Feed for farmed fish including tuna fish, feed group for farmed fish, method for producing feed for farmed fish including tuna fish, and method for farming tuna fish

Abstract

This feed for farmed fish including tuna fish is provided with a body part that is flatted so that the length along a thickness direction that is orthogonal to a width direction orthogonal to a length direction and the length direction becomes shorter than the length along the width direction, and the feed satisfies at least one item selected from the group consisting of items (A) and (B) mentioned below. (A) When the maximum length along the length direction is defined as a (mm), the maximum length along the width direction is defined as b (mm), and the maximum length along the thickness direction is defined as c (mm), a flattening rate f1 calculated in accordance with formula (1): f1 = a×b / c is 110 or more. (B) When the volume of the feed for farmed fish is defined as V (cm3) and the area of the feed for farmed fish when the feed is viewed in a plan view is defined as A (mm2), (V / A)1 / 2 is 0.110 or less.

Description

Tuna farming feed, fish farming feed group, method for producing tuna farming feed, and method for cultivating tuna

[0001] The present disclosure relates to feed for cultivating tuna, a group of fish feeds for cultivating tuna, a method for producing feed for cultivating tuna, and a method for cultivating tuna.

[0002] In fish farming, efforts are being made to switch from live feed to compound feed from the perspectives of nutrition, stable supply, preventing environmental pollution, and sustainable farming, and various compound feeds have been developed. In particular, compound feeds tailored to the preferences of fish species have been proposed so that the switch to compound feed will also progress for highly fish-eating fish species. Patent Document 1 discloses fish farming feed for raising mackerel fish, particularly fish farming feed suitable for tuna farming.

[0003] International Publication No. 2019 / 177024

[0004] In tuna farming, when feeding formulated feed, much of the feed sinks and is not consumed. This is thought to be because when switching from the previous feed, tuna do not recognize the new feed as food immediately due to differences in its sinking speed. Formulated feed is relatively dense and sinks quickly, so feed that sinks more slowly is thought to be desirable. The relationship between shape and sinking speed has been investigated for small objects such as sand and gravel, but little is known about formula feed, which is a larger object. Therefore, the present disclosure provides tuna farming feed with a slow sinking speed, a group of fish farming feeds, and a method for producing tuna farming feed. It also provides a tuna farming method using such tuna farming feed.

[0005] One aspect of the present disclosure provides feed for farming tuna fish, which has a body part that is flattened so that the length along the width direction and the thickness direction perpendicular to the longitudinal direction is shorter than the length in the width direction perpendicular to the longitudinal direction, and satisfies at least one selected from the group consisting of (A) and (B) below: (A) When the maximum length along the longitudinal direction is a (mm), the maximum length along the width direction is b (mm), and the maximum length along the thickness direction is c (mm), the flattening ratio f1 calculated by the following formula (1) is 110 or more: f1 = a × b / c (1); (B) The volume of the fish feed is V (cm ３ ), and the area of ​​the fish feed when viewed in plan is A (mm ２ ) and then (V / A) １／２ is 0.110 or less

[0006] The feed for tuna farming has the flatness f1 of 110 or more and the (V / A) １／２ The flatness f1 of the fish feed, or (V / A) is 0.110 or less. １／２ By keeping the content within this range, the settling rate of the fish feed in the fish cage can be slowed down.

[0007] One aspect of the present disclosure provides feed for tuna farming, which has a sinking velocity of 15.0 cm / s or less at a depth of 15.0 cm to 35.2 cm from the water surface. Such fish farming feed can slow the sinking velocity within a fish pen.

[0008] One aspect of the present disclosure provides a group of fish farming feeds containing a plurality of tuna fish farming feeds, the group having an average sinking velocity of 15.5 cm / s or less at a depth of 15.0 cm to 35.2 cm from the water surface. Such a group of fish farming feeds can slow the sinking velocity in a fish cage.

[0009] One aspect of the present disclosure provides a method for producing feed for farmed tuna fish, comprising a step of radially compressing and crushing a molded article having a body portion of a substantially cylindrical shape, and deforming the body portion so that the radial cross section of the molded article is flattened.

[0010] The method for producing tuna fish feed includes a step of crushing a molded product having a body portion and deforming the body portion so that the radial cross section is flattened. This production method makes it possible to easily produce fish feed with a flattened body portion. The fish feed obtained by this step can slow the settling rate in a fish cage.

[0011] One aspect of the present disclosure provides a method for cultivating tuna using the above-mentioned tuna fish feed, which can reduce the variation in body size of the cultured fish in the cages and improve the growth rate of the cultured fish.

[0012] The present disclosure can provide a fish feed for tuna farming with a slow sinking rate, a group of fish feeds, and a method for producing fish feed for tuna farming, as well as a method for farming tuna using such fish feed for tuna farming.

[0013] 1. A front view of fish feed. A plan view of fish feed. A side view of fish feed. A cross-sectional view taken along line VI-VI in FIG. 1. A cross-sectional view taken along line V-V in FIG. 1. A perspective view showing a part of fish feed. A diagram showing an example of a fish feed manufacturing device. (V / A) of fish feed in Examples and Comparative Examples １／２ 1 is a graph plotting the relationship between the flatness f1 of fish farming feed and the sinking velocity. 2 is a graph plotting the relationship between the flatness f1 of fish farming feed and the sinking velocity in Examples and Comparative Examples. 3 is a graph showing the change in feeding rate of bluefin tuna in the normal feed group and the flat feed group.

[0014] Several embodiments of the present disclosure are described below. However, the following embodiments are merely examples for explaining the present disclosure and are not intended to limit the present disclosure to the following content. The upper or lower limit of a numerical range in the present disclosure may be replaced with any value shown in the examples. Furthermore, individually described upper and lower limit values ​​may be arbitrarily combined. The symbol "to" used in a numerical range indicates a numerical range that includes the upper and lower limit. For example, "X to Y" indicates a numerical range "greater than or equal to X and less than or equal to Y." Unless otherwise specified, the materials or components exemplified in this disclosure can be used alone or in combination of two or more. In the description, identical elements or elements having the same function are denoted by the same reference numerals, and redundant explanations are omitted. Furthermore, positional relationships such as up, down, left, and right used in the description are based on the positional relationships shown in the drawings unless otherwise specified.

[0015] It is known that the settling velocity of relatively large gravel objects correlates with several shape variables (Hachiro Kira, "On the Relationship between Shape Factors and Settling Velocity of Gravel Particles," [online], Agricultural Engineering Research, 1957-1958, Vol. 25, No. 3, pp. 183-187, [Retrieved May 31, 2023], Internet, <URL: https: / / doi.org / 10.11408 / jjsidre1929.25.183>). However, the relationship between shape and settling velocity has not been investigated for fish feed, such as that disclosed here, which differs from gravel in both material and size.

[0016] The fish feed for tuna farming according to the first embodiment has a body portion that is flattened so that the length along the thickness direction perpendicular to the width and longitudinal directions is shorter than the length along the width direction perpendicular to the longitudinal direction, and satisfies at least one selected from the group consisting of (A) and (B) below: (A) When the maximum length along the longitudinal direction is a (mm), the maximum length along the width direction is b (mm), and the maximum length along the thickness direction is c (mm), the flattening ratio f1 calculated by the following formula (1) is 110 or more: f1 = a × b / c (1) (B) The volume of the fish feed is V (cm ３ ), and the area of ​​the fish feed when viewed in plan is A (mm ２ ) and then (V / A) １／２ is 0.110 or less

[0017] The feed for farming tuna species according to the second embodiment has a sinking velocity of 15.0 cm / s or less at a depth of 15.0 cm to 35.2 cm from the water surface.

[0018] The fish feed, which is a common example of the first and second embodiments, has a shape shown in Figures 1, 2, and 3. As shown in Figures 1, 2, and 3, the fish feed 10 includes a pair of tapered portions 12 at both ends in the longitudinal direction, and a body portion 11 between the pair of tapered portions 12. The maximum length a of the fish feed 10 along the longitudinal direction may be equal to the distance between the ends of the pair of tapered portions 12. In the body portion 11, the maximum length c along the thickness direction shown in Figures 1 and 3, in directions perpendicular to the longitudinal direction, is shorter than the maximum length b along the width direction shown in Figures 2 and 3. In other words, b>c.

[0019] b may be 1.1 times or more, 1.2 times or more, 1.3 times or more, 1.4 times or more, 1.5 times or more, 1.6 times or more, or 1.7 times or more than c. Because there is a risk that the fish feed will collapse if it is crushed by applying strong pressure, b is preferably 3 times or less, 2.5 times or less, or 2 times or less than c. In this way, the fish feed 10 has a body portion 11 that is flattened so that the maximum length c along the thickness direction is shorter than the maximum length b along the width direction. For this reason, the fish feed 10 can also be called a flat feed.

[0020] The size of the fish farming feed 10 is adjusted according to the size of the fish. It is preferable that the fish farming feed 10 does not differ significantly in size and shape from the fish that the fish normally feed on in the wild. From the perspective of creating a shape preferred by tuna, the fish farming feed 10 may have a body portion shaped like a slightly flattened cylinder approximately 5 to 20 cm in length and approximately 1 to 5 cm in diameter in the radial cross section. Tuna tend to prefer this shape. When using this type of feed, farmed fish tend to first grab the body portion with their mouths and then hold the feed vertically to swallow it. Because this behavior is consistent with normal feeding behavior, the approximately cylindrical fish farming feed 10 is considered suitable for feeding tuna. Furthermore, differences in growth between farmed fish due to the presence of individuals that are fed early and those that are fed later can lead to variations in fish size. The fish feed 10 has a flattened body 11, which allows it to sink slower in water than fish feed of the same volume that has a cylindrical body, thereby increasing the frequency with which the farmed fish come into contact with the feed. This allows the farmed fish to be fed earlier, reduces the variation in body size of the farmed fish, and improves the growth rate of the farmed fish.

[0021] The maximum lengths a, b, and c can be measured as follows. The fish feed 10 is placed on a flat plate. At this time, the fish feed 10 is placed on the flat plate in the most stable orientation. The maximum length a along the longitudinal direction may be measured when the fish feed 10 is viewed from the front as shown in FIG. 1 , or when the fish feed 10 is viewed from a plane as shown in FIG. 2 . The maximum length b along the width direction may be measured when the fish feed 10 is viewed from a plane as shown in FIG. 2 , or when the fish feed 10 is viewed from a side as shown in FIG. 3 . The maximum length c along the thickness direction may be measured when the fish feed 10 is viewed from the front as shown in FIG. 1 , or when the fish feed 10 is viewed from a side as shown in FIG. 3 . The maximum lengths a, b, and c may be measured using, for example, an electronic caliper or a visual analyzer (trade name: IRIS VA400, manufactured by Alpha Moss Japan Co., Ltd.).

[0022] The width direction and thickness direction of the fish feed 10 are both perpendicular to the longitudinal direction of the fish feed 10. The width direction and thickness direction are perpendicular to each other. As shown in Fig. 4, the maximum length b in the width direction and the maximum length c in the thickness direction may be lengths measured in one cross section perpendicular to the longitudinal direction, i.e., one transverse cross section. In this case, of the transverse cross sections of the fish feed 10, the transverse cross section at which the maximum lengths b and c are measured has the largest cross-sectional area.

[0023] The flatness f1 of the fish farming feed 10 calculated by the above formula (1) may be 110 or more. It is known that the settling velocity of relatively large gravel particles in water shows a negative correlation with the flatness f1 (Hachiro Kira, "On the Relationship between the Shape Factor of Gravel Particles and Settling Velocity," [online], Agricultural Engineering Research, Vol. 25, No. 3, pp. 183-187, [searched May 31, 2023], Internet, <URL: https: / / doi.org / 10.11408 / jjsidre1929.25.183>). The fish farming feed 10 disclosed herein, having a flatness f1 of 110 or more, is sufficiently flat, and therefore easily assumes a shape preferred by tuna species and can sufficiently slow the settling velocity. Using such fish farming feed in tuna farming allows tuna species to be fed earlier, reducing the size variation of farmed fish. It also improves the growth rate of farmed fish.

[0024] As the flatness f1 increases, the sinking velocity tends to slow down. From the viewpoint of further reducing the size variation of cultured fish, the flatness f1 may be 115 or more, 120 or more, 125 or more, 130 or more, 135 or more, or 140 or more. From the viewpoint of sufficiently increasing the durability of the fish feed 10, the flatness f1 may be 200 or less, or 190 or less. The flatness f1 may be in the range of 110 to 200, 115 to 200, 120 to 200, 125 to 200, 130 to 200, 135 to 200, 140 to 200, 110 to 190, 115 to 190, 120 to 190, 125 to 190, 130 to 190, 135 to 190, or 140 to 190.

[0025] The maximum length a may be 40 to 200 mm, 50 to 150 mm, 60 to 100 mm, 70 to 80 mm, or 72 to 78 mm. The maximum length b may be 10 to 70 mm, 20 to 50 mm, 25 to 35 mm, or 27 to 33 mm. The maximum length c may be 3 to 50 mm, 5 to 40 mm, 8 to 30 mm, 10 to 20 mm, or 14 to 18 mm. a, b, and c may be adjusted appropriately depending on the size of the tuna to be fed.

[0026] The volume of the fish feed 10 is V (cm ３ ), and the area of ​​the fish feed 10 when viewed in plan as shown in FIG. ２ ) (V / A) １／２ may be 0.110 or less. V represents the volume of the sediment, and A represents the area when viewed from above. In water with relatively large gravel, the settling velocity in water is (V / A). １／２ It is known that there is a positive correlation between the shape factor of sand and gravel particles and the settling velocity (Hachiro Kira, "On the relationship between the shape factor of sand and gravel particles and the settling velocity," [online], Agricultural Engineering Research, 1957-1958, Vol. 25, No. 3, pp. 183-187, [Retrieved May 31, 2023], Internet, <URL: https: / / doi.org / 10.11408 / jjsidre1929.25.183>).

[0027] (V / A) １／２ By making the ratio of V / A to 0.110 or less, the sinking velocity can be sufficiently slowed. By using such fish feed for tuna farming, tuna can be fed early, and the size variation of farmed fish can be reduced. In addition, the growth rate of farmed fish can be improved. From the viewpoint of further slowing the sinking velocity, (V / A) １／２ From the viewpoint of shortening the time it takes for the farmed fish to take in the feed and improving the farming efficiency, (V / A) １／２ (V / A) may be 0.080 or more, 0.090 or more, or 0.100 or more. １／２may be in the range of 0.080 to 0.110, 0.080 to 0.109, 0.080 to 0.108, 0.080 to 0.107, 0.090 to 0.110, 0.090 to 0.109, 0.090 to 0.108, 0.090 to 0.107, 0.100 to 0.110, 0.100 to 0.109, 0.100 to 0.108, or 0.100 to 0.107.

[0028] The area A when viewed from above can be measured using, for example, a visual analyzer (product name: IRIS VA400, manufactured by Alpha Moss Japan Co., Ltd.). The volume V can be calculated from the weight (g) of the fish feed 10 and the density of the fish feed 10. The density can be determined by the weight of the fish feed 10 and Archimedes' method using water. For example, the weight of the feed is measured, 100 ml of water is added to a 200 ml measuring cylinder, the feed is poured into it, and immediately water is pumped out with a dropper until it reaches the 100 ml line on the measuring cylinder, and the weight of the water is measured. The density of the feed can be determined by the following formula: Density of the feed (g / cm ３ ) = weight (g) / weight of pumped water (g = cm ３ )

[0029] The volume V of the fish feed 10 is 5 to 100 cm ３ , 10 to 40 cm ３ , 12 to 30 cm ３ , 15-25cm ３ , or 18 to 22 cm ３ The area A of the fish feed 10 in plan view is 500 to 3000 mm ２ , 1000~2500mm ２ , 1500~1800mm ２ , or 1550 to 1750 mm ２ The density of the fish feed 10 can be adjusted depending on the components contained therein. Considering the components necessary for the efficient growth of tuna, the density of the fish feed 10 is set to 1.04 to 1.30 (g / cm ３ ), 1.05 to 1.25 (g / cm ３ ), 1.07 to 1.20 (g / cm ３ ), or 1.08 to 1.15 (g / cm ３) range.

[0030] The fish feed 10 has the above-mentioned flatness f1 of 110 or more, and (V / A) １／２ The settling velocity of such fish farming feed 10 is sufficiently slow. Therefore, by using such fish farming feed 10 for tuna farming, tuna can be fed early, and the size variation of farmed fish can be reduced. In addition, the growth rate of farmed fish can be improved.

[0031] The sinking velocity of the fish farming feed 10 between a depth of 15.0 cm and a depth of 35.2 cm from the water surface may be 15.0 cm / s or less. By having the sinking velocity within this range, the frequency with which tuna come into contact with the feed during farming is increased, allowing for earlier feeding and reducing the variation in size of tuna after farming. From the viewpoint of further reducing the variation in size of farmed fish, the sinking velocity may be 14.0 cm / s or less, 13.5 cm / s or less, or 13.0 cm / s or less. From the viewpoint of shortening the time it takes for farmed fish to take in the feed and improving farming efficiency, the sinking velocity may be 1.0 cm / s or more, 3.0 cm / s or more, or 5.0 cm / s or more. The sinking velocity of the fish feed 10 can be determined by dropping the fish feed 10 into a tank filled with 3% salt water at an initial velocity of 0 from a state in which the fish feed 10 is in contact with the water surface with the thickness direction of the fish feed 10 perpendicular to the water surface, measuring the travel time from a depth of 15.0 cm to a depth of 35.2 cm with the water surface as the reference, and dividing the traveled distance (20.2 cm) by the travel time. The settling velocity may be in the range of 1.0 to 15.0 cm / s, 1.0 to 14.0 cm / s, 1.0 to 13.5 cm / s, 1.0 to 13.0 cm / s, 3.0 to 15.0 cm / s, 3.0 to 14.0 cm / s, 3.0 to 13.5 cm / s, 3.0 to 13.0 cm / s, 5.0 to 15.0 cm / s, 5.0 to 14.0 cm / s, 5.0 to 13.5 cm / s, or 5.0 to 13.0 cm / s.

[0032] Multiple fish feeds may be fed by adding them all together into seawater instead of feeding them separately. The required amount of fish feed may be fed in several batches, or the required amount may be fed all at once. In this disclosure, multiple fish feeds are referred to as a fish feed group. The fish feed group will be described later.

[0033] The body 11 may have a tapered portion 13 that becomes thinner from the center toward both ends in the longitudinal direction. By providing the tapered portion 13, the shape of the fish feed 10 becomes closer to that of small fish that are live bait, making it easier for the fish to recognize it as bait, and further increasing the frequency with which the farmed fish come into contact with the fish feed 10. This makes it possible to further reduce the variation in the body size of the farmed fish.

[0034] The constricted portions 12 may be located at both ends of the fish feed 10 in the longitudinal direction, and may protrude in the direction opposite to the center of the fish feed 10. The constricted portions 12 may be configured by being crimped to the ends of the outer shell 20. The tapered portion 13 and the constricted portions 12 of the body portion 11 can be formed by crimping the kneaded raw material composition during extrusion molding using a twin-screw extruder or the like. The presence of the constricted portions 12 can reduce leakage of oils, fats, and fish meal contained in the body portion 11.

[0035] An inflection part 14, which has a curved surface that is concave outward toward the end and whose diameter gradually decreases, is formed between the tapered part 13 and the narrowed part 12. The presence of this inflection part 14 allows the outer diameter to resemble that of small fish that serve as bait, further increasing the palatability of the tuna fish feed 10.

[0036] As shown in Figures 4 and 5, the fish feed 10 may have an inner shell 30 and an outer shell 20 that encloses the inner shell 30. The inner shell 30 may contain a composition containing fish meal and oil. When the inner shell 30 contains a composition containing fish meal and oil, the nutrition contained in the fish feed 10 becomes closer to that of small fish, and the farmed fish can be supplied with the proteins and lipids necessary for their growth. The composition of the composition may be changed as appropriate depending on the type of tuna to be fed.

[0037] The fish meal may be any of various fish meals commonly used as fish feed ingredients, or powder of crustaceans such as krill. The fish meal content in the inclusion 30 may be, for example, 30% by mass or more, 35% by mass or more, or 45% by mass or more. The fish meal content may be 70% by mass or less. By using fish meal, it is possible to supply tuna with proteins necessary for their growth. An example of the fish meal content is 30 to 70% by mass.

[0038] The oils and fats are not particularly limited, and examples include fish oil, soybean oil, corn oil, and rapeseed oil. The oil and fat may be fish oil, as this can supply tuna with lipids rich in omega-3 fatty acids necessary for their growth. The content of the oil and fat in the inclusion 30 may be, for example, 30% by mass or more, 35% by mass or more, or 45% by mass or more. The oil and fat content may also be 70% by mass or less. An example of the oil and fat content is 30 to 70% by mass. By having the oil and fat content in the fish farming feed 10 within this range, it is possible to obtain fish farming feed 10 that enhances the growth efficiency of tuna with the oil and fat, while also providing sufficient addition of other nutrients.

[0039] In order to prevent oil leakage when flattening the fish feed 10, a component that reduces the fluidity of the oil may be blended. Examples of components that reduce fluidity include powdered soy protein New Fujipro SEH (trade name, manufactured by Fuji Oil Co., Ltd.), Vitacel WF200, Vitacel WF600, or Vitacel WF600 / 30 (trade name, manufactured by Rettenmeyer), Oil Q No. 50 or Oil Q-S (trade name, manufactured by Nippon Starch Chemical Co., Ltd.), and dextran (trade name, manufactured by Matsutani Chemical Industry Co., Ltd.), oil-absorbing polysaccharides such as fermented soybeans, oil-absorbing proteins such as isoflavones, and hydrogenated oils. The content of these components that reduce the fluidity of the oil may be 10% by mass or less, or 5% by mass or less, of the composition in the inclusion 30, in order to improve the palatability of tuna.

[0040] The hydrogenated oil may be a white solid fat obtained by solidifying fish oil, soybean oil, corn oil, rapeseed oil, etc. through hydrogenation. Before hydrogenation, the oil contains unsaturated fatty acids such as oleic acid, linoleic acid, linolenic acid, and other highly unsaturated fatty acids as its component fatty acids. Hydrogenated oil is obtained by adding hydrogen to unsaturated fatty acids, reducing the unsaturated fatty acids and ultimately converting them into saturated fatty acids, resulting in solid fat. The addition of hydrogenated oil can transform liquid oil into a paste or solid form. To prevent the oil contained in the encapsulation 30 from leaking or seeping out of the fish feed 10, it is preferable to add hydrogenated oil with a melting point of 50°C or higher. Such hydrogenated oils include those in which the main fatty acid component (the fatty acid with the highest amount in the fatty acid composition) constituting the hydrogenated oil is a fatty acid with 18 or more carbon atoms and has an iodine value (the mass of iodine absorbed by 100 g of oil (unit: g)) of 0 to 2. The iodine value of hydrogenated oils sold as highly hydrogenated oils falls within this range. Examples of hardened oils include lard super hardened oil (trade name, manufactured by Yokoseki Oil Industry Co., Ltd.), Unishort K (trade name, manufactured by Fuji Oil Co., Ltd.), Hi-Elshin rapeseed super hardened oil (trade name, manufactured by Yokoseki Oil Industry Co., Ltd.), beef tallow super hardened oil (trade name, manufactured by New Japan Chemical Co., Ltd.), soybean super hardened oil (trade name, manufactured by Yokoseki Oil Industry Co., Ltd.), rapeseed super hardened oil (trade name, manufactured by Yokoseki Oil Industry Co., Ltd.), and TAISET 50 (trade name, manufactured by Taiyo Kagaku Co., Ltd.). Adding hardened oil improves the viscosity of the encapsulation 30, and improves the mechanical suitability when the encapsulation 30 is wrapped in the outer shell 20 and molded. Furthermore, adding hardened oil improves the viscosity of the oil, thereby further reducing oil leakage when the fish feed 10 is flattened.

[0041] Furthermore, raw materials used in conventional fish feed may be added to the composition in the casing 30. For example, proteins such as raw fish, squid meal, krill meal, soybean meal, and corn gluten meal, starches such as starch, wheat flour, rice flour, tapioca flour, and corn flour, polysaccharides such as alginic acid and its salts, sodium carboxymethylcellulose (CMC), guar gum, dextrin, chitosan, curdlan, pectin, carrageenan, mannan, gellan gum, gum arabic, and edible water-soluble cellulose, vitamins, minerals, and the like may be added.

[0042] The outer shell 20 may contain a heat-induced gel of starch and a protein. The components constituting the outer shell 20 are not particularly limited as long as they can encase the inclusion 30. Heat-induced gelling proteins or starches can be used to improve flexibility and extensibility. Proteins may be protein-containing substances such as fish meat, surimi, krill, gluten, collagen, soy protein, enzymatically hydrolyzed soy protein, gelatin, or egg white, either singly or in mixtures of two or more of these. Starches may be tapioca starch, wheat starch, potato starch, corn starch, soybean starch, waxy corn starch, or modified starches thereof. Food materials rich in the above proteins and starches may also be used. Compositions containing protein and starch solidify into a gel upon heating, maintaining flexibility and a certain strength. Furthermore, components that gel upon heat dissipation or cooling after being heated and melted may be added. Examples of such components include gelatin and agar.

[0043] From the viewpoint of increasing the nutritional efficiency of the fish feed 10, the outer skin 20 may contain fish meal and oil within the range that does not affect the gelation of the outer skin 20. The fish meal content in the outer skin 20 may be 20 to 30% by mass. The oil content may be 5 to 10% by mass.

[0044] There are no particular limitations on the starch used for the outer skin 20, and examples thereof include tapioca starch, wheat starch, potato starch, corn starch, and soy starch, and in particular, modified starches such as etherified, acetylated, acetyl-crosslinked, ether-crosslinked, phosphate-crosslinked, and pregelatinized hydroxypropyl phosphate-crosslinked starches. The starch content in the outer skin 20 may be changed as appropriate depending on the species of fish being farmed. The starch content in the outer skin 20 may be, for example, 20 to 80% by mass, or 20 to 65% by mass.

[0045] In the outer shell 20, starch is kneaded with water, and the heated gel is endowed with elasticity, flexibility, and extensibility. To further enhance the palatability of tuna, two or more types of modified starches may be combined. For example, different types of modified starches may be combined, such as a combination of etherified starch and phosphate-crosslinked starch. Adding proteins such as gluten or soy protein to such starches can produce an even stronger gel. Instead of gluten, gluten-containing wheat flour or the like may be used. Other ingredients that may be added include cereal flours such as wheat flour, proteins such as soy protein, gluten, and egg white, sugars and sugar alcohols such as starch syrup, carrageenan, agar, gellan gum, pullulan, mannan, xanthan gum, locust bean gum, curdlan, pectin, thickeners such as alginic acid and its salts, gum arabic, chitosan, dextrin, and edible water-soluble cellulose, and salts such as phosphates. For example, adding wheat flour to starch can impart strength to the outer shell 20. In addition, adding a certain amount of protein can prevent the surface from becoming sticky after heating.

[0046] To improve the gel quality of the outer shell 20, additives used as quality improvers for fish paste products and the like may be added as appropriate. Specifically, thickening polysaccharides, isolated soy protein, sodium bicarbonate, polymerized phosphate, transglutaminase, various protease inhibitors, and the like may be contained. In particular, to enhance gel strength, thickeners such as agar, gellan gum, pullulan, mannan, carrageenan, xanthan gum, locust bean gum, curdlan, pectin, alginic acid and its salts, gum arabic, chitosan, dextrin, and edible water-soluble cellulose may be appropriately blended. To enhance the palatability of tuna, the content of the thickener in the outer shell 20 may be 10% by mass or less, 5% by mass or less, or 1.5% by mass or less.

[0047] As shown in Figures 3 and 6, the narrowed portion 12 has traces 21 where the outer skin 20 constituting the outer surface has been narrowed toward the end. These traces 21 can be composed of, for example, multiple radial lines. These lines can be distinguished visually or by touch, and are thought to also promote feeding by tuna. These lines may be configured as grooves that do not reach the inner envelope 30. The traces 21 may be formed by narrowing the outer skin 20 toward the axial center.

[0048] A fish farming feed group according to one embodiment includes a plurality of tuna fish farming feeds, and has an average settling velocity of 15.5 cm / s or less between a depth of 15.0 cm and a depth of 35.2 cm from the water surface. The "average settling velocity" in the present disclosure refers to the arithmetic mean value of the settling velocity of each fish farming feed. The number of fish farming feeds constituting a fish farming feed group is not particularly limited, and may be 3 or more, 5 or more, 10 or more, or 15 or more. The number may be 1,000 or less. The number of fish farming feeds constituting a fish farming feed group may be 3 to 1,000, 5 to 1,000, 10 to 1,000, or 15 to 1,000.

[0049] From the viewpoint of further reducing the size variation of farmed fish by increasing the frequency of contact of tuna with feed during farming and feeding them earlier, the average sinking velocity of the fish feed group may be 15.5 cm / s or less, 15.0 cm / s or less, 14.5 cm / s or less, 14.0 cm / s or less, 13.5 cm / s or less, or 13.0 cm / s or less. Furthermore, from the viewpoint of shortening the time it takes for farmed fish to take up feed and improving farming efficiency, the average sinking velocity of the fish feed group may be 1.0 cm / s or more, 3.0 cm / s or more, or 5.0 cm / s or more. The average settling velocity of the fish feed batch may be in the range of 1.0 to 15.5 cm / s, 1.0 to 15.0 cm / s, 1.0 to 14.5 cm / s, 1.0 to 14.0 cm / s, 1.0 to 13.5 cm / s, 1.0 to 13.0 cm / s, 3.0 to 15.5 cm / s, 3.0 to 15.0 cm / s, 3.0 to 14.5 cm / s, 3.0 to 14.0 cm / s, 3.0 to 13.5 cm / s, 3.0 to 13.0 cm / s, 5.0 to 15.5 cm / s, 5.0 to 15.0 cm / s, 5.0 to 14.5 cm / s, 5.0 to 14.0 cm / s, 5.0 to 13.5 cm / s, or 5.0 to 13.0 cm / s.

[0050] The more consistent the settling speed of the fish farming feed group as a whole, the less fish farming feed is recognized as food by tuna, and the less fish farming feed is wasted, thereby reducing the variation in the growth rate of tuna. For example, the standard deviation of the settling speed of the fish farming feed included in the fish farming feed group may be 1.30 cm / s or less, 1.20 cm / s or less, 1.10 cm / s or less, 1.00 cm / s or less, 0.90 cm / s or less, 0.80 cm / s or less, or 0.70 cm / s or less. The standard deviation may also be 0.01 cm / s or more. The range of standard deviation of the settling velocity of the fish feeds included in the fish feed group may be 0.01 to 1.30 cm / s, 0.01 to 1.20 cm / s, 0.01 to 1.10 cm / s, 0.01 to 1.00 cm / s, 0.01 to 0.90 cm / s, 0.01 to 0.80 cm / s, or 0.01 to 0.70 cm / s.

[0051] A method for producing tuna fish feed according to one embodiment includes a step of radially compressing and crushing a molded product having a substantially cylindrical body portion, thereby deforming the body portion so that the radial cross section of the molded product is flattened. Pressurizing the molded product changes the radial length of the molded product, thereby obtaining fish feed with a flattened body portion. Changing the pressure applied when compressing the molded product makes it possible to adjust the maximum widthwise length b, the maximum thicknesswise length c, and the flattening ratio f1. The longitudinal length a of the fish feed 10 may also be changed in the above step. The fish feed obtained by this production method has a slower sinking rate in water, increasing the frequency with which farmed fish come into contact with the fish feed 10.

[0052] The shaped product is obtained by molding a mixture of raw material compositions into a generally cylindrical shape. The raw material composition can be obtained by mixing the raw materials constituting the encapsulation 30 and the outer shell 20 described above. The shaped product can be obtained by separately mixing the raw materials for the encapsulation 30 and the outer shell 20 and enveloping them using an extruder with a double nozzle or an encrusting machine. Alternatively, a twin-screw extruder with a double nozzle may be used to continuously mix and shape the raw materials while heating and mixing them. Heating may be performed at a temperature of 60 to 120°C or 70 to 100°C from the viewpoint of gelling the starch and protein. T-Sage (manufactured by Farm Choice Co., Ltd.) may be used as the shaped product produced in this manner.

[0053] The term "approximately cylindrical shape" in this disclosure does not necessarily mean a strict geometric cylindrical shape, but rather means a shape that can be recognized as a cylindrical shape or a similar shape at a glance. Therefore, it is acceptable for the cross section to be somewhat irregular or flattened, or for the cross section to be flattened due to its own weight or the accumulation of feed. The length and width of this approximately cylindrical shape can be adjusted appropriately depending on the species and size of the tuna fish to be fed.

[0054] The obtained molded product is pressed in the radial direction to deform the body portion so that the cross section in the radial direction is flattened. Pressurization may be performed manually by an operator, or may be performed by pressing in the radial direction while rotating a roller.

[0055] 7 shows an example of a manufacturing device for producing fish feed 10 by pressing molded products 32 while rotating rollers. The pressurizing device 50 includes a conveyor 40 that transports the molded products 32 before and the fish feed 10 after being pressed, and a roller 34 disposed above the conveyor 40. A shaft 36 that rotatably supports the roller 34 may be suspended by a suspension jig (not shown). A gap is provided between the conveyor 40 and the roller 34, and as the molded products 32 transported by the conveyor 40 pass through this gap, the roller 34 rotates and pressurizes the molded products 32 in the radial direction. The pressure applied to the molded products 32 can be adjusted by adjusting the size of this gap.

[0056] The shaft 36 supporting the roller 34 may be suspended so as to be movable in the vertical direction. The amount of deformation of the shaped product 32, i.e., the maximum lengths a, b, and c of the fish feed 10, may be adjusted by changing the amount of vertical movement. By using the pressure device 50, the shaped product 32 can be deformed more efficiently than when flattened by hand, thereby improving the production efficiency of the fish feed 10. Furthermore, variation in shape can be reduced. The manufacturing apparatus for producing the fish feed 10 is not limited to the structure shown in FIG. 7. For example, the fish feed 10 may be produced without a conveyor by pressing the shaped products 32 arranged on a stationary table with rollers attached to a horizontally moving shaft.

[0057] When producing multiple fish feeds 10, the multiple fish feeds 10 may be produced using the same method. Such fish feeds 10 can suppress variations in sedimentation speed. A group of fish feeds made up of such fish feeds 10 can have all of the fish feeds 10 in contact with tuna for a long period of time, thereby increasing the probability that the tuna will recognize the fish feeds 10 as food.

[0058] A tuna farming method according to one embodiment may include a step of feeding the fish feed 10 to the farmed fish. In this farming method, the farmed fish come into contact with the fish feed 10 more frequently, allowing the farmed fish to be fed earlier. This reduces the variation in body size of the farmed fish, improving their growth rate. The body size of the tuna in the fish pen can be measured using a commercially available camera for measuring fish size. Feeding can be done manually or by using an air feeder. Using an air feeder reduces the burden on workers and allows feeding to be done over a wide area at once.

[0059] The present disclosure includes the following embodiments: [1] Feed for farming tuna fish, comprising a body part that is flattened so that the length along the width direction and the thickness direction perpendicular to the longitudinal direction is shorter than the length in the width direction perpendicular to the longitudinal direction, and satisfying at least one selected from the group consisting of (A) and (B) below: (A) When the maximum length along the longitudinal direction is a (mm), the maximum length along the width direction is b (mm), and the maximum length along the thickness direction is c (mm), the flattening ratio f1 calculated by the following formula (1) is 110 or more: f1 = a × b / c (1); (B) The volume of the fish feed is V (cm ３ ), and the area of ​​the fish feed when viewed in plan is A (mm ２ ) and then (V / A) １／２[2] The feed for farming tuna fish according to [1], wherein the sinking velocity between a depth of 15.0 cm and a depth of 35.2 cm relative to the water surface is 15.0 cm / s or less. [3] The feed for farming tuna fish according to [1] or [2], wherein the body portion has a tapered portion that narrows from the center toward both ends in the longitudinal direction. [4] The feed for farming tuna fish according to any one of [1] to [3], which is provided with a pair of narrowed portions at both ends in the longitudinal direction, and the body portion between the pair of narrowed portions. [5] The feed for farming tuna fish according to any one of [1] to [4], wherein the body portion has a composition containing fish meal and oil and fat, and an outer skin containing a heat-generated starch gel that encapsulates the composition, and has narrowed portions formed by crimping the ends of the outer skin at both ends in the longitudinal direction. [6] Tuna farming feed, having a sedimentation rate of 15.0 cm / s or less between a depth of 15.0 cm and a depth of 35.2 cm from the water surface. [7] A group of fish farming feeds including a plurality of tuna farming feeds, wherein the average sedimentation rate of 15.5 cm / s or less between a depth of 15.0 cm and a depth of 35.2 cm from the water surface. [8] The group of fish farming feeds according to [7], wherein the standard deviation of the sedimentation rates of the fish farming feeds is 1.30 cm / s or less. [9] A method for producing tuna farming feed, comprising a step of radially compressing and crushing a molded article having a substantially cylindrical body portion, and deforming the body portion so that the radial cross section of the molded article is flattened.

[10] A method for producing tuna farming feed according to [9], wherein the step of deforming the body portion is performed by pressing a roller against the body portion while rotating.

[11] A method for cultivating tuna, comprising a step of feeding tuna fish feed according to any one of [1] to [6] above, the group of fish feeds according to [7] or [8], or the tuna fish feed obtained by the production method according to [9] or

[10] .

[0060] The present disclosure will be described in more detail below with reference to examples and comparative examples, but the present disclosure is not limited to the following examples.

[0061] [Preparation of Flat Feed] (Examples 1 to 16, Comparative Examples 1 to 17) A number of tuna farming feeds (manufactured by Farm Choice Co., Ltd., product name: T to Sage, standard: SS) having a cylindrical body were prepared. The density of 33 feeds was measured by Archimedes' method, and the average density was 1.117 (g / cm ３ ), and the standard deviation of the density is 0.017 (g / cm ３ The minimum density was 1.071 (g / cm ３ ), and the maximum density is 1.148 (g / cm ３ Of these, 17 were used as control feeds (Comparative Examples 1 to 17). Another 16 feeds were compressed in the radial direction of the body, and flattened feeds with flattened body parts were used as examples (Examples 1 to 16).

[0062] A visual analyzer (product name: IRIS VA400, manufactured by Alpha Moss Japan Co., Ltd.) was used to measure the area A (mm ２ ) were measured. The maximum length a (mm) along the longitudinal direction, the maximum length b (mm) along the width direction, and the maximum length c (mm) along the thickness direction of each of the control feeds and flat feeds were measured using an electronic caliper. The weight Ws (g) was measured using an electronic balance. The maximum length a (mm) along the longitudinal direction, the maximum length b (mm) along the width direction, the maximum length c (mm) along the thickness direction, and the area A (mm ２ The measurement results of a, b, and c are shown in Table 1. The measured values ​​of a, b, and c were substituted into the following formula (1) to calculate the flatness f1. The volume V (cm ３ ) and calculate (V / A) from the volume V and area A. １／２ The volume V (cm ３ ), flatness f1 and (V / A) １／２ The calculation results are shown in Table 2. f1 = a × b / c (1)

[0063] [Measurement of Sedimentation Rate] Each feed was held at a pair of narrowed portions with fingers and brought close to the water surface with the thickness direction perpendicular to the water surface of the tank. When the bottom of the feed reached the water surface, the feed was released and the sample was dropped into the tank. The time required for the feed to sink from a depth of 15 cm to a depth of 35.2 cm relative to the water surface was measured. The sedimentation rate of each feed was calculated from the distance traveled (20.2 cm) and the required time. The results are shown in Table 2.

[0064]

[0065]

[0066] In FIG. 8, the vertical axis represents the sedimentation velocity and the horizontal axis represents (V / A). １／２ 9 is a graph showing the results of Table 2 plotted with the settling velocity on the vertical axis and the oblateness f1 on the horizontal axis.

[0067] The average settling velocity of the fish feed groups of Examples 1 to 16 was 13.58 cm / s, and the average settling velocity of the fish feed groups of Comparative Examples 1 to 17 was 15.59 cm / s. The standard deviation of the settling velocity of the fish feed groups of Examples 1 to 16 was 0.62 cm / s, and the standard deviation of the settling velocity of the fish feed groups of Comparative Examples 1 to 17 was 1.31 cm / s. As shown in FIG. 8 , (V / A) １／２As the value of f1 increased, the settling velocity tended to increase. As shown in Figure 9, as the flattening ratio f1 increased, the settling velocity tended to decrease. Furthermore, as shown in Figures 8 and 9, by using flat feed, the variation in settling velocity was reduced, and the settling velocity of the entire feed at the time of feeding could be slowed. By using such a fish farming feed group, the entire feed can be brought into contact with the tuna more efficiently. One factor that causes the settling velocity to decrease is that flattening the feed increases the area A of the feed, making it more susceptible to resistance when falling through the water. By using such feed with a slow settling velocity in tuna farming, the frequency of contact between the feed and the tuna can be increased, and the variation in feeding of the tuna in the fish pens can be reduced. Furthermore, by increasing the frequency of contact between the tuna and the feed, the size of the tuna can be increased, making it possible to farm tuna of higher quality.

[0068] [Bluefin tuna farming experiment] In order to confirm the effectiveness of flat feed, a control feed and flat feed were fed in a cage where bluefin tuna are actually farmed, and an experiment was conducted to compare the feeding rate and the growth rate of the bluefin tuna in the cage for each feed.

[0069] Several tuna fish feeds (manufactured by Farm Choice Co., Ltd., product names: T to Sage, specification: SSS) with cylindrical body portions were prepared. Some of these were used as control feeds. The remaining roughly cylindrical body portions were pressed against the body portions by rotating a roller, applying radial pressure and crushing to obtain flattened feeds having the shapes shown in Figures 1 to 6. Fifteen control feeds and flattened feeds were prepared. A control feed group consisting of 15 control feeds was designated Comparative Example 18, and a flattened feed group consisting of 15 flattened feeds was designated Example 17. The settling velocity of each feed within the group was measured in Comparative Example 18 and Example 17, and the average settling velocity and standard deviation were calculated. The average settling velocity of Comparative Example 18 was 16.2 cm / s, with a standard deviation of 1.4 cm / s. The average settling velocity of Example 17 was 14.3 cm / s, with a standard deviation of 0.7 cm / s.

[0070] A feeding test of bluefin tuna was conducted using the control feed group (control: Comparative Example 18) and the flat feed group (test: Example 17) prepared as described above. The net pens fed with the control feed were designated as the control feed area, and the net pens fed with the flat feed were designated as the flat feed area, and were used for bluefin tuna farming, to compare the growth conditions of the bluefin tuna depending on the feed. The bluefin tuna that had been raised on moist pellets were deprived of food for one day, and then the control feed was fed to the control feed area, and the flat feed to the flat feed area. The feeding period was three months for each. Feeding was carried out by satiation once in the morning and once in the afternoon (twice per day), and the amount of feed fed in each test area was recorded. In the flat feed area, the flat feed was used for one month from the start of feeding, and thereafter the control feed was used as in the control feed area.

[0071] The transition of the feeding rate of bluefin tuna from the start of feeding is shown in Figure 10. The feeding rate shown in Figure 10 was calculated as the ratio of the amount of feed consumed to the body weight of the bluefin tuna, using a five-day moving average.

[0072] As shown in Figure 10, the feeding rate of bluefin tuna in the flat feed group increased more quickly than in the normal feed group. This is thought to be because the average sinking speed of flat feed in water is slower, which increased the frequency with which the bluefin tuna came into contact with the feed, allowing the bluefin tuna to recognize the feed as food earlier. Therefore, it was confirmed that using flat feed makes it possible to feed bluefin tuna earlier.

[0073] Next, the growth status of the bluefin tuna was checked three months after the start of feeding. Schools of fish were photographed using a fish size measurement camera (product name: UC-600, manufactured by Furuno Electric Co., Ltd.) submerged in each cage, and the average growth rate was calculated from the weight of the bluefin tuna from the beginning to the end of the period through image analysis. The weight data from the UC-600 was classified into four levels depending on the data accuracy of each individual observed. Of the four levels, data from levels A, B, and C, which had relatively high data accuracy, were used. The results three months after the start of feeding are shown in Table 3.

[0074]

[0075] As shown in Table 3, when comparing schools of bluefin tuna three months after the start of feeding, the standard deviation of the weight of the fish at the end of the period was smaller in the flat feed area. Therefore, it was confirmed that using flat feed can reduce the variation in fish size within the school of fish. Furthermore, when the growth rates of bluefin tuna three months after the start of feeding were compared, it was found that the growth rate of bluefin tuna in the flat feed area was higher than that of bluefin tuna in the control feed area, and the bluefin tuna were larger. From the above, it was confirmed that bluefin tuna farmed using flat feed can produce larger bluefin tuna with less variation in quality than those farmed using the control feed.

[0076] The present disclosure can provide a fish feed for tuna farming with a slow sinking rate, a group of fish feeds, and a method for producing fish feed for tuna farming, as well as a method for farming tuna using such fish feed for tuna farming.

[0077] 10...fish feed, 11...body portion, 12...narrowed portion, 13...tapered portion, 14...inflection portion, 21...trace, 20...outer skin, 30...inner part, a...maximum length along the longitudinal direction, b...maximum length along the width direction, c...maximum length along the thickness direction, 50...pressurizing device, 32...molded product, 34...roller, 36...shaft, 40...conveyor.

Claims

1. Fish feed for farming tuna fish, comprising a body part that is flattened so that the length along the width direction perpendicular to the longitudinal direction and the thickness direction perpendicular to the longitudinal direction is shorter than the length along the width direction perpendicular to the longitudinal direction, and satisfying at least one selected from the group consisting of (A) and (B) below: (A) When the maximum length along the longitudinal direction is a (mm), the maximum length along the width direction is b (mm), and the maximum length along the thickness direction is c (mm), the flattening ratio f1 calculated by the following formula (1) is 110 or more: f1 = a × b / c (1); (B) The volume of the fish feed is V (cm ３ ), and the area of ​​the fish feed when viewed in a plane is A (mm ２ ) then (V / A) １／２ is 0.110 or less 2. The feed for cultivating tuna fish according to claim 1, wherein the sinking velocity from a depth of 15.0 cm to a depth of 35.2 cm relative to the water surface is 15.0 cm / s or less.

3. Feed for farming tuna fish as described in claim 1, wherein the body portion has a tapered portion that becomes narrower from the center toward both ends in the longitudinal direction.

4. The feed for farming tuna fish according to claim 1, comprising a pair of narrowed portions at both ends in the longitudinal direction, and the body portion being located between the pair of narrowed portions.

5. The feed for farming tuna fish according to claim 1, wherein the body portion has a composition containing fish meal and oils and fats, and an outer skin containing a heat-generated gel of starch that encapsulates the composition, and has narrowed portions formed by crimping the ends of the outer skin at both ends in the longitudinal direction.

6. Feed for farmed tuna fish, having a sinking velocity of 15.0 cm / s or less between a depth of 15.0 cm and a depth of 35.2 cm from the water surface.

7. A group of fish farming feeds containing a plurality of tuna farming feeds, the group having an average sinking velocity of 15.5 cm / s or less between a depth of 15.0 cm and a depth of 35.2 cm from the water surface.

8. The fish feed according to claim 7, wherein the standard deviation of the settling velocity of the fish feed is 1.30 cm / s or less.

9. A method for producing feed for farmed tuna fish, comprising a step of radially compressing and crushing a molded object having a roughly cylindrical body portion, and deforming the body portion so that the radial cross section of the molded object is flattened.

10. A method for producing feed for farmed tuna fish as described in claim 9, wherein in the process, a roller is pressed against the body portion while rotating to deform the body portion.

11. A method for cultivating tuna, comprising a step of feeding tuna with the fish feed according to any one of claims 1 to 6, the group of fish feeds according to claim 7 or 8, or the fish feed obtained by the production method according to claim 9 or 10.