Yellowtail farmed fish

Abstract

To provide a yellowtail cultured fish that is hard to get thinner after the opportune time of a genital organ, and is superior in durability.SOLUTION: A breeding method of yellowtail cultured fishes comprises the steps of: obtaining larvae of the yellowtail fishes by artificially collecting eggs after breeding yellowtail fishes for at least 2-months, under an adjustment breeding environment where at least one of a day length condition and a water temperature condition is adjusted; starting the breeding from the obtained larvae of the yellowtail fishes, and making the yellowtail fishes grow up; obtaining a male individual having GSI of 0.5% or more and 10.0% or less or a female individual having the GSI of 0.5% or more and 4.5% or less in the genital organ opportune time, and obtaining the yellowtail cultured fishes having the obesity index of 18 or more and the weight of 3.5 kg or more in opportune time; and obtaining the yellowtail cultured fishes having the obesity index of 17 or more and the weight of 3.5 kg or more and having the GSI lower than a numerical value at the genital organ opportune time, after the genital organ opportune time from the obtained opportune time yellowtail cultured fishes. The yellowtail cultured fishes obtained by the breeding method are provided.SELECTED DRAWING: None

Description

Technical Field

[0001] This disclosure relates to Phosphorus nutrition cultured yellowtail.

Background Art

[0002] Yellowtail is a fish generally known as a fish in season in winter. From the viewpoints of maintaining natural resources, quality control, etc., not only natural yellowtail but also cultured yellowtail is on the market. Generally, it is known that when yellowtail matures and enters the spawning period, nutrients are taken into the eggs around that time, resulting in weight loss. For this reason, in the case of natural yellowtail, growth stagnation or the like often occurs during or after the spawning period from February to April, and in the case of cultured yellowtail, during or after the spawning period from May to June, and the fat spread deteriorates, resulting in a decrease in commercial value. For this reason, various techniques for reducing the effects of growth stagnation, weight loss, etc. in cultured yellowtail have been studied.

[0003] Patent Document 1 provides a culturing method in which there is no stagnation or decline in the growth of fish caused by the maturation of reproductive organs and spawning and sperm release organs, and the fish constantly matures without stagnating shipment. Specifically, a culturing method is disclosed in which amberjack, etc. are reared while irradiating an electric lamp with a certain illuminance from evening to the next morning at least during the period from October to May of the following year. According to this method, it is described that the growth of the reproductive organs of the fish is almost suppressed, spawning and the release of sperm into the water do not occur, and the fish continues to grow even during this period.

[0004] Patent Document 2 describes a fish feed containing 90 mg or less of vitamin E per kg and at least one antioxidant selected from the group consisting of coenzyme Q10, sesaminol, α-lipoic acid, and astaxanthin, and it is described that by using this fish feed, stagnation of fish growth due to reproductive activity can be suppressed.

[0005] In addition, Non-Patent Document 1 discloses that by restricting feed intake from winter to just before the breeding season, the body weight increases compared to the non-restricted group, and the development of the gonads is suppressed in yellowtail during the breeding season.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0007]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, the commercial value of yellowtail depends in part on its size. If the body weight is suppressed before the maturity of the reproductive organs, or if the fish becomes significantly emaciated after the maturity of the reproductive organs and the body weight drops to about 3 kg, the commercial value is not sufficient. In addition, when aiming to maintain good traits as cultured fish and continue culturing, the maturity of the reproductive organs is essential. Therefore, in cultured fish in which the maturity of the reproductive organs is completely suppressed, the sustainability of culturing is lost.

[0009] Therefore, an object of the present disclosure is to obtain yellowtail cultured fish that are difficult to lose weight after the maturity of the reproductive organs and have excellent sustainability.

Means for Solving the Problems

[0010] The present disclosure includes the following. <1> After culturing Seriola fishes in a controlled breeding environment for at least two months, start breeding using the fry of Seriola fishes obtained by artificially collecting eggs, and grow the Seriola fishes. <2> At the reproductive organ maturity stage, obtain mature Seriola cultured fish with a gonadosomatic index (GSI) of 0.5% or more and 10.0% or less for male individuals, or 0.5% or more and 4.5% or less for female individuals, and a condition factor of 18 or more and a weight of 3.5 kg or more. <3> From the obtained mature Seriola cultured fish, after the reproductive organ maturity stage, obtain Seriola cultured fish with a condition factor of 17 or more and a weight of 3.5 kg or more, and a gonadosomatic index (GSI) lower than the value at the reproductive organ maturity stage. A breeding method for Seriola cultured fish including the above. <2> The breeding method according to <1> above, wherein the GSI of the Seriola cultured fish after the reproductive organ maturity stage is 2.5% or less for male individuals and 1.0% or less for female individuals. <3> The breeding method according to <1> or <2> above, wherein the water temperature in the breeding environment of Seriola fishes is adjusted to 15°C to 28°C starting from the beginning of breeding the fry of Seriola fishes. <4> The breeding method according to any one of <1> to <3> above, including removing individuals with morphological abnormalities and / or growth deficiencies during the breeding in the above growth process, and selecting individuals of Seriola fishes. <5> The breeding method according to any one of <1> to <4> above, wherein the breeding in the above growth process includes at least 5 months of mariculture at a depth of 10 m to 18 m below the water surface and is carried out for 15 months or more. <6> The breeding method according to any one of <1> to <5> above, including performing weight management of Seriola fishes during the breeding in the above growth process. <7> The breeding method according to any one of <1> to <6> above, including feeding Seriola fishes with a feed containing 0.1 to 0.3 parts by weight of capsicum per 100 parts by weight of feed for at least 1 month during the breeding in the above growth process. <8> At the reproductive organ maturity stage, with a condition factor of 18 or more and a weight of 3.5 kg or more, and a gonadosomatic index (GSI) of 0.5% or more and 10.0% or less for males and 0.5% or more and 4.5% or less for females. After the reproductive organs reach maturity, with a fatness of 17 or more and a body weight of 3.5 kg or more, and the gonadosomatic index (GSI) being lower than the value at the reproductive organ maturity stage, Cultured fish of the genus Seriola. <9> The cultured fish of the genus Seriola according to <8> above, wherein the GSI of the cultured fish of the genus Seriola after the reproductive organs reach maturity is 2.5% or less in male individuals and 1.0% or less in female individuals. <10> Cultured fish of the genus Seriola that are individuals at the reproductive organ maturity stage, with a fatness of 18 or more and a body weight of 3.5 kg or more, and the gonadosomatic index (GSI) is 0.5% or more and 10.0% or less in males and 0.5% or more and 4.5% or less in females. <11> Cultured fish of the genus Seriola that are individuals after the reproductive organs reach maturity, with a fatness of 17 or more and a body weight of 3.5 kg or more, and the gonadosomatic index (GSI) is less than 0.5% in males and less than 0.5% in females. <12> The cultured fish of the genus Seriola according to <8> or <10> above, wherein male individuals of the cultured fish of the genus Seriola at the reproductive organ maturity stage satisfy at least one of the following (1) to (3): (1) The blood concentration of 11-ketotestosterone (11-KT) is 1800 pg / mL to 4500 pg / mL, (2) The blood concentration of 17α,20β-dihydroxy-4-pregnen-3-one (DHP) is 100 pg / mL to 450 pg / mL, and (3) The blood concentration of estradiol (E2) is 130 pg / mL to 400 pg / mL. <13> The cultured fish of the genus Seriola according to <8> or <10> above, wherein female individuals of the cultured fish of the genus Seriola at the reproductive organ maturity stage satisfy at least one of the following (4) to (6): (4) The blood concentration of 11-ketotestosterone (11-KT) is 20 pg / mL to 175 pg / mL, (5) The blood concentration of 17α,20β-dihydroxy-4-pregnen-3-one (DHP) is 100 pg / mL to 350 pg / mL, and (6) The blood concentration of estradiol (E2) is 300 pg / mL to 10000 pg / mL. <14> The cultured fish of the genus Seriola according to any one of <8> to <13> above, with a fork length of 50 cm or more. <15> The yellowtail, Japanese amberjack, greater amberjack, or longtail amberjack according to any one of <8> to <14> above. <16> The yellowtail cultured fish obtained by the breeding method according to any one of <1> to <7> above. <17> Breeding is started using fry of yellowtail cultured fish obtained by artificially collecting eggs after breeding yellowtail fish in a controlled breeding environment for at least two months, and growing the yellowtail fish. At the reproductive organ maturation stage, a male individual with a gonadosomatic 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, and obtaining a mature yellowtail cultured fish with a condition factor of 18 or more and a weight of 3.5 kg or more. A method for breeding mature yellowtail cultured fish including the above.

Advantages of the Invention

[0011] According to the present disclosure, it is possible to obtain a yellowtail cultured fish that is difficult to lose weight after the maturation stage of the reproductive organs and has excellent persistence.

Embodiments for Carrying Out the Invention

[0012] The method for breeding yellowtail cultured fish according to one aspect of the present disclosure includes breeding yellowtail fish in a controlled breeding environment for at least two months, then starting breeding using fry of yellowtail cultured fish obtained by artificially collecting eggs, and growing the yellowtail fish; at the reproductive organ maturation stage, obtaining a mature yellowtail cultured fish that is a male individual with a gonadosomatic 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, and having a condition factor of 18 or more and a weight of 3.5 kg or more; and obtaining a yellowtail cultured fish having a condition factor of 17 or more and a weight of 3.5 kg or more after the reproductive organ maturation stage, and having a gonadosomatic index (GSI) lower than the value at the reproductive organ maturation stage, from the obtained mature yellowtail cultured fish.

[0013] The yellowtail cultured fish according to another aspect of the present disclosure is the yellowtail cultured fish obtained by the method for breeding yellowtail cultured fish according to the above aspect. Moreover, the cultured yellowtail fish according to another aspect of the present disclosure has a fatness of 18 or more and a weight of 3.5 kg or more at the reproductive organ maturity stage, and the gonadosomatic index (GSI) is 0.5% or more and 10.0% or less for males and 0.5% or more and 4.5% or less for females. After the reproductive organ maturity stage, the cultured yellowtail fish has a fatness of 17 or more and a weight of 3.5 kg or more, and the gonadosomatic index (GSI) is lower than the value at the reproductive organ maturity stage.

[0014] According to the method for raising the cultured yellowtail fish according to one aspect of the present disclosure, it is possible to obtain a cultured yellowtail fish that is not easily emaciated after the maturity stage of the reproductive organs and has excellent persistence.

[0015] To further explain this, in the method for raising the cultured yellowtail fish of the present disclosure, yellowtail fish are grown from the fry of yellowtail fish obtained through artificial spawning. At the reproductive organ maturity stage, a mature cultured yellowtail fish with a weight of 3.5 kg or more, a fatness of 18 or more, and a predetermined GSI can be obtained. From such a mature cultured yellowtail fish with a weight of 3.5 kg or more, a fatness of 18 or more, and showing a predetermined GSI, although the GSI decreases, it is possible to obtain a cultured yellowtail fish that maintains a weight of 3.5 kg or more and has a fatness of 17 or more. Such a cultured yellowtail fish with a weight of 3.5 kg or more and a fatness of 17 or more has sufficient commercial value even after the maturity stage of the reproductive organs and does not correspond to a so-called "emaciated individual after the maturity period". Therefore, according to the method for raising the cultured yellowtail fish of the present disclosure, it is possible to obtain a cultured yellowtail fish with a weight of 3.5 kg or more and a fatness of 17 or more that is not an "emaciated individual after the maturity period" even after the maturity stage of the reproductive organs. Therefore, according to the method for raising the cultured yellowtail fish of the present disclosure, it is possible to obtain a cultured yellowtail fish with a weight of 3.5 kg or more and a fatness of 17 or more that is not an "emaciated individual after the maturity period" even after the maturity stage of the reproductive organs.

[0016] The cultured yellowtail fish according to one aspect of the present disclosure has a weight of 3.5 kg or more, a fatness of 18 or more, and a GSI in a not-too-low range at the reproductive organ maturity stage, and even after the reproductive organ maturity stage, it has a weight of 3.5 kg or more and a fatness of 17 or more, even if the GSI decreases compared to the reproductive organ maturity stage. Therefore, it can provide functional sperm or eggs during the reproductive organ maturation period, has excellent sustainability in aquaculture, and is an individual with a sufficiently high fatness and a weight of 3.5 kg or more after the reproductive organ maturation period. Therefore, it has a high nutritional value, a sufficiently high proportion of edible parts, and also has the advantage of high commercial value.

[0017] The cultured yellowtail fish according to another aspect of the present disclosure is an individual in the reproductive organ maturation period, with a fatness of 18 or more and a weight of 3.5 kg or more, and a gonadosomatic index (GSI) of 0.5% or more and 10.0% or less in the case of males and 0.5% or more and 4.5% or less in the case of females. The cultured yellowtail fish in the reproductive organ maturation period according to another aspect of the present disclosure has a high fatness and sufficient weight, and is an individual whose GSI is not too low compared to wild yellowtail. This cultured yellowtail fish in the reproductive organ maturation period can efficiently provide the cultured yellowtail fish after the reproductive organ maturation period according to the above-described aspect.

[0018] The method for culturing yellowtail fish in the reproductive period according to another aspect of the present disclosure includes culturing yellowtail fish in a regulated breeding environment for at least two months, then artificially collecting eggs to obtain fry of yellowtail fish, starting breeding from the obtained fry of yellowtail fish, growing the yellowtail fish, and obtaining a mature cultured yellowtail fish with a male individual having a GSI of 0.5% or more and 10.0% or less, or a female individual having a GSI of 0.5% or more and 4.5% or less, and a fatness of 18 or more and a weight of 3.5 kg or more during the reproductive organ maturation period. According to the method for culturing yellowtail fish in the reproductive period according to this aspect, the above-described useful cultured yellowtail fish in the reproductive organ maturation period can be provided.

[0019] In this specification, the term "step" includes not only an independent step but also a step that is not clearly distinguishable from other steps as long as the intended purpose of the step is achieved. In this specification, the numerical range indicated by using "~" indicates a range including the numerical values described before and after as the minimum value and the maximum value, respectively.

[0020] In this specification, unless otherwise specified when there are multiple substances corresponding to each component in the mixture, the amount of each component in the mixture means the total amount of the multiple substances present in the mixture. In this specification, unless otherwise specified when there are multiple substances corresponding to each component in the mixture, the content rate of each component in the mixture means the total content rate of the multiple substances present in the mixture. In this specification, the terms "below" or "less than" regarding percentages mean a range including 0%, that is, "not containing" when the lower limit value is not specifically described, or a value that is undetectable by current means. Hereinafter, the present disclosure will be described.

[0021] The cultured yellowtail of the genus Seriola according to one embodiment of the present disclosure has a fatness of 18 or more and a weight of 3.5 kg or more at the reproductive organ maturity stage, and the gonadosomatic index (GSI) is 0.5% or more and 10. 0% or less in the case of males, and 0.5% or more and 4.5% or less in the case of females. After the reproductive organ maturity stage, it is a cultured yellowtail of the genus Seriola with a fatness of 17 or more and a weight of 3.5 kg or more, and the gonadosomatic index (GSI) is lower than the value at the reproductive organ maturity stage.

[0022] Examples of the genus Seriola of cultured yellowtail of the genus Seriola include Seriola dumerili, Seriola lalandi Valenciennes, Seriola quinqueradiata, Seriola rivoliana Valenciennes, Seriola carpenteri, Seriola fasciata, Seriola hippos Gunther, Seriola peruana Steindachner, and Seriola zonata. Examples of the cultured yellowtail of the genus Seriola with a low GSI can be yellowtail, amberjack, greater amberjack, or longfin yellowtail, and particularly can be yellowtail.

[0023] The farmed yellowtail can be obtained by any method, and preferably, it is obtained by breeding and management with feed containing compound feed. The "compound feed" means feed in which materials are combined to satisfy nutrients such as proteins, vitamins, and minerals necessary for the growth of fish. The "breeding management" means being bred using feed selected to achieve a specific purpose.

[0024] The weight (total weight) of the farmed yellowtail according to the present disclosure is 3.5 kg or more both during and after the reproductive organ maturation period. The weight of the farmed yellowtail during and after the reproductive organ maturation period 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. Also, there may be a change in weight before and after the reproductive organ maturation period of the farmed yellowtail, and such a change in weight may be an increase or a decrease in weight before and after the reproductive organ maturation period. In the case of a decrease in weight, the decrease range of the weight can be, for example, within 0.5 kg, preferably within 0.3 kg, or within 0.2 kg.

[0025] In this specification, the "reproductive organ maturation period" refers to the period when the reproductive organs of yellowtail fish generally have reproductive functions, and in the case of male individuals, sperm ejaculation is possible, and in the case of female individuals, egg laying is possible. In the case of yellowtail, it generally corresponds to the age of 26 to 27 months after hatching, and usually corresponds to the period from April to May when the water temperature is 16°C to 19°C. In this specification, the "after the reproductive organ maturation period" means the period after the reproductive organ maturation period, and in the case of male individuals, after sperm ejaculation, in the case of female individuals, after egg laying, or in the case of no sperm ejaculation or egg laying, it means the period after the reproductive organ weight reaches its maximum at the reproductive organ maturation period and starts to decrease. In the case of yellowtail, it generally corresponds to the age of 28 months or more, and usually corresponds to the period from May to September when the water temperature is 20°C or more. In this specification, "the mature stage of reproductive organs" may sometimes be simply referred to as "the mature stage", and "after the mature stage of reproductive organs" may sometimes be simply referred to as "after the mature stage".

[0026] In this specification, "male" refers to an individual that produces testes and has a ZZ chromosomal combination. In this specification, "female" refers to an individual that produces ovaries and has a ZW or WW chromosomal combination.

[0027] In cultured yellowtail, the GSI in the mature stage is 0.5% or more and 10.0% or less for males and 0.5% or more and 4.5% or less for females, and after the mature stage, it becomes lower than the GSI in the mature stage. Hereinafter, cultured yellowtail with a weight of 3.5 kg or more and a GSI in the mature stage of 0.5% or more and 10.0% or less for males and 0.5% or more and 4.5% or less for females may sometimes be referred to as "cultured yellowtail with low GSI". The gonadosomatic index (GSI) in this specification refers to a fish with internal organs which is the ratio of the gonad weight to the body weight and is calculated based on the following formula: GSI (%) = gonad weight (kg) / body weight with internal organs (kg) × 100

[0028] When the cultured yellowtail with low GSI is male, since the GSI is 0.5% or more in the mature stage, it can be judged that the reproductive organs are sufficiently mature 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 weight loss associated with the maturation of the reproductive organs after the mature stage. The lower limit value of the GSI in the mature stage can be 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% or more, 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. The upper limit value of the GSI in the mature stage can be 9.5% or less, 9.0% or less, or 8.8% or less.

[0029] When the cultured fish of the low GSI bream genus is male, the reproductive organ is the testis. The weight of the reproductive organ, that is, the testis, generally should be 100 g or more in the mature stage, and can 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. There is no particular limitation on the upper limit value of the testis weight, but from the perspective of reducing the influence of weight loss associated with the maturation of the reproductive organ, it can be 450 g or less, 430 g or less, or 400 g or less.

[0030] When the cultured fish of the low GSI bream genus is female, since the GSI is 0.5% or more in the mature stage, it can be judged that the reproductive organ is 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 has a small influence of weight loss associated with the maturation of the reproductive organ after the mature stage. The lower limit value of the GSI in the mature stage can be 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 value of the GSI in the mature stage can be 4.5% or less, 4.3% or less, 4.2% or less, or 4.0% or less.

[0031] When the cultured fish of the low GSI bream genus is female, the reproductive organ is the ovary. The weight of the reproductive organ, that is, the ovary, generally should be 20 g or more in the mature stage, and can 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. There is no particular limitation on the upper limit value of the ovary weight, but from the perspective of reducing the influence of weight loss associated with the maturation of the reproductive organ, it can be 300 g or less, 250 g or less, or 200 g or less.

[0032] Since the GSI of low GSI cultured yellowtail is within a predetermined range as described above, the concentrations of various reproductive hormones during the maturation period can be lower than those of natural yellowtail fish. Examples of reproductive hormones include 11-ketotestosterone (11-KT), 17α,20β-dihydroxy-4-pregnen-3-one (DHP), estradiol (E2), etc.

[0033] 11-KT is one of the male hormones that function as an endogenous androgen-like hormone and is known as a hormone involved in the mid-stage of the sperm maturation process. The blood concentration of 11-KT in low GSI cultured yellowtail during the maturation period may be 1800 pg / mL or more, 2000 pg / mL or more, 2300 pg / mL or more, 2500 pg / mL or more, 2700 pg / mL or more, or 3000 pg / mL or more in male individuals, and may be 4500 pg / mL or less, or 4300 pg / mL or less.

[0034] Also, 11-KT can be produced by female individuals. The blood concentration of 11-KT in low GSI cultured yellowtail during the maturation period may be 20 pg / mL or more, 25 pg / mL or more 30 pg / mL or more, 50 pg / mL or more, or 100 pg / mL or more in female individuals, and may be 200 pg / mL or less, 180 pg / mL or less, or 160 pg / mL or less.

[0035] There are no particular restrictions on the method for measuring blood 11-KT, and any known measurement method may be used. For example, it can be measured by time resolved fluoroimmunoassay (TR-RIA). The measurement method using TR-RIA can apply, for example, the method described in Gen. Comp. Endocrinol. 106, 181-188. TR-RIA) can be used for measurement. The measurement method using TR-RIA can apply, for example, the method described in Gen. Comp. Endocrinol. 106, 181-188.

[0036] DHP, also known as 17α,20β-dihydroxy-4-pregnen-3-one, is a luteinizing hormone that acts as active testosterone and is known as a hormone involved in the late stage of the maturation process of sperm or eggs. In mature low GSI cultured yellowtail, the blood concentration of DHP in male individuals may be 100 pg / mL or more, 110 pg / mL or more, 130 pg / mL or more, 150 pg / mL or more, or 200 pg / mL or more, and may be 450 pg / mL or less, 400 pg / mL or less, or 350 pg / mL. In female individuals of mature low GSI cultured yellowtail, the blood concentration of DHP may be 100 pg / mL or more, 120 pg / mL or more, 150 pg / mL or more, or 200 pg / mL or more, and may be 350 pg / mL or less, 320 pg / mL or less, or 300 pg / mL or less. There is no particular limitation on the method for measuring blood DHP, and any known measurement 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.

[0037] E2, also known as 17-β-estradiol, is one of the female hormones and is known as a hormone that is directly or indirectly involved in the early stage of the maturation process of sperm or eggs through the liver. In male individuals of mature low GSI cultured yellowtail, the blood concentration of E2 may be 130 pg / mL or more, 150 pg / mL or more, or 200 pg / mL or more, and may be 400 pg / mL or less, 380 pg / mL or less, or 350 pg / mL or less. In female individuals of mature low GSI cultured yellowtail, the blood concentration of E2 may be 300 pg / mL or more, 500 pg / mL or more, 800 pg / mL or more, or 1000 pg / mL or more, and may be 15000 pg / mL or less, 10000 pg / mL or less, or 7000 pg / mL or less. There are no particular restrictions on the method for measuring E2 in the blood, and any known measurement method may be used. For example, it can be measured by Radioimmunoassay (RIA). The measurement method using RIA is described, for example, in Cell Tissue Res., 218, 315 - 329.

[0038] The cultured fish of the low GSI sea bream genus only needs to have any of the above - described reproductive hormones within the above - described range. For example, the cultured fish of the low GSI sea bream genus in the mature stage can have the following combinations of reproductive hormones: When the cultured fish of the sea bream genus is a male individual, at least one of the following (1) - (3): (1) The blood concentration of 11 - keto - testosterone (11 - KT) is 1800 pg / mL - 4500 pg / mL, (2) The blood concentration of 17α,20β - dihydroxy - 4 - pregnen - 3 - one (DHP) is 100 pg / mL - 450 pg / mL, and, (3) The blood concentration of estradiol (E2) is 130 pg / mL - 400 pg / mL. When the cultured fish of the sea bream genus is a female individual, at least one of the following (4) - (6): (4) The blood concentration of 11 - keto - testosterone (11 - KT) is 20 pg / mL - 1 75 pg / mL, (5) The blood concentration of 17α,20β - dihydroxy - 4 - pregnen - 3 - one (DHP) is 100 pg / mL - 350 pg / mL, and, (6) The blood concentration of estradiol (E2) is 300 pg / mL - 10000 pg / mL.

[0039] In the case of a male individual, at least one of the above (1) - (3) can be satisfied. For example, it can be a combination of (1) and (2), a combination of (1) and (3), a combination of (2) and (3), or a combination of (1) - (3). In the case of female individuals, at least one of the above (4) to (6) can be satisfied. For example, it can be a combination of (4) and (5), a combination of (4) and (6), a combination of (5) and (6), or a combination of (4) to (6).

[0040] In cultured fish of the low GSI sea bream genus, the GSI is within a predetermined range during the maturation period and decreases after the maturation period. Regarding the decrease range of GSI before and after the maturation period, there is no particular limitation as long as the body weight is maintained at 3.5 kg or more and the condition factor is 17 or more after the maturation period. The GSI after the maturation period may be 95% or less, 90% 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 of the GSI during the maturation period.

[0041] In cultured fish of the low GSI sea bream genus, the GSI after the maturation period only needs to be lower than the GSI value during the maturation period, that is, less than the GSI value during the maturation period. For example, it may be less than the GSI value during the maturation period and 2.5% or less in the case of males and 1.0% or less in the case of females. In other words, cultured sea bream after the maturation period has a condition factor of 17 or more and a body weight of 3.5 kg, and the GSI is lower than the GSI during the maturation period, and may be 2.5% or less in the case of males and 1.0% or less in the case of females. The GSI after the maturation period of male individuals is less than the GSI value during the maturation period, and in the case of male individuals, it may be 2.5% or less, 2.0% or less, 1.8% or less, 1.5% or less, 1.3% or less, 1.0% or less, 0.8% or less, 0.5% or less, or 0.3% or less. The GSI after the maturation period of female individuals is lower than the GSI during the maturation period and may be 2.0% or less, 1.5% or less, 1.0% or less, 0.9% or less, 0.8% or less, 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.

[0042] The fatness of cultured fish of the low GSI sea bream genus is 18 or more at maturity, preferably 19 or more, more preferably 20 or more, and even more preferably 21 or more. Regarding the upper limit value of the fatness at maturity, there is no particular limitation as long as the fatness after maturity is 17 or more, and it can be, for example, 30 or less, or 29 or less. In addition, the fatness of cultured fish of the low GSI sea bream genus can be 17 or more after maturity, preferably 18 or more, and more preferably 19 or more. Cultured fish of the low GSI sea bream genus with a fatness of 17 or more after maturity can provide more edible parts with so-called fat compared to wild fish. There is no particular limitation on the upper limit value of the fatness after maturity, and it can be, for example, 29 or less, or 28 or less.

[0043] The fatness can generally be evaluated based on the following formula [1]. Fatness = Weight (g) / {fork length (cm) × fork length (cm) × fork length (cm)} × 1000 ··· [1]

[0044] The cultured fish of the low GSI sea bream genus of the present disclosure maintains a body weight of 3.5 kg or more at maturity and thereafter. Regarding the fatness, even when the fatness is lower than that at maturity, it is maintained at 17 or more after maturity. There is no particular limitation on the fluctuation range of the fatness between maturity and after maturity in cultured fish of the low GSI sea bream genus as long as the fatness is 17 or more after maturity, but it can preferably be within 2, and more preferably within 1.

[0045] The fork length of cultured fish of the low GSI yellowtail genus can be 50 cm or more, 55 cm or more, 57 cm or more, or 60 cm or more for both males and females. Cultured fish of the low GSI yellowtail genus with a fork length of 50 cm or more tend to have a higher fatness compared to wild fish and can provide more edible parts. The fork length refers to the distance from the tip of the fish's head to the end of the center of the tail fin, which is an indicator of the external morphology well-known to those skilled in the art. The measurement of the fork length is to measure the straight-line distance in a plan view from the tip of the fish's head to the end of the center of the tail fin. There is no particular limitation on the upper limit value of the fork length of cultured fish of the low GSI yellowtail genus, and it can be, for example, 200 cm or less.

[0046] The weight of a fish individual is measured by first bleeding the fish body obtained after landing and then measuring the weight, which is defined as the "total fish body weight". Thereafter, the internal organs are removed, and the gonad weight and liver weight can be measured respectively. For the weight measurement, measuring instruments commonly used when measuring the weight of fish and measuring instruments commonly used when measuring the internal organ weight can be used.

[0047] Cultured fish of the low GSI yellowtail genus in one aspect of the present disclosure can have the following characteristics during the reproductive organ maturation period: (A1-1) Male individuals with a body weight of 3.5 kg or more, a fatness of 20 or more, and a GSI of 2.5% or more and 10.0% or less, (A1-2) Male individuals with a body weight of 4.0 kg or more, a fatness of 20 or more, and a GSI of 5.0% or more and 9.0% or less, (B1-1) Female individuals with a body weight of 3.5 kg or more, a fatness of 19 or more, and a GSI of 1.0% or more and 4.5% or less, (B1-2) Female individuals with a body weight of 4.0 kg or more, a fatness of 19 or more, and a GSI of 2.0% or more and 4.0% or less.

[0048] The cultured yellowtail with low GSI according to one aspect of the present disclosure can have the following characteristics: (A2-1) Male individuals with a body weight of 3.5 kg or more and a condition factor of 20 or more, with a GSI at maturity of 2.5% or more and 10.0% or less, and a GSI after maturity of less than 2.5%; (A2-2) Male individuals with a body weight of 4.0 kg or more and a condition factor of 20 or more, with a GSI at maturity of 5.0% or more and 9.0% or less, and a GSI after maturity of less than 5.0%. (B2-1) Male individuals with a body weight of 3.5 kg or more and a condition factor of 19 or more, with a GSI at maturity of 1.0% or more and 4.5% or less, and a GSI after maturity of less than 1.0%. (B2-2) Male individuals with a body weight of 4.0 kg or more and a condition factor of 19 or more, with a GSI at maturity of 2.0% or more and 4.0% or less, and a GSI after maturity of less than 2.0%.

[0049] The cultured yellowtail with low GSI of the present disclosure has the above-described body weight and condition factor and has a GSI lower than that of wild yellowtail. The cultured yellowtail with low GSI having such characteristics can be at least 1.2 years old or more, or 1.5 years old or more, generally 2 years old, or 3 years old or more. In particular, it can be not only cultured yellowtail with spring spawning like wild yellowtail, but also cultured yellowtail with autumn spawning. The cultured yellowtail with autumn spawning can be obtained by shifting the timing of collecting eggs or sperm from broodstock by artificially controlling conditions such as light irradiation and water temperature, applying administration of maturation hormones, and the like.

[0050] Other cultured yellowtail of the present disclosure are individuals in the reproductive organ maturity period, which are cultured yellowtail with a body weight of 3.5 kg or more and a condition factor of 18 or more, and a GSI of 0.5% or more and 20.0% or less in the case of males and 0.5% or more and 4.5% or less in the case of females. When particularly indicating this cultured yellowtail, it may be referred to as "cultured yellowtail with low GSI in the maturity period" in this specification. Cultured yellowtail with low GSI in the maturity period may have the characteristics of (A1-1) to (A1-2) or (B1-1) to (B1-2) described above. The cultured yellowtail with low GSI in the maturity period is preferable for efficiently obtaining the cultured yellowtail with low GSI after maturity.

[0051] Other cultured yellowtail fish of the present disclosure are individuals after the reproductive organ maturation period, with a body weight of 3.5 kg or more and a condition factor of 17 or more, and a GSI lower than the GSI value during the maturation period. This cultured yellowtail fish may be referred to as "cultured yellowtail fish with low GSI after the maturation period" in this specification. Examples of the cultured yellowtail fish with low GSI after the maturation period include, for example, cultured yellowtail fish with a body weight of 3.5 kg or more and a condition factor of 17 or more, and a GSI of less than 2.5% in the case of males and less than 1.0% in the case of females, or cultured yellowtail fish with a body weight of 3.5 kg or more and a condition factor of 17 or more, and a GSI of less than 0.5% in the case of males and less than 0.5% in the case of females.

[0052] Regarding the cultured yellowtail fish with low GSI during the maturation period and the cultured yellowtail fish with low GSI after the maturation period, the matters related to body weight, GSI, reproductive hormones, condition factor, fork length, etc. described above for the cultured yellowtail fish with low GSI of the present disclosure can be applied as they are.

[0053] The cultured yellowtail fish with low GSI according to the present disclosure can be obtained by adjusting the GSI within a predetermined range by managing or adjusting the composition of the formulated feed used for aquaculture, day length conditions, water temperature conditions, aquaculture period, feeding amount, body weight, etc. Examples of methods capable of adjusting the maturation of the gonads include, for example, the methods described in JP-A-2013-188207, JP-A-2013-188207, and JP-T-2015-510878. Among them, it is preferable to apply a method of adjusting the maturation of the gonads based on the composition of the formulated feed capable of adjusting the maturation of the gonads, the day length conditions capable of adjusting the maturation of the gonads, and the water temperature conditions, in terms of less introduction of foreign substances. The cultured yellowtail fish according to the present disclosure can be obtained by the method for breeding cultured yellowtail fish described in this specification.

[0054] <Method for Breeding Cultured Yellowtail Fish> The breeding method of Japanese amberjack with low GSI according to the present disclosure is to breed Japanese amberjack fish for at least two months in a regulated breeding environment, and then start breeding using the fry of Japanese amberjack fish obtained by artificially collecting eggs to grow Japanese amberjack fish (hereinafter sometimes referred to as the "breeding process"). At the reproductive organ maturity stage, male individuals with a GSI of 0.5% or more and 10.0% or less, or female individuals with a GSI of 0.5% or more and 4.5% or less, and mature Japanese amberjack farmed fish with a condition factor of 18 or more and a weight of 3.5 kg or more are obtained (hereinafter sometimes referred to as the "mature individual acquisition process"). From the obtained mature Japanese amberjack farmed fish, after the reproductive organ maturity stage, Japanese amberjack farmed fish with a condition factor of 17 or more and a weight of 3.5 kg or more, and a GSI lower than the value at the reproductive organ maturity stage are obtained (hereinafter sometimes referred to as the "post-mature individual acquisition process"), and other processes are included as necessary. According to the breeding method of Japanese amberjack farmed fish in this breeding method, it is possible to obtain Japanese amberjack farmed fish that are difficult to lose weight after the maturity stage of the reproductive organs and have excellent persistence. Note that the "breeding method" can be regarded as a method for producing Japanese amberjack farmed fish with low GSI of the present disclosure, and can be used interchangeably with any term such as "production method" and "manufacturing method". In addition, "regulated breeding" means breeding while appropriately adjusting the day length conditions and water temperature conditions.

[0055] 〔Breeding process〕 In the breeding process, in a regulated breeding environment, Japanese amberjack fish are bred for at least two months and then the fry of Japanese amberjack fish obtained by artificially collecting eggs are used. As the above fry, fry of Japanese amberjack fish obtained by artificially collecting eggs from Japanese amberjack fish bred for two months in a regulated breeding environment may be obtained by means such as purchase, or those obtained by the person performing the above breeding process by performing at least one selected from the group consisting of breeding for at least two months in the above regulated breeding environment and the above egg collection may also be used. In addition, the eggs collected are subjected to a fertilization process after collection in order to obtain fry. However, the person who performs the above breeding process may perform the above fertilization process, or the person who performs the above breeding process may obtain the fry obtained after the above fertilization process by means such as purchase and use them for growth in the breeding process. The day-length conditions in regulated breeding mean appropriately combining a light period of 9 to 15 hours and a dark period of 9 to 15 hours. For example, under short-day conditions, a light period of 10 hours and a dark period of 14 hours can be carried out for 30 days, and under long-day conditions, a light period of 14 hours and a dark period of 10 hours can be carried out for 60 days. The water temperature conditions mean 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 regulated breeding can be appropriately adjusted according to the breeding. For example, in a natural environment, if a preferable light-dark cycle or water temperature can be achieved, those conditions can be directly applied.

[0056] Breeding under a regulated breeding 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, the maturation of the reproductive organs of female individuals can be promoted, and as a result, egg collection can be carried out at least 3 months earlier than natural yellowtail.

[0057] Egg collection is carried out artificially. Here, "artificially" means inducing spawning under an externally controlled environment such as environmental adjustment and administration of drugs during egg collection. As a result, for example, egg collection can be carried out earlier than natural yellowtail. In Japan, egg collection can be carried out at any time throughout the year. The eggs collected are then subjected to a fertilization process. By holding the fertilized eggs after fertilization under a predetermined environment, fry of Seriola fish can be obtained. The fry of Seriola fish are used for growth.

[0058] In the breeding process, breeding is started using larvae of Seriola fish to grow Seriola fish. In order to start breeding from the larvae of Seriola fish and grow Seriola fish, breeding may be carried out using a method normally performed in an environment suitable for the growth stage from the larvae of Seriola fish to adult fish. Seriola fish that have reached a size suitable for sea farming can be bred in the sea. The breeding of Seriola fish may generally be carried out in an environment where Seriola fish grow. In this specification, the "larvae of Seriola fish" means individuals with a fork length of less than about 5 cm after hatching, and the subsequent juvenile fish and adult fish are collectively referred to as "Seriola fish".

[0059] From the perspective of the growth efficiency of Seriola fish, the water temperature in the breeding environment of Seriola fish is preferably adjusted to 15°C to 28°C. 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 larvae of Seriola fish, the growth rate of Seriola fish can be increased from the initial stage of the breeding stage of Seriola fish rather than starting from a later stage, and low-GSI Seriola cultured fish can be efficiently obtained. The adjustment of the water temperature in the breeding process can be changed according to the breeding stage. For example, for the breeding of the larvae of Seriola fish, it can be adjusted to 18°C to 22°C, and after the larvae grow into Seriola fish, it can be adjusted to 15°C to 28°C. Examples of the adjustment of the water temperature include adding water, heating, adjusting the ambient temperature, shading, adjusting the sunshine duration, selecting a sea farming site, and transferring the cultured fish to another tank. In the breeding process, it may include a period of high water temperature exceeding 28°C. For example, exposing mature Seriola fish to a high water temperature of 30°C or higher may be effective for maturity adjustment by imposing appropriate stress on the individuals. 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 period of high water temperature may be a continuous period or an intermittent period.

[0060] In the breeding process, in order to more effectively obtain the target cultured yellowtail, during the breeding in the growth stage, it may include removing individuals with morphological abnormalities and / or poor growth, and selecting individuals of yellowtail fish. The morphological abnormalities and / or poor growth can be judged based on feeding efficiency, feeding rate, body weight, body length, fork length, etc. Body weight, body length, fork length, etc. are collectively referred to as simply "size" in this specification. Examples of morphological abnormalities include head depression, spinal curvature, short body, jaw abnormalities, etc. The selection rate due to morphological abnormalities or poor growth can be evaluated by the following formula. Selection rate (%) = Number of normal fish individuals / (Number of individuals with morphological abnormalities or poor growth + Number of normal fish individuals) × 100

[0061] In the breeding process, the measurement management of individuals can be carried out. The measurement management of individuals may be carried out in combination with the individual selection based on morphological abnormalities and / or poor growth. Measurement management means regularly measuring or estimating the size of cultured yellowtail fish and managing it. There is no particular limitation on the method of measurement management, and examples include body weight measurement, image analysis, etc. For example, the weight of individuals can be measured every month. In this case, the weight of each individual, that is, the body weight, may be measured, or dozens of individuals can be measured together, the average value can be calculated, and the management can be carried out with the average value. Also, as image analysis means, for example, "AM-100" (AQ1 systems) can be used. As body weight measurement means, for example, "AM-100" (AQ1 systems) can be used.

[0062] The breeding period of yellowtail fish in the breeding process can continue until mature individuals with a body weight of 3.5 kg or more are obtained, and it may be 12 months or more, 15 months or more, 18 months or more, 20 months or more, or 22 months or more. The breeding process can continue until the post-mature individual acquisition process described later.

[0063] The breeding in the breeding process may be carried out in the ocean or on land. From the viewpoints of ease of individual management and acquisition efficiency of low-GSI group cultured fish, it is preferable to include sea farming at a depth of 10 m to 18 m below the water surface for at least 5 months. Such sea farming, also referred to as submerged farming, is excellent in water temperature stability and easily provides a breeding environment less affected by waves and the like. The sea farming can be carried out 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 sea farming, and it can be appropriately set according to the breeding period.

[0064] In the range of 10 m to 18 m below the water surface where sea farming is carried out, 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 below the water surface where sea farming is carried out may be a position shallower than 10 m or a position deeper than 18 m. At the time of feeding, the position of sea farming can be lifted from the sea to the sea surface. Also, usually, the water temperature is higher at shallower positions and lower at deeper positions. Utilizing this, the water temperature can also be adjusted according to the position where surface farming is carried out. Further, the breeding at a high water temperature described above may be applied when carrying out sea farming. In this case, for example, by moving the breeding position closer to the sea surface where the water temperature is more likely to be higher, a breeding environment at a high water temperature can be simply provided, and maturation adjustment can be carried out more efficiently. In the present disclosure, the case where the upper limit of the net cage used for aquaculture is at a position above the sea surface is referred to as surface farming, and the case where the upper limit of the net cage is at a position below the sea surface is referred to as sea farming.

[0065] The feed used in the breeding process is not particularly limited, and any feed commonly used for cultured yellowtail can be used without limitation. As the feed for cultured yellowtail, a feed containing 0.1 to 0.3 parts by weight of capsicum 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 an effect of improving or maintaining the color tone of the dark muscle in cultured yellowtail (for example, Japanese Patent Application Laid-Open No. 2009-232864), and is also effective for obtaining cultured yellowtail with a low GSI. The capsicum in the capsicum-containing feed can be in the form of a capsicum component or capsicum powder.

[0066] As the capsicum-containing feed, in addition to capsicum, it can contain clove oil. The blending amount of clove oil can be 0.1 to 0.25 parts by weight per 100 parts by weight of the feed. There is no particular limitation on the feeding period with the capsicum-containing feed, and it can be fed, for example, for at least 1 month, at least 2 months, or at least 3 months.

[0067] Feeding the yellowtail fish in the breeding process is preferably carried out without limitation during the breeding period from the viewpoint of efficiently obtaining cultured yellowtail with a low GSI. That is, in the breeding process, it is preferable to perform satiation feeding without setting restrictions on the amount and composition of the feed, etc. Satiation feeding means feeding until no individuals demanding food on the water surface are observed. From the viewpoint of more efficiently obtaining cultured yellowtail with a low GSI, it is preferable to perform highly satiated feeding. Highly satiated feeding means feeding while observing with an underwater camera until feeding is no longer seen. Thereby, the feeding behavior underwater that cannot be confirmed on the water surface is also taken into account, and satiation can be achieved in more individuals, preferably all individuals under breeding. By performing highly satiated feeding, the growth rate of yellowtail fish in the breeding process is fast, and mature cultured yellowtail with a low GSI can be obtained more reliably.

[0068] In the breeding process, it is preferable to remove individuals having at least one growth defect selected from the group consisting of morphological abnormalities and growth retardation. By removing individuals having such growth defects, individuals with a better growth state than the growth state of the gonads can be selected, and low-GSI yellowtail cultured fish can be obtained more efficiently. An individual having a morphological abnormality refers to an individual in which head depression, spinal curvature, short body, jaw abnormality, etc. are observed, and an individual in which an obvious external abnormality can be confirmed by observation. An individual having growth retardation refers to an individual in which it can be clearly confirmed by observation that it is inferior to the growth state of the same period. Since individuals with morphological abnormalities are restricted in growth, they are likely to cause growth retardation from the viewpoint of total weight. When the morphological abnormality does not stop the growth of the gonads, by removing the individuals with morphological abnormalities, individuals with high GSI and growth retardation can be excluded.

[0069] 〔Adult individual acquisition process〕 In the adult individual acquisition process, at the reproductive organ maturity stage, male individuals with a GSI of 0.5% or more and 10.0% or less, or female individuals with a GSI of 0.5% or more and 4.5% or less, and yellowtail cultured fish at maturity with a condition factor of 18 or more and a weight of 3.5 kg or more can be obtained. The yellowtail cultured fish obtained here are adult individuals having a weight of 3.5 kg or more and a condition factor of 18 or more, and have a lower GSI than natural or other cultured fish of adult individuals. By obtaining such yellowtail cultured fish, matured low-GSI yellowtail cultured fish in the subsequent adult post-individual acquisition process can be obtained. In the adult individual acquisition process, individuals having the target GSI, weight, and condition factor can be selected by measuring the size, measuring the blood hormone concentration, etc. The methods described above for metrology management can be applied to the size measurement. Examples of blood hormones include 11-KT, DHP, E2, etc. The measurement of 11-KT, DHP, and E2 can apply the methods described above.

[0070] The fatness of cultured fish of the genus yellowtail at maturity is relatively high, and preferably may be 19 or more, 20 or more, or 21 or more. There is no particular limitation on the upper limit value of the fatness of cultured fish of the genus yellowtail at maturity, and for example, it can be 28 or less, or 27 or less. Regarding the cultured fish of the genus yellowtail at maturity, the above-mentioned matters can be applied as they are. By a breeding method including up to the mature individual acquisition step, cultured fish of the genus yellowtail at maturity can be obtained. Since the reproductive organs of the cultured fish of the genus yellowtail at maturity obtained here are sufficiently mature, eggs or sperm can be obtained from this individual. The eggs or sperm obtained from the cultured fish of the genus yellowtail at maturity obtained here can be used as seeds for obtaining fry of the genus yellowtail having useful traits. That is, it can be said that the breeding method of the cultured fish of the genus yellowtail according to the present disclosure is excellent in the sustainability of aquaculture. In addition, the cultured fish of the genus yellowtail at maturity may be supplied to the next post-mature individual acquisition step.

[0071] 〔Post-mature individual acquisition step〕 In the post-mature individual acquisition step, from the obtained cultured fish of the genus yellowtail at maturity, cultured fish of the genus yellowtail having a fatness of 17 or more and a weight of 3.5 kg or more, and a GSI lower than the value at the reproductive organ maturity stage, that is, post-mature cultured fish of the genus yellowtail are obtained. Regarding the post-mature cultured fish of the genus yellowtail, the above-mentioned matters regarding the post-mature low-GSI cultured fish of the genus yellowtail can be applied as they are. The obtained post-mature cultured fish of the genus yellowtail are cultured fish of the genus yellowtail in which weight loss to less than 3.5 kg or fatness less than 17 is avoided, and such useful traits can be continued to the next generation. Individuals having the target GSI, weight, and fatness can be selected by values such as size and blood hormone concentration, similar to the cultured fish of the genus yellowtail at maturity, or can also be selected by weighing the reproductive organs after landing.

[0072] 〔Use〕 Moreover, by using the method for culturing farmed yellowtail according to the present disclosure, it is possible to adjust the supply timing of farmed yellowtail having good traits. The farmed yellowtail after the maturation stage according to the present disclosure can be supplied at an appropriate time according to the state of the farmed fish and the like. For example, it can be supplied within six months, within four months, within three months, or within two months from the maturation stage. For example, when obtaining 3-year-old mature farmed yellowtail from April to May, the farmed yellowtail after the maturation stage can be supplied from May to September. Thereby, for example, it is possible to stably supply farmed yellowtail showing good fatness and body weight before summer when red tides are likely to occur.

[0073] The farmed yellowtail with low GSI according to the present disclosure has sufficient body weight and fatness, so it has high nutritional value as farmed fish. Therefore, compared with wild yellowtail and, by extension, farmed yellowtail with a fatness of less than 17 and a high GSI, the farmed yellowtail with low GSI according to the present disclosure can have a higher proportion of high-quality edible parts. The edible part of farmed yellowtail is preferably used as processed foods, for example, the following heated foods and non-heated foods, and can also be applied as animal feed. The processed foods and animal feed according to one embodiment can contain the edible part of farmed yellowtail with low GSI.

[0074] Examples of animal feed include cat food, dog food, fish feed for aquaculture, chicken feed, livestock feed, and the like. There is no particular limitation on the proportion of the edible part of farmed yellowtail with low GSI in animal feed, and it can be, for example, 0.1% by weight to 100% by weight. In addition to the edible part of farmed yellowtail with low GSI, animal feed can appropriately contain other nutrients such as vitamins, acceptable carriers for animal feed such as water, and other additives such as excipients, depending on the type of target animal. The animal feed may be contained in a container described later. Examples of foods include non-heated foods, heated foods, and the like.

[0075] One embodiment of the present disclosure is an edible part of farmed yellowtail with low GSI and a container for containing the edible part It includes processed foods of farmed fish belonging to the genus Buri with low GSI. The processed foods can include heated and non-heated products. The non-heated product means the edible part that has not been subjected to heat cooking, and examples include minced fish, sashimi, sakuramasu, blocks and slices, as well as frozen, chilled, freeze-dried, dried, pickled products, etc. Whether it has not been subjected to heat cooking can be judged by the color tone of the surface of the edible part. In this specification, "heating" means that heat is applied to such an extent that actomyosin is denatured to a visible state. When the edible part of farmed fish is heat-treated, the edible part changes color due to the denaturation of actomyosin, so it can be judged based on the color change of the edible part. The heated product means the edible part that has been subjected to heat cooking, and examples include boiled foods, grilled foods, steamed foods, fried foods, kneaded products, etc.

[0076] The shape of the edible part included in the processed food is not particularly limited, and it may have a shape specific to the part of the edible part, may be an irregular shape obtained by cutting, or may be formed into a specific shape.

[0077] The processed food can optionally include at least one selected from the group consisting of other foods, food materials, and accessories. Examples of other foods include rice, tubers (daikon radish, seaweeds, etc.), pickled ginger, sprouts, etc. Examples of food materials include leeks for negitoro, etc. Examples of accessories include, for example, parsley, labels, cold storage agents, coolants, ice, dry ice, sherbet ice, etc. The accessories may be housed in the container together with the edible part, may be arranged outside the container, may be integrally inseparable from the container, or may be detachably attached. The other foods, food materials, and accessories may each be one or a combination of two or more.

[0078] The container may be any container used for containing edible parts, and examples thereof include those made of materials such as polystyrene foam, paper, vinyl, soft plastic, hard plastic, metal, and glass. The shape of the container may be any shape that can contain edible parts, and examples thereof include packaging sheets, trays with or without lids, bags, cans, and bottles.

[0079] The cultured yellowtail of the present disclosure with low GSI can be crossed with other cultured yellowtail with low GSI or cultured yellowtail with other traits. Thus, offspring having the genetic traits of the cultured yellowtail with low GSI can be obtained and used as fry for aquaculture.

Example

[0080] Hereinafter, the present disclosure will be described in detail with reference to examples. However, the present invention is not limited thereto. Unless otherwise specified, "parts" or "%" are based on mass.

[0081] [Example 1] Larvae of yellowtail were reared in a natural environment for 24 months, and then, starting from the 29th month, rearing was started by adjusting the day-length condition and water temperature. Feeding was carried out once a day to satiation under normal conditions and once every two days to satiation in winter. As the day-length conditions, short-day conditions and long-day conditions were adopted. In addition, the rearing conditions were adjusted according to the conditions described in JP-A-2007-300837.

[0082] A hormone agent was injected to induce spawning, and eggs were collected from female individuals. Sperm was collected from male individuals for fertilization to obtain larvae of yellowtail. The larvae were started to be reared on land at a water temperature of 18°C to 20°C. From the third month when they grew into juveniles, they were reared in a net cage installed on the sea surface. The above-mentioned juveniles were submerged to 10 m to 18 m below the water surface to start marine aquaculture. During the juvenile stage, the water temperature was adjusted to 15°C to 22°C. During the adult stage, the water temperature was adjusted to 15°C to 28°C Also, during the rearing period, days with a temperature of at least 30°C were continuously provided for at least two days during the period when the weight of the growing individuals reached about 500 g to 1 kg, so that the growing individuals experienced high water temperature.

[0083] Feeding was usually carried out once a day with high satiation feeding, and once every two days with high satiation feeding in winter. High satiation feeding was carried out throughout the year without feeding restriction. However, the high satiation feeding at this time was not the high satiation feeding based on the usual water surface observation, but was based on the optimal high satiation feeding method obtained by observing the feeding behavior in water with a camera. During the sea farming period, the juvenile fish or adult fish reared by sinking them to 10 m to 18 m below the water surface were pulled up to the water surface every time they were fed. As the feed, a commercially available EP (extruded pellet) with 0.1 to 0.3 parts by weight of pepper powder added to 100 parts by weight of the feed was used. In addition, when the juvenile fish reached 2 g to 20 g, they were taken out from the land aquarium and transferred to the sea raft. The above operation is also called "washing out". After washing out during the breeding period, the body length, size, morphology, etc. were confirmed at any time, and the body weight was measured every month. For the body weight measurement, the body weight measurement method using AM-100 (AQ1 system) was adopted. Based on these results, only the individuals without morphological abnormalities (head depression, spinal curvature, short body, jaw abnormality) and with a good growth rate were reared. The selection rate for morphological abnormalities and the like was 50 to 95%.

[0084] At the reproductive organ maturity stage, which is 5 months or more after the start of sea farming, 2-year-old male fish with an average body weight of 4.63 kg, an average fork length of 61.03 cm, and an average condition factor of 20.35, and 2-year-old female fish with an average body weight of 4.66 kg, an average fork length of 61.60 cm, and an average condition factor of 19.91 were obtained respectively. The gonad weights of these 2-year-old fish were measured to calculate the GSI, and the blood hormone concentration was measured as follows.

[0085] Blood was extracted from the heart of the fish, and the supernatant was collected after centrifugation and stored at -80°C until analysis. When extracting blood, a syringe treated with sodium heparin (concentration: 5,000 units / mL, Wako Pure Chemical Industries, Ltd.) was used. The amount of 11-KT was measured using Testosterone, 11-Keto-, EIA Kit (Strip Plate) (Cayman Chemicals). For the amount of DHP, using Maturation-Inducing Steroid (salmonid) AChE Tracer, Maturation-Inducing Steroid (salmonid) EIA Antiserum, Precoated (Mouse Anti-Rabbit IgG) EIA 96well Strip Plate, according to the method described in Gen. Comp. Endocrinol. 106, 181-188, it was measured by Time Resolved Fluoroimmunoassay (TR-FIA). For the amount of E2 , it was measured using Estradiol, EIA Kit (Strip Plate) (Cayman Chemicals). The results are shown in Table 1.

[0086]

Table 1

[0087] As shown in Table 1, while having a low GSI, mature yellowtail farmed fish with a body weight of 3.5 kg or more and a fatness of 18 or more were obtained.

[0088] These mature yellowtail farmed fish were able to spawn or ejaculate. When the obtained yellowtail farmed fish with low GSI were crossed with each other, next-generation yellowtail fry were obtained. That is, it can be said that the yellowtail farmed fish obtained in this example are excellent in the sustainability of farming. The obtained mature yellowtail farmed fish were confirmed to have a body weight of 3.5 kg or more and a fatness of 17 or more in June, two months after reaching maturity, and a GSI of less than 0.5 for both male and female individuals.

[0089] [Example 2] In the same manner as in Example 1, rearing was carried out from fry obtained by early spawning, and mature yellowtail cultured fish as female individuals at 2 years old and post-mature yellowtail cultured fish as female individuals in April, 74 days after maturity were obtained. For these mature yellowtail cultured fish and post-mature yellowtail cultured fish, the body weight, condition factor, and GSI were measured in the same manner as in Example 1. The results are shown in Table 2. As shown in Table 2, even after maturity, the individuals had a body weight of 3.5 kg or more and a condition factor of 17 or more.

[0090]

Table 2

[0091] Since the GSI of this yellowtail cultured fish was sufficiently low, the proportion of edible parts was high, and because the condition factor was also high, the commercial value was high, and it was delicious when eaten.

[0092] Thus, according to the present disclosure, it is possible to obtain cultured fish of the genus Seriola that are difficult to lose weight after the maturity of the reproductive organs and have excellent persistence.

Claims

1. A female yellowtail aquaculture fish, at the reproductive organ maturity stage, having a condition factor of 18 or more and a fork length of 50 cm, and a gonadosomatic index (GSI) of 0.5% or more and 4.5% or less, after the reproductive organ maturity stage, having a condition factor of 17 or more and a fork length of 50 cm or more, and a gonadosomatic index (GSI) lower than the value at the reproductive organ maturity stage, yellowtail aquaculture fish.

2. The yellowtail aquaculture fish according to Claim 1, wherein the GSI of the female yellowtail aquaculture fish after the reproductive organ maturity stage is 1.0% or less.

3. A female yellowtail aquaculture fish after the reproductive organ maturity stage, having a condition factor of 17 or more and a fork length of 50 cm or more, and a gonadosomatic index (GSI) of less than 0.5%.

4. The yellowtail aquaculture fish according to Claim 1, wherein the female yellowtail aquaculture fish at the reproductive organ maturity stage satisfies at least one of the following (4) to (6): (4) The blood concentration of 11-ketotestosterone (11-KT) is 20 pg / mL to 175 pg / mL, (5) The blood concentration of 17α,20β-dihydroxy-4-pregnen-3-one (DHP) is 100 pg / mL to 350 pg / mL, and (6) The blood concentration of estradiol (E2) is 300 pg / mL to 10,000 pg / mL.

Images