Methods for raising farmed yellowtail fish

Abstract

To provide a culturing method capable of efficiently classifying a farmed fish of genus Seriola into female or male and culturing the fish.SOLUTION: A farmed fish of genus Seriola is cultured by administering sex hormone or a sex hormone-like substance to the fish being a juvenile fish before sex differentiation.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for raising cultured yellowtail fish, in which cultured yellowtail fish are feminized or masculinated and raised. [Background technology]

[0002] Attempts are being made to shorten the growing period for farmed fish in order to reduce farming costs, etc. In the case of yellowtail farming, in order to ship earlier than usual, especially in the summer when supply is low, methods such as selecting and growing only the larger juvenile fish (mojako) collected, or cultivating artificial seedlings by collecting eggs from parent fish and hatching them, are being used.

[0003] Patent Document 1 describes a method for shortening the rearing period for yellowtail, in which male and female artificially reared yellowtail broodstock are placed in land-based tanks in early September, and their ovaries are enlarged by controlling the photoperiod and water temperature. After that, eggs are harvested in December using an early egg-harvesting technique in which a maturation-inducing hormone is injected to induce spawning. Some of the resulting larvae are cultured for one year, and the resulting adult fish are shipped. The remaining larvae are then reared as broodstock for two years, and the above-mentioned early egg-harvesting technique is repeated to harvest eggs in December. This method shortens the rearing period for yellowtail and broodstock by approximately one year. It is known that the rearing period for farmed yellowtail fish can be shortened by using artificial seedlings, which are placed in an artificial environment from the hatching stage, and by managing and controlling the rearing environment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-300837 Summary of the Invention [Problem to be solved by the invention]

[0005] The present inventors have found that early rearing of hatched cultured yellowtail fish results in accelerated growth of both sexes. However, to separate the sexes of yellowtail fish, for example, separation by observation of the shape of the gonads in the fish body or by detection of genetic sex identification markers is required. The former requires rearing the yellowtail fish until gonad formation is observed, making early separation difficult, while the latter requires collecting samples from all individuals for genetic detection, requiring extremely cumbersome work.

[0006] An object of the present invention is to provide a breeding method that enables efficient breeding of cultured yellowtail fish by separating the sexes. [Means for solving the problem]

[0007] The present invention provides the following: [1] A method for raising cultured yellowtail fish, comprising administering a sex hormone or a sex hormone-like substance to juvenile yellowtail fish before they have sex. [2] The method according to [1], wherein the administration of the sex hormone or sex hormone-like substance to the fry before sex differentiation is initiated 30 to 90 days after hatching. [3] The method according to [1] or [2], wherein the sex hormone or sex hormone-like substance is at least one selected from male hormones, female hormones, and analogs of either of these. [4] The method according to any one of [1] to [3], wherein the sex hormone or sex hormone-like substance is at least one selected from the group consisting of estrogen and phytoestrogen. [5] The method according to [4], wherein the sex hormone or sex hormone-like substance is a phytoestrogen. [6] The method according to any one of [1] to [3], wherein the sex hormone or sex hormone-like substance is testosterone. [7] The method according to any one of [1] to [6], wherein the sex hormone or sex hormone-like substance is administered for a period of 7 to 60 days. [8] obtaining a group containing only female cultured fish of the genus Seriola or a group containing only male cultured fish of the genus Seriola after the administration period of the sex hormone or sex hormone-like substance; and raising the group including only female cultured fish of the genus Yellowtail or the group including only male cultured fish of the genus Yellowtail; The method according to any one of [1] to [7], comprising: [9] A step of administering a male hormone to a group of pre-sexed juvenile fish of the genus Yellowtail to form a group of male Yellowtail cultured fish, including cultured Yellowtail fish having a female genotype (ZW); a step of mating female cultured yellowtail fish having a female genotype (ZW) with male cultured yellowtail fish having the female genotype (ZW), and collecting eggs; a step of hatching the eggs obtained by the egg collection, selecting female cultured yellowtail fish of the genus having a female genotype (WW) from the resulting fry, and raising them; A step of mating male cultured yellowtail fish having a male genotype (ZZ) with female cultured yellowtail fish having the female genotype (WW) and collecting eggs; and hatching and raising the eggs obtained by the egg collection to obtain a group containing only female cultured yellowtail fish having female genes (ZW); A method for sexing female cultured fish of the genus Yellowtail, comprising:

[10] A step of administering a female sex hormone to a group of pre-sexed juvenile fish of the genus Seriola to form a group of female Seriola cultured fish, including Seriola cultured fish having a male genotype (ZZ); A step of mating male cultured yellowtail fish having a male genotype (ZZ) with female cultured yellowtail fish having the male genotype (ZZ) and collecting eggs; and hatching and raising the eggs obtained by the egg collection to obtain a group containing only male cultured yellowtail fish having the male genotype (ZZ); A method for sexing males of cultured yellowtail fish, comprising:

[11] A method for raising cultured yellowtail fish, comprising raising cultured yellowtail fish that have been sex-separated by the method described in [9] or

[10] in an environment containing only female yellowtail fish or only male yellowtail fish. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a breeding method that enables efficient breeding of cultured yellowtail fish by separating the males and females. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing the principle of a method for separating female cultured yellowtail fish using sex-reversed fish as parent fish. [Figure 2] FIG. 1 is a schematic diagram showing the principle of a method for separating male cultured yellowtail fish using sex-reversed fish as parent fish. [Figure 3] 1 is a graph showing the changes in average fish weight of farmed yellowtail in the male, female, and mixed groups. [Figure 4] 1 is a graph showing the fish weights of farmed yellowtail in the male, female, and mixed groups as of late May. [Figure 5] These are photographs of stained tissues of the gonads of farmed yellowtail from the control group and from test group 2 where female hormones were administered. A shows a photograph of stained tissues of the gonads of farmed yellowtail from the control group, and B shows a photograph of stained tissues of the gonads of farmed yellowtail from test group 2. [Figure 6] Photographs of stained tissues of the gonads of farmed yellowtail from the control group and from test group 2 where male hormones were administered. A shows a photograph of stained tissues of the gonads of farmed yellowtail from the control group, and B shows a photograph of stained tissues of the gonads of farmed yellowtail from test group 2. DETAILED DESCRIPTION OF THE INVENTION

[0010] 1.Definition As used herein, the term "genus Seriola" refers to fish classified in the family Carangidae of the order Perciformes, and known by the scientific name Seriola. Fish of the genus Seriola include yellowtail (Seriola quinqueradiata), amberjack (Seriola dumerili), yellowtail (Seriola lalandi), long-finned amberjack (Seriola rivoliana), Seriola carpenteri, Seriola fasciata, Seriola hippos, Seriola peruana, and Seriola zonata. In particular, yellowtail or amberjack is included. In particular, yellowtail is included.

[0011] As used herein, "farmed fish" refers to fish that have been fed and raised under controlled rearing conditions in a fish preserve or the like before shipping, regardless of the length of the period. As used herein, "farmed fish" includes both natural seedlings and artificially hatched seedlings. In contrast, "wild fish" refers to fish that have not been fed or raised under controlled rearing conditions after being caught at sea until shipping. "Under controlled rearing conditions" as used here refers to an environment in which various conditions are artificially controlled. Specific conditions are described in the section "2. Raising methods for farmed yellowtail fish" below.

[0012] As used herein, "sex hormones" refer to "female hormones" or "male hormones," which are steroid hormones secreted by vertebrates and which act on the gonads to contribute to the maturation of the testes and follicles. "Female hormones" are not particularly limited as long as they are hormones involved in the maturation of the female reproductive organs, and known examples include estrogen (estradiol, estriol, estrone), gestagen, and progesterone. "Male hormones" are not particularly limited as long as they are hormones involved in the maturation of the male reproductive organs, and known examples include testosterone, dihydrotestosterone, and dehydroepiandrosterone.

[0013] In this specification, the term "before sex differentiation" refers to the period from hatching of fish of the genus Seriola until the reproductive organs mature with growth and completely form ovaries or testes.

[0014] As used herein, the term "sex hormone-like substance" refers to a "female hormone-like substance" or a "male hormone-like substance," and refers to a substance derived from an organism other than a vertebrate, particularly a plant, that exhibits physiological activity similar to that of a sex hormone in the animal's body. Examples of "female hormone-like substances" include plant estrogens, particularly plant (e.g., soy) isoflavones. Isoflavones are found in large amounts mainly in soybean germ. Isoflavone is a general term for flavonoid compounds with an isoflavone skeleton. Known isoflavones include glycoside types such as genistin, daidzin, and glycitin, and aglycone types such as genistein, daidzein, and glycitein.

[0015] 2. Cultivation method for farmed yellowtail fish A first embodiment of the present invention is a method for raising farmed Seriola spp. The method of this embodiment is characterized by comprising administering sex hormones or sex hormone-like substances (hereinafter also referred to as "sex hormones, etc.") to juvenile Seriola spp. before sexual differentiation.

[0016] The present inventors discovered that administering female sex hormones to juvenile Seriola spp. before sex differentiation can feminize genotypically male (ZZ) Seriola spp., and that administering male sex hormones can masculinize genotypically female (ZW) Seriola spp., leading to the completion of the present invention. This makes it possible to feminize or masculinize all Seriola spp. in the same pen or tank, and then raise Seriola spp. in a pen or tank containing only female Seriola spp. or only male Seriola spp. Raising Seriola spp. in separate pens or tanks significantly increases the growth rate and reduces maturity compared to raising Seriola spp. in a mixed-sex pen or tank. The principle behind this is not yet fully understood, but it is thought that when male and female farmed yellowtail fish are raised in the same fish pen or tank, the presence of the opposite sex stimulates them to mature more quickly, and nutrients are used more for the formation of the gonads than for the growth of the fish itself, whereas when the sexes are raised separately, more nutrients are used for the growth of the fish itself.

[0017] The cultured yellowtail fish raised by the method of this embodiment may be wild-caught fry (natural seedlings) or may be eggs collected from parent fish and artificially hatched (artificial seedlings). When natural seedlings are used, unlike artificial seedlings, the period after hatching cannot be accurately determined in days, but can be estimated from the spawning period of normal wild yellowtail fish. In the method of this embodiment, it is preferable to raise artificial seedling fry.

[0018] Administration of sex hormones and other hormones to cultured Seriola spp. fish begins before sex differentiation, i.e., before the gonads fully mature and form ovaries or testes. It has been reported that the sex of Seriola spp. fish is determined by a single SNP in the gene encoding the steroid metabolic enzyme 17β-hydroxysteroid dehydrogenase 1 (HSD17B1), and that expression of HSD17B1 was observed in the gonads of Seriola spp. fish 46 days after fertilization (Koyama et al., Curr. Biol. Vol. 29, pp. 1-9 (2019)). Based on these findings, it is estimated that sex differentiation in Seriola spp. fish begins approximately 46 days after fertilization (approximately 43-44 days after hatching). It is more preferable to start administration of sex hormones and other hormones at or before the onset of sex differentiation. More specifically, it is preferable to start administration of sex hormones and other hormones to cultured Seriola spp. fish 30-90 days after hatching, particularly 35-70 days, or 40-60 days. Alternatively, it is preferable to start administering sex hormones to cultured yellowtail fish when their body weight is 1.0 g or less, particularly 0.3 to 1.0 g. By starting the administration of sex hormones within 90 days after hatching or when their body weight is 1.0 g or less, it is possible to highly accurately change the phenotype of cultured yellowtail fish to the desired sex.

[0019] The administration period of the sex hormones and the like is preferably 7 to 60 days, particularly 14 to 42 days, and more preferably 21 to 35 days.

[0020] The sex hormones etc. to be administered are at least one selected from female sex hormones, male sex hormones and analogues of either of these. The sex hormones etc. to be administered to one fish preserve or aquarium are preferably female sex hormones and / or female sex hormone-like substances, or male sex hormones and / or male sex hormone-like substances, i.e. sex hormones etc. to induce one of the sexes.

[0021] The administered sex hormones are preferably female hormones and / or female hormone-like substances. In particular, at least one selected from estrogen and phytoestrogens is preferred. Furthermore, phytoestrogens, particularly soy isoflavones, are preferred. Alternatively, the administered sex hormones are preferably male hormones and / or androgen-like substances. In particular, testosterone is preferred.

[0022] The route of administration of sex hormones and the like is not particularly limited, and may be any of oral administration, intraperitoneal injection, intramuscular injection, sustained-release implants such as cholesterol pellets, immersion, etc. Oral administration is particularly preferred. Furthermore, it is preferable to administer sex hormones by mixing them with feed. For sex hormones, the dosage is preferably 0.01 to 10 μg / g body weight. For example, 0.01 μg / g body weight or more, 0.02 μg / g body weight or more, 0.03 μg / g body weight or more, 0.04 μg / g body weight or more, 0.05 μg / g body weight or more, 0.06 μg / g body weight or more, 0.07 μg / g body weight or more, 0.08 μg / g body weight or more, 0.09 μg / g body weight or more, 0.1 μg / g body weight or more, 0.2 μg / g body weight or more, 0.3 μg / g body weight or more, 0.4 μg / g body weight or more, 0.5 μg / g body weight or more, 0. 6 μg / g body weight or more, 0.7 μg / g body weight or more, 0.8 μg / g body weight or more, 0.9 μg / g body weight or more, 1.0 μg / g body weight or more, 1.1 μg / g body weight or more, 1.2 μg / g body weight or more, 1.3 μg / g body weight 1.4 μg / g body weight or more, 1.5 μg / g body weight or more, 1.6 μg / g body weight or more, 1.7 μg / g body weight or more, 1.8 μg / g body weight or more, 1.9 μg / g body weight or more, 2.0 μg / g body weight or more, 2.1 μg / g body weight or more, 2.2 μg / g body weight or more, 2.3 μg / g body weight or more, 2.4 μg / g body weight or more, 2.5 μg / g body weight or more, 2.6 μg / g body weight or more, 2.7 μg / g body weight or more, 2.8 μg / g body weight or more, 2.9 μg / g body weight or more, 3.0 μg / g body weight or more, 3.1 μg / g body weight or more, 3.2 μg / g body weight or more, 3.3 μg / g body weight or more, 3.4 μg / g body weight or more, 3.5 μg / g body weight or more, 3.6 μg / g body weight It is preferable that the amount is 3.7 μg / g body weight or more, 3.8 μg / g body weight or more, 3.9 μg / g body weight or more, 4.0 μg / g body weight or more, 4.1 μg / g body weight or more, 4.2 μg / g body weight or more, 4.3 μg / g body weight or more, 4.4 μg / g body weight or more, 4.5 μg / g body weight or more, 4.6 μg / g body weight or more, 4.7 μg / g body weight or more, 4.8 μg / g body weight or more, 4.9 μg / g body weight or more, or 5.0 μg / g body weight or more.Or, 10.0μg / g body weight or less, 9.0μg / g body weight or less, 8.0μg / g body weight or less, 7.0μg / g body weight or less, 6.0μg / g body weight or less, 5.0μg / g body weight or less, 4.9μg / g body weight or less, 4.8μg / g body weight or less, 4.7μg / g body weight or less, 4.6μg / g body weight or less, 4.5μg / g body weight or less, 4.4μg / g body weight or less, 4.3μg / g body weight or less, 4.2μg / g body weight or less, 4.1μg / g body weight or less, 4.0μg / g body weight or less, 3.9μg / g body weight or less, 3.8μg / g body weight or less, 3.7 It is preferable that the amount be 2.9μg / g body weight or less, 2.8μg / g body weight or less, 2.7μg / g body weight or less, 2.6μg / g body weight or less, 2.5μg / g body weight or less, 2.4μg / g body weight or less, 2.3μg / g body weight or less, 2.2μg / g body weight or less, 2.1μg / g body weight or less, or 2.0μg / g body weight or less.

[0023] In the case of sex hormone-like substances, the concentration is preferably 0.01 to 10 mg / g body weight. For example, the concentration is 0.01 mg / g body weight or more, 0.02 mg / g body weight or more, 0.03 mg / g body weight or more, 0.04 mg / g body weight or more, 0.05 mg / g body weight or more, 0.06 mg / g body weight or more, 0.07 mg / g body weight or more, 0.08 mg / g body weight or more, 0.09 mg / g body weight or more, 0.1 mg / g body weight or more, 0.2 mg / g body weight or more, 0.3 mg / g body weight or more, 0.4 mg / g body weight or more, 0.5 mg / g body weight or more, 0. 6mg / g body weight or more, 0.7mg / g body weight or more, 0.8mg / g body weight or more, 0.9mg / g body weight or more, 1.0mg / g body weight or more, 1.1mg / g body weight or more, 1.2mg / g body weight or more, 1.3mg / g body weight or more, 1.4mg / g body weight or more, 1.5mg / g body weight or more, 1.6mg / g body weight or more, 1.7mg / g body weight or more, 1.8mg / g body weight or more, 1.9mg / g body weight or more, 2.0mg / g body weight or more, 2.1mg / g body weight or more, 2.2 mg / g body weight or more, 2.3 mg / g body weight or more, 2.4 mg / g body weight or more, 2.5 mg / g body weight or more, 2.6 mg / g body weight or more, 2.7 mg / g body weight or more, 2.8 mg / g body weight or more, 2.9 mg / g body weight or more, 3.0 mg / g body weight or more, 3.1 mg / g body weight or more, 3.2 mg / g body weight or more, 3.3 mg / g body weight or more, 3.4 mg / g body weight or more, 3.5 mg / g body weight or more, 3.6 mg / g body weight It is preferable that the amount of niacin produced is 3.7mg / g body weight or more, 3.8mg / g body weight or more, 3.9mg / g body weight or more, 4.0mg / g body weight or more, 4.1mg / g body weight or more, 4.2mg / g body weight or more, 4.3mg / g body weight or more, 4.4mg / g body weight or more, 4.5mg / g body weight or more, 4.6mg / g body weight or more, 4.7mg / g body weight or more, 4.8mg / g body weight or more, 4.9mg / g body weight or more, or 5.0mg / g body weight or more.Or, 10.0mg / g body weight or less, 9.0mg / g body weight or less, 8.0mg / g body weight or less, 7.0mg / g body weight or less, 6.0mg / g body weight or less, 5.0mg / g body weight or less, 4.9mg / g body weight or less, 4.8mg / g body weight or less, 4.7mg / g body weight or less, 4.6mg / g body weight or less, 4.5mg / g body weight or less, 4.4mg / g body weight or less, 4.3mg / g body weight or less, 4.2mg / g body weight or less, 4.1mg / g body weight or less, 4.0mg / g body weight or less, 3.9mg / g body weight or less, 3.8mg / g body weight or less, 3.7 It is preferable that the amount of the serotonin produced is 2.9 mg / g body weight or less, 2.8 mg / g body weight or less, 2.7 mg / g body weight or less, 2.6 mg / g body weight or less, 2.5 mg / g body weight or less, 2.4 mg / g body weight or less, 2.3 mg / g body weight or less, 2.2 mg / g body weight or less, 2.1 mg / g body weight or less, or 2.0 mg / g body weight or less.

[0024] When sex hormones are mixed with feed, the amount of sex hormones mixed can be 0.01 μg to 10 μg per 1 g of feed. For example, 0.01μg or more, 0.02μg or more, 0.03μg or more, 0.04μg or more, 0.05μg or more, 0.06μg or more, 0.07μg or more, 0.08μg or more, 0.09μg or more, 0.1μg or more, 0.2μg or more, 0.3μg or more, 0.4μg or more, 0.5μg or more, 0.6μg or more, 0.7μg or more, 0.8μg or more, 0.9μg or more, 1.0μg or more, 1.1μg or more, 1.2μg or more, 1.3μg or more, 1.4μg or more, 1.5μg or more, 1.6μg or more, 1.7μg or more, 1.8μg or more, 1.9μg or more, 2.0μg or more, 2.1μg or more It is preferable that the amount is 2.2μg or more, 2.3μg or more, 2.4μg or more, 2.5μg or more, 2.6μg or more, 2.7μg or more, 2.8μg or more, 2.9μg or more, 3.0μg or more, 3.1μg or more, 3.2μg or more, 3.3μg or more, 3.4μg or more, 3.5μg or more, 3.6μg or more, 3.7μg or more, 3.8μg or more, 3.9μg or more, 4.0μg or more, 4.1μg or more, 4.2μg or more, 4.3μg or more, 4.4μg or more, 4.5μg or more, 4.6μg or more, 4.7μg or more, 4.8μg or more, 4.9μg or more or 5.0μg or more. Or, per 1g of feed, 10.0μg or less, 9.0μg or less, 8.0μg or less, 7.0μg or less, 6.0μg or less, 5.0μg or less, 4.9μg or less, 4.8μg or less, 4.7μg or less, 4.6μg or less, 4.5μg or less, 4.4μg or less, 4.3μg or less, 4.2μg or less, 4.1μg or less, 4.0μg or less, 3.9μg or less, 3.8μg or less , 3.7 μg or less, 3.6 μg or less, 3.5 μg or less, 3.4 μg or less, 3.3 μg or less, 3.2 μg or less, 3.1 μg or less, 3.0 μg or less, 2.9 μg or less, 2.8 μg or less, 2.7 μg or less, 2.6 μg or less, 2.5 μg or less, 2.4 μg or less, 2.3 μg or less, 2.2 μg or less, 2.1 μg or less, or 2.0 μg or less.

[0025] When a sex hormone-like substance is mixed with feed, the amount of the sex hormone-like substance mixed is preferably 0.01 to 10 mg per 1 g of feed, for example, 0.01 mg or more, 0.02 mg or more, 0.03 mg or more, 0.04 mg or more, 0.05 mg or more, 0.06 mg or more, 0.07 mg or more, 0.08 mg or more, 0.09 mg or more, 0.1 mg or more, 0.2 mg or more, 0.3 mg or more, 0.4 mg or more, 0.5 mg or more, 0.6 mg or more, 0.7 mg or more, 0.8 mg or more, 0.9 mg or more, 1.0 mg or more, 1.1 mg or more, 1.2 mg or more, 1.3 mg or more, 1.4 mg or more, 1.5 mg or more, 1.6 mg or more, 1.7 mg or more, 1.8 mg or more, 1.9 mg or more, 2.0 mg or more, 2.1 mg or more, 2.2 mg or more, 2.3 mg or more, 2.4 mg or more, 2.5 mg or more, 2.6 mg or more, 2.7 mg or more, 2.8 mg or more, 2 ...1 mg or more, 2.2 mg or more, 2.3 mg or more, 2.4 mg or more, 2.5 mg or more, 2.6 mg or more, 2.7 mg or more, 2.8 mg or more, 2.9 mg or more, 2 mg or more, 2.2 mg or more, 2.3 mg or more, 2.4 mg or more, 2.5 mg or more, 2.6 mg or more, 2.7 mg or more, 2.8 mg or more, 2.9 mg or more, 3.0 mg or more, 3.1 mg or more, 3.2 mg or more, 3.3 mg or more, 3.4 mg or more, 3.5 mg or more, 3.6 mg or more, 3.7 mg or more, 3.8 mg or more, 3.9 mg or more, 4.0 mg or more, 4.1 mg or more, 4.2 mg or more, 4.3 mg or more, 4.4 mg or more, 4.5 mg or more, 4.6 mg or more, 4.7 mg or more, 4.8 mg or more, 4.9 mg or more or 5.0 mg or more is preferred. Alternatively, it is preferable that the amount per 1g of feed be 10.0mg or less, 9.0mg or less, 8.0mg or less, 7.0mg or less, 6.0mg or less, 5.0mg or less, 4.9mg or less, 4.8mg or less, 4.7mg or less, 4.6mg or less, 4.5mg or less, 4.4mg or less, 4.3mg or less, 4.2mg or less, 4.1mg or less, 4.0mg or less, 3.9mg or less, 3.8mg or less, 3.7mg or less, 3.6mg or less, 3.5mg or less, 3.4mg or less, 3.3mg or less, 3.2mg or less, 3.1mg or less, 3.0mg or less, 2.9mg or less, 2.8mg or less, 2.7mg or less, 2.6mg or less, 2.5mg or less, 2.4mg or less, 2.3mg or less, 2.2mg or less, 2.1mg or less, or 2.0mg or less.

[0026] During the administration period, the water temperature in the cage or tank is preferably 13 to 28°C, particularly 18 to 27°C, and more preferably 20 to 25°C. Raising of fry is preferably carried out in a land-based tank. The rearing density of cultured yellowtail fish in the cage is 0.01 to 10 kg / m. 3 , especially 0.01 to 3 kg / m 3 The size of the fish preserve or tank is not particularly limited as long as each individual fish can swim without coming into contact with other fish, but for example, it can be approximately 8 to 60 m in length and width and 8 to 25 m in depth.

[0027] During the administration period, feeding is preferably carried out by spraying the feed into the aquarium at least once every two days, preferably once a day. Regarding the feed used, any feed known to be suitable for fry of farmed yellowtail fish can be used before they reach adulthood. For example, live feed such as small sardines, granular or pelleted compound feed, moist pellets, etc. can be used. After the administration period, during the rearing period after the fish reach adulthood, any feed known to be suitable for farmed yellowtail fish, such as live feed such as mackerel or sardines, or compound feed such as pellets, can be used.

[0028] In the method of this embodiment, after the administration of sex hormones, etc., it is preferable that a group containing only female or only male cultured Seriola fish is obtained in the fish preserve or tank. Furthermore, it is preferable that the method of this embodiment further includes a step of cultivating a group containing only female or only male cultured Seriola fish. According to the above step, by administering sex hormones, etc., it is possible to separately raise cultured Seriola fish of male and female without the need for complicated procedures such as gonad observation or genotype detection.

[0029] The rearing period for the sexed cultured yellowtail fish after the administration period is 2 months or more, preferably 3 months or more, 4 months or more, 5 months or more, 6 months or more, 7 months or more, 8 months or more, 9 months or more, 10 months or more, 11 months or more, 12 months or more, 18 months or more, 19 months or more, 20 months or more, 21 months or more, 22 months or more, 23 months or more, 2 years or more, or 3 years or more. Preferably, the rearing period is 6 years or less, 5 years or less, 4 years or less, 3 years or less, 2 years or less, 23 months or less, 22 months or less, 21 months or less, or 20 months or less.

[0030] 3. Method for sexing female cultured yellowtail fish A second embodiment of the present invention is a method for sexing female cultured yellowtail fish. The method of this embodiment is characterized by including the steps of administering male hormones or substances similar thereto (hereinafter also referred to as "male hormones, etc.") to a group of juvenile Seriola spp. farmed before sex differentiation to form a group of male Seriola spp. farmed fish including juvenile Seriola spp. having a female genotype (ZW); mating female Seriola spp. farmed fish having a female genotype (ZW) with male Seriola spp. farmed fish having the female genes (ZW) and collecting eggs; hatching the eggs obtained from the egg collection and selecting and raising female Seriola spp. farmed fish having a female genotype (WW) from the resulting group of juvenile fish; mating male Seriola spp. farmed fish having a male genotype (ZZ) with female Seriola spp. farmed fish having the female genotype (WW) and collecting eggs; and hatching and raising the eggs obtained from the egg collection to obtain a group including only female Seriola spp. farmed fish having female genes (ZW).

[0031] As described above, cultured yellowtail fish raised separately for male and female can grow faster than cultured yellowtail fish raised in a mixed sex mixture. According to the method of this embodiment, it is possible to obtain a group of cultured yellowtail fish that contain only female genotypes and phenotypes.

[0032] Figure 1 shows a schematic diagram of the principle of the female sex sorting method of this embodiment. First, fry from artificial or natural seedlings before sex differentiation are prepared, and individuals with the ZW genotype are selected. A portion of this population is then administered male hormones or the like to obtain a group of male Seriola aquacultured fish with the female genotype (ZW). In the F0 generation, male Seriola aquacultured fish with the female genotype (ZW) are mated with female Seriola aquacultured fish with the female genotype (ZW), and the eggs are collected and hatched to obtain a group of Seriola aquacultured fish with the male genotype (ZZ), female genotype (ZW), and female genotype (WW) in a population ratio of 1:2:1 in the F1 generation. Of these, by selecting male Seriola aquaculture fish with the male genotype (ZZ) and female Seriola aquaculture fish with the female genotype (WW), mating them, and then collecting and hatching eggs, it is possible to obtain a group of F2 generation fish that contains only female Seriola aquaculture fish with the female genotype (ZW).

[0033] The genotype of an individual can be determined by detecting a sex-identification marker using a sample such as a caudal fin or blood collected from the individual. Known sex-identification markers for cultured yellowtail fish include those described in JP 2014-180233 A.

[0034] A group of male Seriola genus cultured fish with a female genotype (ZW) can be obtained by selecting a group of individuals with the ZW genotype from among pre-sex differentiation juvenile fish and administering male hormones or the like to differentiate each individual into a male. The administration route, administration start time, administration period, and dosage of male hormones or the like can be the same as those described in Section 2, "Raising Method for Seriola genus Cultured Fish." Specifically, the administration of male hormones or the like is initiated before sex differentiation, preferably 30 to 90 days, particularly 35 to 70 days, or 40 to 60 days after hatching. The administration period of male hormones or the like is preferably 7 to 60 days, particularly 14 to 42 days, and more preferably 21 to 35 days. The administration route of male hormones or the like is preferably oral. The dosage of male hormones or the like is preferably 0.01 to 10 μg / g body weight. In the case of a substance analogous to a male hormone, the amount is preferably 0.01 to 10 mg / g body weight. When a male hormone or the like is mixed with a sample and administered, the amount of male hormone mixed can be 0.01 μg to 10 μg per 1 g of feed. The amount of a substance analogous to a male hormone mixed is preferably 0.01 to 10 mg per 1 g of feed.

[0035] A group containing only female farmed yellowtail fish obtained by the method of this embodiment can be grown under conditions where only females are present, allowing them to grow faster than under normal mixed sex conditions.

[0036] 4. Method for sexing males of cultured yellowtail fish A third embodiment of the present invention is a method for sexing males of cultured Seriola spp. This method includes the steps of administering female sex hormones or analogs thereof (hereinafter also referred to as "female sex hormones, etc.") to a group of juvenile Seriola spp. before sex differentiation to form a group of female Seriola spp. cultured fish including cultured Seriola spp. with the male genotype (ZZ); mating male Seriola spp. cultured fish having the male genotype (ZZ) with female Seriola spp. cultured fish having the male genotype (ZZ) and collecting eggs; and hatching and raising the eggs obtained from the egg collection to obtain a group including only male Seriola spp. cultured fish having the male genotype (ZZ).

[0037] According to the method of this embodiment, it is possible to obtain a group of farmed yellowtail fish that contain only male genotypes and phenotypes through breeding.

[0038] Figure 2 shows a schematic diagram of the principle of the male sex sorting method of this embodiment. First, fry before sex differentiation from artificial or natural seedlings are prepared, and individuals having the ZZ genotype are selected. A portion of this population is then administered female sex hormones to obtain a group of female cultured Seriola spp. having the male genotype (ZZ). In the F0 generation, female cultured Seriola spp. having the male genotype (ZZ) are mated with male cultured Seriola spp. having the male genotype (ZZ), and the eggs are collected and hatched, thereby obtaining a group of only male cultured Seriola spp. having the male genotype (ZZ) in the F1 generation.

[0039] The genotype of an individual can be determined by detecting a sex-identification marker using a sample such as a caudal fin or blood collected from the individual. Known sex-identification markers for cultured yellowtail fish include those described in JP 2014-180233 A.

[0040] A group of female Seriola genus cultured fish with a male genotype (ZZ) can be obtained by selecting a group of individuals with the ZZ genotype from among pre-sex differentiation juvenile fish and administering female hormones to differentiate each individual into a female. The administration route, start time, duration, and dosage of female hormones can be the same as those described in Section 2, "Raising Method for Seriola genus Cultured Fish." Specifically, the administration of female hormones should be initiated before sex differentiation, preferably 30 to 90 days, particularly 35 to 70 days, or 40 to 60 days after hatching. The administration period of female hormones should be 7 to 60 days, particularly 14 to 42 days, and more preferably 21 to 35 days. The preferred route of administration of female hormones is oral administration. The preferred dosage of female hormones is 0.01 to 10 μg / g body weight. In the case of female hormone analogues, the amount is preferably 0.01 to 10 mg / g body weight. When female hormones or the like are mixed with a sample and administered, the amount of female hormone mixed can be 0.01 μg to 10 μg per 1 g of feed. The amount of female hormone analogue mixed is preferably 0.01 to 10 mg per 1 g of feed.

[0041] A group containing only male farmed yellowtail fish obtained by the method of this embodiment can be grown under conditions where only males are present, allowing them to grow faster than under normal mixed sex conditions.

[0042] 5. Cultivation method of farmed yellowtail fish A fourth embodiment of the present invention is a method for raising cultured yellowtail fish. The method of this embodiment is characterized by including raising cultured yellowtail fish that have been sexed by the method described in Section "3. Method for sexing female yellowtail cultured fish" or the method described in Section "4. Method for sexing male yellowtail cultured fish" in an environment containing only female yellowtail cultured fish or only male yellowtail cultured fish.

[0043] According to the method of this embodiment, it is possible to efficiently obtain groups containing only female or only male Seriola aquaculture fish, and by raising these, it is possible to obtain fast-growing Seriola aquaculture fish. [Example]

[0044] [Reference example] Survey of growth status of sex-segregated yellowtail aquaculture (1) Raising artificial Mojako On January 18, first-generation artificially hatched yellowtail (12 females and 8 males) were artificially inseminated to obtain fertilized eggs. After confirming hatching on January 20, the fish were placed in land-based tanks for rearing. From February 28 to March 5, they were released into the ocean and continued rearing in the fish pens. Fish weight was measured on June 9, with an average weight of 74.4 g. Vaccination and weight measurement were performed on July 11, with an average weight of 176.7 g. Individual fish were then tagged for individual identification and sexed. On August 9, the fish were divided into 250 males (male group), 250 females (female group), and 259 mixed-sex groups (mixed group) and placed in separate pens for further rearing. The pens for each group were spaced at least 30 m apart. The distance between each cage was set so that the yellowtail raised in each cage could not recognize each other directly by sight or indirectly by secreting sex hormones. For example, the separation distance was set to approximately three times the length and width of the cage, but this is not limited to this. The size of each cage was 4m long x 4m wide x 4m deep, and from the 15th month of sea surface rearing onwards, it was set to 8m long x 8m wide x 8m deep. The water temperature in the cages was 15.2-31.0°C. Formulated feed was used.

[0045] (2) Rearing and fish weight measurement After measuring the fish body weight on July 11th, the yellowtail in each cage were reared for approximately 10 months until May of the following year, during which time fish weight was measured 10 times at regular intervals of approximately one month. Figure 3 shows the change in average fish weight in each area. Fish weight was measured by randomly sampling 50 fish from each test area. Figure 4 shows the fish weight in each area as of late May. Fish weight was high in all cages reared separately for males and females, with the female area showing particularly high fish weight. On the other hand, fish weight in the mixed area was lower than in the female and male areas, and no difference between males and females was observed.

[0046] [Example 1] Sex reversal test in yellowtail by administering female hormones Artificially hatched yellowtail seedlings (average body length 37.1 mm, average body weight 0.5 g) aged 45 days after hatching were raised in a 3000 L free-flowing tank. Each fish pen was fed a diet containing 1 μg / g estrogen (E2) (Test Area 1), 10 μg / g estrogen (Test Area 2), or a standard diet (control) at a sufficient supply once daily for four weeks. Estrogen was administered at 58 μg to 148 μg / kg of fish body weight per day in Test Area 1, and at 679 μg to 1,607 μg / kg of fish body weight per day in Test Area 2. Subsequently, all fish pens were fed a standard diet at a sufficient supply once daily for four weeks. The fish were raised at a supply of 0.01 to 2.7 kg / m 3 The density was

[0047] After the rearing period, the fork length of the yellowtail ranged from 183.2 to 192.2 mm, and the average body weight was 89.0 to 108.4 g. After the rearing period, the yellowtail were sampled, and individuals with the male genotype (ZZ) were selected and their gonads were collected. Histological staining of each gonad was performed using hematoxylin and eosin, and the formation of ovarian follicles or testes was observed through histological observation. Ovarian formation was confirmed in all four ZZ individuals observed in Experimental Area 1 and all seven ZZ individuals observed in Experimental Area 2. In other words, the phenotype of all ZZ individuals observed was confirmed to be feminized. On the other hand, no follicles were formed in any of the ZZ individuals in the control area.

[0048] Figure 5 shows histologically stained photographs of the gonads of ZZ-type individuals from the control group and experimental group 2 after the rearing period. Figure 5A shows a histologically stained photograph of the gonads of a ZZ-type individual from the control group, and Figure 5B shows a histologically stained photograph of the gonads of a ZZ-type individual from experimental group 2. Testes were observed in the individuals from the control group, whereas follicles were observed in the individuals from experimental group 2. This indicates that the administration of estrogen caused sex reversal in the ZZ-type individuals in experimental group 2.

[0049] [Example 2] Sex reversal test in yellowtail by administering male hormones Artificially hatched yellowtail seedlings (average body length 37.1 mm, average body weight 0.5 g) aged 45 days after hatching were raised in a 3000 L free-flowing tank. Each fish pen was fed a methyltestosterone (MT) formulated feed containing 1 μg / g (Test Area 1), a methyltestosterone formulated feed containing 10 μg / g (Test Area 2), or a regular feed (control) at a satiation rate once daily for 4 weeks. MT was administered at 79 μg to 175 μg / kg of fish body weight per day in Test Area 1, and 752 μg to 1,477 μg / kg of fish body weight per day in Test Area 2. Subsequently, all fish pens were fed a regular feed at a satiation rate once daily for 4 weeks. The fish were raised at a 0.01 to 2.9 kg / m 3 The density was

[0050] After the rearing period, the average body length of the yellowtail was 193.3-196.0 mm, and the average body weight was 109.3-113.8 g. After the rearing period, the yellowtail were sampled, and individuals with the male genotype (ZW) were selected and their gonads were collected. Histological staining of each gonad was performed using hematoxylin and eosin, and the formation of ovarian follicles or testes was observed through histological observation. Testis formation was confirmed in one of seven ZW individuals (1 / 7) observed in Experimental Area 1, and in two of eight ZW individuals (2 / 8) observed in Experimental Area 2. However, no testis formation was observed in the ZW individuals in the control area.

[0051] Figure 6 shows histologically stained photographs of the gonads of ZW-type individuals from the control group and experimental group 2 after the rearing period. Figure 6A shows a photograph of the gonad of a ZW-type individual from the control group, and Figure 6B shows a photograph of the gonad of a ZW-type individual from experimental group 2. Follicles were observed in the individuals from the control group, whereas sperm cells were observed in the individuals from experimental group 2. This indicates that the administration of MT caused sex reversal in ZW-type individuals in experimental group 2.

Claims

1. The method comprises administering a sex hormone or a sex hormone-like substance to pre-sexisting fry of cultured yellowtail fish, Obtaining a group containing only female Seriola genus farmed fish or a group containing only male Seriola genus farmed fish after the administration period of the sex hormone or sex hormone-like substance; and raising the group including only female cultured fish of the genus Seriola or the group including only male cultured fish of the genus Seriola; A method for raising farmed yellowtail fish, including:

2. 2. The method according to claim 1, wherein the administration of sex hormones or sex hormone-like substances to the fry before sex differentiation begins 30 to 90 days after hatching.

3. 2. The method according to claim 1, wherein the sex hormone or sex hormone-like substance is at least one selected from male hormones, female hormones, and analogs of either of these.

4. 2. The method according to claim 1, wherein the sex hormone or sex hormone-like substance is at least one selected from the group consisting of estrogen and phytoestrogen.

5. 5. The method of claim 4, wherein the sex hormone or sex hormone-like substance is a phytoestrogen.

6. 2. The method of claim 1, wherein the sex hormone or sex hormone-like substance is testosterone.

7. 2. The method of claim 1, wherein the sex hormone or sex hormone-like substance is administered for a period of 7 to 60 days.

8. A method for obtaining a group containing only female cultured fish of the genus Yellowtail, comprising the following steps (a) to (e): (a) administering a male hormone to a group of pre-sexisting juvenile fish of cultured Seriola spp., thereby forming a group of male cultured Seriola spp. fish, including cultured Seriola spp. fish having a female genotype (ZW); (b) mating female Seriola genus farmed fish having a female genotype (ZW) with male Seriola genus farmed fish having the female genotype (ZW), and collecting eggs; (c) hatching the eggs obtained by the egg collection, and selecting and raising female cultured yellowtail fish of the genus having a female genotype (WW) from the resulting fry group; (d) mating male Seriola genus farmed fish having the male genotype (ZZ) with female Seriola genus farmed fish having the female genotype (WW) and collecting eggs; and (e) hatching and raising the eggs obtained by the egg collection to obtain a group containing only female cultured yellowtail fish having female genes (ZW); A method for raising cultured yellowtail fish includes raising the obtained group containing only female yellowtail fish in an environment containing only female yellowtail fish.

9. A method for producing a group of farmed male Seriola spp. fish, comprising the steps of (i) to (iii) below: (i) administering a female sex hormone to a group of pre-sexed juvenile fish of cultured Yellowtail to form a group of female Yellowtail cultured fish including cultured Yellowtail fish having a male genotype (ZZ); (ii) mating male Seriola genus farmed fish having the male genotype (ZZ) with female Seriola genus farmed fish having the male genotype (ZZ) and collecting eggs; and (iii) hatching and raising the eggs obtained by the egg collection to obtain a group containing only male cultured yellowtail fish having the male genotype (ZZ); A method for raising cultured yellowtail fish includes raising the obtained group containing only male yellowtail fish in an environment containing only male yellowtail fish.

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