Cultured japanese amberjack fish

Abstract

To provide cultured amberjack fish that are resistant to weight loss after the maturation period of the reproductive organs and have excellent persistence.SOLUTION: A method for rearing cultured amberjack fish comprises: under an adjusted rearing environment in which at least one of a day-length condition and a water temperature condition is adjusted, rearing amberjack fish for at least two months and then artificially collecting eggs to obtain larvae of the amberjack fish; starting rearing from the obtained amberjack fish larvae to raise them to the amberjack fish; during the reproductive organ maturation period, obtaining the cultured mature amberjack fish in which males have a GSI from 0.5% to 10.0% inclusive or females have a GSI from 0.5% to 4.5% inclusive and which have an obesity factor of 18 or more and a body weight of 3.5 kg or more; and, from the obtained cultured mature amberjack fish, obtaining amberjack fish after the reproductive organ maturation period having an obesity factor of 17 or more, a body weight of 3.5 kg or more, and a GSI lower than the value during the reproductive organ maturation period. Also there are provided amberjack fishes obtained by the rearing method.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to farmed yellowtail fish. [Background technology]

[0002] Yellowtail is generally known as a fish that is in season in winter, and from the perspective of maintaining natural resources and quality control, not only wild yellowtail but also farmed yellowtail is distributed. It is generally known that when yellowtail matures and reaches spawning age, it loses nutrients to its eggs around the time of spawning, causing it to lose weight. For this reason, in the case of wild yellowtail, during or after the spawning season (February to April), and in the case of farmed yellowtail, during or after the spawning season (May to June), growth often slows and the fat content decreases, resulting in a decrease in commercial value. For this reason, various technologies are being investigated to reduce the effects of growth slowdown and leanness in farmed yellowtail.

[0003] Patent Document 1 provides an aquaculture method that prevents the stagnation or decline in fish growth caused by the maturation of reproductive organs and the organs for spawning and sperm release, allowing fish to steadily mature and preventing delays in shipping. Specifically, the method discloses a method of raising yellowtail and other fish by irradiating them with electric lights of a certain intensity from evening until the following morning, from October to May at the latest. It states that this method almost completely suppresses the growth of the fish's reproductive organs, prevents spawning and the release of sperm into the water, and allows the fish to continue growing even during this period.

[0004] Patent Document 2 describes a fish feed containing 90 mg or less of vitamin E per 1 kg and at least one antioxidant selected from the group consisting of coenzyme Q10, sesaminol, alpha lipoic acid, and astaxanthin, and describes that use of this fish feed can suppress stagnation of fish growth due to reproductive activity, etc.

[0005] Furthermore, Non-Patent Document 1 discloses that restricting feed intake from winter to spring until just before the breeding season increases body weight compared to unrestricted groups, and also suppresses reproductive gland development in yellowtail during the breeding season. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-333953 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-188207 [Non-patent literature]

[0007] [Non-Patent Document 1] Aquaculture, 424-425 (2014) 10-17 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the commercial value of yellowtail depends to some extent on its size, and if its weight is suppressed before its reproductive organs mature, or if it loses weight significantly after its reproductive organs mature and weighs only around 3 kg, it cannot be said to have sufficient commercial value. Furthermore, if the goal is to maintain the good characteristics of farmed fish and continue farming them, maturation of the reproductive organs is essential, so farmed fish in which the maturation of the reproductive organs is completely suppressed will lose their sustainability as farmed fish.

[0009] Therefore, the object of the present disclosure is to obtain farmed yellowtail fish that are less likely to lose weight after the maturation of their reproductive organs and have excellent sustainability. [Means for solving the problem]

[0010] The present disclosure includes the following: <1> Raising fish of the genus Seriola for at least two months in a regulated rearing environment, and then starting rearing using larvae of fish of the genus Seriola obtained by artificially collecting eggs, and growing the fish of the genus Seriola; Obtaining mature cultured yellowtail fish of the genus Seriola, which are male individuals with a gonadosomatic index (GSI) of 0.5% to 10.0% or female individuals with a GSI of 0.5% to 4.5% at the maturity stage of reproductive organs, with a body mass index of 18 or more and a body weight of 3.5 kg or more; From the obtained mature cultured yellowtail fish, after the maturation of the reproductive organs, a body mass index of 17 or more and a body weight of 3.5 kg or more are obtained, and the gonadosomatic index (GSI) is lower than the value at the maturation of the reproductive organs. A method for raising farmed fish of the genus Yellowtail, including <2> The GSI of the cultured yellowtail fish after maturation of the reproductive organs is 2.5% or less for males and 1.0% or less for females. <1> The rearing method described. <3> From the start of rearing the yellowtail larvae, the water temperature in the rearing environment for the yellowtail larvae is adjusted to 15°C to 28°C. <1> or <2> The rearing method described. <4> During the rearing process, individuals with morphological abnormalities and / or poor growth are removed, and individuals of the genus Yellowtail are selected. <1> ~ <3> The rearing method described in any one of the above. <5> The rearing in the growing stage includes submerged cultivation at 10 to 18 meters below the surface for at least 5 months, and is carried out for 15 months or more. <1> ~ <4> The rearing method described in any one of the above. <6> The method for measuring and managing the weight of yellowtail fish during the rearing of the fish. <1> ~ <5> The rearing method described in any one of the above. <7> During the rearing of the fish of the genus Seriola, a feed containing 0.1 to 0.3 parts by weight of chili pepper per 100 parts by weight of feed is fed to the fish of the genus Seriola for at least one month. <1> ~ <6> The rearing method described in any one of the above. <8> At the time of reproductive organ maturation, the obesity index is 18 or more, the body weight is 3.5 kg or more, 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 reproductive organ maturity, the obesity index is 17 or higher, the body weight is 3.5 kg or higher, and the gonadosomatic index (GSI) is lower than the value at the time of reproductive organ maturity. A farmed fish of the genus Yellowtail. <9> The GSI of the cultured yellowtail fish after maturation of the reproductive organs is 2.5% or less for males and 1.0% or less for females. <8> A farmed fish of the genus Yellowtail. <10> Farmed fish of the genus Yellowtail that are at the maturity stage of their reproductive organs, have a body mass index of 18 or more, a body 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. <11> A farmed fish of the genus Yellowtail that has undergone reproductive organ maturation, has a body mass index of 17 or more, weighs 3.5 kg or more, and has a gonadosomatic index (GSI) of less than 0.5% for males and less than 0.5% for females. <12> The above-mentioned farmed male yellowtail fish of the genus Seriola at the stage of reproductive organ maturation satisfy at least one of the following (1) to (3): <8> or <10> Listed farmed yellowtail fish: (1) Blood concentration of 11-ketotestosterone (11-KT) is 1800pg / mL to 4500pg / mL, (2) 17α,20β-dihydroxy-4-pregnen-3-one (DHP) blood concentration is 100 pg / mL to 450 pg / mL, and (3) Blood estradiol (E2) concentration is 130pg / mL to 400pg / mL. <13> The above-mentioned farmed female yellowtail fish of the genus Seriola at the stage of maturation of reproductive organs satisfies at least one of the following (4) to (6): <8> or <10> Listed farmed yellowtail fish: (4) 11-ketotestosterone (11-KT) blood concentration 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) Blood estradiol (E2) concentration is 300pg / mL to 10,000pg / mL. <14> The fork length is 50cm or more. <8> ~ <13> A cultured fish of the genus Yellowtail described in any one of the above. <15> The fish is a yellowtail, a amberjack, a greater amberjack, or a long-finned amberjack. <8> ~ <14> A cultured fish of the genus Yellowtail described in any one of the above. <16> The aforementioned <1> ~ <7> A cultured fish of the genus Yellowtail obtained by the breeding method described in any one of the above. <17> Raising fish of the genus Seriola for at least two months in a regulated rearing environment, and then starting rearing using larvae of fish of the genus Seriola obtained by artificially collecting eggs, and growing the fish of the genus Seriola; Obtaining mature cultured yellowtail fish of the genus Seriola, which are male individuals with a gonadosomatic index (GSI) of 0.5% to 10.0% or female individuals with a GSI of 0.5% to 4.5% at the maturity stage of reproductive organs, and have a body mass index of 18 or more and a body weight of 3.5 kg or more; A method for raising mature cultured yellowtail fish, including: [Effects of the Invention]

[0011] According to the present disclosure, it is possible to obtain farmed yellowtail fish that are less likely to lose weight after the maturation of their reproductive organs and have excellent sustainability. DETAILED DESCRIPTION OF THE INVENTION

[0012] A method for raising cultured yellowtail fish according to one embodiment of the present disclosure includes raising yellowtail fish in a regulated rearing environment for at least two months, then starting rearing using yellowtail larvae obtained by artificially collecting eggs and growing the yellowtail fish; obtaining mature yellowtail cultured fish that are male individuals with a gonadosomatic index (GSI) of 0.5% or more and 10.0% or female individuals with a GSI of 0.5% or more and 4.5% or less at the time of reproductive organ maturity, have a body mass index of 18 or more, and a body weight of 3.5 kg or more; and obtaining from the obtained mature yellowtail cultured fish, after reproductive organ maturity, yellowtail cultured fish that have a body mass index of 17 or more, a body weight of 3.5 kg or more, and have a gonadosomatic index (GSI) lower than the value at the time of reproductive organ maturity.

[0013] Another aspect of the present disclosure provides farmed yellowtail fish obtained by the method for raising farmed yellowtail fish according to the above aspect. Another aspect of the present disclosure relates to farmed fish of the genus Yellowtail, which, at the time of reproductive organ maturation, have a body mass index of 18 or more and a body weight of 3.5 kg or more, with a gonadosomatic index (GSI) of 0.5% to 10.0% for males and 0.5% to 4.5% for females, and which, after the time of reproductive organ maturation, have a body mass index of 17 or more and a body weight of 3.5 kg or more, with a gonadosomatic index (GSI) lower than the values ​​at the time of reproductive organ maturation.

[0014] According to the method for raising cultured yellowtail fish in one aspect of the present disclosure, it is possible to obtain cultured yellowtail fish that are less likely to lose weight after the maturation of their reproductive organs and that have excellent sustainability.

[0015] To explain this further, in the method for raising cultured yellowtail fish of the present disclosure, yellowtail fish are raised from yellowtail larvae obtained through artificial egg collection, and mature cultured yellowtail fish are obtained that have a body weight of 3.5 kg or more, a body fatness index of 18 or more, and a predetermined GSI at the time of reproductive organ maturation. From such mature cultured yellowtail fish that have a body weight of 3.5 kg or more, a body fatness index of 18 or more, and a predetermined GSI, it is possible to obtain cultured yellowtail fish that maintain a body weight of 3.5 kg or more and a body fatness index of 17 or more, although the GSI will decrease. Such cultured yellowtail fish that have a body weight of 3.5 kg or more and a body fatness index of 17 or more have sufficient commercial value even after their reproductive organs have matured, and do not correspond to so-called "individuals that have become thin after the maturation period." Therefore, according to the method for raising farmed yellowtail fish disclosed herein, it is possible to obtain farmed yellowtail fish weighing 3.5 kg or more and with a body fatness index of 17 or more, which are not "individuals that have become thin after the maturation period", even after the maturation of their reproductive organs.

[0016] In one embodiment of the present disclosure, even if the GSI after reproductive organ maturation is lower than that at the time of reproductive organ maturation, the farmed fish of the genus Yellowtail have a body weight of 3.5 kg or more, an obesity index of 18 or more, and a GSI that is not too low at the time of reproductive organ maturation, and even after reproductive organ maturation, they have a body weight of 3.5 kg or more and an obesity index of 17 or more. Therefore, it can provide functional sperm or eggs at the stage of reproductive organ maturity, making it highly sustainable for aquaculture. After reproductive organ maturity, the fish have a sufficiently high degree of obesity and weigh more than 3.5 kg, so they have high nutritional value and a sufficiently high proportion of edible parts, which gives them the advantage of high commercial value.

[0017] Another aspect of the present disclosure relates to farmed fish of the genus Yellowtail, which are individuals in the maturation stage of their reproductive organs, have a body mass index of 18 or more, a body 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. According to another embodiment of the present disclosure, the reproductively matured cultured yellowtail fish have a high degree of obesity, a sufficient body weight, and a GSI that is not too low compared to wild-caught yellowtail. These reproductively matured cultured yellowtail fish can efficiently provide the reproductively matured cultured yellowtail fish according to the above-described embodiment.

[0018] Another aspect of the present disclosure relates to a method for raising reproductive-stage cultured yellowtail fish, which includes raising yellowtail fish in a regulated rearing environment for at least two months, then artificially collecting eggs to obtain yellowtail larvae, initiating rearing of the obtained yellowtail larvae and raising them to become yellowtail fish, and obtaining mature yellowtail cultured fish that, at the time of reproductive organ maturation, are 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, have a body mass index of 18 or more, and weigh 3.5 kg or more. According to the method for raising reproductive-stage cultured yellowtail fish of this embodiment, it is possible to provide the above-mentioned useful cultured yellowtail fish in the reproductive organ maturity stage.

[0019] In this specification, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved. In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after it as the minimum and maximum values, respectively.

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

[0021] In one embodiment of the present disclosure, farmed fish of the genus Yellowtail have a body mass index of 18 or more and a body weight of 3.5 kg or more at the time of reproductive organ maturation, and a gonadosomatic index (GSI) of 0.5% to 10.0% for males and 0.5% to 4.5% for females, and after the time of reproductive organ maturation, have a body mass index of 17 or more and a body weight of 3.5 kg or more, and a gonadosomatic index (GSI) lower than the values ​​at the time of reproductive organ maturation.

[0022] Examples of farmed fish of the genus Seriola Cuvier include amberjack (Seriola dumerili), yellowtail (Seriola lalandi Valenciennes), Japanese amberjack (Seriola quinqueradiata), long-finned amberjack (Seriola rivoliana Valenciennes), Seriola carpenteri, Seriola fasciata, Seriola hippos Gunther, Seriola peruana Steindachner, and Seriola zonata. Low GSI farmed fish of the genus Seriola can be yellowtail, yellowtail, amberjack, or long-finned amberjack, and in particular, yellowtail.

[0023] The cultured fish of the genus Yellowtail may be cultured fish obtained by any method, and it is preferable that they are obtained by raising and managing them with a feed containing a compound feed. "Formulated feed" means feed that combines ingredients to meet the nutrients such as protein, vitamins, and minerals required for fish growth. "Raising management" means that fish are raised using feed selected to achieve a specific purpose.

[0024] The body weight (total body weight) of cultured Seriola genus fish according to the present disclosure is 3.5 kg or more both at and after reproductive organ maturation. The body weight of cultured Seriola genus fish at and after reproductive organ maturation may be preferably 3.8 kg or more, more preferably 4.0 kg or more, even more preferably 4.2 kg or more, and even more preferably 4.5 kg or more. Furthermore, there may be a change in body weight before and after reproductive organ maturation of cultured Seriola genus fish, and such a change in body weight may be either an increase or decrease in body weight before and after reproductive organ maturation. If there is a decrease in body weight, the extent of the decrease may be, for example, within 0.5 kg, preferably within 0.3 kg or within 0.2 kg.

[0025] As used herein, the term "reproductive organ maturation" refers to the period in which the reproductive organs of fish of the genus Seriola generally become fully functional, allowing males to ejaculate and females to spawn. In the case of yellowtail, this generally corresponds to the period 26 to 27 months after hatching, which usually corresponds to April to May when the water temperature is between 16°C and 19°C. As used herein, "after reproductive organ maturation" refers to the period after reproductive organ maturation, i.e., after sperm release in male individuals, after spawning in female individuals, or after the weight of the reproductive organs reaches a maximum during the reproductive organ maturation period and then begins to decrease if sperm release or spawning is not performed. In the case of yellowtail, this generally corresponds to the period from 28 months of age onward, which usually corresponds to the period from May to September when the water temperature is above 20°C. In this specification, "reproductive organ maturation" may be simply referred to as "maturity", and "post-reproductive organ maturation" may be simply referred to as "post-maturity".

[0026] As used herein, "male" refers to an individual that produces testes and has a chromosomal combination of ZZ type. As used herein, "female" refers to an individual that produces ovaries and has a chromosomal combination of ZW type or WW type.

[0027] The GSI of farmed yellowtail fish is 0.5% to 10.0% for males and 0.5% to 4.5% for females at maturity, and becomes lower after maturity than at maturity. Hereinafter, farmed yellowtail fish weighing 3.5 kg or more and having a GSI of 0.5% to 10.0% for males and 0.5% to 4.5% for females at maturity may be referred to as "low GSI farmed yellowtail fish." In this specification, the Gonad Somatic Index (GSI) is the total weight of the fish including the internal organs. The ratio of gonad weight to body weight is calculated based on the following formula: GSI (%) = gonad weight (kg) / body weight including internal organs (kg) × 100

[0028] In the case of low-GSI farmed male yellowtail fish, the GSI at maturity is 0.5% or more, so it can be determined 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 determined that the individual will not lose much weight due to the maturation of the reproductive organs after maturity. The lower limit of the GSI at maturity 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 of the GSI at maturity can be 9.5% or less, 9.0% or less, or 8.8% or less.

[0029] When the low-GSI farmed fish of the genus Yellowtail is male, the reproductive organs include the testes. The weight of the reproductive organs, i.e., the testes, at maturity is generally 100 g or more, 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 upper limit on the weight of the testes, but from the viewpoint of reducing the effect of leanness associated with maturation of the reproductive organs, it can be 450 g or less, 430 g or less, or 400 g or less.

[0030] When low-GSI farmed yellowtail fish are female, their GSI is 0.5% or higher at maturity, meaning that their reproductive organs are sufficiently mature to produce functional eggs. On the other hand, because their GSI is 4.5% or less, they can be determined to be individuals that are less susceptible to the effects of leanness that accompanies maturation of the reproductive organs after maturity. The lower limit of the GSI at maturity 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, and the upper limit of the GSI at maturity can be 4.5% or less, 4.3% or less, 4.2% or less, or 4.0% or less.

[0031] When the low-GSI farmed fish of the genus Yellowtail are female, the reproductive organs include the ovaries. The weight of the reproductive organs, i.e., the ovaries, at maturity is generally 20 g or more, 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 upper limit on the weight of the ovaries, but from the viewpoint of reducing the effect of leanness associated with maturation of the reproductive organs, it can be 300 g or less, 250 g or less, or 200 g or less.

[0032] Because the GSI of low-GSI farmed Seriola is within a specified range, the concentrations of various reproductive hormones at maturity can be lower than those of wild Seriola fish. Reproductive hormones include 11-ketotestosterone (11-KT), 17α,20β-dihydroxy-4-pregnen-3-one (DHP), and estradiol (E2).

[0033] 11-KT is a male hormone that functions as an endogenous androgen-like sex hormone and is known to be involved in the mid-stage of sperm maturation. The blood 11-KT concentration in mature, low-GSI farmed Seriola spp. males 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, or 4500 pg / mL or less, or 4300 pg / mL or less.

[0034] 11-KT can also be produced in female individuals. The blood concentration of 11-KT in mature, low-GSI farmed Seriola spp. fish 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, or may be 200 pg / mL or less, 180 pg / mL or less, or 160 pg / mL or less.

[0035] There are no particular limitations on the method for measuring blood 11-KT, and any of the known measurement methods may be used. For example, time-resolved fluoroimmunoassay (TFA) is a method for measuring blood 11-KT. Measurement using TR-RIA can be performed using, 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 progestin that acts as an active form of testosterone and is known as a hormone involved in the later stages of the maturation process of sperm or eggs. The blood concentration of DHP in mature low-GSI cultured Seriola spp. for 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 or less. The blood concentration of DHP in mature low-GSI cultured Seriola spp. for female individuals 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 are no particular limitations on the method for measuring blood DHP, and any known measurement method may be used. For example, time-resolved fluoroimmunoassay (TR) Measurement using TR-FIA can be performed using, for example, the method described in Gen. Comp. Endocrinol. 106, 181-188.

[0037] E2, also known as 17-β-estradiol, is a female sex hormone known to be involved directly or indirectly via the liver in the early stages of sperm or egg maturation. The blood E2 concentration in low-GSI Seriola aquacultured fish (males) may be 130 pg / mL or more, 150 pg / mL or more, or 200 pg / mL or more, and 400 pg / mL or less, 380 pg / mL or less, or 350 pg / mL or less. The blood E2 concentration in mature low-GSI Seriola aquacultured fish (females) may be 300 pg / mL or more, 500 pg / mL or more, 800 pg / mL or more, or 1000 pg / mL or more, and 15,000 pg / mL or less, 10,000 pg / mL or less, or 7,000 pg / mL or less. There are no particular limitations on the method for measuring blood E2, and any known measurement method may be used. For example, measurement can be performed by radioimmunoassay (RIA). Measurement methods using RIA are described, for example, in Cell Tissue Res., 218, 315-329.

[0038] Low GSI cultured Seriola fish may have any of the above-mentioned reproductive hormones in the above-mentioned ranges. For example, mature low GSI cultured Seriola fish may have the following combination of reproductive hormones: If the farmed yellowtail is a male, at least one of the following (1) to (3): (1) Blood concentration of 11-ketotestosterone (11-KT) is 1800pg / mL to 4500pg / mL, (2) 17α,20β-dihydroxy-4-pregnen-3-one (DHP) blood concentration is 100 pg / mL to 450 pg / mL, and (3) Blood estradiol (E2) concentration is 130pg / mL to 400pg / mL. If the farmed yellowtail is a female, at least one of the following (4) to (6): (4) 11-ketotestosterone (11-KT) blood concentration 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) Blood estradiol (E2) concentration is 300pg / mL to 10,000pg / mL.

[0039] 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), a combination of (2) and (3), or a combination of (1) to (3). In the case of female individuals, at least one of the above (4) to (6) can be satisfied, for example, 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] The GSI of low-GSI farmed yellowtail fish is within a predetermined range at maturity and decreases after maturity. The degree of decrease in GSI before and after maturity is not particularly limited, as long as the fish maintain a body weight of 3.5 kg or more and a body fatness index of 17 or more after maturity. The GSI after maturity 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 at maturity.

[0041] For low-GSI cultured Seriola 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, 2.5% or less for males and 1.0% or less for females. In other words, cultured Seriola fish after maturity may have a body fat index of 17 or more and a body weight of 3.5 kg, and a GSI that is lower than the GSI at maturity, 2.5% or less for males and 1.0% or less for females. The GSI of a male individual after maturation may be less than the GSI value at maturity, and 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 for males. The GSI of a female individual after maturation may be a lower GSI than the GSI at maturity, 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 obesity index of low GSI cultured yellowtail fish at maturity is 18 or more, preferably 19 or more, more preferably 20 or more, and even more preferably 21 or more. There is no particular upper limit to the obesity index at maturity, as long as the obesity index after maturity is 17 or more, and it can be, for example, 30 or less, or 29 or less. Furthermore, the fatness index of low-GSI cultured fish of the genus Seriola after maturity can be 17 or more, preferably 18 or more, and more preferably 19 or more. Low-GSI cultured fish of the genus Seriola having a fatness index of 17 or more after maturity can provide a larger amount of so-called fatty edible parts compared to wild fish. There is no particular upper limit to the fatness index after maturity, and it can be, for example, 29 or less, or 28 or less.

[0043] Obesity can generally be assessed based on the following formula [1]: Obesity level = Weight (g) / {Fork length (cm) x Fork length (cm) x Fork length (cm)} x 1000 ... [1]

[0044] The low GSI cultured fish of the genus Seriola according to the present disclosure maintain a body weight of 3.5 kg or more at maturity and thereafter, and even if the obesity level drops below that at maturity, the obesity level is maintained at 17 or more after maturity. There are no particular restrictions on the range of change in obesity level between maturity and post-maturity in low GSI cultured fish of the genus Seriola, as long as the obesity level is 17 or more after maturity, but it is preferably set to 2 or less, and more preferably 1 or less.

[0045] The fork length of low-GSI farmed fish of the genus Seriola can be 50 cm or more, 55 cm or more, 57 cm or more, or 60 cm or more for both males and females. Low-GSI farmed fish of the genus Seriola with a fork length of 50 cm or more tend to be more obese than wild fish, and can provide more edible portions. Fork length refers to the distance from the tip of the fish's head to the center of the tail fin, and is an indicator of external morphology well known to those skilled in the art. Fork length is measured by measuring the linear distance in a plan view from the tip of the fish's head to the center of the tail fin. There is no particular upper limit for the fork length of low-GSI farmed fish of the genus Seriola, and it can be, for example, 200 cm or less.

[0046] To measure the weight of individual fish, first bleed the fish after landing and measure the weight of the remaining body, which is called the "total fish weight." Then, the internal organs are removed and the gonad weight and liver weight can be measured. To measure the weight, a measuring device normally used for measuring fish weight and a measuring device normally used for measuring internal organ weight can be used.

[0047] In one embodiment of the present disclosure, low GSI farmed yellowtail fish may have the following characteristics at the stage of reproductive organ maturation: (A1-1) A male individual with a body weight of 3.5 kg or more, an obesity index of 20 or more, and a GSI of 2.5% to 10.0%. (A1-2) A male individual with a body weight of 4.0 kg or more, an obesity index of 20 or more, and a GSI of 5.0% to 9.0%. (B1-1) A female individual with a body weight of 3.5 kg or more, an obesity index of 19 or more, and a GSI of 1.0% to 4.5%. (B1-2) Female individuals with a body weight of 4.0 kg or more, an obesity index of 19 or more, and a GSI of 2.0% to 4.0%.

[0048] In one embodiment of the present disclosure, low GSI farmed fish of the genus Seriola may have the following characteristics: (A2-1) a male individual having a body weight of 3.5 kg or more and a body fatness index of 20 or more, a GSI of 2.5% or more and 10.0% or less at maturity, and a GSI of less than 2.5% after maturity; (A2-2) a male individual having a body weight of 4.0 kg or more and a body fatness index of 20 or more, a GSI of 5.0% or more and 9.0% or less at maturity, and a GSI of less than 5.0% after maturity; (B2-1) A male individual with a body weight of 3.5 kg or more, an obesity index of 19 or more, a GSI of 1.0% or more and 4.5% or less at maturity, and a GSI of less than 1.0% after maturity; (B2-2) A male individual with a body weight of 4.0 kg or more, an obesity index of 19 or more, a GSI of 2.0% to 4.0% at maturity, and a GSI of less than 2.0% after maturity.

[0049] The low-GSI cultured fish of the genus Seriola according to the present disclosure have the body weight and fatness index described above, and have a lower GSI than wild-caught yellowtail. Low-GSI cultured fish of the genus Seriola with these characteristics can be at least 1.2 years old, or 1.5 years old or older, and generally 2 or 3 years old or older. In particular, the fish may be cultured in spring, as with wild-caught yellowtail, or in autumn, where eggs are collected. Cultured yellowtail in autumn can be obtained by shifting the time of egg or sperm collection from parent fish, for example, by artificially controlling conditions such as light exposure and water temperature, or by administering maturation hormones.

[0050] Another type of cultured fish of the genus Seriola disclosed herein is a cultured fish of the genus Seriola that is at the stage of reproductive organ maturity, weighs 3.5 kg or more, has a body mass index of 18 or more, and has a GSI of 0.5% to 20.0% for males and 0.5% to 4.5% for females. When specifically referring to such cultured fish of the genus Seriola, this specification may refer to them as "low-GSI cultured fish of the genus Seriola at maturity." Low-GSI cultured fish of the genus Seriola at maturity may have the characteristics (A1-1) to (A1-2) or (B1-1) to (B1-2) described above. Mature low GSI cultured yellowtail fish is preferred for efficiently obtaining mature low GSI cultured yellowtail fish.

[0051] Another type of cultured fish of the genus Seriola disclosed herein is a cultured fish of the genus Seriola that has reached reproductive organ maturity, weighs 3.5 kg or more, has a body mass index of 17 or more, and has a GSI lower than the GSI value at maturity. In this specification, such cultured fish of the genus Seriola may be referred to as a "post-maturity low-GSI cultured fish of the genus Seriola." Examples of post-maturity low-GSI cultured fish of the genus Seriola include a cultured fish of the genus Seriola that weighs 3.5 kg or more, has a body mass index of 17 or more, and has a GSI of less than 2.5% for males and less than 1.0% for females, or a cultured fish of the genus Seriola that weighs 3.5 kg or more, has a body mass index of 17 or more, and has a GSI of less than 0.5% for males and less than 0.5% for females.

[0052] The matters regarding body weight, GSI, reproductive hormones, obesity level, fork length, etc. described above in relation to the low GSI cultured yellowtail fish of the present disclosure can be applied directly to mature low GSI yellowtail cultured fish and post-mature low GSI yellowtail cultured fish.

[0053] The low-GSI cultured yellowtail fish according to the present disclosure can be obtained by adjusting the GSI within a predetermined range by managing or adjusting the composition of the compound feed used in aquaculture, photoperiod conditions, water temperature conditions, culture period, feed amount, body weight, etc. Examples of methods that can adjust gonad maturation include those described in JP 2013-188207 A and JP 2015-510878 A. Among these, applying a method that adjusts gonad maturation based on the composition of compound feed that can adjust gonad maturation, photoperiod conditions and water temperature conditions that can adjust gonad maturation is preferred because it reduces the introduction of exogenous substances. The cultured yellowtail fish of the present disclosure can be obtained by the method for raising cultured yellowtail fish described in this specification.

[0054] <Raising methods for farmed yellowtail fish> The breeding method for low-GSI cultured yellowtail fish according to the present disclosure includes raising yellowtail fish in a regulated breeding environment for at least two months, then starting breeding using yellowtail larvae obtained by artificially collecting eggs and growing the yellowtail fish (hereinafter sometimes referred to as the "breeding process"); obtaining mature yellowtail cultured fish that are male individuals with a GSI of 0.5% or more and 10.0% or female individuals with a GSI of 0.5% or more and 4.5% or less at the time of reproductive organ maturity, have a body mass index of 18 or more, and a body weight of 3.5 kg or more (hereinafter sometimes referred to as the "mature individual obtaining process"); and obtaining from the obtained mature yellowtail cultured fish, after reproductive organ maturity, have a body mass index of 17 or more, a body weight of 3.5 kg or more, and have a GSI lower than the value at the time of reproductive organ maturity (hereinafter sometimes referred to as the "post-maturity individual obtaining process"); and may include other processes as necessary. According to this rearing method for rearing cultured fish of the genus Yellowtail, it is possible to obtain cultured fish of the genus Yellowtail that are less likely to lose weight after maturation of their reproductive organs and that have excellent sustainability. The term "breeding method" can be understood as a method for producing the low GSI Seriola aquaculture fish disclosed herein, and can be used interchangeably with terms such as "production method" and "production method." Furthermore, "controlled rearing" refers to rearing while appropriately adjusting the photoperiod and water temperature conditions.

[0055] [Breeding process] In the rearing process, fish of the genus Seriola are reared in a regulated rearing environment for at least two months, and then eggs are artificially collected to obtain larvae of the fish of the genus Seriola. The larvae used may be those obtained by purchasing or other means, which are obtained by artificially collecting eggs from Seriola fish that have been raised in a regulated rearing environment for two months, or those obtained by the person carrying out the rearing process by carrying out at least one of the following: rearing for at least two months in the regulated rearing environment, and collecting the eggs. Furthermore, the collected eggs are subjected to a fertilization treatment after collection in order to obtain larvae. The fertilization treatment may be carried out by the person carrying out the rearing step, or the person carrying out the rearing step may obtain the larvae obtained after the fertilization treatment by means of purchase or the like and use them for rearing in the rearing step. Photoperiod conditions in regulated rearing refer to an appropriate combination of a 9-15 hour light period and a 9-15 hour dark period. For example, short-day conditions include a 10 hour light period and a 14 hour dark period for 30 days, and long-day conditions include a 14 hour light period and a 10 hour dark period for 60 days. Water temperature conditions refer to adjusting the water temperature within the range of 15°C to 30°C or 16°C to 28°C. The photoperiod and water temperature conditions for regulated rearing can be adjusted as appropriate to suit the rearing. For example, if a preferable light-dark cycle or water temperature can be achieved in a natural environment, then those conditions can be applied as is.

[0056] Rearing in a regulated rearing environment can be carried out for at least 2 months, preferably 3 months or more, and more preferably 7 months or more. By adjusting the photoperiod 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 3 months earlier than in wild yellowtail.

[0057] Egg collection is carried out artificially. Here, "artificially" means that spawning is induced under an externally controlled environment, such as by adjusting the environment or administering chemicals. As a result, eggs can be collected earlier than those of wild yellowtail, for example. In Japan, egg collection can be carried out at any time of the year. The collected eggs are then subjected to a fertilization treatment. After fertilization, the fertilized eggs are maintained under a predetermined environment to obtain yellowtail larvae. The yellowtail larvae are then raised.

[0058] In the rearing step, rearing is started using larvae of fish of the genus Seriola to grow the fish. In order to start rearing larvae of fish of the genus Seriola and grow the fish of the genus Seriola, the fish may be reared using a method normally used in an environment suitable for the growth stage from larvae to adult fish of the genus Seriola. Once Seriola fish reach a size suitable for marine aquaculture, they can be reared at the sea surface. Rearing of fish of the genus Seriola may be carried out in an environment generally used for rearing yellowtail. In this specification, "fry of fish of the genus Seriola" refers to individuals whose fork length is less than about 5 cm after hatching, and subsequent juvenile fish and adult fish are collectively referred to as "fish of the genus Seriola."

[0059] From the viewpoint of growth efficiency of yellowtail fish, the water temperature in the rearing environment is preferably adjusted to 15° C. to 28° C. In this case, by adjusting the water temperature in the rearing environment to within the range of 15° C. to 28° C. from the start of rearing yellowtail fish larvae, the growth rate of yellowtail fish can be increased from the early stage of the rearing stage, rather than starting at a later stage, and low-GSI yellowtail fish can be efficiently obtained. The water temperature during the rearing process can be adjusted depending on the rearing stage. For example, when rearing larvae of yellowtail, the temperature can be adjusted to 18°C ​​to 22°C, and then adjusted to 15°C to 28°C after the larvae have grown into yellowtail. Examples of ways to adjust the water temperature include adding water, heating, adjusting the ambient temperature, shading, adjusting the hours of sunlight, selecting a sea surface farm, and transferring the reared fish to a tank. The rearing process may include a period of high water temperatures exceeding 28°C. For example, exposing maturing Seriola species to high water temperatures of 30°C or higher may be effective in adjusting maturation by imposing a moderate amount of stress on the individuals. A water temperature that constitutes a "high water temperature" in the rearing process may be, for example, 29°C, 30°C, or 31°C. The period of high water temperature may be one day or more, two days or more, three days or more, or five days or more. The period of high water temperature may be continuous or intermittent.

[0060] In order to more effectively obtain the desired cultured fish of the genus Yellowtail, the rearing process may include removing individuals with morphological abnormalities and / or poor growth during the rearing process and selecting individuals of Yellowtail. Morphological abnormalities and / or poor growth can be determined based on criteria such as feeding efficiency, feeding rate, body weight, body length, fork length, etc. In this specification, weight, body length, fork length, etc. may be collectively referred to simply as "size." Examples of morphological abnormalities include a sunken head, curvature of the spine, short body, and jaw abnormalities. The selection rate due to morphological abnormalities or poor growth can be evaluated using the following formula. Selection rate (%) = number of normal fish / (number of morphologically abnormal or growth-stunted fish + number of normal fish) x 100

[0061] In the rearing process, weighing management of individuals can be performed. Weighing management of individuals may be performed in combination with individual selection based on morphological abnormalities and / or poor growth. Weighing management refers to managing the size of farmed yellowtail fish by periodically measuring or estimating it. There are no particular limitations on the method of weighing management, and examples include weight measurement and image analysis. For example, the weight of individuals can be measured monthly. In this case, the weight of each individual, i.e., body weight, may be measured, or several dozen fish may be measured at once, the average may be calculated, and management may be based on the average weight. Furthermore, for example, "AM-100" (AQ1 systems) can be used as the image analysis means. For example, "AM-100" (AQ1 systems) can be used as the weight measurement means.

[0062] The rearing period of the fish of the genus Yellowtail in the rearing step can be continued until mature individuals weighing 3.5 kg or more are obtained, and can be 12 months or more, and can be 15 months or more, 18 months or more, 20 months or more, or 22 months or more. The rearing step can be continued until the post-mature individual obtaining step described below.

[0063] The rearing process may be carried out in the ocean or on land. From the viewpoint of ease of individual management and the efficiency of obtaining low GSI yellowtail farmed fish, it is preferable to include underwater farming at a depth of 10 to 18 meters below the water surface for at least 5 months. This type of underwater farming, also known as submerged farming, is excellent in water temperature stability and is likely to provide a rearing environment that is less susceptible to the effects of waves, etc. Underwater farming can be carried out for at least 5 months, at least 6 months, or at least 8 months. There is no particular upper limit to the period of underwater farming, and it can be set appropriately depending on the rearing period.

[0064] The water temperature at a depth of 10 to 18 meters below the surface where marine culture is carried out is often constant in the range of 15°C to 28°C, which is preferable from the viewpoint of environmental stability. However, the subsurface location where marine culture is carried out may be shallower than 10 meters or deeper than 18 meters. When feeding, the location of marine culture can be raised from the sea surface. In addition, the shallower the location, the higher the water temperature, and the deeper the location, the lower the water temperature. Utilizing this, the water temperature can be adjusted depending on the location where marine culture is carried out. Furthermore, the above-mentioned high-water temperature rearing may be applied to marine culture. In this case, for example, by moving the rearing location closer to the sea surface, where the water temperature is more likely to be high, a rearing environment with high water temperature can be easily provided, allowing for more efficient maturation adjustment. In the present disclosure, when the upper limit of the cage used for aquaculture is located above sea level, it is referred to as marine aquaculture, and when the upper limit of the cage is located below sea level, it is referred to as submarine aquaculture.

[0065] There are no particular limitations on the feed used in the rearing process, and any feed commonly used for cultured Seriola can be used without limitation. Feed for cultured Seriola can be feed containing 0.1 to 0.3 parts by weight of chili pepper per 100 parts by weight of feed. Hereinafter, this feed will be referred to as "chili pepper-containing feed." Chili peppers are known to improve or maintain the color tone of dark muscle in cultured Seriola (for example, JP 2009-232864 A), and are also effective in obtaining cultured Seriola with low GSI. The chili pepper in the chili pepper-containing feed can be chili pepper components or chili pepper powder.

[0066] The chili pepper-containing feed may also contain clove oil in addition to chili peppers. The amount of clove oil to be added may be 0.1 to 0.25 parts by weight per 100 parts by weight of the feed. There is no particular limitation on the period of feeding with the chili pepper-containing feed, and the feeding can be carried out for, for example, at least one month, at least two months, or at least three months.

[0067] In order to efficiently obtain low-GSI cultured yellowtail fish, it is preferable to feed yellowtail fish without any restrictions during the rearing period during the rearing process. That is, in the rearing process, it is preferable to perform satiation feeding without any restrictions on the amount and composition of feed. Saturation feeding refers to feeding until no individuals are observed on the water surface demanding food. In order to more efficiently obtain low-GSI cultured yellowtail fish, it is preferable to perform high-saturation feeding. High-saturation feeding refers to feeding until no feeding is observed while observing with an underwater camera. This takes into account underwater feeding behavior that cannot be observed on the water surface, and satiation can be achieved for a larger number of individuals, preferably all individuals under rearing. High-saturation feeding can accelerate the growth rate of yellowtail fish in the rearing process and more reliably obtain mature low-GSI cultured yellowtail fish.

[0068] In the rearing process, it is preferable to remove individuals with at least one type of growth deficiency selected from the group consisting of morphological abnormalities and poor growth. By removing individuals with such growth deficiencies, individuals with a better growth condition than the gonad growth condition can be selected, allowing for more efficient production of low-GSI cultured yellowtail fish. Individuals with morphological abnormalities refer to individuals exhibiting features such as a sunken head, curvature of the spine, short body, or jaw abnormalities, and are clearly confirmed to have external abnormalities through observation. Individuals with poor growth refer to individuals clearly confirmed to be inferior in growth condition to those of the same age through observation. Since individuals with morphological abnormalities have limited growth, they are likely to suffer from poor growth in terms of overall body weight. If morphological abnormalities do not stop gonad growth, removing individuals with morphological abnormalities can eliminate individuals with high GSI and poor growth.

[0069] [Mature individual acquisition process] In the process of obtaining mature individuals, mature cultured yellowtail fish are obtained that are male individuals with a GSI of 0.5% to 10.0% or female individuals with a GSI of 0.5% to 4.5% at the maturity stage of their reproductive organs, and have a body mass index of 18 or more and a body weight of 3.5 kg or more. The mature cultured yellowtail fish obtained here are mature individuals with a body weight of 3.5 kg or more and a body fatness index of 18 or more, and have a lower GSI than wild or other cultured mature individuals. By obtaining such mature cultured yellowtail fish, it is possible to obtain post-maturity low-GSI cultured yellowtail fish in the subsequent post-maturity individual acquisition step. In the step of obtaining mature individuals, individuals having the desired GSI, body weight, and obesity level can be selected by measuring size, blood hormone concentrations, etc. The methods described above for measurement control can be applied to measure size. Examples of blood hormones include 11-KT, DHP, and E2. The methods described above can be applied to measure 11-KT, DHP, and E2.

[0070] The obesity index of mature cultured Seriola spp. is relatively high, and may be preferably 19 or more, 20 or more, or 21 or more. There is no particular upper limit to the obesity index of mature cultured Seriola spp., and it may be, for example, 28 or less, or 27 or less. The above points can be applied as they are to mature cultured yellowtail fish. Mature-stage cultured yellowtail fish can be obtained by a rearing method that includes a mature-stage individual acquisition step. Because the reproductive organs of the mature-stage cultured yellowtail fish obtained here are sufficiently mature, eggs or sperm can be obtained from these individuals. The eggs or sperm from the mature-stage cultured yellowtail fish obtained here can be used as seedlings for obtaining cultivated yellowtail larvae with useful traits. In other words, the rearing method for cultured yellowtail fish according to the present disclosure can be said to be excellent in the sustainability of aquaculture. Furthermore, mature-stage cultured yellowtail fish may be supplied to the next post-mature individual acquisition step.

[0071] [Post-maturity individual acquisition process] In the post-maturity individual acquisition step, from the obtained mature-stage cultured yellowtail fish, there are obtained cultured yellowtail fish with a body fatness index of 17 or more, a body weight of 3.5 kg or more, and a GSI lower than that at the maturity stage of reproductive organs, i.e., post-maturity cultured yellowtail fish. The matters described above regarding post-maturity low-GSI cultured yellowtail fish can be applied as is to the mature-stage cultured yellowtail fish. The resulting post-maturity cultured yellowtail fish are yellowtail fish that have been prevented from losing weight to a body weight of less than 3.5 kg or a fatness index of less than 17, and these useful traits can be passed on to the next generation. Individuals with the desired GSI, body weight, and obesity can be selected based on size, blood hormone concentrations, etc., as with mature cultured yellowtail fish, or by landing them and measuring the weight of their reproductive organs.

[0072] [Application] Furthermore, by using the breeding method for cultured yellowtail fish according to the present disclosure, it is possible to adjust the timing of providing cultured yellowtail fish with good characteristics. The post-maturity cultured yellowtail fish according to the present disclosure can be provided at an appropriate time depending on the condition of the cultured fish, for example, within six months, four months, three months, or two months of maturity. For example, if three-year-old mature cultured yellowtail fish are obtained between April and May, the post-maturity cultured yellowtail fish can be provided between May and September. This allows for a stable provision of cultured yellowtail fish with good fatness and body weight before the summer, when red tides are likely to occur.

[0073] The low-GSI cultured fish of the genus Seriola according to the present disclosure have sufficient body weight and body fatness, and therefore have high nutritional value as cultured fish. Therefore, compared with wild-caught Seriola, and even compared with cultured fish of the genus Seriola with a body fatness level of less than 17 and a high GSI, the low-GSI cultured fish of the genus Seriola according to the present disclosure can have a higher proportion of high-quality edible parts. The edible parts of farmed yellowtail fish are preferably used as processed foods, such as the following heated and uncooked foods, and can also be used as animal feed. The processed food and animal feed according to one embodiment can contain the edible parts of low GSI farmed yellowtail fish.

[0074] Examples of animal feed include cat food, dog food, farmed fish feed, poultry feed, and livestock feed. The proportion of the edible portion of low-GSI farmed yellowtail fish in the animal feed is not particularly limited and can be 0.1% to 100% by weight, for example. In addition to the edible portion of low-GSI farmed yellowtail fish, the animal feed can also contain other nutrients such as vitamins, carriers acceptable for animal feed such as water, and other additives such as excipients, as needed, depending on the type of target animal. The animal feed may be contained in a container as described below. Examples of foods include uncooked foods and cooked foods.

[0075] One embodiment of the present disclosure includes a processed food product of low GSI farmed fish of the genus Seriola, including an edible portion of the low GSI farmed fish of the genus Seriola and a container for containing the edible portion. The processed food product can include cooked and uncooked products. Unheated products refer to edible parts that have not been cooked with heat, and examples thereof include surimi, sashimi, fillets, blocks, and fillets, as well as frozen, chilled, freeze-dried, dried, and pickled products. The fact that a product has not been cooked with heat can be determined by the color tone of the surface of the edible part. In this specification, "heating" means applying heat to a state in which actomyosin is denatured to a visible extent. When the edible parts of farmed fish are heat-treated, the edible parts discolor due to the denaturation of actomyosin, so the discoloration of the edible parts can be determined based on the discoloration of the edible parts. The term "heated food" refers to edible parts that have been cooked by heating, and examples thereof include boiled food, baked food, steamed food, fried food, and paste products.

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

[0077] The processed food may optionally contain at least one selected from the group consisting of other foods, food ingredients, and accessories. Examples of other foods include rice, garnish (radish, seaweed, etc.), ginger, and sprouts. Examples of food ingredients include green onions for negitoro. Examples of accessories include, for example, a scale, a label, ice packs, cooling agents, ice, dry ice, and sherbet ice. The accessories may be contained within the container together with the edible portion, or may be placed on the outside of the container, or may be integrally formed with the container or detachably attached. Each of the other foods, food ingredients, and accessories may be one or a combination of two or more.

[0078] The container may be any material that can be used to contain the edible portion, such as polystyrene foam, paper, vinyl, soft plastic, hard plastic, metal, glass, etc. The shape of the container may be any shape that can contain the edible portion, such as a packaging sheet, a tray with or without a lid, a bag, a can, a bottle, etc.

[0079] The low GSI cultured yellowtail fish of the present disclosure can be crossed with other low GSI cultured yellowtail fish or with cultured yellowtail fish with other traits, thereby obtaining offspring with the genetic traits of the low GSI cultured yellowtail fish and using them as seed for aquaculture. [Example]

[0080] The present disclosure will be described in detail below with reference to examples. However, the present invention is not limited to these examples. Unless otherwise specified, "parts" and "%" are by mass.

[0081] [Example 1] Yellowtail larvae were reared in a natural environment for 24 months, and then rearing was initiated from the 29th month by adjusting the photoperiod and water temperature. Feeding was normally conducted once a day with satiation, and once every two days in winter. Photoperiod conditions included short and long days. Other rearing conditions were adjusted in accordance with those described in JP 2007-300837 A.

[0082] Spawning was induced by injection of a hormone, and eggs were collected from female individuals. Sperm were collected from male individuals and fertilized to produce yellowtail larvae. The larvae were reared on land at a water temperature of 18 to 20°C. From the third month after they had matured into fry, they were reared in fish cages installed on the sea surface. The fry were lowered 10 to 18 m below the water surface to begin submerged culture. During the fry stage, the water temperature was adjusted to 15 to 22°C. During the adult stage, the water temperature was adjusted to 15 to 28°C. During the rearing period, the water temperature was adjusted to at least 30°C for two or more consecutive days during the period when the growing individuals reached a weight of approximately 500 g to 1 kg, allowing the growing individuals to experience high water temperatures.

[0083] Feeding was performed by high-saturation feeding once a day during normal conditions and once every two days in winter. High-saturation feeding was performed throughout the year, with no feed restriction. However, this high-saturation feeding was not based on the usual high-saturation feeding method observed at the water surface, but rather on an optimal high-saturation feeding method obtained by observing underwater feeding behavior with a camera. During the marine culture period, juvenile or adult fish were raised submerged 10 to 18 m below the water surface and brought back to the surface each time they were fed. The feed used was commercially available extruded pellets (EP) supplemented with 0.1 to 0.3 parts by weight of chili powder per 100 parts by weight of feed. Additionally, when the fry reached 2-20g, they were removed from the land-based tanks and transferred to a surface fish pen. This process is also known as "release into the ocean." After the release into the ocean, the fish were regularly checked for body length, size, and morphology, and weighed every month. Weight measurements were taken using the AM-100 (AQ1 system). Based on these results, only those individuals with no morphological abnormalities (depressed head, curvature of the spine, short body, or jaw abnormalities) and deemed to have a good growth rate were raised. The selection rate for morphological abnormalities was 50-95%.

[0084] At the stage of reproductive organ maturation, more than five months after the start of marine culture, two-year-old male fish were obtained, with an average weight of 4.63 kg, an average fork length of 61.03 cm, and an average body mass index of 20.35, and two-year-old female fish with an average weight of 4.66 kg, an average fork length of 61.60 cm, and an average body mass index of 19.91. The gonad weights of these two-year-old fish were measured to calculate GSI, and blood hormone concentrations were measured as follows.

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

[0086] [Table 1]

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

[0088] These mature cultured yellowtail fish were able to spawn or be spermatize. When the resulting cultured yellowtail fish were crossed with individuals with low GSI, yellowtail larvae could be obtained in the next generation. In other words, the cultured yellowtail fish obtained in this example can be said to have excellent sustainability in aquaculture. The mature yellowtail fish obtained weighed 3.5 kg or more and had a body mass index of 17 or more in June, two months after maturity, and both males and females were confirmed to have a GSI of less than 0.5.

[0089] [Example 2] Larvae obtained by early egg collection were reared in the same manner as in Example 1, and mature-stage cultured yellowtail fish were obtained as 2-year-old female individuals, and post-maturity cultured yellowtail fish as female individuals in April, 74 days after maturity. The body weight, body fatness index, and GSI of these mature-stage cultured yellowtail fish and post-maturity cultured yellowtail fish 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 weighed 3.5 kg or more and had an obesity index of 17 or more.

[0090] [Table 2]

[0091] This farmed yellowtail fish has a sufficiently low GSI, so the edible portion is high, and the fatness level is high, making it highly valuable commercially.It is also delicious when eaten.

[0092] Thus, according to the present disclosure, it is possible to obtain farmed yellowtail fish that are less likely to lose weight after the maturation of their reproductive organs and that have excellent sustainability.

Claims

1. A two-year-old male farmed yellowtail fish, At the stage of reproductive organ maturity, the body mass index is 18 or more, the fork length is 50 cm or more, and the gonadosomatic index (GSI) is 0.5% or more and 10.0% or less; After reproductive organ maturity, the body mass index is 17 or more, the fork length is 50 cm or more, and the gonadosomatic index (GSI) is lower than the value at the time of reproductive organ maturity. Farmed yellowtail fish.

2. 2. The cultured yellowtail fish according to claim 1, wherein the GSI of the cultured yellowtail fish after maturation of the reproductive organs is 2.5% or less.

3. The cultured yellowtail fish according to claim 1, which is a male individual of a two-year-old fish at the stage of reproductive organ maturation, satisfies 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) a blood concentration of 17α,20β-dihydroxy-4-pregnen-3-one (DHP) of 100 pg / mL to 450 pg / mL, and (3) Blood estradiol (E2) concentration is 130 pg / mL to 400 pg / mL.

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