish may be farmed fish obtained by any method, and is preferably obtained by being reared and managed with a feed containing a compound feed.
A "mixed feed" means a feed in which materials are combined so as to satisfy nutrients such as proteins, vitamins, and minerals necessary for the growth of fish. "Freshly managed" means raised using a diet selected to achieve a specific purpose.

The body weight (total body weight) of the Seriola farmed fish according to the present disclosure is 3.5 kg or more both at the reproductive organ maturity stage and after the reproductive organ maturity stage. The weight of the reproductive organ maturation period and after the reproductive organ maturation period in Seriola farmed fish is preferably 3.8 kg or more, more preferably 4.0 kg or more, still more preferably 4.2 kg or more, and even more preferably 4.5 kg or more. may be In addition, there may be a change in body weight before and after the reproductive organ maturity of the Seriola farmed fish, and such a change in body weight may be an increase or a decrease in body weight before and after the reproductive organ maturity. . In the case of weight loss, the extent of weight loss can be, for example, within 0.5 kg, preferably within 0.3 kg, or within 0.2 kg.

As used herein, the term “reproductive organ maturation stage” refers to the time when the reproductive organs of Seriola fish are generally equipped with reproductive functions, and male individuals are capable of ejaculation and female individuals are capable of spawning. . In the case of yellowtail, this generally corresponds to the age of 26 to 27 months after hatching, usually from April to May when the water temperature reaches 16°C to 19°C.
As used herein, the term “after reproductive organ maturity” means the period after reproductive organ maturity, after ejaculation in the case of male individuals, and after spawning in the case of female individuals. After, or when there is no fertilization or spawning, it means the period after the reproductive organ weight peaks in the reproductive organ maturity stage and begins to decrease. In the case of yellowtail, this generally corresponds to the period after the 28th month of age, and usually corresponds to the period from May to September when the water temperature is 20°C or higher.
In the present specification, "reproductive organ maturation stage" may be simply referred to as "maturation stage", and "post-reproductive organ maturation stage" may simply be referred to as "post-maturation stage".

As used herein, the term “male” refers to an individual that produces testes, and refers to an individual that has a ZZ type chromosome combination. As used herein, the term "female" refers to an individual that produces ovaries, and refers to an individual that has a ZW type or WW type chromosome combination.

The GSI in Seriola farmed fish is 0.5% or more and 10.0% or less for males and 0.5% or more and 4.5% or less for females in the maturity period, and after the maturity period, mature lower than the early GSI.
Below, yellowtail farming with a body weight of 3.5 kg or more and a GSI at maturity of 0.5% or more and 10.0% or less for males and 0.5% or more and 4.5% or less for females The fish may be referred to as "low GSI Seriola farmed fish".
The gonad somatic index (GSI) used herein is the ratio of gonad weight to visceral fish weight, calculated based on the following formula:
GSI (%) = gonad weight (kg) / visceral weight (kg) x 100

When the low GSI Seriola farmed fish is male, the GSI is 0.5% or more in the maturity stage, so it can be judged that the reproductive organs have matured sufficiently to produce functional sperm. On the other hand, since the GSI is 10.0% or less, it can be judged that the individual has a small degree of leanness due to the maturation of the reproductive organs after the adult stage.
The lower limit of GSI in maturity is 0.7% or more, 1.0% or more, 1.5% or more, 2.0% or more, 2.5% or more, 3.0% or more, 4.0% 5.0% or more, 6.0% or more, 7.0% or more, 7.2% or more, 7.5% or more, 7.7% or more, 8.0% or more, or 8.2% or more can be The upper limit of GSI in the mature stage can be 9.5% or less, 9.0% or less, or 8.8% or less.

When the low GSI Seriola farmed fish is male, the reproductive organs include the testes. The weight of the reproductive organs, i.e., the testes, may generally be 100 g or more at maturity, and may be 120 g or more, 150 g or more, 180 g or more, 200 g or more, 250 g or more, 300 g or more, or 350 g or more, The upper limit is not particularly limited, but may be 450 g or less, 430 g or less, or 400 g or less from the viewpoint of reducing the effect of leanness accompanying maturation of reproductive organs.

When the low GSI Seriola farmed fish is female, the GSI is 0.5% or more in the maturity stage, so it can be judged that the reproductive organs are sufficiently mature to produce functional eggs, On the other hand, since the GSI is 4.5% or less, it can be judged that the individual is less affected by the leanness associated with the maturation of the reproductive organs after the maturity stage.
The lower limit of GSI at maturity is 0.7% or more, 1.0% or more, 1.5% or more, 2.0% or more, 2.5% or more, 3.0% or more, or 3.5%. % or more. The upper limit of GSI in the mature stage can be 4.5% or less, 4.3% or less, 4.2% or less, or 4.0% or less.

When the low GSI Seriola farmed fish is female, reproductive organs include ovaries. The weight of the reproductive organs, ie, ovaries, may generally be 20 g or more at maturity, and may be 30 g or more, 40 g or more, 50 g or more, 80 g or more, 100 g or more, 120 g or more, or 140 g or more. The upper limit is not particularly limited, but may be 300 g or less, 250 g or less, or 200 g or less from the viewpoint of reducing the effects of leanness accompanying maturation of reproductive organs.

Since the low GSI Seriola farmed fish has a GSI within a predetermined range as described above, the concentrations of various reproductive hormones in the maturity stage can be lower than those of natural Seriola fish. Reproductive hormones include 11-ketotestosterone (11-KT), 17α,20β-dihydroxy-4-pregnen-3-one (DHP), estradiol (E2) and the like.

11-KT is one of androgenic sex hormones that function as an endogenous androgenic sex hormone, and is known as a hormone involved in the middle stage of the sperm maturation process. The blood concentration of 11-KT in mature low GSI Seriola cultured fish is 1800 pg/mL or higher, 2000 pg/mL or higher, 2300 pg/mL or higher, 2500 pg/mL or higher, 2700 pg/mL or higher for male individuals, or It may be 3000 pg/mL or more, 4500 pg/mL or less, or 4300 pg/mL or less.

11-KT can also produce female individuals. The blood concentration of 11-KT in low GSI Seriola cultured fish at maturity is 20 pg/mL or higher, 25 pg/mL or higher, 30 pg/mL or higher, 50 pg/mL or higher, or 100 pg/mL or higher for female individuals. 200 pg/mL or less, 180 pg/mL or less, or 160 pg/mL or less.

The method for measuring 11-KT in blood is not particularly limited, and any known measuring method may be used. For example, it can be measured by time resolved fluoroimmunoassay (TR-RIA). As a measurement method using TR-RIA, for example, the method described in Gen. Comp. Endocrinol. 106, 181-188 can be applied.

DHP, also called 17α,20β-dihydroxy-4-pregnen-3-one, is a luteinizing hormone that acts as an active form of testosterone and is known as a hormone involved in the later stages of the sperm or egg maturation process.
The blood concentration of DHP in mature low GSI Seriola cultured fish is 100 pg/mL or higher, 110 pg/mL or higher, 130 pg/mL or higher, 150 pg/mL or higher, or 200 pg/mL or higher for male individuals. may be 450 pg/mL or less, 400 pg/mL or less, or 350 pg/mL. The blood concentration of DHP in low GSI Seriola farmed fish may be 100 pg/mL or higher, 120 pg/mL or higher, 150 pg/mL or higher, or 200 pg/mL or higher, 350 pg/mL or lower, in the case of female individuals. It may be 320 pg/mL or less, or 300 pg/mL or less.
The method for measuring DHP in blood is not particularly limited, and any known measuring method may be used. For example, it can be measured by time resolved fluoroimmunoassay (TR-FIA). As a measurement method using TR-FIA, for example, the method described in Gen. Comp. Endocrinol. 106, 181-188 can be applied.

E2, also called 17-β-estradiol, is one of the female sex hormones, and is known as a hormone that participates directly or indirectly through the liver in the early stage of sperm or egg maturation process. The blood concentration of E2 in low-GSI Seriola farmed fish may be 130 pg/mL or more, 150 pg/mL or more, or 200 pg/mL or more for male individuals, 400 pg/mL or less, 380 pg/mL or less, Or it may be 350 pg/mL or less. The blood concentration of E2 in mature low GSI Seriola cultured fish may be 300 pg/mL or higher, 500 pg/mL or higher, 800 pg/mL or higher, or 1000 pg/mL or higher, and may be 15000 pg/mL or higher for female individuals. mL or less, 10000 pg/mL or less, or 7000 pg/mL or less.
The method for measuring E2 in blood is not particularly limited, and any known measuring method may be used. For example, it can be measured by radioimmunoassay (RIA). A measurement method using RIA is described, for example, in Cell Tissue Res., 218, 315-329.

The low GSI Seriola farmed fish may have any of the above reproductive hormones in the above range. For example, the mature low GSI Seriola farmed fish may have the following combinations of reproductive hormones: can:
If the Seriola farmed fish is a male individual, at least one of the following (1) to (3):
(1) blood concentration of 11-ketotestosterone (11-KT) is 1800 pg/mL to 4500 pg/mL,
(2) 17α,20β-dihydroxy-4-pregnen-3-one (DHP) blood concentration is 100 pg/mL to 450 pg/mL, and
(3) Blood concentration of estradiol (E2) is 130 pg/mL to 400 pg/mL.
If the Seriola farmed fish is a female individual, at least one of the following (4) to (6):
(4) blood concentration of 11-ketotestosterone (11-KT) is 20 pg / mL ~ 175 pg / mL,
(5) 17α,20β-dihydroxy-4-pregnen-3-one (DHP) blood concentration is 100 pg/mL to 350 pg/mL, and
(6) Blood concentration of estradiol (E2) is 300 pg/mL to 10000 pg/mL.

In the case of male individuals, at least one of the above (1) to (3) can be satisfied, for example, a combination of (1) and (2), a combination of (1) and (3), (2) and (3) ) and combinations of (1) to (3).
In the case of female individuals, at least one of (4) to (6) above can be satisfied, for example, a combination of (4) and (5), a combination of (4) and (6), (5) and (6) ) and combinations of (4) to (6).

The GSI in low GSI Seriola farmed fish is within a predetermined range at maturity and decreases after maturity. The extent of GSI reduction before and after maturity is not particularly limited as long as body weight of 3.5 kg or more and obesity level of 17 or more are maintained after maturity, and GSI at maturity is 95% or less, 90% or less. % or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less post-mature GSI.

For low GSI Seriola farmed fish, the GSI after maturity may be lower than the GSI value at maturity, i.e., less than the GSI value at maturity, for example, less than the GSI value at maturity, It may be 2.5% or less for males and 1.0% or less for females. In other words, the Seriola farmed fish after maturity have a degree of obesity of 17 or more and a body weight of 3.5 kg, and the GSI is lower than the GSI at maturity, and is 2.5% or less in the case of males. , may be 1.0% or less in the case of females.
GSI after maturity in male individuals is less than the GSI value in maturity, and in the case of male individuals, 2.5% or less, 2.0% or less, 1.8% or less, 1.5% or less, It may be 1.3% or less, 1.0% or less, 0.8% or less, 0.5% or less, or 0.3% or less. The GSI after maturity of female individuals is lower than the GSI at maturity and is 2.0% or less, 1.5% or less, 1.0% or less, 0.9% or less, 0.8%. 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, or 0.1% or less.

The low GSI Seriola farmed fish may have a degree of obesity of 18 or more at maturity, preferably 19 or more, more preferably 20 or more, and even more preferably 21 or more. The upper limit of the degree of obesity in maturity is not particularly limited as long as the degree of obesity after maturity is 17 or more, and can be, for example, 30 or less, or 29 or less.
In addition, the low GSI Seriola farmed fish may have a degree of obesity of 17 or more, preferably 18 or more, more preferably 19 or more after maturity. Low GSI Seriola farmed fish with a degree of obesity of 17 or more after maturity can provide more so-called fatty edible parts compared to wild fish. The upper limit of the degree of obesity after maturity is not particularly limited, and can be, for example, 29 or less, or 28 or less.

Obesity can generally be evaluated based on the following formula [1].
Obesity =
Weight (g) / {fork length (cm) x fork length (cm) x fork length (cm)} x 1000 ... [1]

The low GSI Seriola farmed fish of the present disclosure maintains a body weight of 3.5 kg or more during and after maturity, and even if the degree of obesity is lower than the degree of obesity in maturity, after maturity Maintained above 17. The fluctuation range of the degree of obesity between maturity and after maturity in low GSI Seriola farmed fish is not particularly limited as long as the degree of obesity is 17 or more after maturity, preferably within 2, more preferably within 1 can be

The fork length of the low GSI Seriola farmed fish can have a fork length of 50 cm or more, 55 cm or more, 57 cm or more, or 60 cm or more for both males and females. Low GSI Seriola farmed fish with a fork length of 50 cm or more tend to have a higher degree of obesity than wild fish, and can provide more edible parts. The fork length is the distance from the tip of the fish's head to the central end of the tail fin, and is an index of external morphology well known to those skilled in the art. Fork length is measured by measuring the straight line distance from the tip of the fish's head to the central end of the tail fin. The upper limit of the fork length of the low-GSI Seriola farmed fish is not particularly limited, and can be, for example, 200 cm or less.

For the measurement of the weight of individual fish, the weight of the fish body obtained by first removing the blood after landing is measured, and the weight is taken as the "total fish weight". After that, the internal organs can be removed and the gonad weight and liver weight can be measured, respectively. For measuring the weight, a measuring instrument that is usually used for measuring the weight of fish and a measuring instrument that is usually used for measuring the weight of internal organs can be used.

The low GSI Seriola farmed fish in one aspect of the present disclosure can have the following characteristics at reproductive organ maturity:
(A1-1) a male individual with a body weight of 3.5 kg or more, a degree of obesity of 20 or more, and a GSI of 2.5% or more and 10.0% or less;
(A1-2) a male individual with a body weight of 4.0 kg or more, a degree of obesity of 20 or more, and a GSI of 5.0% or more and 9.0% or less;
(B1-1) a female individual with a body weight of 3.5 kg or more, a degree of obesity of 19 or more, and a GSI of 1.0% or more and 4.5% or less;
(B1-2) A female individual with a body weight of 4.0 kg or more, a degree of obesity of 19 or more, and a GSI of 2.0% or more and 4.0% or less.

The low GSI Seriola farmed fish in one aspect of the present disclosure can have the following characteristics:
(A2-1) Body weight of 3.5 kg or more, obesity degree of 20 or more, GSI at maturity of 2.5% or more and 10.0% or less, and GSI after maturity of 2.5 % male individuals,
(A2-2) Body weight of 4.0 kg or more, obesity degree of 20 or more, GSI at maturity of 5.0% or more and 9.0% or less, and GSI after maturity of 5.0 % male individuals,
(B2-1) Body weight of 3.5 kg or more, obesity index of 19 or more, GSI at maturity of 1.0% or more and 4.5% or less, and GSI after maturity of 1.0 % male individuals,
(B2-2) Body weight of 4.0 kg or more, obesity index of 19 or more, GSI at maturity of 2.0% or more and 4.0% or less, and GSI after maturity of 2.0 % of male individuals.

The low-GSI Seriola farmed fish of the present disclosure have the body weight and obesity degree as described above, and have a lower GSI than wild-caught Seriola. Low GSI Seriola farmed fish with such characteristics may be at least 1.2 years old or older, or 1.5 years old or older, and generally 2 years old or older, or 3 years old or older. In particular, as with natural yellowtail, not only spring spawning farmed fish but also autumn spawning farmed fish may be used. Yellowtail aquaculture fish harvested in autumn can be obtained by artificially controlling light irradiation, water temperature, and other conditions, and by applying maturation hormones, thereby shifting the timing of collecting eggs or sperm from parent fish. can.

Other Seriola cultured fish of the present disclosure are individuals in the reproductive organ maturity stage, weighing 3.5 kg or more, having a degree of obesity of 18 or more, and having a GSI of 0.5% or more in the case of males20. Seriola farmed fish with a content of 0% or less, and 0.5% or more and 4.5% or less in the case of females. When specifically referring to this Seriola farmed fish, it may be referred to herein as "mature stage low GSI Seriola farmed fish". The mature low GSI Seriola aquaculture fish may have the characteristics of (A1-1) to (A1-2) or (B1-1) to (B1-2) described above.
The mature stage low GSI Seriola farmed fish is preferable in order to efficiently obtain the post-mature stage low GSI Seriola farmed fish.

Other Seriola farmed fish of the present disclosure are individuals after reproductive organ maturity, having a body weight of 3.5 kg or more, a degree of obesity of 17 or more, and a GSI lower than the GSI value in the maturity period. It is a genus farmed fish. This Seriola farmed fish may be referred to herein as "post-maturity low GSI Seriola farmed fish". For post-maturity low GSI Seriola farmed fish, for example, the body weight is 3.5 kg or more and the degree of obesity is 17 or more, and the GSI is less than 2.5% for males and 1.0% for females. or Seriola farmed fish with a body weight of 3.5 kg or more and a degree of obesity of 17 or more and a GSI of less than 0.5% for males and less than 0.5% for females fish, and can be.

For the mature low GSI Seriola farmed fish and the post-maturity low GSI Seriola farmed fish, the above-described weight, GSI, reproductive hormones, degree of obesity, fork length, etc. regarding the low GSI Seriola farmed fish of the present disclosure are unchanged. can be applied.

The low GSI Seriola farmed fish according to the present disclosure adjusts the GSI within a predetermined range by managing or adjusting the composition of the compound feed used for farming, day length conditions, water temperature conditions, farming period, feeding amount, body weight, etc. can be obtained by Examples of methods capable of regulating gonadal maturation include the methods described in JP-A-2013-188207, JP-A-2013-188207, and JP-A-2015-510878. Among them, it is possible to apply a method of adjusting the maturation of the gonads based on the composition of the compound feed that can adjust the maturation of the gonads, the day length conditions and the water temperature conditions that can adjust the maturation of the gonads, and the introduction of foreign substances. It is preferable because it is small.
The Seriola farmed fish according to the present disclosure can be obtained by the method for raising Seriola farmed fish described herein.

<Method of breeding Seriola farmed fish>
The method for rearing low GSI Seriola farmed fish according to the present disclosure uses Seriola larvae obtained by artificially collecting Seriola fish after breeding Seriola fish for at least two months under a controlled environment. Starting breeding and growing Seriola fish (hereinafter sometimes referred to as "breeding process"), male individuals with a GSI of 0.5% or more and 10.0% or less at the reproductive organ maturity stage, or Obtaining adult Seriola farmed fish with a GSI of 0.5% or more and 4.5% or less, a degree of obesity of 18 or more and a body weight of 3.5 kg or more (hereinafter referred to as "mature individual acquisition step") ), from the obtained mature-stage Seriola cultured fish, after the reproductive organ maturity, the degree of obesity is 17 or more and the body weight is 3.5 kg or more, and the GSI is lower than the value at the reproductive organ maturity It includes obtaining Seriola farmed fish (hereinafter sometimes referred to as “post-maturity individual acquisition step”), and includes other steps as necessary.
According to this breeding method, according to the method for breeding Seriola farmed fish, it is possible to obtain Seriola farmed fish that are less likely to lose weight after the reproductive organ matures and that are excellent in sustainability.
In addition, the “breeding method” can be regarded as a method for producing the low-GSI Seriola farmed fish of the present disclosure, and can be used interchangeably with any of the terms such as “production method” and “production method”. can be done.
"Controlled rearing" refers to rearing while properly adjusting the day length and water temperature conditions.

[Breeding process]
In the breeding process, larval fish of the genus Seriola obtained by artificially collecting eggs after breeding the genus Seriola for at least two months under a controlled breeding environment is used.
As the larvae, larvae of the genus Seriola obtained by artificially extracting eggs from Seriola fish bred for two months under a controlled breeding environment may be used. Alternatively, those obtained by a person who carries out the breeding step by carrying out at least one selected from the group consisting of breeding for at least two months under the controlled breeding environment and collecting the eggs.
In addition, the collected eggs are subjected to fertilization treatment after egg collection in order to obtain larval fish. The larvae obtained later may be obtained by means such as purchase and used for growth in the breeding process.
The day length condition in controlled rearing means appropriately combining a light period of 9 to 15 hours and a dark period of 9 to 15 hours. For example, short day conditions can be 10 hours light and 14 hours dark for 30 days, and long day conditions can be 14 hours light and 10 hours dark for 60 days. The water temperature condition means adjusting the water temperature within the range of 15°C to 30°C or 16°C to 28°C.
The day length conditions and water temperature conditions in controlled rearing can be appropriately adjusted in accordance with the rearing. For example, if a preferable light-dark cycle or water temperature can be achieved in a natural environment, those conditions may be applied as they are.

Rearing under a controlled rearing environment can be carried out for at least 2 months, preferably 3 months or more, more preferably 7 months or more. By adjusting the day length conditions and water temperature conditions, for example, it is possible to promote the maturation of the reproductive organs of female individuals, which makes it possible to collect eggs at least three months earlier than natural yellowtails.

Egg collection is done artificially. Here, the term "artificial" means that egg laying is induced under externally controlled conditions such as environmental adjustment, drug administration, and the like. As a result, for example, eggs can be collected earlier than natural yellowtail. In Japan, eggs can be collected at any time of the year.
The collected eggs are then subjected to fertilization treatment. Larvae of the genus Seriola are obtained by holding the fertilized eggs under a predetermined environment. Larvae of the genus Seriola are used for growth.

In the breeding step, breeding is started using larval fish of the genus Seriola to grow the genus Seriola. In order to start breeding from larvae of the genus Seriola and grow the genus Seriola fish, the larvae to adult fish of the genus Seriola may be bred using a method normally carried out under an environment suitable for the growth stage. Seriola fish that have reached a size suitable for marine aquaculture can be reared on the surface of the sea. Breeding of Seriola fish may generally be carried out under an environment in which Seriola grows.
In the present specification, "larval fish of the genus Seriola" means an individual with a fork length of less than about 5 cm after hatching, and juvenile fish and adult fish thereafter are collectively referred to as "seriola fish".

It is preferable to adjust the water temperature in the breeding environment for Seriola fish to 15° C. to 28° C. from the viewpoint of growth efficiency of Seriola fish. At this time, by adjusting the water temperature in the breeding environment within the range of 15°C to 28°C from the start of breeding of the larval fish of the genus Seriola, the breeding stage of the larval fish of the genus Seriola can be improved rather than starting at a later time. The growth rate of Seriola fish can be accelerated from the beginning, and low GSI Seriola farmed fish can be efficiently obtained.
Adjustment of the water temperature in the breeding process can be changed according to the breeding stage. For example, when breeding larvae of the genus Seriola, the temperature can be adjusted to 18°C to 22°C, and after the larvae have grown to become genus Seriola, the temperature can be adjusted to 15°C to 28°C. Examples of water temperature adjustment include addition of water, heating, adjustment of ambient temperature, shading, adjustment of sunshine duration, selection of marine aquaculture farms, transfer of reared fish, and the like.
The breeding process may include a period of high water temperature exceeding 28°C. For example, allowing a maturing Seriola fish to experience a high water temperature of 30° C. or higher can be effective in regulating maturity by applying appropriate stress to the individual. The water temperature that becomes "high water temperature" in the breeding process can be, for example, 29°C, 30°C, or 31°C. The period of high water temperature can be 1 day or more, 2 days or more, 3 days or more, or 5 days or more. The high water temperature period may be continuous or intermittent.

In the breeding process, in order to more effectively obtain the target Seriola farmed fish, individuals with morphological abnormalities and/or poor growth are removed during the breeding in the above-mentioned growth, and individuals of Seriola fish are selected. may include Abnormal morphology and/or poor growth can be determined based on feeding efficiency, feeding rate, body weight, body length, fork length, and the like. The weight, body length, fork length, etc. may be collectively referred to simply as "size" in this specification. Morphological abnormalities include, for example, head depression, spinal curvature, short stature, jaw abnormalities, and the like. The selection rate due to morphological abnormalities or poor growth can be evaluated by the following formula.
Selection rate (%) = normal fish population / (morphologically abnormal or poorly grown population + normal fish population) × 100

In the breeding process, weighing and management of individuals can be performed. Individual weight management may be combined with individual selection based on morphological abnormalities and/or poor growth. Accounting control means that the size of Seriola farmed fish is measured or estimated on a regular basis and controlled. The method of weighing management is not particularly limited, and may include weight measurement, image analysis, and the like. For example, an individual can be weighed on a scale on a monthly basis. In this case, the weight of each individual, that is, body weight may be measured, or several tens of animals may be collectively measured, the average calculated, and the average value may be used for management. As the image analysis means, for example, "AM-100" (AQ1 systems) can be used. As a weight measuring means, for example, "AM-100" (AQ1 systems) can be used.

The breeding period of Seriola fish in the breeding process can be continued until a mature individual having a body weight of 3.5 kg or more is obtained, and may be 12 months or more, 15 months or more, 18 months or more, 20 months or more. It can be months or more, or 22 months or more. The breeding process can be continued until the post-maturity stage individual acquisition process described below.

Breeding in the breeding step may be performed in the ocean or on land. From the viewpoint of ease of individual management and acquisition efficiency of low GSI Seriola farmed fish, it is preferable to include submarine farming at 10 m to 18 m below the water surface for at least 5 months. Such aquaculture, which is also called a subsidence type, is excellent in water temperature stability and tends to provide a breeding environment that is less affected by waves and the like. Marine farming can be conducted for at least 5 months, at least 6 months, or at least 8 months. There is no particular limitation on the upper limit of the period of marine aquaculture, and it can be appropriately set according to the breeding period.

At 10m to 18m below the water surface where submarine aquaculture is performed, the water temperature is often constant in the range of 15°C to 28°C, which is preferable from the viewpoint of environmental stability. However, the position under the surface of the water where the aquaculture is performed may be a position shallower than 10m or a position deeper than 18m. During feeding, the subsea farming position can be raised from the sea to the surface. Generally, the shallower the water, the higher the water temperature, and the deeper the water, the lower the water temperature. Taking advantage of this, it is also possible to adjust the water temperature depending on the location of the sea surface culture. In addition, the breeding using high water temperature as described above may be applied when performing marine aquaculture. In this case, for example, by moving the breeding position near the surface of the sea where the water temperature tends to be higher, a breeding environment with a high water temperature can be easily provided, and the maturation can be adjusted more efficiently.
In the present disclosure, when the upper limit of the cage used for aquaculture is above the sea level, it is called marine aquaculture, and when the upper limit of the cage is below the sea level, it is called submarine aquaculture.

Feed used in the breeding process is not particularly limited, and those commonly used for Seriola farmed fish can be used without limitation. As the feed for Seriola farmed fish, feed containing 0.1 to 0.3 parts by weight of hot pepper per 100 parts by weight of the feed can be used. Hereinafter, this feed will be referred to as "capsicum-containing feed". Capsicum is known to have the effect of improving or maintaining blood color tone in Seriola farmed fish (for example, Japanese Patent Laid-Open No. 2009-232864), and is also effective for obtaining low GSI Seriola farmed fish. The chili in the chili-containing feed can be a chili component or chili powder.

The chili-containing feed may contain clove oil in addition to chili. The content of clove oil can be 0.1 to 0.25 parts by weight per 100 parts by weight of feed.
The period of feeding with the hot pepper-containing feed is not particularly limited, and can be, for example, at least 1 month, at least 2 months, or at least 3 months.

Feeding to Seriola fish in the breeding process is preferably carried out without restriction during the breeding period from the viewpoint of efficiently obtaining low-GSI Seriola farmed fish. That is, in the breeding process, it is preferable to feed the animals with sufficient food without limiting the amount, composition, etc. of the feed. Satiation feeding refers to feeding until no individual requesting food is observed on the surface of the water. From the viewpoint of obtaining low GSI farmed fish of the genus Seriola more efficiently, it is preferable to feed the fish with a high degree of satiety. High satiety feeding refers to feeding until feeding is no longer observed while observing with an underwater camera. As a result, feeding behavior in water that cannot be confirmed on the surface of the water is taken into consideration, and satiation can be achieved in a larger number of individuals, preferably all individuals in captivity. By performing highly saturated feeding, the growth rate of Seriola fish in the breeding process is increased, and mature low GSI Seriola farmed fish can be obtained more reliably.

In the breeding step, it is preferable to remove individuals having at least one of the growth defects selected from the group consisting of morphological abnormalities and growth defects. By removing such individuals with poor growth, it is possible to select individuals with a better growth state than the growth state of the gonads, and to more efficiently obtain low GSI Seriola aquaculture fish. An individual with a morphological abnormality is an individual with a sunken head, a curved spine, a short body, an abnormal jaw, or the like. An individual having poor growth refers to an individual that can be clearly confirmed by observation to be inferior to the growth state of the same period. Individuals with morphological abnormalities are subject to growth restrictions, so they tend to cause poor growth in terms of overall weight. If the malformation does not stop the gonad growth, removing the malformed individual can eliminate the stunted individual with high GSI.

[Step of acquiring mature individuals]
In the mature stage individual acquisition step, a male individual with a GSI of 0.5% or more and 10.0% or less or a female individual with a GSI of 0.5% or more and 4.5% or less in the reproductive organ maturity stage, Mature Seriola cultured fish with a degree of obesity of 18 or more and a body weight of 3.5 kg or more can be obtained.
The adult Seriola farmed fish obtained here is a mature individual having a body weight of 3.5 kg or more and a degree of obesity of 18 or more, and has a GSI lower than that of the mature individual in nature or other cultured fish. By obtaining such mature stage Seriola cultured fish, post-mature low GSI Seriola cultured fish in the subsequent post-mature stage individual acquisition process can be obtained.
In the adult stage individual acquisition step, individuals having the desired GSI, body weight and degree of obesity can be selected by measuring size, blood hormone concentration, and the like. For size measurement, the methods already described for metrological control can be applied. Examples of blood hormones include 11-KT, DHP, E2, and the like. For the measurement of 11-KT, DHP and E2, the methods described above can be applied.

The degree of obesity of adult Seriola cultured fish is relatively high, and may be preferably 19 or more, 20 or more, or 21 or more. The upper limit of the degree of obesity in adult Seriola farmed fish is not particularly limited, and can be, for example, 28 or less, or 27 or less.
Mature Seriola farmed fish can be obtained by a breeding method including the step of acquiring mature individuals. Since the reproductive organs of the mature-stage Seriola cultured fish obtained here are sufficiently mature, eggs or sperm can be obtained from this individual. Eggs or sperm from mature Seriola farmed fish obtained here can be used as seedlings for obtaining Seriola farmed larvae having useful traits. That is, it can be said that the method for raising Seriola farmed fish according to the present disclosure is excellent in the sustainability of farming. In addition, the mature Seriola farmed fish may be supplied to the next post-mature individual acquisition step.

[Individual Acquisition Process after Maturity Period]
In the post-maturity stage individual acquisition step, from the obtained mature stage Seriola farmed fish, Seriola aquaculture fish that have a degree of obesity of 17 or more and a body weight of 3.5 kg or more and a GSI that is lower than the value at the reproductive organ maturity stage That is, Seriola cultured fish are obtained after maturity. For post-maturity Seriola farmed fish, the above-mentioned matters regarding post-maturity low GSI Seriola farmed fish can be applied as they are.
The obtained post-maturity Seriola farmed fish is a Seriola farmed fish that has avoided losing weight to less than 3.5 kg in body weight or less than 17 obesity, and it is possible to continue such useful traits to the next generation. can.
Individuals having the desired GSI, body weight and degree of obesity can be selected based on values such as size and blood hormone concentration, as with mature Seriola farmed fish, or can be landed and the weight of reproductive organs measured. You can also select by

[Use]
In addition, by using the method for raising Seriola farmed fish according to the present disclosure, it is possible to adjust the timing of providing Seriola farmed fish having good traits. The post-maturity Seriola farmed fish according to the present disclosure can be provided at an appropriate time according to the state of the farmed fish, for example, within half a year, within 4 months, within 3 months, or 2 months from the maturity period. can be provided within For example, if 3-year-old adult Seriola farmed fish is obtained in April-May, post-mature Seriola farmed fish can be provided in May-September. As a result, it is possible to stably provide Seriola farmed fish that exhibit favorable levels of obesity and body weight before summer, when red tide is likely to occur, for example.

The low GSI Seriola farmed fish of the present disclosure has sufficient body weight and obesity, and thus has a high nutritional value as a farmed fish. For this reason, the low GSI Seriola farmed fish of the present disclosure has a higher proportion of good quality edible parts compared to wild Seriola, and thus the Seriola farmed fish with a obesity index of less than 17 and a high GSI. be able to.
Edible parts of Seriola farmed fish are preferably used as processed foods, for example, the following heated foods and non-heated foods, and can also be applied as animal feed. Processed foods and animal feeds according to one embodiment may comprise edible parts of low GSI Seriola farmed fish.

Examples of animal feed include cat food, dog food, farmed fish feed, poultry feed, livestock feed, and the like. The proportion of the edible portion of the low-GSI Seriola farmed fish in the animal feed is not particularly limited, and may be 0.1% by weight to 100% by weight or the like. In addition to the edible parts of the low GSI Seriola farmed fish, animal feed may contain other nutrients such as vitamins, carriers and excipients acceptable for animal feed such as water, depending on the type of target animal. Other additives such as may be included as appropriate, if necessary. The animal feed may be housed in a container to be described later. Examples of foods include non-heated foods and heated foods.

One embodiment of the present disclosure includes a low GSI Seriola farmed fish processed food product comprising a low GSI Seriola farmed fish edible portion and a container containing said edible portion. Processed foods can include heated and non-heated foods.
Non-heated products mean edible parts that have not been subjected to heat cooking, and include surimi, sashimi, fillet, blocks and fillets, as well as frozen products, chilled products, freeze-dried products, dried fish, pickles, etc. be able to. It can be judged from the color tone of the surface of the edible part that it has not been cooked. As used herein, the term “heating” means that heat is applied to a state where actomyosin is visibly denatured. When the edible part of cultured fish is heat-treated, the edible part changes color due to the denaturation of actomyosin.
A heated product means an edible part that has been subjected to heat cooking, and can include boiled food, grilled food, steamed food, fried food, paste product, and the like.

The shape of the edible part contained in the processed food is not particularly limited. It may be molded in the shape of

Processed foods can contain at least one selected from the group consisting of other foods, food materials, and accessories, if necessary. Other foods include rice, tsuma (Japanese radish, seaweed, etc.), ginger, sprouts, and the like. Examples of the food material include scallions for scallion paste. Examples of accessories include baluns, labels, refrigerants, coolants, ice, dry ice, and sherbet ice. The accessory may be housed in the container together with the edible part, may be arranged outside the container, may be integral with the container, or may be detachably attached. . Each of the other foods, food ingredients and accessories may be one or a combination of two or more.

The container may be of any type as long as it is used to contain edible parts, and examples thereof include polystyrene foam, paper, vinyl, soft plastics, hard plastics, metals, glass, and the like. The container may have any shape as long as it can accommodate the edible part, and examples thereof include packaging sheets, trays with or without lids, bags, cans, and bottles.

The low GSI Seriola farmed fish of the present disclosure can be crossed with other low GSI Seriola farmed fish or with other traits of Seriola farmed fish. As a result, progeny having genetic traits of the low GSI Seriola farmed fish can be obtained and used as seedlings for aquaculture.

Hereinafter, the present disclosure will be described in detail with examples. However, the present invention is by no means limited to them. "Parts" or "%" are based on mass unless otherwise specified.

[Example 1]
Yellowtail larvae were reared for 24 months in a natural environment, and from the 29th month, rearing was started by adjusting the day length conditions and water temperature. Feeding was carried out normally once a day and once every two days in winter. Short-day and long-day conditions were adopted as day length conditions. In addition, breeding conditions were adjusted according to the conditions described in JP-A-2007-300837.

Oviposition was induced by injection of a hormone agent, and eggs were collected from female individuals. Sperm were collected from male individuals and fertilized to obtain yellowtail larvae. The larval fish were reared on land at a water temperature of 18°C to 20°C. From the 3rd month after they grew into juvenile fish, they were reared in a cage set on the surface of the sea. The fry were submerged 10m to 18m below the surface of the water to start subsea culture. The water temperature was adjusted to 15°C to 22°C during the juvenile stage. The water temperature is adjusted to 15°C to 28°C in the adult stage, and during the rearing period, the body weight of the growing individual is about 500g to 1kg, and there are two consecutive days when the temperature reaches at least 30°C. Over a period of days, the growing individuals were allowed to experience high water temperatures.

Feeding was carried out once a day in general, once a day in winter, and once every two days in winter. However, the high satiety feeding at this time is based on the optimum high satiety feeding method obtained by observing the feeding behavior in the water with a camera, not the high satiety feeding by normal observation of the water surface. During the period of sea surface culture, juvenile fish or adult fish raised submerged 10 m to 18 m below the surface of the water were raised to the surface of the sea each time they were fed. The feed used was a commercially available EP (extruded pellet) to which 0.1 to 0.3 parts by weight of red pepper powder was added per 100 parts by weight of the feed.
In addition, when the juvenile fish reached 2 to 20 g, they were picked up from the land tank and moved to the sea cage. The above operation is also called "offshore delivery". During the rearing period, the fish were checked for their body length, size, shape, etc., and their weight was measured every other month after they were taken out to sea. Body weight was measured using AM-100 (AQ1 system). Based on these results, only individuals considered to have good growth rate without morphological abnormalities (head depression, spine curvature, short body, jaw abnormalities) were bred. The selection rate for morphological abnormalities was 50-95%.

At the reproductive organ maturity stage, which is 5 months or more after the start of marine aquaculture, a male with an average weight of 4.63 kg, an average fork length of 61.03 cm, and an average degree of obesity of 20.35, and an average weight of 4.66 kg and an average Two-year-old female fish with a fork length of 61.60 cm and an average degree of obesity of 19.91 were obtained. The gonad weights of these 2-year-old fish were measured, the GSI was calculated, and the blood hormone concentrations were measured as follows.

Blood was drawn from the heart of the fish and the supernatant portion was collected after centrifugation and stored at -80°C until analysis. A syringe treated with heparin sodium (concentration: 5,000 units/mL, Wako Pure Chemical Industries, Ltd.) was used for drawing blood.
The amount of 11-KT was measured using Testosterone, 11-Keto-, EIA Kit (Strip Plate) (Cayman Chemicals). The amount of DHP was measured using Maturation-Inducing Steroid (salmonid) AChE Tracer, Maturation-Inducing Steroid (salmonid) EIA Antiserum, Precoated (Mouse Anti-Rabbit IgG) EIA 96well Strip Plate, Gen. Comp. Endocrinol. , 181-188, by Time Resolved Fluoroimmunoassay (TR-FIA). The amount of E2 was measured using Estradiol, EIA Kit (Strip Plate) (Cayman Chemicals).
Table 1 shows the results.

As shown in Table 1, mature yellowtail farmed fish with a low GSI but a body weight of 3.5 kg or more and a degree of obesity of 18 or more could be obtained.

These mature yellowtail farmed fish were able to spawn or release sperm. When the obtained yellowtail farmed fish were crossed with individuals having low GSI, the next generation yellowtail larvae could be obtained. That is, it can be said that the Seriola farmed fish obtained in this example are excellent in the sustainability of farming.
The obtained mature yellowtail cultured fish had a body weight of 3.5 kg or more, a degree of obesity of 17 or more, and a GSI of less than 0.5 for both male and female individuals in June, two months after the maturity period. It was confirmed that

[Example 2]
In the same manner as in Example 1, larval fish obtained by early egg collection were bred, and mature yellowtail cultured fish as female individuals of 2-year-old fish, and after maturity as female individuals in April 74 days after maturity. I got yellowtail farmed fish. The body weight, degree of obesity, and GSI were measured in the same manner as in Example 1 for these mature stage yellowtail cultured fish and post-mature stage yellowtail cultured fish. Table 2 shows the results.
As shown in Table 2, even after maturity, the individuals weighed 3.5 kg or more and had a degree of obesity of 17 or more.

This yellowtail farmed fish has a sufficiently low GSI and therefore has a high percentage of edible parts. It also has a high degree of obesity, and thus has a high commercial value.

Thus, according to the present disclosure, it is possible to obtain Seriola farmed fish that are less likely to lose weight after the reproductive organ maturity stage and that are excellent in persistence.

Claims (9)

After breeding the Seriola fish for at least two months under a controlled breeding environment, starting breeding using the larvae of the Seriola fish obtained by artificial egg retrieval to grow the Seriola fish;
A 2-year-old male fish with a gonadal body index (GSI) of 0.5% or more and 10.0% or less at the reproductive organ maturity stage, and a maturity Seriola farmed fish with a degree of obesity of 18 or more and a fork length of 50 cm or more. to obtain
From the obtained adult Seriola farmed fish, after the reproductive organ maturity, the degree of obesity is 17 or more and the fork length is 50 cm or more, and the gonadal body index (GSI) is lower than the value at the reproductive organ maturity. A method for raising Seriola farmed fish, comprising obtaining Seriola farmed fish. 2. The breeding method according to claim 1, wherein the GSI of the Seriola farmed fish after reproductive organ maturity is 2.5% or less. After breeding the Seriola fish for at least two months under a controlled breeding environment, starting breeding using the larvae of the Seriola fish obtained by artificial egg retrieval to grow the Seriola fish;
To obtain adult-stage Seriola cultured fish that are female individuals having a gonadal body index (GSI) of 0.5% or more and 4.5% or less at the reproductive organ maturity stage, having a degree of obesity of 18 or more and a fork length of 50 cm or more. ,
From the obtained adult Seriola farmed fish, after the reproductive organ maturity, the degree of obesity is 17 or more and the fork length is 50 cm or more, and the gonadal body index (GSI) is lower than the value at the reproductive organ maturity. A method for raising Seriola farmed fish, comprising obtaining Seriola farmed fish. 4. The breeding method according to claim 3, wherein the GSI of the Seriola farmed fish after reproductive organ maturity is 1.0% or less. 5. The breeding method according to any one of claims 1 to 4, wherein the water temperature in the breeding environment of the genus Seriola is adjusted to 15°C to 28°C from the start of breeding of the larval fish of the genus Seriola. 6. The breeding method according to any one of claims 1 to 5, which comprises removing individuals with morphological abnormalities and/or poor growth during breeding and selecting individuals of the genus Seriola. 7. The breeding method according to any one of claims 1 to 6, wherein the rearing in the growing comprises subsea farming at 10m to 18m below the water surface for at least 5 months and is carried out for 15 months or longer. 8. The breeding method according to any one of claims 1 to 7, wherein weighing of Seriola fish is carried out during breeding for said growth. 1 to 1, which comprises feeding Seriola fish with a feed containing 0.1 to 0.3 parts by weight of hot pepper per 100 parts by weight of the feed for at least one month during breeding in the growth. The breeding method according to claim 8 .