Method for feeding a crustacean or fish with one or more fatty acid alkaline metal salts

Abstract

The present invention relates to a method for feeding an aquatic animal in a hatchery or farm with feed containing one or more fatty acid alkaline metal salts. The invention also relates to a feed for fish or crustaceans containing one or more fatty acid alkaline metal salts, the use of said feed to increase the efficiency of biomass production, the survival rate and / or omega 3 fatty acid content of a crustacean or fish in a hatchery or farm. The invention also relates to a method for producing a processed product from fish or crustaceans fed with said feed, and a method for producing a feed for fish or crustaceans.

Description

[0001]FEEDING FOR AN AQUATIC ANIMAL AND METHOD OF FEEDING AN AQUATIC ANIMAL BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a method for feeding an aquatic animal in breeding facilities or aquaculture farms with a feed comprising one or more alkali metal salts of fatty acids. The present invention also relates to a feed for fish or crustaceans comprising one or more alkali metal salts of fatty acids, the use of said feed comprising one or more alkali metal salts of fatty acids to increase the biomass production efficiency, survival rate, and / or omega-3 fatty acid content of a crustacean or fish in a hatchery or farm, a method for producing a processed product from a fish or crustacean fed with said feed, and a method for producing a feed for fish or crustaceans. Description of the State of the Art.Aquaculture, commonly known as fish farming, involves the raising of aquatic animals. This dynamic and rapidly evolving industry is increasingly contributing to the production of food for human consumption, as well as to the supply of processed materials derived from these aquatic animals. A hatchery serves as a center for the artificial rearing, hatching, and early rearing of various animals, with a particular focus on fish and crustaceans. Once fed during these initial life stages, the animals are transferred to grow-out systems or farms until they reach a harvestable size suitable for human consumption or other types of processing. Maximizing biomass production efficiency (i.e., the increase in biomass per unit of time) is a key objective in aquaculture, reflecting the efficiency and success of the operation.Factors influencing biomass production efficiency include feed quality, environmental conditions, disease management, feeding practices, and overall management strategies employed in the aquaculture system. Monitoring and optimizing biomass production efficiency are crucial for sustainable aquaculture practices, ensuring adequate yields while maintaining environmental sustainability and animal welfare. Maximizing biomass production efficiency is a primary objective in aquaculture. Achieving this involves strategies aimed at improving the weight gain of aquatic animals per unit of time (rate of weight gain) and reducing mortality rates (i.e., increasing the survival rate).Among the various approaches to increasing biomass production efficiency, such as improving water quality or veterinary care, the choice of feed type emerges as a crucial factor. While biomass production efficiency is a quantitative measure, another relevant aspect in aquaculture is the quality and composition of the biomass produced. It would be desirable to improve biomass production not only by maximizing biomass production per se (biomass production efficiency) but also by obtaining higher-quality biomass, expressed as a higher content—for example, as a percentage by weight relative to the total biomass weight—of desirable biomass components.This is because aquatic animals and processed products derived from them are often purchased by consumers to contribute to a healthy diet, as they can be rich in desirable components such as polyunsaturated fatty acids (PUFAs), in particular. PUFAs. These compounds are known to be beneficial, for example, in the prevention or treatment of cardiovascular diseases. Aquatic animals are also used to obtain processed products, such as EPA and DHA extracts derived from marine oils and marketed, for example, as food supplements. An aquatic animal with a higher PUFA content therefore has greater commercial value, making methods for increasing PUFA content in aquacultured animals highly desirable. In light of this, the ongoing exploration of new products, compositions, methods, and applications for aquaculture feeds, especially those designed to nourish the early life stages of fish and crustaceans (larvae), is considered extremely advantageous.There is a clear demand in the sector for reliable, efficient, and reproducible products, compositions, methods, and applications specifically designed for the cultivation of aquatic animals, particularly fish and crustaceans such as shrimp, especially during larval rearing. Aquaculture feed must be easy to administer and distribute and have a long shelf life. This is usually achieved with feeds in solid form, preferably as a free-flowing mass or particulate materials such as pellets. The mass or pellets formed can have the size, stability, and buoyancy characteristics required at different life stages of aquatic animals, or they can have size, stability, and buoyancy characteristics that facilitate handling during production, storage, and / or use.As an example of conventional aquaculture feed compositions, WO 2022 / 182248 A1, entitled "AQUACULTURE FEED COMPOSITION WITH CHARCOAL," describes an aquaculture feed composition in pellet form containing more than 60% protein by weight, in addition to charcoal. Conventional aquaculture feed compositions often incorporate fish and / or vegetable oils into the pellets. However, the incorporation of lipids in the form of oils presents several disadvantages, as will be described later. The composition described in WO 2022 / 182248 A1 may contain at least 2.2% charcoal by weight, but it is not disclosed whether higher concentrations of charcoal increase the survival and biomass of aquatic animals.Furthermore, increasing the amount of charcoal has a drawback, as it dilutes the nutrients in the feed and consequently decreases its total energy content. As another example, the use of dry powdered soaps with omega-3 fatty acids to feed Artemia is described in US patent 6,261,590, entitled "METHODS FOR ENRICHING LIVE FOOD WITH ESSENTIAL NUTRIENTS FOR FISH LARVAE." The authors describe that the "powdered soaps" showed no positive effect on the length, weight, or survival rate of the animals, as indicated in the paragraph following Table 6, and are toxic to Artemia when used in emulsion. The use of powdered soap did not contribute to increased biomass or improved survival rates of the Artemia. The "powdered soaps" described in US patent 6,261,590 are derived from a lipid composition derived from the alkaline washing of fish oil and algae oil.This lipid composition, known in the industry as "soaps"—a term used by the authors of US patent 6,261,590—is a mixture composed primarily of 45% triglycerides, 28% free fatty acids, and 21% phospholipids (see Table 1 of the patent). The patent authors prepared a "soap powder" by washing the "soaps" with cold acetone at pH 4.0 and recovering the solids, or "acetone-washed soap." This "soap powder" is composed mainly of phospholipids and fatty acids. The authors discovered that the direct use of this "soap powder" in a tank with Artemia allows for its enrichment, unlike the use of the soap powder in emulsion, which is toxic. Therefore, the fatty acids in the composition of “powdered soap” disclosed in document US 6,261,590 are primarily in acid or esterified form, such as in phospholipid or triglyceride form, but not in the form of fatty acid salts.Furthermore, Artemia and penaeid shrimp, or simply shrimp, are two different aquatic organisms and exhibit several key biological differences, including their taxonomy. For example, Artemia can efficiently utilize omega-3 fatty acid ethyl esters (see Table 5 and lines 40-50 of US patent 6,261,590). In contrast, shrimp poorly digest and / or metabolize fatty acid methyl or ethyl esters, and their growth on free fatty acids is markedly lower than on triglycerides (Brett D. Glencross and David M. Smith, “Comparison of Triacylglycerols, Esterified and Free Fatty Acids as Neutral Lipid Sources in the Diet of Penaeus monodon Shrimp,” Aquaculture, Volume 159, Numbers 1-2, December 30, 1997, pages 67-85).In rainbow trout, fatty acid ethyl ester oils have been shown to replace 25% of fish oil in starter diets without significantly affecting fish growth or performance; however, at higher levels (≥50%), growth and feed conversion were reduced. See John Grayson and Konrad Dabrowski, “Partial and total replacement of fish oil with fatty acid ethyl esters in starter diets of rainbow trout (Oncorhynchus mykiss),” Aquaculture, Volume 522, May 30, 2020, 735018. A pet food additive comprising at least one calcium salt of an unsaturated fatty acid and antioxidant caramel is described in document JP2014138564A, entitled “Pet food, pet food additive and method of production.”At least one calcium salt of an unsaturated fatty acid is mixed with an antioxidant caramel obtained by heating an aqueous solution of a monosaccharide selected from the group consisting of pentoses and hexoses. Document JPH06319465A, entitled "Food and its Production," describes a food containing omega-3 fatty acids in free form, obtained by neutralizing a saponified substance containing omega-3 fatty acids. The food or feed is used for livestock such as cattle, pigs, or chickens, or for pets such as dogs, cats, or small birds.Patent EP 1800546 A1, entitled “Method for producing calcium, sodium, or magnesium soaps from fatty acids or oleins of animal or vegetable fats and their use as nutrients in the feeding of monogastric animals,” discloses that the use of these soaps in monogastric animals, such as pigs and poultry, reduces feed costs compared to the use of whole fats (triglycerides) commonly used in monogastric nutrition. OBJECTIVES OF THE INVENTION One objective of the invention is to provide a means for increasing the biomass production efficiency of an aquatic animal in a hatchery or farm. Another objective of the invention is to provide a means for increasing the survival rate of aquatic animals kept in a hatchery or farm. A further objective of the present invention is to provide a means for increasing the polyunsaturated fatty acid content. in an aquatic animal kept in a hatchery or farm, or in a processed product obtained from it. Another objective of the present invention is to improve the utilization of raw materials obtained from aquatic plants or animals, the aquatic animals being kept in a hatchery or farm or obtained from natural habitats. Another objective of the invention is to provide a feed for aquatic animals formed in mass or pellets that may have the size, stability, and buoyancy characteristics required at the different life stages of aquatic animals and / or may have size, stability, and buoyancy characteristics that facilitate the handling of the feed during production, storage, and / or use. Another objective of the invention is to provide a diluent or carrier for mineral, vitamin, and other premixes present in the feed.which may be in pellet form. Another objective of the present invention is to provide a feed that offers benefits in terms of simple logistics, production, storage, and shelf life. Other advantages and objectives of the present invention will become apparent in light of the following disclosure. SUMMARY OF THE INVENTION These and other objectives of the invention have been achieved by the invention and are described below. The invention is based on the surprising finding that the increase in biomass production and survival of aquatic animals, preferably fish and / or crustacean larvae, both in hatcheries and farms, is greater with increasing concentrations of alkali metal salts of fatty acids in the feed. Furthermore,It was surprisingly discovered that this feed can increase the PUFA content in aquatic animals. The present invention includes the following embodiments: 1. A method for feeding a crustacean or fish in a crustacean or fish hatchery or farm, the method comprising feeding the fish or crustacean with a feed comprising one or more alkali metal salts of fatty acids. The method of embodiment 1, wherein the alkali metal of the alkali metal salts of fatty acids is selected from the group consisting of sodium, potassium, and mixtures thereof. The method of either embodiment 1 and 2, wherein the crustacean is Pacific white shrimp, black tiger shrimp, Indian white shrimp, Kurume shrimp, northern white shrimp, banana shrimp, Chinese white shrimp or Kona shrimp, giant river shrimp, or giant tiger shrimp. The method of embodiment 1 or 2, wherein the fish is carp, tilapia, goldfish, roho, trout,Wuchang seabream, salmon, shad, coho, or sea bass. The method of any of the preceding embodiments, wherein one or more alkali metal salts of fatty acids comprise alkali metal salts of one or more monounsaturated or polyunsaturated fatty acids, in particular C16-C30 monounsaturated or polyunsaturated fatty acids, and wherein preferably the amount of alkali metal salts of monounsaturated or polyunsaturated fatty acids is 10% by weight or more, relative to all fatty acids forming alkali metal salts of fatty acids. The method of any of the preceding embodiments, wherein the fatty acids of the alkali metal salts of fatty acids are derived from a marine oil and comprise at least three fatty acids selected from palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, alpha-linolenic acid, arachidonic acid,eicosapentaenoic acid and docosahexaenoic acid. Method 5 or 6, wherein the weight percent of the alkali metal salts of fatty acids is as follows: alkali metal salts of palmitic acid between 0.1 and 80%, alkali metal salts of palmitoleic acid between 0.1 and 50%, alkali metal salts of stearic acid between 0.1 and 50%, alkali metal salts of oleic acid between 0.1 and 80%, alkali metal salts of linoleic acid between 0.1 and 80%, alkali metal salts of alpha-linolenic acid between 0.1 and 80%, alkali metal salts of arachidonic acid between 0.1 and 20%, alkali metal salts of eicosapentaenoic acid between 0.1 and 60%, alkali metal salts of docosahexaenoic acid between 0.1 and 60%, and between 1 and 25% of one or more salts of alkaline metals of fatty acids selected from the group consisting of C14:0, C20:0, C22:0, C24:0, C26:0, C18:1 n-7, C20:1 n-9, C22:1 n-9, C22:1 n-11, C24:1 n-11, C18:4 n-3,C20:2 n-6, C20:4 n-3, C21:5: n-3, C22:5 n-6, C22:5 n-3, C24:4 n-3, C24:5 n-3, C24:6 n-3, C26:4 n-3, C26:5 n-3, C26:6 n-3, C26:7 n-3, C28:4 n-3, C28:5 n-3, C28:6 n-3, C28:7 n-3, C28:8 n-3, C30:5 n-3 and C30:6 n-3; and wherein the % by weight of alkali metal salts of fatty acids is expressed in relation to the total content of fatty acid salts in the food. 8. The method of any of embodiments 5 to 7, wherein the fatty acids forming the alkali metal salts of fatty acids are derived from a by-product obtained in a process for producing an EPA and / or DHA concentrate from a marine oil. 9. The method of embodiments 1 to 7, wherein the fatty acids of the alkali metal salts of fatty acids are derived from vegetable oil, such as linseed oil, or mixtures of one or more vegetable oils and one or more marine oils or processed marine oil products.such as a mixture of linseed oil and a product or by-product of a process for producing EPA and DHA concentrates from marine oil, for example, the heavy fraction. 10. The method of any of embodiments 1 to 9, wherein feeding is carried out continuously or intermittently several times a day, such as 2 to 12 times a day. 11. The method of any of embodiments 1 to 10, wherein the feed comprises between 0.5 and 40% by weight of alkali metal salts of fatty acids, relative to the total weight of the feed. The method of any of embodiments 1 to 11,leading to an increase in biomass growth and / or survival rate and / or omega-3 fatty acid content of the crustacean or fish compared to a crustacean or fish receiving the same amount of feed containing the same quantity (expressed in g / day) of oil instead of the alkali metal salts of fatty acids. The method of any of embodiments 1 to 12, wherein the feed is in powder or pellet form. The method of any of embodiments 1 to 13, wherein the feed further comprises one or more components selected from the group consisting of animal protein, vegetable protein, carbohydrates, vitamins, minerals, cholesterol, and lecithin. Feed for fish or crustaceans comprising one or more alkali metal salts of fatty acids or made from a composition comprising one or more alkali metal salts of fatty acids. Feed according to embodiment 15,wherein the alkali metal of one or more fatty acid alkali metal salts is selected from the group consisting of sodium, potassium, and mixtures thereof. 17. Food according to embodiment 15 or 16, wherein the fatty acids forming the fatty acid alkali metal salts comprise monounsaturated or polyunsaturated fatty acids, in particular C16-C30 monounsaturated or polyunsaturated fatty acids, and wherein preferably the amount of monounsaturated or polyunsaturated fatty acids is 10% by weight or more, relative to all the fatty acids forming fatty acid alkali metal salts. 18. Food according to any of embodiments 15 to 17, wherein the fatty acids of the one or more alkali metal salts of fatty acids are derived from a marine oil and comprise at least three fatty acids selected from palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, alpha-linolenic acid,Arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid. 19. Food according to any of embodiments 15 to 18, wherein the fatty acids forming one or more alkali metal salts of fatty acids are derived from a by-product obtained in a process for producing an EPA and / or DHA concentrate from a marine oil. 20. Food according to any of embodiments 15 to 17, wherein the fatty acids of the one or more alkali metal salts of fatty acids are derived from vegetable oil, such as linseed oil, or mixtures of one or more vegetable oils and one or more marine oils or processed marine oil products, such as from a mixture of linseed oil and a by-product of a process for producing EPA and DHA concentrates from marine oil, for example, the heavy fraction. Food according to any of embodiments 15 to 20,wherein the weight percent of alkali metal salts of fatty acids is as follows: alkali metal salts of palmitic acid between 0.1 and 80%, alkali metal salts of palmitoleic acid between 0.1 and 50%, alkali metal salts of stearic acid between 0.1 and 50%, alkali metal salts of oleic acid between 0.1 and 80%, alkali metal salts of linoleic acid between 0.1 and 80%, alkali metal salts of alpha-linolenic acid between 0.1 and 80%, alkali metal salts of arachidonic acid between 0.1 and 20%, alkali metal salts of eicosapentaenoic acid between 0.1 and 60%, alkali metal salts of docosahexaenoic acid between 0.1 and 60%, and between 1 and 25% of one or more alkali metal salts of one or more fatty acids selected from the group consisting of C14:0, C20:0, C22:0, C24:0, C26:0, C18:1 n-7, C20:1 n-9, C22:1 n-9, C22:1 n-11, C24:1 n-11, C18:4 n-3, C20:2 n-6, C20:4 n-3,C21:5: n-3, C22:5 n-6, C22:5 n-3, C24:4 n-3, C24:5 n-3, C24:6 n-3, C26:4 n-3, C26:5 n-3, C26:6 n-3, C26:7 n-3, C28:4 n-3, C28:5 n-3, C28:6 n-3, C28:7 n-3, C28:8 n-3, C30:5 n-3 and C30:6 n-3; and wherein the weight % of alkali metal salts of fatty acids is expressed in relation to all fatty acids that form alkali metal salts of fatty acids. Feed according to any of embodiments 15 to 21, wherein the feed comprises between 0.5 and 40% by weight of alkali metal salts of fatty acids, relative to the total weight of the feed. Feed according to any of embodiments 15 to 22, in powder or pellet form. Feed according to any of embodiments 15 to 23, wherein the feed further comprises one or more components selected from the group consisting of animal protein, vegetable protein, carbohydrates, vitamins, minerals, cholesterol, and lecithin. Use of alkali metal salts of fatty acids.or of a feed comprising alkali metal salts of fatty acids as defined in any of embodiments 15 to 23, for increasing the biomass production, survival rate, and / or omega-3 fatty acid content of a crustacean or fish in a hatchery or farm. The method of feeding a crustacean or fish in a hatchery or farm, the feed, or the use according to any of embodiments 1 to 25 above, wherein the method, feed, or use is, or is suitable for, increasing the efficiency of biomass production in the hatchery or farm. 27. The method of feeding a crustacean or fish in a hatchery or farm, the feed, or the use according to any of embodiments 1 to 25 above, wherein the method, feed, or use is, or is suitable for, increasing the survival rate of the crustacean or fish. 28. The method of feeding a crustacean or fish in a hatchery or farm,The feed or use according to any of embodiments 1 to 25 above, wherein the method, feed, or use is, or is suitable for, increasing the PUFA content in the fish or crustacean. 29. A method for producing a processed product from a fish or crustacean, the method comprising: a. Feeding a fish or crustacean using the method according to any of embodiments 1 to 14, and b. Processing the fish or crustacean to obtain the desired product. The method according to embodiment 29, wherein processing step b. comprises a purification step to obtain a product comprising PUFA, such as to produce a product comprising more than 1% by weight of EPA and / or DHA, such as 10% by weight or more, relative to the total weight of the product. A method for producing a feed for feeding a fish or crustacean as defined for any of embodiments 15 to 24,comprising mixing one or more alkali metal salts of fatty acids or a composition comprising one or more alkali metal salts of fatty acids with one or more other compositions, said other compositions comprising one or more components selected from the group consisting of animal protein, vegetable protein, carbohydrates, vitamins, minerals, cholesterol, lecithin, or said other composition being a processed marine oil product, such as a product or by-product of a process for producing EPA and DHA concentrates from marine oil, for example, the heavy fraction. The method for producing a food according to embodiment 31, further comprising one or more steps selected from heating, homogenizing, pelletizing, extruding, drying, or packaging the material obtained from the mixing step. 33. The method for producing a food according to embodiment 31 or 32,wherein the composition comprising one or more alkali metal salts of fatty acids comprises at least three fatty acids selected from palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, alpha-linolenic acid, arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid, and optionally further contains cholesterol. 34. A food obtained by the method according to any of embodiments 31 to 33. 35. Use of the food according to embodiment 33 in a method as defined in any of embodiments 1 to 14. 36. Use of a composition comprising one or more alkali metal salts of fatty acids to produce a food for feeding a crustacean or a fish. DEFINITIONS Although the terms used below generally have their common meaning in the art, the following restricted definitions and meanings apply, unless otherwise indicated: In the present invention,The term "feed" refers to any material or composition intended to nourish aquatic animals through ingestion. The term encompasses both materials and compositions used alone without other nutrients, as well as supplements provided to the aquatic animal in addition to other sources of nutrition. The term includes both a "complete feed" and a "feed additive," as defined below. The term "fatty acid" refers to carboxylic acids obtained or obtainable by the hydrolysis of fats and oils of animal or vegetable origin. Fats and oils contain fatty acids primarily in the form of triglycerides. Fatty acids can be represented by the general formula R-COOH, where R is a linear or branched (alkyl or alkenyl) aliphatic hydrocarbon group with between 12 and 36 carbon atoms. The term "saturated fatty acid" (SAFA) denotes compounds of the formula R-COOH.where R is a linear or branched alkyl group, typically straight, having 12 or more carbon atoms, such as 12 to 36 or 14 to 30. The term “monounsaturated fatty acid” (MUFA) denotes compounds of the formula R-COOH, where R is a linear or branched alkenyl group, typically linear, having 12 or more carbon atoms, such as 12 to 36 or 14 to 30, and containing one carbon-carbon double bond. The term “polyunsaturated fatty acid” (PUFA) refers to compounds of the formula R-COOH, where R is a linear or branched alkenyl group, typically linear, with 12 to 36 carbon atoms and containing two or more carbon-carbon double bonds, such as 2 to 8 or 2 to 6. Examples of PUFAs include eicosapentaenoic acid (EPA),Docosahexaenoic acid (DHA) and arachidonic acid (ARA). The term “very long-chain polyunsaturated fatty acid” (VLCPUFA) denotes polyunsaturated fatty acids having 24 to 36 carbon atoms and containing two or more carbon-carbon double bonds, such as 2 to 8 carbon-carbon double bonds or 2 to 6 carbon-carbon double bonds. The term “fatty acid ^3” is used to designate a MUFA, PUFA, or VLCPUFA having a carbon-carbon double bond located at the third carbon atom from the methyl end (omega-3 position). The term “crustacean” is used in the present invention to refer to animals belonging to the subphylum Crustacea whose natural habitat is salt or fresh water. Examples include crabs, lobsters, shrimp, crayfish, and prawns. The term "fish" is used in the present invention to refer to the animals included in the paraphyletic group called Pisces,encompassing both freshwater and saltwater fish. In the present invention, the term "fish" also includes non-crustacean shellfish, such as mollusks, whose natural habitat is saltwater or freshwater, and which are not included in the paraphyletic group Pisces. Examples of the Pisces group include carp, tilapia, goldfish, roho, trout, Wuchang gilthead seabream, salmon, shad, coho, and bass. Examples of non-crustacean shellfish include oysters, clams, scallops, and mussels. The term "hatchery" denotes a facility where fish or crustaceans are reared, hatched, and raised under controlled conditions. The term "farm" refers to a facility where fish or crustaceans are reared, cultivated, and harvested in controlled environments for commercial purposes.recreational or conservation purposes. Fish farming is a form of aquaculture that consists of the cultivation of fish or crustaceans in tanks, ponds, channels, or other closed systems. A farm typically includes a water management system, such as pumps and oxygen delivery systems, and optionally a feeding system and a health monitoring system. The term "alkali metal" is used in the present invention to refer to lithium, sodium, potassium, and rubidium. In one embodiment, the alkali metal is lithium, sodium, potassium, or mixtures thereof, and in another embodiment, the alkali metal is selected from sodium, potassium, and mixtures thereof. The term "alkali metal salt of a fatty acid" refers to a salt formed from an alkali metal cation and a fatty acid anion, where the alkali metal and fatty acid are defined as above. The term encompasses the alkali metal salts of SAFA, MUFA,PUFAs and VLCPUFAs. Specific examples of alkali metal salts of a fatty acid include sodium stearate or potassium docosahexaenoate. The term "oil" is used as a general term to encompass fats and oils, that is, compositions formed primarily of triglycerides, regardless of their melting point. An oil may be composed solely of triglycerides, but it may also contain smaller amounts (e.g., 15 wt. or less, such as 10 wt. or 5 wt. or less) of one or more free fatty acids, phospholipids, and optionally other lipids such as sterols. The term "glyceride" refers to monoglycerides, diglycerides, triglycerides, and their mixtures, and thus to esters of glycerol with one or more fatty acids. The fatty acid fraction can be any fatty acid, such as SAFAs, MUFAs, PUFAs, and VLCPUFAs. The term "marine oil" is used to refer to an oil, as defined above,Derived from animals or plants that have their natural habitat in the sea or freshwater. In one embodiment, marine oil is derived from fish and crustaceans, as defined above, whose natural habitat is saltwater. A marine oil typically contains triglycerides comprising fatty acids formed from at least one of the following: MUFAs and PUFAs. The term "processed oil product" is used to refer to a processed product obtained from oils. A processed oil product typically contains at least one MUFA and one PUFA, or their derivatives, where the MUFA or PUFA fraction is present in a form other than triglyceride, for example, as a free fatty acid, fatty acid alkyl ester (typically methyl or ethyl), or fatty acid salt or adduct. In a "processed oil product," triglycerides may be entirely absent or may be included in an amount equal to or less than 80% by weight, such as 50% by weight or less.such as 10% by weight or less. A specific type of processed marine oil product is the Omega-3 industry by-product fraction. Typically, a distillate fraction (or "light fraction") is obtained through a marine oil distillation process, and a heavy residue (or "heavy fraction") is obtained through a distillation process of an alkyl ester fatty acid composition derived from marine oil. The light or heavy fraction, which do not contain most of the desired compounds (such as EPA or DHA), is usually discarded. These fractions represent valuable sources of fatty acid alkali metal salts for the present invention. In this case, the fatty acid alkali metal salts can be obtained by hydrolyzing the light or heavy fraction and forming salts with bases such as sodium hydroxide or potassium hydroxide. The term "heavy fraction",when referring to a fraction (residue or distillate) obtained from the distillation of processed marine oil products, in particular fatty acid alkyl esters (particularly methyl or ethyl), denotes a fraction (residue or distillate) containing between 0.1 and 10% by weight of free fatty acids (typically having a carbon chain length of 20 or more, such as 20 to 36 or 22 to 30), 20 to 60% of glycerides, 20 to 60% by weight of fatty acid alkyl ester (where the fatty acid fraction typically has 18 to 36 carbon atoms, such as 20 to 30 carbon atoms), and 2 to 40% by weight of cholesterol. The term “light fraction”, when referring to a fraction (residue or distillate) obtained from the distillation of marine oil, particularly crude marine oils or mixtures of crude marine oils, denotes a fraction (residue or distillate) containing between 30 and 90% free fatty acids, 0.1 to 10% glycerides, 0,1 to 60% alkyl fatty acids and 1 to 20% cholesterol. The term "powder" denotes particulate matter having an average particle size of 1 mm or less, the average particle size being defined as D. 50in a volume-based particle size distribution obtained by a common method in the art, for example, by sieve analysis or laser light scattering. The term "pellet" or "granule" refers to particulate matter with an average particle size greater than 1 mm, such as 1.5 mm or more, or 2 mm or more. In this case, the average particle size is defined as D50 in a volume-based particle size distribution obtained by a common method in the art, for example, by granulometric analysis or laser light scattering. The granule may be round or cylindrical and is typically obtained by compressing or extruding a mass of material. A cylindrical granule may have a major axis of 1 mm or more, such as 2 mm or more, and typically 5 cm or less, such as 2 cm or less. A cylindrical granule may have a diameter between 0,1 and less than 1 times the major axis. The term “premix” denotes a composition intended to be processed by mixing with other components, for example, to prepare a complete feed. The term “biomass” refers to the total weight of an animal, such as an animal raised in a hatchery or on a farm. The term “biomass production efficiency” refers to the total biomass growth in a hatchery or on a farm during a given period, for example, monthly, weekly, or daily, relative to the number of animals at the beginning of that period. Therefore, this term reflects not only the weight gain of each animal but also its survival rate. The term “survival rate” is defined as the relative number of animals that survive in a given period of time, for example, a month, a week, or a day.and can be evaluated following the protocol described in the Examples section below. The term "complete feed" is used to refer to a feed intended to provide the majority of the energy (expressed in joules) to a fish or crustacean fed that feed. In this context, the majority of the energy is defined as 50% or more of the total energy supplied to the fish or crustacean, for example, 60% or more, 70% or more, and up to 100% or less, for example, 95% or less. The term "feed additive" is used to refer to a feed intended to provide a small amount of energy (expressed in joules) to a fish or crustacean, which is generally fed as a supplement in combination with a complete feed. In this context, the small amount of energy is defined as less than 50% of the total energy supplied to the fish or crustacean, for example, 45% or 40% or less, but typically 1% or more, 3% or more, 5% or more.or 10% or more. The term “minor component” is used to designate a component having a content of less than 1% by weight, such as 0.9% by weight or less, 0.5% by weight or less, or 0.1% by weight or less, with respect to the total weight of the composition (or food). The term “major component” is used to designate a component having a content of 1% by weight or more, such as 5% by weight or more or 10% by weight or more, with respect to the total weight of the composition (or food). The term “one or more” means one, or more than one, such as two or more, three or more, four or more, or five or more. The term “at least one” has the same meaning. The term “comprising” is used to indicate that a composition of matter contains the respective material, without excluding the presence of additional components. However, the term also encompasses the meanings “consisting of” and “consisting essentially of,”except where the context clearly indicates that other components are required. In this case, the term "consisting essentially of" generally means that components other than those mentioned may be present in an amount typically of 10% by weight or less of the respective component. Where in the present invention ranges are defined by upper and lower limits, such as "from 2 to 5", the ranges include the stated upper and lower limits and any intermediate values. DESCRIPTION OF THE INVENTION Aquaculture typically requires a prepared composition of aquaculture feed to meet the dietary requirements of farmed animals and provide the essential nutrients necessary for the growth and health of aquatic organisms. Furthermore, the dietary requirements of different aquaculture species vary,as well as those of the same species during different growth stages. Standard complete aquaculture feeds are composed of minor and major components. Minor components include vitamins, cholesterol, minerals, trace elements, antibiotics, mold inhibitors, and flavorings, and are added primarily as premixes at doses of 1 to 50 kg per ton of complete feed. They are premixed with a suitable diluent or carrier, either organic or inorganic, to achieve a homogeneous distribution of the minor components in the complete feed. The major and minor components of a complete feed are subdivided into components with nutritional functions and components with technical functions. Components with technical functions improve the physical quality of the aquaculture feed composition or its appearance, or they may facilitate processing, manufacturing, or handling. On the other hand,Nutritional components provide the aquatic animal being fed with energy and essential, beneficial components such as vitamins, minerals, and, optionally, pharmaceutical agents like antibiotics. The main nutritional components provide aquatic animals with the protein and energy necessary for their growth and performance. The main components of a complete nutritional feed typically include: 1) Proteins and amino acids, which serve as the building blocks of proteins. Suitable protein sources include marine proteins such as fishmeal, krill meal, and squid meal; vegetable proteins such as soybean meal, rapeseed meal, wheat gluten, corn gluten, lupin meal, pea meal, sunflower seed meal, rice flour, and alfalfa meal; and slaughterhouse byproducts such as blood meal, bone meal, feather meal, and chicken meal.Poultry meal, egg powder, liver meal, meat meal, meat and bone meal, silkworm pupae meal, whey powder, etc. Protein hydrolysates are commonly used in aquaculture feeds as a source of high-quality protein. These hydrolysates are derived from the enzymatic or chemical breakdown of proteins into smaller peptides and amino acids, making them more digestible for aquatic species. The most common protein hydrolysates include fish hydrolysate, shrimp hydrolysate, squid hydrolysate, krill hydrolysate, soy protein hydrolysate, wheat gluten hydrolysate, casein hydrolysate, alfalfa hydrolysate, bacterial hydrolysate, and enzymatic hydrolysates, among others. Protein hydrolysates are valuable in aquaculture due to their digestibility.Amino acid content and contribution to overall feed efficiency. By mixing different protein sources and protein hydrolysates, it is possible to achieve a desired protein content and amino acid profile adapted to the aquatic animal species and life stage for which the feed is intended. 2) Lipids, which serve as a source of fatty acids for energy (especially for the heart and skeletal muscles). Lipids also aid in the absorption of vitamins; for example, vitamins A, K, D, E, and K are fat-soluble or can only be digested, absorbed, and transported along with fats. Suitable lipid sources include animal oils such as fish, krill, and squid oil, or vegetable oils such as rapeseed, soybean, flaxseed, sunflower, and olive oil, as well as others such as microbial, algae, and insect oils. As the expert will understand, these oils can also be present in meals (e.g.,fishmeal or algae meal). By blending different oils, it is possible to achieve the desired fatty acid profile and total lipid content in the feed, tailored to the aquatic animal species for which it is intended. Other suitable lipids include processed animal or vegetable oil products obtained from by-product streams of the fish oil and vegetable oil refining industries, such as streams comprising oils, free fatty acids, or alkyl fatty acid esters from the oil neutralization process, or the distilled fraction from the high-vacuum distillation of oils (stripping process), streams comprising stearin from winterization processes, and streams comprising ethyl or methyl fatty acid esters from the omega-3 industry.such as the heavy fraction from the distillation of alkyl esters of omega-3 fatty acids. Other suitable lipids include animal oils (fats) from the rendering industry. Examples of marine oils are fish oil, usually derived from the tissues of a fish, such as menhaden, anchovy, sardine, herring, capelin, cod, tuna, mackerel, salmon, and the like; or vegetable oil, which refers to any crude or edible oil obtained from a plant, such as soybean oil, sunflower oil, canola oil, olive oil, corn oil, palm oil, coconut oil, safflower oil, linseed oil, rapeseed oil, rice oil, and the like; or fats and oils from the fat recycling industry or byproducts of the oil refining and concentration industry, such as the omega-3 industry; or restaurant grease, microbial oil,Algal oil or any mixture of the fats and oils mentioned. Vegetable oil is typically extracted from the seed or grain of a plant. Oils are incorporated into the composition of aquaculture feed, generally in liquid form. Lipids are important as an energy source, providing more calories per gram than carbohydrates and proteins. However, most importantly, they are a source of essential fatty acids from the omega-3 and omega-6 series, such as linoleic acid (LOA), alpha-linolenic acid (LNA), arachidonic acid (ARA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). These are vital for the development of cell membranes, as well as for various biological processes, including reproduction, immune response, and overall health. Fish and shrimp cannot synthesize these fatty acids and must obtain them from their diet. In the current state of the art,Standard aquaculture feed compositions for aquatic animals, which include animal or vegetable oils, contain all essential and non-essential fatty acids, typically in the form of triacylglycerols. Triacylglycerols are neutral lipids composed of three fatty acyl residues esterified to a glycerol molecule. They are also known as phospholipids. Most neutral lipids also contain small amounts of monoglycerides, diglycerides, and free fatty acids. These may occur naturally, but most are the result of various processes that modify triacylglycerols. Phospholipids, such as phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol,These are the most common classes of phospholipids present in lipid mixtures known as "lecithins" and represent more than 50% of the total lipids in lecithin. Vegetable lecithins contain C18 fatty acids from the n-3 and n-6 ​​essential fatty acid series (linoleic acid, C18:2 n-6, and linolenic acid, C18:3 n-3), but are virtually free of C20 and C22 polyunsaturated fatty acids, including arachidonic acid (20:4 n-6), eicosapentaenoic acid (EPA, C20:5 n-3), and docosahexaenoic acid (DHA, C22:6 n-3). This does not limit the use of lecithins, as these fatty acids can be supplied, independently of added lecithins, by other food ingredients. Commercial lecithins are available in both powder and liquid form. 3) Carbohydrates. Carbohydrates play an important role in aquaculture feeds, as they constitute a valuable source of energy for aquatic organisms. Normally,The carbohydrates used in aquaculture feeds are primarily of plant origin (e.g., wheat, sunflower, corn, soybean). Some feeds may also contain fibers, binders, and stabilizers to improve pellet quality and feed shelf life, probiotics and prebiotics, and, in the case of certain species, colorants, attractants, hormones, enzymes, and immunostimulants may be added. It was surprisingly discovered that alkali metal salts of fatty acids can partially or completely replace fats and oils in standard aquaculture feed compositions. The increased level of substitution, compared to a standard feed, also results in increased biomass production in aquatic animals fed the aquaculture feed composition of the invention. In particular,The increase in biomass production can be accompanied by increased survival (or decreased mortality), contributing to a better feed conversion ratio (FCR) compared to a standard aquaculture feed composition characterized by the absence of alkali metal salts of fatty acids. Essential fatty acids (EFAs) are a specific type of fatty acid that aquatic animals, particularly fish and crustaceans such as shrimp, cannot synthesize and must obtain through their diet. In this invention, the term crustacean encompasses both shrimp and prawns, although there are some general characteristics that differentiate them, including claw and body structure, habitat, and size. However, both have a similar life cycle (eggs, nauplius, zoea, mysis, larva, postlarvae,juvenile and adult) and both can utilize the feed of the invention with the same remarkable effect described herein. Non-essential fatty acids also play a vital role in the nutrition and physiology of aquatic animals, particularly fish and crustaceans such as shrimp, fulfilling various functions in the body, including providing a source of energy, forming cell membranes, and serving as precursors to important signaling molecules. In the state of the art, standard aquaculture feed compositions for aquatic animals, composed of animal or vegetable fats and oils, all containing both essential and non-essential fatty acids, are typically in the form of triacylglycerols, neutral lipids composed of three fatty acyl residues esterified to a glycerol molecule,but also in the form of phospholipids. Most lipids also contain small amounts of monoglycerides, diglycerides, and free fatty acids. These may occur naturally, but most result from various processes that cause the hydrolysis of triacylglycerols. Phospholipids, such as phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol, are the most common classes of phospholipids found in lipid mixtures known as lecithins and make up more than 50% of the total lipids in lecithin. Plant lecithins contain C18 fatty acids from the n-3 and n-6 ​​essential fatty acid series (linoleic acid, C18:2 n-6, and linolenic acid, C18:3 n-3), but are virtually free of C20 and C30 polyunsaturated fatty acids, including arachidonic acid (C20:4 n-6), eicosapentaenoic acid (EPA, C20:5 n-3), and docosahexaenoic acid (DHA, C22:6 n-3). This does not limit the use of lecithins.These fatty acids can be supplied separately from added lecithins by other feed ingredients. Commercial lecithins are available in both liquid and powder form. A typical standard aquaculture feed composition comprises between 2% and 40% total or crude lipid content, primarily in the form of triglycerides (e.g., fish oil, vegetable oil, algae oil, etc.), measured as a percentage by weight of the feed composition. Approximately 85% of the lipids are fatty acids. Standard aquaculture feed compositions do not contain fatty acids in the form of alkali metal salts. Aquaculture feed compositions are formulated as a molded mass of considerable size or as pellets. However, the incorporation of liquid oils with dry ingredients (proteins,Adding oil (carbohydrates) to pelleted feeds can present numerous challenges due to the physical properties of oil and the pellet manufacturing process. The following difficulties may arise: Oil leakage: Oil tends to seep out of pellets, especially if they are not properly formulated or processed. This can reduce the nutritional content of the pellets and lead to handling and storage problems. To address this, feed manufacturers often use binders or emulsifiers to help retain the oil within the pellet. Pellet durability: Adding oil to pellet formulations can affect their durability and stability. The presence of oil can make pellets more susceptible to breaking or crumbling during transport, storage, or feeding.This leads to a loss of integrity and reduced feeding efficiency. Processing Challenges: Oil can affect the feed's processing characteristics during pelleting. It can hinder the extrusion of the feed mix, resulting in poor pellet quality or increased energy consumption during the production process. Adjusting manufacturing parameters may be necessary to optimize oil incorporation into the pellets. Oxidation and Rancidity: Oils are prone to oxidation, especially when exposed to heat, light, and oxygen. This can lead to rancid flavors, reduced nutritional quality, and potential health risks for aquatic animals. Feed manufacturers may add antioxidants or use specific processing techniques to mitigate oxidation and extend the shelf life of oil-containing pellets. Pellet Size: Typically,The pellets are extruded to sizes larger than 1 mm. To obtain micro-feed particles (e.g., 10 to 500 microns), the pellets are crushed into smaller particles, usually by milling, and then sorted or separated by size using a sieve. This process is very inefficient with pellets formulated with fats and oils, as these ingredients promote agglomeration and tend to clog the sieves. Overcoming these difficulties requires careful formulation and processing techniques. Feed manufacturers typically conduct extensive research and development to optimize pellet formulations, use appropriate binders and emulsifiers, adjust processing parameters, and incorporate antioxidants to ensure proper oil incorporation into the pelleted feed. However,It has been surprisingly discovered that these difficulties can be overcome or mitigated by using one or more alkali metal salts of fatty acids, or a composition containing them, in the pelleting process; that is, in a way that allows the formulation of a feed composition for aquatic animals with a reduced level of liquid oil inclusion, or even without any liquid oil inclusion. By replacing all liquid oil inclusion with alkali metal salts of fatty acids, it is possible to obtain a feed formulation composed solely of dry powder ingredients, which simplifies the logistics, production, storage, and shelf life of the feed compositions. In the present invention, the feed contains one or more alkali metal salts of fatty acids, or is prepared from a composition comprising one or more alkali metal salts of fatty acids. In the latter case,One or more alkali metal salts of fatty acids may undergo partial conversion or reaction with other species during the production process, for example, forming other species such as free fatty acids, or adducts or reaction products with other feed components, such as amino acids, due to processing conditions (e.g., water and heat). This can result in an actual alkali metal salt content in the finished feed that is lower than the theoretical amount (defined as the amount of alkali metal salts of fatty acids that would be expected based on the content and amount of alkali metal salts of fatty acids in the initial raw materials used to produce the feed). The ratio of actual content,defined as [(actual content of alkali metal salts of fatty acids in the feed / theoretical content of alkali metal salts of fatty acids calculated from the content of alkali metal salts of fatty acids in the starting material) x 100] is greater than 0%, such as 10%, 20%, 30%, or 40% or more, but preferably greater than 50%, 60%, 70%, 80%, or 90%. The upper limit is 100%, meaning that no conversion or reaction of one or more alkali metal salts of fatty acids to other species occurs during the aquaculture feed manufacturing process. Then,The description of the nature and relative quantity of one or more alkali metal salts of fatty acids applies both to the final food product and to the composition used for its preparation. It should be noted that the effects of the invention can also be obtained if one or more alkali metal salts of fatty acids undergo partial conversion into other species during the manufacturing process. However, it is a requirement of the present invention that the final food product contain one or more alkali metal salts of fatty acids, although its content may be lower compared to the theoretical amount calculated based on the composition of the components before food production. The incorporation of alkali metal salts into the food product increases oxidation stability, particularly in the case of alkali metal salts of monounsaturated and polyunsaturated fatty acids, and reduces oil leakage or exudation.and increases the hydrophilic characteristics of the pellets or granules made with this aquaculture feed, allowing for the management of their buoyancy, from naturally floating or slow-sinking pellets to sinking pellets. Naturally floating or slow-sinking pellets are used for shrimp in the mysis and early post-larval stages, which require higher oil levels. High oil levels, in addition to the oil leakage problem mentioned earlier, also have other disadvantages for the production of small-sized pellets or powders, such as those less than 100 µm in diameter or with a longer shaft. While these smaller sizes can be beneficial for the mysis and early post-larval stages of shrimp, they cause the grinding and sieving process of the pellets to be slow and inefficient, mainly due to clogging of the sieve mesh. To address this problem,These pellets could be prepared with microalgae powder instead of oil, but this is a restrictive solution, as microalgae oils have a complex production process, limited global supply, and a relatively high cost. Another option is the use of microencapsulated oils (e.g., with cyclodextrins), but as before, they have a complex production process, limited global supply, and a relatively high cost. Furthermore, both dried microalgae and microencapsulated oils have a relatively low lipid content, typically less than 40%, requiring the use of at least 2–3 times the weight of these ingredients, compared to using a fat or oil directly, to achieve the desired lipid content in the pellet. Dried forms of alkali metal salts are suitable and easy to produce.They are readily available and constitute a more economical substitute for microalgae powders or microencapsulated oils. Furthermore, they have the surprising effect of increasing biomass production. When feed containing one or more alkali metal salts of fatty acids is derived from marine oils or by-product fractions produced by the omega-3 industry, it generally also contains cholesterol, an essential nutrient in the diet of aquatic animals such as salmon and shrimp. The present invention relates to any method or use of such alkali metal salts of fatty acids that results in the ingestion of such salts, or fatty acids derived from them, or other reaction products obtained from them, by fish or crustaceans. Such method or use may utilize any form of one or more alkali metal salts of fatty acids, for example, as a component of a complete feed, as a feed additive,as a premix together with other components, such as vitamins or minerals, which are mixed with other components before feeding, or in pure form. In one embodiment of the present invention, a complete aquaculture feed, generally in powder or granule form, is provided comprising one or more alkali metal salts of fatty acids, or is prepared from a composition comprising one or more alkali metal salts of fatty acids. In other embodiments, the alkali metal salts of fatty acids may be present in a premix together with other components or may be present independently. In one embodiment, the feed of the present invention comprises one or more alkali metal salts of fatty acids in an amount of 0.1 to 100% by weight, preferably from 0.5 to 40%. In one embodiment, the feed, or the composition used for its production, comprises, as alkali metal salts of fatty acids,Alkali metal salts of palmitic acid (PA), palmitoleic acid (POA), stearic acid (SA), oleic acid (OA), linoleic acid (LOA), alpha-linolenic acid (LNA), arachidonic acid (ARA), eicosapentaenoic acid (EPA), and / or docosahexaenoic acid (DHA). This applies to all forms of the food, for example, complete foods, food additives, or premixes. In one embodiment, the one or more alkali metal salts of fatty acids present in the food, or in the composition used for its production, comprise alkali metal salts of monounsaturated or polyunsaturated fatty acids, in particular C16-C30 monounsaturated or polyunsaturated fatty acids. The amount of salts of monounsaturated or polyunsaturated fatty acids may be 10% by weight or higher, with respect to all the alkali metal salts of fatty acids that form them, for example, 20% by weight or higher, 30% by weight or higher, 40% by weight or higher,of 50% by weight or higher, 60% by weight or higher, 70% by weight or higher, 80% by weight or higher, 90% by weight or higher, or 95% by weight or higher, and its content may be 100% by weight. This applies to all presentations of the food, for example, complete foods, food additives, or premixes. In one embodiment, the one or more alkali metal salts of fatty acids present in the food, or the composition used for its production, comprise alkali metal salts of polyunsaturated fatty acids, in particular C16-C30. The amount of polyunsaturated fatty acid salts may be 10% by weight or higher, with respect to all the alkali metal salts of fatty acids that form them, for example, 20% by weight or higher, 30% by weight or higher, 40% by weight or higher, 50% by weight or higher, 60% by weight or higher, 70% by weight or higher, 80% by weight or higher,of 90% by weight or higher, or 95% by weight or higher, and its content may be 100% by weight. This applies to all presentations of the food, for example, complete foods, food additives, or premixes. In one embodiment, the one or more alkali metal salts of fatty acids present in the food, or the composition used for its production, comprise C20 to C30 alkali metal salts or polyunsaturated fatty acids. The amount of salts of polyunsaturated fatty acids from C20 to C30 may be 10% by weight or higher, with respect to all the alkali metal salts of fatty acids that form them, for example, 20% by weight or higher, 30% by weight or higher, 40% by weight or higher, 50% by weight or higher, 60% by weight or higher, 70% by weight or higher, 80% by weight or higher, 90% by weight or higher, or 95% by weight or higher.and its content may be 100% by weight. This applies to all forms of the feed, for example, complete feeds, feed additives, or premixes. In another embodiment, the alkali metal salts of fatty acids present in the feed, or the composition used for its production, comprise alkali metal salts of C14-C20 monounsaturated or polyunsaturated fatty acids. The amount of salts of monounsaturated or C14-C20 polyunsaturated fatty acids may be equal to or greater than 10% by weight, with respect to all alkali metal salts of fatty acids that form alkali metal salts of fatty acids, for example, 20% by weight or more, 30% by weight or more, 40% by weight or more, 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 90% by weight or more, or 95% by weight or more, and their content may be 100% by weight. In one embodiment,The food may contain cholesterol in addition to one or more alkali metal salts of fatty acids. In one particular embodiment of this embodiment, the cholesterol content is 0.5% by weight or less, relative to the total weight of the food. In the case of food additives or premixtures, the cholesterol content may be higher than that of the food, for example, 1% or more, relative to the food additives or premixtures, for example, 5% or more, 10% or more, 20% or more, 30% or more, 40% or more, or 50% or more. In one embodiment, the food may contain monoglycerides in addition to one or more alkali metal salts of fatty acids. In one particular embodiment of this embodiment, the monoglyceride content is 2% by weight or less, relative to the total weight of the food. In the case of food additives or premixes, the monoglyceride content may be higher than that of the food, for example, 2% or more.With respect to feed additives or premixtures, for example, 5% by weight or more, 10% by weight or more, or 20% by weight or more. In one embodiment, the fatty acids of the alkali metal salts present in the feed, or in the composition used for its production, are derived from a marine oil. In this embodiment, the fatty acid forming the alkali metal salts present in the feed preferably comprises at least three fatty acids selected from palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, alpha-linolenic acid, arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid. In one embodiment of the invention, the one or more alkali metal salts of fatty acids comprise, in % by weight of all alkali metal salts of fatty acids, palmitic acid (PA) between 0.1 – 80%, palmitoleic acid (POA) between 0.1 – 50%, stearic acid (SA) between 0.1 – 50%, oleic acid (OA) between 0,1-80%, linoleic acid (LOA) between 0.1-80%, alpha-linolenic acid (LNA) between 0.1-80%, arachidonic acid (ARA) between 0.1-20%, eicosapentaenoic acid (EPA) between 0.1-60%, docosahexaenoic acid (DHA) between 0.1-60% and between 1-25% of one or more alkali metal salts of a fatty acid selected from the group consisting of the fatty acids C14:0, C20:0, C22:0, C24:0, C26:0, C18:1 n-7, C20:1 n-9, C22:1 n-9, C22:1 n-11, C24:1 n-11, C18:4 n-3, C20:2 n-6, C20:4 n-3, C21:5: n-3, C22:5 n-6, C22:5 n-3, C24:4 n-3, C24:5 n-3, C24:6 n-3, C26:4 n-3, C26:5 n-3, C26:6 n-3, C26:7 n-3, C28:4 n-3, C28:5 n-3, C28:6 n-3, C28:7 n-3, C28:8 n-3, C30:5 n-3 and C30:6 n-3. In one embodiment of the invention, the one or more alkali metal salts of fatty acids comprise, in % by weight of all alkali metal salts of fatty acids in a food, palmitic acid (PA) between 0.1 – 80%, palmitoleic acid (POA) between 0.1 – 25%, stearic acid (SA) between 0.1 – 50%,oleic acid (OA) between 1-80%, linoleic acid (LOA) between 1-80%, and alpha-linolenic acid (LNA) between 1-80%, and at least one alkali metal salt of a fatty acid selected from the group consisting of the fatty acids C14:0, C20:0, C22:0, C24:0, C26:0, C20:1 n-9, C22:1 n-11, and C22:1n-9. In one embodiment of the invention, the alkali metal salts of fatty acids in the aquaculture feed for feeding aquatic animals are obtained from marine oils and comprise alkali metal salts of palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, alpha-linolenic acid, arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid. In one embodiment of the invention, the alkali metal salts of fatty acids in the aquaculture feed or the composition used to produce the feed, do not contain either eicosapentaenoic acid and / or docosahexaenoic acid and are obtained from vegetable oils,such as linseed oil, and comprise alkali metal salts of palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, and alpha-linolenic acid. In one embodiment of the invention, the alkali metal salts of fatty acids in the aquaculture feed for feeding aquatic animals are obtained from mixtures of one or more vegetable oils (such as linseed oil) and one or more marine oils or processed marine oil by-products, such as the light fraction or the heavy fraction. In another embodiment of the invention, the alkali metal salts of fatty acids in the aquaculture feed for feeding aquatic animals are obtained from a processed marine oil by-product and further comprise cholesterol in an amount of 0.5 to 40 parts by weight, preferably 1 to 20 parts by weight.with respect to 100 parts by weight of one or more alkali metal salts of fatty acids. The foregoing description applies to all feeds of the present invention, including complete feeds, feed additives, and premixtures. These can be differentiated as follows: Complete Feed In one embodiment of the present invention, a feed comprising one or more alkali metal salts of fatty acids constitutes a complete feed. In this case, the feed comprises, in addition to the one or more alkali metal salts of fatty acids, other components, in particular carbohydrates and proteins, and preferably both. Optionally, other components may be present, such as lipids other than alkali metal salts of fatty acids, minerals, and vitamins. Pharmaceutical agents such as antibiotics and processing aids such as binders may also be present.Antioxidants or preservatives. The content of one or more alkali metal salts of fatty acids in the complete food is not particularly limited, but is typically 40% by weight or less, for example, 35% by weight or less, 30% by weight or less, or 25% by weight or less, with respect to the total weight of the complete food. To maximize the results of the present invention, the content of one or more alkali metal salts of fatty acids in the complete food is preferably 0.1% by weight or more, for example, 0.5% by weight or more, 1% by weight or more, 2% by weight or more, 3% by weight or more, 4% by weight or more, 5% by weight or more, 6% by weight or more, or 7% by weight or more, for example, 8% by weight or more. In one embodiment of the invention, alkali metal salts of fatty acids replace the fat and oil content of a standard aquaculture feed (which normally has a total fat and oil content of between 2 and 40% by weight) by between 1 and 100%,preferably between 25 and 100%, most preferably between 50 and 100%, and herein the food preferably comprises at least three alkali metal salts of fatty acids chosen from palmitic acid (PA), palmitoleic acid (POA), stearic acid (SA), oleic acid (OA), linoleic acid (LOA), alpha-linolenic acid (LNA), arachidonic acid (ARA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). In one embodiment of the invention, the content of alkali metal salts of fatty acids in the feed is higher than the standard percentage of fats or oils in a standard aquaculture feed by between 50% and 300%, preferably between 100% and 200%, and most preferably between 100% and 175%, and the composition comprises at least three alkali metal salts of palmitic acid (PA), palmitoleic acid (POA), stearic acid (SA), oleic acid (OA), linoleic acid (LOA), alpha-linolenic acid (LNA), arachidonic acid (ARA),eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Formulations with higher concentrations of alkali metal salts of fatty acids, compared to standard formulations with fats and oils in standard aquaculture feed compositions, can be achieved by adjusting the ingredient formulation through the reduction or elimination of fats or oils and / or the reduction of carbohydrate concentration. This ensures that the protein content in the feed remains unchanged even with higher concentrations of alkali metal salts of fatty acids. The alkali metal of one or more alkali metal salts of fatty acids is preferably selected from sodium,Potassium and its mixtures. The relative proportion of sodium and potassium salts can be adjusted according to the nutritional requirements of the fish or crustacean. The sodium content in the feed can be adjusted to balance the sodium contribution from the sodium salts of fatty acids. Feed Additive. In one embodiment of the present invention, feed comprising, or obtained from, a composition comprising one or more alkali metal salts of fatty acids is a feed additive. A feed additive is supplied as a supplement to feed that provides most of the energy to the fish or crustaceans, so that no additional components other than the alkali metal salts of fatty acids are required, although these are not excluded. Such additional components can be selected, for example, from vitamins and minerals, cholesterol, lecithin, and combinations thereof. In the feed additive of the present invention,The content of one or more alkali metal salts of fatty acids can be increased, since fish or crustaceans also consume other foods. Therefore, in one embodiment, the total content of one or more alkali metal salts of fatty acids can be set in a range of 20 to 100% by weight, relative to the total weight of the feed additive. The lower limit can also be 30, 40, 50, 60, or 70% by weight, and the upper limit can be less than 100%, for example, 95%, 90%, or 80% by weight, relative to the total weight of the feed additive. The remainder is usually composed of vitamins, minerals, cholesterol, lecithin, and other micronutrients, and optionally, technical aids such as drying agents, binders, emulsifiers, antioxidants, and colorants. In the method of the present invention, the feed additive is administered directly to the fish or crustaceans.in addition to a food that provides them with most of their energy. The feeds can be administered simultaneously or at different times, with the same or different administration frequencies. Premix: A premix can have the same characteristics and composition as the feed additive, but it is not used to feed fish or crustaceans directly, but rather for the production of a complete feed by mixing it with other necessary or desired components. The formulation of one or more alkali metal salts of fatty acids in a premix before combining them with other components to form a complete feed allows the use of the alkali metal salts of fatty acids as a matrix or vehicle for other micronutrients, vitamins, and minerals. In one embodiment of the invention, the alkali metal salts are used in the formulation of premixes for animal feed,especially for aquaculture. The exact formulation and quantities of the components of a premix can vary significantly depending on the nutritional needs of the farmed animal, which are influenced by factors such as species, life stage, environmental conditions, and the formulation of the base feed. The premix can be prepared by mixing powdered alkali metal salts with a fatty acid composition containing vitamins, minerals, cholesterol, amino acids, lecithin, enzymes, antioxidants, and other ingredients such as immunostimulants, growth promoters, and attractants. Method for feeding a crustacean or fish. In one aspect, the present invention relates to a method for feeding crustaceans or fish in a hatchery or fish farm. The method comprises feeding the fish or crustaceans with a feed comprising, or made from, a composition comprising,one or more alkali metal salts of fatty acids. In this case, the preceding description regarding the feed in general and the additive and complete feed applies analogously. Feeding may be carried out during a part or period of the life of the fish or crustacean, or it may be carried out throughout its entire life. Preferably, feeding is carried out in the early life stages, from the larval stage, as this yields greater benefits in biomass production compared to a feed without alkali metal salts of fatty acids. In this case, the early life stage may be defined as the first 120 days after hatching, for example, the first 90 days after hatching (e.g., the first 60 or 45 days after hatching), or only the first 30 or 15 days after hatching. The frequency of administration of the feed of the present invention is not particularly limited.and can be continuous or intermittent. Administration can be performed manually or automatically, for example, by means of an automatic feeding system controlled by an operator or that provides the feed according to a pre-programmed feeding schedule (for example, once every 2 to 6 hours). Preferably, feeding is performed continuously or at least once a day to take full advantage of the benefits of the present invention. The frequency and timing of feeding can be adjusted to the day-night cycle of the fish or crustacean, for example, 3 to 5 times, or 4 times, during the daytime period and none or only one feeding during the nighttime period. The total amount of feed administered in a single feeding, or the amount administered over time, can be adjusted according to the number of animals, their life stage, the desired increase in biomass production efficiency,etc. The duration of feed administration can be freely configured and has no upper limit, but to maximize the benefits of the present invention, the feed is preferably administered for one day or more, such as three days or more, five days or more, ten days or more, or fifteen days or more. An interesting and surprising finding of the present invention is that the fatty acid profile (particularly that of PUFAs) of the fish or crustaceans produced does not reflect that of the feed. While the reasons are not fully understood, it is assumed that the fish and crustaceans, at least during their early life stages, are able to extend the chain length of the fatty acids present in the feed of the present invention in the form of alkali metal salts. Therefore, the present invention also allows for maximizing PUFA production by converting natural sources considered to be of lower value (e.g.,PUFA C18) in the desired compounds (such as EPA and DHA). Therefore, the findings of the present invention allow obtaining valuable materials from a raw material that is generally considered waste in a production process for omega-3 enriched compositions, such as in a process for producing compositions enriched with omega-3 fatty acids such as EPA and DHA. The biomass production efficiency, i.e., the total weight gain of live aquatic organisms cultivated in aquaculture systems during a specific period,can be calculated using various methods known to the expert. The survival of the aquatic animal over a period is measured as the percentage of survival throughout the culture cycle. The determination of the number of survivors can also be carried out using various methods known to the expert. Method for producing a feed The present invention further provides a method for producing a feed for feeding a fish or crustacean as described above, which method comprises mixing one or more alkali metal salts of fatty acids or a composition comprising one or more alkali metal salts of fatty acids with one or more other compositions, said other compositions comprising one or more components selected from the group consisting of animal protein, vegetable protein, carbohydrates, vitamins, minerals, cholesterol, lecithin, or said other composition being a processed marine oil product,such as a product or byproduct of a process for producing EPA and DHA concentrates from marine oil, for example, the heavy fraction. In one embodiment of the invention, the method for preparing a feed, whether in granule or powder form, for feeding aquatic animals is carried out by mixing the alkali metal salt composition of fatty acids with the solid ingredients of the feed formulation, and subsequently pelleting or extruding the mixture. The feed may be complete, a feed additive, or a premix. In one embodiment, the method for producing a feed comprises one or more steps selected from heating, homogenizing, pelleting, extruding, drying, or packaging the material obtained from the mixing step. In one embodiment of the invention,The method for preparing a feed pellet or granule for feeding an aquatic animal involves mixing the alkali metal salt composition of fatty acids with the solid ingredients of the feed formulation. The mixture is then pelletized, ground, and sieved to collect granules of different sizes. In one embodiment of the invention, the pellets or granules are prepared solely from solid ingredients. In general, the method for preparing such pellets or granules can be carried out using the following protocol: • Grinding the solid ingredients to obtain a desired particle size. • Combining the ground ingredients in a mixer to create a homogeneous mixture. • Optionally adding a liquid ingredient, such as oils. • Optionally subjecting the mixture to a conditioning process where it is heated and moistened. • Feeding the conditioned mixture into a pellet mill or extruder.where it undergoes compression and shaping. • Optionally, cutting the resulting pellets to the desired length. • Optionally, drying the pellets to reduce moisture content. • Optionally, coating the pellets with additional nutrients, attractants, or medications to improve palatability and nutritional content. • If the aquaculture feed pellet is intended for small aquatic animals or aquatic larvae, the pellet may be ground and sieved to achieve a desired particle size distribution of the pellets and / or powder. Alkali metal salts of fatty acids may be present in the ground ingredients that are introduced into the mixer. If the optional coating is provided, alkali metal salts of fatty acids may be present in the coating, either alternatively or additionally. The alkali metal salts of fatty acids may be derived from any source, whether of plant or animal origin.or mixtures thereof. Alkali metal salts of fatty acids may be derived from by-products of the omega-3 industry or from mixtures of products of said industry with vegetable or marine oils. In one embodiment, the composition comprising one or more alkali metal salts of fatty acids, used for food production, comprises at least three fatty acids selected from palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, alpha-linolenic acid, arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid, and optionally contains cholesterol. Such compositions are typically obtained from by-products (light or heavy fraction) of the omega-3 industry. In one embodiment of the present invention, the fatty acids of the alkali metal salts of fatty acids, or the alkali metal salts of fatty acids, are derived from marine oils. In a particular aspect of this embodiment,The fatty acids from alkali metal salts of fatty acids, or the alkali metal salts of fatty acids, are derived from a distillation process stream that is part of a process for producing omega-3 fatty acid-enriched compositions for the omega-3 industry, for example, a process such as that described in Breivik, Harald, Long-Chain Omega-3 Specialty Oils, Chapter 4, The Oily Press, 2007 (see Figures 10 and 11). In this case, marine oils, such as fish oil, are typically subjected to high-vacuum distillation to obtain a light distillate fraction as a byproduct comprising free fatty acids and cholesterol, and a residual stream of vacuum-refined fish oil, which is typically transesterified with ethanol to produce ethyl esters. The ethyl esters are then fractionated by molecular distillation to obtain, among other fractions, a heavy fraction,comprising a mixture of glycerides, ethyl esters, and cholesterol, rich in C22 fatty acid ethyl esters (DHA) and very long-chain polyunsaturated fatty acid ethyl esters. When the alkali metal salts of fatty acids used in the present invention are derived from a fraction of a distillation process carried out with alkyl (methyl or ethyl) fatty acid esters, these can be converted to the respective alkali metal salts by hydrolysis or saponification under alkaline conditions using a suitable alkali metal base, such as KOH or NaOH, or a mixture of NaOH and KOH, using between 75% and 100% of the saponification value, preferably between 90% and 99% of the saponification value, which can subsequently be removed, for example, by precipitation or solvent removal. This also results in a mixture of water and alkanol (for example, methanol or ethanol).which can be recycled to the initial stage of hydrolysis. In a specific embodiment of the invention, the alkali metal salts of fatty acids are obtained by saponifying an oil (a marine oil or a vegetable oil or a processed oil product, such as the light fraction or heavy fraction by-product of the omega-3 industry, or mixtures thereof) with aqueous sodium or potassium hydroxide or a mixture of aqueous sodium and potassium hydroxide, using between 75 and 100% of the saponification value of the oil, preferably between 90 and 99% of the saponification value, at a temperature of 30 to 170 °C, to form a saponified mixture, followed by the evaporation of water, glycerol, and ethanol (the latter if the oil comprises fatty acid ethyl esters) from the saponified mixture in an evaporator to obtain a residue stream comprising a dry fluid saponified mixture,The evaporator operates at a pressure between 500 and 1000 mbar and a temperature between 250 and 350 °C, followed by feeding the residue stream to a spray or spray cooling (or granulation) unit, or to a drum or belt cooler, or to a flake forming unit, to produce a mixture of solid particles of alkali metal salts of fatty acids of different sizes, composed of at least three alkali metal salts of fatty acids selected from the following: palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, alpha-linolenic acid, arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid. The alkali metal salt mixture can be ground and sieved to separate into fractions of different sizes or used as such. Preferred evaporators are short-path evaporators and thin-film evaporators. In a specific embodiment of the invention,Alkali metal salts of fatty acids are obtained by saponifying an oil (a marine oil or a vegetable oil or a processed oil product, such as the light fraction or heavy fraction by-product of the omega 3 industry, or mixtures thereof) with aqueous sodium or potassium hydroxide or a mixture of aqueous sodium and potassium, using between 75 and 100% of the saponification value of the oil, preferably between 90 and 98% of the saponification value, at a temperature of 30 to 170 °C, to form a saponified mixture, followed by the evaporation of water and ethanol (the latter if the oil comprises ethyl esters of fatty acids) from the saponified mixture to form a dry fluid saponified mixture in a first evaporator, operating at a pressure of between 800 and 1200 mbar and a temperature of between 200 and 320 °C, then evaporating the glycerol from the dry fluid saponified mixture in a second evaporator,operating at a pressure of between 100 and 800 mbar and a temperature of 250 to 350 °C, followed by feeding the residue stream from the second evaporator to a spray or spray cooling (or granulation) unit, or to a drum or belt cooler, or to a flake forming unit, to produce a mixture of solid particles of alkali metal salts of fatty acids of different sizes comprising at least three alkali metal salts of fatty acids selected from alkali metal salts of palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, alpha-linolenic acid, arachidonic acid,Eicosapentaenoic acid and docosahexaenoic acid. The mixture of alkali metal salt particles can be ground and sieved to separate it into fractions of different sizes or used as is. The preferred evaporators are short-path evaporators and thin-film evaporators. In one embodiment of the invention, the fatty acid alkali metal salts are obtained by saponifying the light fraction (a byproduct of the Omega 3 industry), composed of free fatty acids and cholesterol, with aqueous sodium or potassium hydroxide or an aqueous mixture of sodium and potassium, using between 75% and 100% of the saponification value of the light fraction, preferably between 90% and 98%, at a temperature of 30 to 170 °C to form a saponified mixture. Subsequently,Water and ethanol are removed from the saponified mixture to obtain a solid mixture composed of at least three alkali metal salts selected from the alkali metal salts of palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, alpha-linolenic acid, arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid, and which also comprises cholesterol. The mixture can be ground and sieved to separate it into fractions of different sizes or used as such. The water and ethanol are preferably removed by spray drying or using one or two evaporators in series as described in the two preceding embodiments. In one embodiment of the invention, the alkali metal salts of fatty acids are prepared by saponifying the heavy fraction from the distillation process for the production of omega-3 concentrates (a byproduct of the omega-3 industry), which comprises ethyl esters of fatty acids, mono-,Di- and triglycerides of fatty acids (glycerides) and cholesterol, with aqueous sodium or potassium hydroxide or a mixture of aqueous sodium and potassium hydroxide, using between 75 and 100% of the saponification value of the heavy fraction, preferably between 90 and 98% of the saponification value of the heavy fraction, at a temperature of 30 to 170 °C, to form a saponified mixture, followed by evaporation of water, glycerol, and ethanol from the saponified mixture in an evaporator to obtain a residue stream comprising a dry, fluid saponified mixture, the evaporator operating at a pressure of between 500 and 1000 mbar and a temperature of between 250 and 350 °C, followed by feeding the residue stream to a spray or spray cooling (or granulation) unit, or to a drum or belt cooler, or to a flake forming unit,for producing a mixture of solid particles of alkali metal salts of fatty acids of different sizes, composed of at least three alkali metal salts of fatty acids selected from palmitic, palmitoleic, stearic, oleic, linoleic, alpha-linolenic, arachidonic, eicosapentaenoic, and docosahexaenoic acids, and also comprising cholesterol. The mixture of alkali metal salt particles can be ground and sieved to separate into fractions of different sizes or used as such. Preferred evaporators are short-path evaporators and thin-film evaporators. In one embodiment of the invention, the alkali metal salts of fatty acids are prepared by saponifying the heavy fraction from the distillation process for the production of omega-3 concentrates (a byproduct of the omega-3 industry), comprising fatty acid ethyl esters, mono-, di-, and triglycerides of fatty acids (glycerides), and cholesterol.with aqueous sodium or potassium hydroxide or a mixture of aqueous sodium and potassium hydroxide, using between 75 and 100% of the saponification value of the heavy fraction, preferably between 90 and 98% of the saponification value of the heavy fraction, at a temperature of 30 to 170 °C, to form a saponified mixture, followed by evaporation of water and ethanol from the saponified mixture to form a dry, fluid saponified mixture, in a first evaporator operating at a pressure of between 800 and 1200 mbar and a temperature of between 200 and 320 °C, and then evaporating the glycerol from the water- and ethanol-free saponified mixture, in a second evaporator operating at a pressure of between 100 and 800 mbar and a temperature of 250 to 350 °C, followed by feeding the residue stream from the second evaporator to a spray unit or spray cooling (or granulation), or to a drum or belt cooler, or to a flake forming unit,for producing a mixture of alkali metal salts of fatty acids comprising at least three alkali metal salts of fatty acids selected from the group consisting of palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, alpha-linolenic acid, arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid, and also comprising cholesterol. The mixture of solid alkali metal salt particles can be ground and sieved to separate it into fractions of different sizes or used as such. Preferred evaporators are short-path evaporators and thin-film evaporators. In one embodiment of the invention,Alkali metal salts of fatty acids are obtained by saponifying a mixture of vegetable oil and the heavy fraction from the distillation process for the production of omega-3 concentrates (a byproduct of the omega-3 industry). The weight ratio of the vegetable oil to the heavy fraction is 10:1 to 1:1. Saponification is typically carried out with aqueous sodium or potassium hydroxide, or a mixture of aqueous sodium and potassium hydroxide, using between 75 and 100% of the saponification value of the vegetable oil and heavy fraction mixture, preferably between 90 and 98%, at a temperature of 30 to 170 °C to form a saponified mixture. This is followed by evaporation of water, glycerol, and ethanol from the saponified mixture in an evaporator to obtain a residue stream comprising a dry, fluid saponified mixture.the evaporator operating at a pressure between 500 and 1000 mbar and a temperature between 250 and 350 °C, followed by feeding the residue stream to a spray or spray cooling (or granulation) unit, or to a drum or belt cooler, or to a flake forming unit, to produce a mixture of solid particles of alkali metal salts of fatty acids of different sizes comprising at least three alkali metal salts of fatty acids selected from alkali metal salts of palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, alpha-linolenic acid, arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid,which also includes cholesterol. The mixture of alkali metal salt particles can be ground and sieved to separate it into fractions of different sizes or used as is. The preferred evaporators are short-path evaporators and thin-film evaporators. In one embodiment of the invention, the alkali metal salts of fatty acids are obtained by saponifying a mixture of vegetable oil and the heavy fraction from the distillation process for the production of omega-3 concentrates (a byproduct of the omega-3 industry). The weight ratio of the vegetable oil to the heavy fraction is from 10:1 to 1:1. Saponification is typically carried out with aqueous sodium or potassium hydroxide or a mixture of aqueous sodium and potassium hydroxide, using between 75 and 100% of the saponification value of the vegetable oil and heavy fraction mixture, preferably between 90 and 98% of the saponification value.at a temperature of 30 to 170 °C to form a saponified mixture, followed by the evaporation of water and ethanol from the saponified mixture to form a water- and ethanol-free saponified mixture in a first evaporator operating at a pressure between 800 and 1200 mbar and a temperature between 200 and 320 °C, then evaporating the glycerol from the water- and ethanol-free saponified mixture in a second evaporator operating at a pressure between 100 and 800 mbar and a temperature between 250 and 350 °C, followed by feeding the residue stream from the second evaporator to a spray or spray-cooling (or granulation) unit, or to a drum or belt cooler, or to a flake-forming unit, to produce a mixture of solid alkali metal salts of fatty acids comprising at least three alkali metal salts of fatty acids selected from the group consisting of palmitic acid, acid palmitoleic acid, stearic acid, oleic acid, linoleic acid,The mixture contains alpha-linolenic acid, arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid, and also includes cholesterol. The solid alkali metal salt particles can be ground and sieved to separate them into different size fractions or used as is. Preferred evaporators are short-path evaporators and thin-film evaporators. In one embodiment of the invention, the alkali metal salts of fatty acids are obtained by saponifying an oil (a marine oil, a vegetable oil, or a processed oil product, such as the light or heavy fraction derived from the omega-3 industry, or mixtures thereof) with aqueous sodium or potassium hydroxide, or a mixture of aqueous sodium and potassium hydroxide, using between 75% and 100% of the saponification value of the oil, preferably between 90% and 98%, at a temperature of 30°C to 100°C, preferably between 40°C and 80°C.to form a saponified mixture. This mixture is then acidified with an aqueous solution of an inorganic or organic acid, such as sulfuric acid, hydrochloric acid, citric acid, etc. The acidified mixture is decanted or centrifuged, and a free fatty acid composition is recovered from the light phase. The free fatty acid composition is neutralized with aqueous sodium or potassium hydroxide, or with an aqueous mixture of sodium and potassium, and the water is then evaporated from the neutralized mixture to obtain a solid mixture comprising at least three alkali metal salts of fatty acids, selected from the group consisting of palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, alpha-linolenic acid, arachidonic acid,Eicosapentaenoic acid and docosahexaenoic acid. The mixture can be ground and sieved to separate it into fractions of different sizes or used as is. Evaporation is preferably carried out by spray drying. Method for increasing the concentration of omega-3 fatty acids in a fish or crustacean. In one embodiment of the invention, the present invention provides a method for increasing the concentration of omega-3 fatty acids in the flesh of an aquatic animal, the process comprising: a) providing an aquatic animal in a hatchery or farm; b) feeding said aquatic animal with a feed comprising alkali metal salts of fatty acids; c) harvesting said aquatic animal at which it has a higher concentration of omega-3 fatty acids. The feeding is the same as described above. The aquatic animal can be a fish or a crustacean. The feeding can be carried out for the desired time.but preferably at least once or several times a day for at least one day, for example, 2, 3, or 5 days, for example, 10 days, or until the animal reaches its target growth. In one embodiment of the invention, the method for increasing the concentration of omega-3 fatty acids in fish flesh is carried out by a process of: a) providing a fish in a hatchery or farm; b) feeding said fish with a feed comprising alkali metal salts of fatty acids; c) harvesting said fish. Fish obtained by this method exhibit a higher concentration of omega-3 fatty acids, particularly PUFAs, compared to fish obtained with a feed without alkali metal salts of fatty acids. Feeding can be carried out for the desired period, but preferably at least once or several times a day for at least one day, for example, 2, 3, or 5 days, for example, 10 days.or until the animal reaches its target growth. In another embodiment, the method for increasing the concentration of omega-3 fatty acids in shrimp comprises the steps of: a) providing a shrimp in a hatchery or farm; b) feeding said shrimp with a feed comprising alkali metal salts of fatty acids; c) harvesting said shrimp. Feeding can be carried out for a desired period of time, but preferably at least once or several times a day for a period of at least one day, such as at least 2, 3, or 5 days, for example, at least 10 days, or until the shrimp has reached its target growth. Shrimp obtained by this method exhibit a higher concentration of omega-3 fatty acids, in particular PUFAs,compared to shrimp obtained from a feed that does not contain alkali metal salts of fatty acids. Examples 1. Production of a composition comprising alkali metal salts of fatty acids from tuna oil. 10 kg of tuna oil were introduced into a 20-liter stainless steel reactor equipped with stirring and a heating jacket (manufactured by Pfaudler). The oil was heated to 80 °C under a nitrogen atmosphere. 3.35 kg of a NaOH solution, obtained by mixing 2.0 kg of water and 1.35 kg of NaOH, were introduced into the reactor under stirring. The reactor was then sealed in a nitrogen atmosphere and the mixture was heated to 110 °C for 15 minutes to obtain a saponified mixture. The saponified mixture was fed into two-stage short-path evaporators in series (manufactured by Pfaudler), of 0.2 and 0.1 m²,respectively. The first short-path evaporator was fed at 5 kg / h and operated at 270 °C and atmospheric pressure. A distillate stream consisting mainly of water was produced. The residue stream was continuously fed to the second short-path evaporator, which operated at 290 °C and 200 mbar. The distillate stream from the second evaporator consisted mainly of glycerol. The residue from the second short-path evaporator was continuously fed to a water-cooled drum flaker to recover solid flakes of alkali metal salts of fatty acids. The alkali metal salt flakes of fatty acids were ground in a blade mill and then sieved through a #100 mesh sieve (149 microns). The composition of the starting tuna oil and the final alkali metal salts of the fatty acid composition are shown in Table 1. Note: Fatty acid analysis was performed according to AOAC method 991.39. For the analysis of the alkali metal salt composition of fatty acids, a sample was first neutralized with an aqueous HCl solution, free fatty acids were recovered by hexane extraction, and finally, the hexane extract was evaporated using a vacuum rotary evaporator. The recovered and dried fatty acids were then analyzed according to AOAC method 991.39. ND: Not Detected (absent or below the detection limit). The solid particles of the alkali metal salt composition of fatty acids are glycerin-free, free-flowing, do not tend to agglomerate, and sieve efficiently through a 100-mesh screen. If necessary, the alkali metal salt composition of fatty acids in powder form can be mixed with anti-caking agents such as silicon dioxide, calcium silicates, magnesium stearates, and others.Typically, between 0.1% and 2% anti-caking agents can be used. The alkali metal salts of fatty acids powder exhibited a lower TOTOX value than the starting tuna oil and a similar fatty acid profile. No fatty acid losses were detected during the manufacturing process of the alkali metal salts of fatty acids powder composition. This is primarily due to the short residence time of the short-path evaporators, less than one minute, resulting in minimal exposure of the alkali metal salts of fatty acids to high temperatures, which allows for remarkable stability of the alkali metal salts of fatty acids composition. The process is highly efficient for refining oils with a high TOTOX index and obtaining an alkali metal salts of fatty acids composition with low oxidation parameters, typically with a TOTOX index below 10.The powdered composition of alkali metal salts of fatty acids can be blended with antioxidants such as BHT or BHA to enhance its oxidative lifetime. Typically, between 0.002% and 0.2% BHA or BHT can be used. 2. Production of a composition comprising alkali metal salts of fatty acids from the heavy fraction of the Omega-3 industry. In the Omega-3 industry, for the production of EPA and DHA concentrates, crude fish oils or mixtures thereof, or refined fish oils or mixtures thereof, are transesterified with ethanol and then concentrated by high-vacuum short-path distillation. The process yields one or more heavy fractions as a byproduct, or heavy fraction, comprising fatty acid ethyl esters, fatty acid glycerides (mono-, di-, and triglycerides), and cholesterol.Any fraction from the high-vacuum short-path distillation is suitable for producing alkali metal salts of fatty acids of the present invention; however, the heavy fraction is particularly useful due to its high concentration of cholesterol and omega-3 fatty acids. Ten kilograms of a heavy fraction sample of anchovy oil were processed in the same processing equipment described in Example 1. The heavy fraction was introduced into the reactor and heated to 80 °C. Three kilograms of a NaOH solution, obtained by mixing 2.0 kg of water and 1.0 kg of NaOH, were introduced into the reactor under stirring. The reactor was then sealed under a nitrogen atmosphere, and the mixture was heated to 115 °C for 15 minutes to obtain a saponified mixture. The saponified mixture was fed to the two-stage short-path evaporators in series described in Example 1. The first short-path evaporator was fed at 5 kg / h and operated at 250 °C and atmospheric pressure.A distillate stream consisting primarily of water and ethanol was produced. The residue stream was continuously fed to the second short-path evaporator, which operated at 270 °C and 250 mbar. The residue from the second short-path evaporator was continuously fed to a water-cooled drum flaker to recover fatty acid alkali metal salt flakes. The flakes were ground in a knife mill and then sieved through a #100 mesh (149-micron) sieve. The composition of the initial heavy fraction material and the final fatty acid alkali metal salt composition are shown in Table 2. The analysis was performed as described below Table 1. The solid particles of the alkali metal salts of fatty acids composition are glycerin-free, free of fatty acid ethyl esters, free-flowing, do not tend to agglomerate, and sieve efficiently through a #100 mesh screen. The alkali metal salts of fatty acids powder composition, obtained from the heavy fraction, is particularly useful in formulating premixes for aquaculture feeds due to its high omega-3 and cholesterol content, typically exceeding 30% omega-3 fatty acids and more than 3% cholesterol. The premix can be formulated by blending the alkali metal salts of fatty acids powder with vitamins (A, K, D, C, E), minerals, and lecithin. Dried lecithin can be used, allowing for the preparation of a premix using only powdered ingredients. 3.Production of an alkali metal salt composition of fatty acids from linseed oil. In a 10-liter glass-lined reactor, equipped with stirring and jacketed with a hot oil heating system (manufactured by Buchi), 2 kg of linseed oil were loaded and mixed with 3 kg of a solution prepared with 2.740 kg of water and 260 g of sodium hydroxide. The reactor was heated with stirring to 80 °C for 45 minutes and then cooled to 50 °C. The saponified mixture was then acidified with 2 kg of a sulfuric acid solution prepared with 1.650 kg of water and 350 g of sulfuric acid. A two-phase mixture was recovered and allowed to settle. The lighter phase, composed mainly of free fatty acids, was separated and washed with hot water. The acid number of the washed light phase was 184.01 with 98.3% non-volatile matter. One kilogram of the washed light phase was loaded into a one-gallon reactor.100 mg of BHA were added, and the mixture was heated to 80 °C. Then, 1.13 kg of a NaOH solution was added with stirring. This solution was prepared by mixing 1.0 kg of water and 0.13 kg of NaOH. After adding the NaOH solution, the mixture was stirred for 15 minutes at 80 °C to obtain a neutralized mixture. The neutralized mixture was dried in a laboratory glass spray dryer (Buchi, model B-190). The drying process was carried out at a feed rate of 5 mL / min with an airflow at 170 °C. The dried sodium salts from the fatty acid composition of linseed oil were recovered as a free-flowing powder with an average particle size of 710 µm. The composition of the dry sodium salts of the fatty acids of linseed oil was ground in a blade mill and then sieved through a # 100 mesh sieve (149 microns).The analysis of the starting linseed oil and the final composition after sieving are shown in Table 3. The analysis was performed as described below Table 1. The solid particles of the sodium alkali metal salts of fatty acids composition are glycerin-free, free-flowing, do not tend to agglomerate, and sieve efficiently through a #100 mesh. 4. Production of an alkali metal salts of fatty acids composition from the light fraction of the Omega 3 industry. In the Omega 3 industry, crude fish oils or mixtures of crude fish oils are generally refined by high-vacuum distillation (physical refining), which produces a distilled byproduct fraction, or light fraction, comprising free fatty acids, cholesterol, and in some cases, fatty acid ethyl esters. Ten kilograms of a light fraction sample, produced from a mixture of sardine oil and mackerel oil, were processed on the same processing equipment described in Example 1.The light fraction was introduced into the reactor and heated to 80 °C. Five hundred kilograms of an alkaline solution, prepared by mixing 3.8 kg of water with 1,160 g of NaOH and 40 g of KOH, were then introduced into the reactor under stirring. The reactor was subsequently sealed under a nitrogen atmosphere, and the mixture was heated to 80 °C for 45 minutes to obtain a saponified mixture. The saponified mixture was fed to the two-stage short-path evaporators in series described in Example 1. The first short-path evaporator was fed at 5 kg / h, operating at 260 °C and atmospheric pressure. A distillate stream consisting mainly of water and ethanol was produced. The residue stream was continuously fed to the second short-path evaporator, operating at 270 °C and 210 mbar.The residue stream from the second short-path evaporator was continuously fed to a water-cooled drum flaker to recover flakes of an alkali metal salts fatty acid composition. The alkali metal salts fatty acid flakes were ground in a knife mill and then sieved through a #100 mesh (149-micron) sieve. The composition of the initial light fraction material and the final composition are shown in Table 4. The analysis was performed as described below Table 1. Typically, the light fraction byproduct of the omega-3 industry contains high levels of persistent organic pollutants (POPs), such as dioxins, furans, PCBs, and PAHs. Table 5 shows the POP concentration of the light fraction and the composition of alkali metal salts of fatty acids produced from it. As can be seen above, the manufacturing process of sodium salts of fatty acids in high-vacuum short-path evaporators significantly reduces the presence of COP. 5. Production of an alkali metal fatty acid salt composition from linseed oil and the heavy fraction of the Omega 3 industry. A mixture of 3 kg of heavy fraction (same as used in Example 2) and 7 kg of linseed oil (same as used in Example 3) was processed in the same equipment described in Example 1. The mixture was introduced into the reactor and heated to 80 °C. 4.5 kg of a NaOH solution, obtained by mixing 3.5 kg of water and 1,150 g of NaOH, were introduced into the reactor under stirring. The reactor was then sealed under a nitrogen atmosphere, and the mixture was heated to 85 °C for 50 minutes to obtain a saponified mixture. The saponified mixture was fed only to the first stage of the two short-path evaporators.The first short-path evaporator was fed at 5 kg / h and operated at 305 °C and atmospheric pressure. A distillate stream consisting primarily of water and glycerol was produced. The residue from the short-path evaporator was continuously fed to a granulation tower, equipped with a Spraying System Co. model 1 / 4M-316SS1 nozzle, and countercurrently cooled with air to 20 °C, to recover beads of an alkali metal salt composition of fatty acids. The beads were recovered as a free-flowing powder with an average size of 930 microns. The beads were ground in a blade mill and then sieved through a #100 mesh sieve (149 microns). The final composition analysis after sieving is shown in Table 6. The analysis was performed as described below Table 1. The solid particles of the alkali metal salts of fatty acids composition are free of glycerin and fatty acid ethyl esters, flow freely, do not tend to agglomerate, and sieve efficiently through a 100-mesh screen. No fatty acid degradation was detected. 6. Production of shrimp larvae feed. The ingredients in Table 7 were ground and sieved to less than 300 micrometers. The sieved ingredients were mixed and preconditioned with steam (>90 °C) and post-conditioned for 20 minutes (>90 °C), then extruded through a 1.5 mm die. Subsequently, the pellets were ground and sieved into 4 fractions: Fraction 1: < 50 microns (for Mysis 2) Fraction 2: 50 – 100 microns (for Mysis 3 to PL2) Fraction 3: 100 – 200 microns (for PL3 – PL5) Fraction 4: 200 – 300 microns (for PL6 – PL15) All ingredients are expressed as a percentage by weight based on the total weight of the feed. All feeds in Table 7 had a nominal crude protein content of 54%. Feed A had a crude lipid content of 11%. Six percent tuna oil was used in the formulation. The tuna oil used was the same as that used in Example 1. This feed was used as the control group, representing a standard formulation for shrimp larvae made with fish oil (tuna oil, triglycerides). The composition of Feed D contained 6% alkali metal salts of fatty acids derived from tuna oil, as produced in Example 1. No tuna oil was used in Feed D. The use of the dry powder alkali metal salts of fatty acids composition for oil replacement was done directly, without the need to modify the original formulation composition or dilute the crude protein.In feed D, 100% of the original oil in the standard formulation (feed A) was replaced with the alkali metal salts of fatty acids composition. Feed B contained 6% of the alkali metal salts of fatty acids composition from linseed oil and the heavy fraction of the Omega 3 industry, as produced in Example 5. Tuna oil was not used in feed B. In feed B, 100% of the original oil in the standard formulation (feed A) was replaced with the alkali metal salts of fatty acids composition. Feed C contained 9% alkali metal salts of fatty acids from linseed oil and the heavy fraction of the Omega 3 industry, as produced in Example 5, 50% more than in feed B. Tuna oil was not used in feed C.Feed C contained 3% less wheat flour than the other feeds to balance the additional 3% of alkaline fatty acid salts. The higher lipid content in the formulation, in the form of alkaline fatty acid salts, can be easily achieved by reducing the use of carbohydrates (wheat flour) without reducing the crude protein content. In Feed C, 150% of the original oil in the standard formulation (Feed A) was replaced with the alkaline fatty acid salt composition. Feed E contained 4% alkali metal fatty acid salts from the light fraction of the Omega 3 industry, as produced in Example 2. No tuna oil was used in Feed E. In Feed E, 100% of the original oil in the standard formulation (Feed A) was replaced with the alkali metal fatty acid salt composition.All feeds were formulated with a 0.42% cholesterol addition based on the feed. Due to the high cholesterol content of the alkali metal salts of the fatty acids in the light fraction, no cholesterol addition was required in feed E (lanolin cholesterol, SF91%). All ingredients in feed formulations B through E were available in powder form; therefore, they were made using only solid ingredients, which facilitated and simplified mixing. Furthermore, sieving feeds B through E yielded between 180% and 340% more product passing through 50 microns compared to feed A. This was due to the sticky property of the liquid tuna oil present in feed A, which caused particles to adhere to the sieve surface and gradually clog the openings. 7. Production of Post-Larval Shrimp Feeds. The ingredients in Table 8 were ground and sieved to less than 300 microns.The sieved ingredients were mixed and pre-conditioned with steam (>90 °C) and post-conditioned for 20 minutes (>90 °C), then extruded through a 1.5 mm die. All ingredients are expressed as a percentage by weight based on the total weight of the feed. All feeds in Table 8 had a nominal crude protein content of 38%. Feed F had a crude lipid content of 8%. 2.5% tuna oil was used in the formulation. The tuna oil used was the same as in Example 1. This group was used as a control group, representing a standard feed formulation for post-larval (PL) shrimp, made with fish oil (tuna oil, triglycerides). Feed G contained 2.5% alkali metal salts of fatty acids derived from the tuna oil produced in Example 1. No tuna oil was used in Feed G. In Feed G, 100% of the original oil in the standard formulation (Feed F) was replaced with alkali metal salts of fatty acids.Feed formulation H contained 2.5% alkali metal salts of fatty acids from linseed oil produced in Example 3. Tuna oil was not used in Feed H. In Feed H, 100% of the original oil in the standard formulation (Feed F) was replaced with alkali metal salts of fatty acids. All ingredients in Feeds G and H were available in powder form; therefore, these two formulations were made using only solid ingredients, which facilitated and simplified ingredient mixing. 8. Salmon Feed Production. The control group (FEED I) and the experimental diet (FEED II) were made using the ingredients in Tables 9.1 and 9.2, respectively. All powdered ingredients were mixed and ground to less than 400 microns. In FEED II, the alkali metal salts of fatty acids composition was added along with the powdered ingredients.The mixed ingredients were extruded in a twin-screw extruder with a 1.2 mm die. Granulated diets (0.4–1 mm) were prepared by grinding and sieving. The diets were dried in a vibrating fluidized bed dryer. In the control diet, tuna oil was added by vacuum coating the pellets and granules (700 mbar). In contrast, vacuum coating was unnecessary in the experimental diets, as the alkali metal salts of the fatty acid composition were added along with all the powdered ingredients. The use of solid particles of the alkali metal salts of fatty acids simplifies the pelleting process. All diets were cooled and packaged in sealed plastic containers. All ingredients are expressed as a percentage of weight based on the total weight of the food. Feeding. 9. Shrimp Larvae Growth Trial. A single brood of Litopenaeus vannamei larvae was cultured to Mysis 2 in a 1000-liter tank. The larvae hatched on day 1 and metamorphosed to Zoea 1 after 36 hours. Zoea 3 was reached on day 5 and Mysis 1 on day 8. On day 10, the Mysis 2 larvae were divided into 5 tanks. The number of larvae per tank was approximately 2000 Mysis 2 (1980, 1823, 1890, 1920, and 1938, respectively). The feeding schedule for Mysis 2 to PL is shown in Table 9. ANC: Frozen Artemia Naupii. Upon arrival at Mysis 3, the food was changed to a size of 50-100 microns. On day 12, the larvae began to transform into postlarvae (PL). The transformation unfolded as shown in Table 10: It can be observed that the Mysis shrimp that received feeds comprising alkali metal salts of fatty acids progressed more rapidly to the postlarval stage than the group that received the feed formulated with tuna oil (feed A). The feeding schedule for the postlarval stage (up to PL2, day 15) is shown in Table 11. ANC: Frozen Artemia Naupii. From PL3 onwards, the experimental feed size was changed to 100–200 µm. From PL5 onwards, the experimental feed size was changed to 200–300 µm. Feed was automatically distributed by a belt feeder (7 times daily). At 10 am, 3 pm, and 11 pm, postlarvae received frozen copepods. At PL15, all copepods were counted and some were measured. The length of the copepods at PL15 is shown in Table 12. (*) The PL weight was estimated from the correlation published by Radulovich, R. and JP Fuentes-Quesada.2019. Artisanal shrimp (Litopenaeus vannamei) production in floating cages at sea and polyculture with oyster (Crassostrea gigas). Aquaculture 512: 734-354, Figure 4. In PL15, a size of 15 mm is commonly accepted as very good, which was the result of Feed A, confirming that this feed with fish oil (tuna oil) is an efficient standard formulation for shrimp larvae. However, it can be observed that all diets with alkali metal salts of fatty acids produced longer PLs, from 17 to 19 mm, revealing the surprisingly superior bioavailability of fatty acids in the form of alkali metal salts of fatty acids compared to triglycerides, probably also as a more digestible energy nutrient.Without limiting ourselves to theory, it is assumed that the surfactant properties of alkali metal salts of fatty acids can improve the emulsification of feed in the shrimp's gastrointestinal system, which could contribute to increased nutrient bioavailability. This aspect may also allow for the reduction or elimination of lecithin use in shrimp feed formulations by replacing it with alkali metal salts of fatty acids. As can be seen in the table above, in the feeds where the oil (Tuna Oil in Feed A) was replaced with alkali metal salts of fatty acids at the same percentage (6%), the weight gain was greater than 50%. In the group with 9% alkali metal salts of fatty acids (Feed C), the weight gain was greater than 100% compared to Feed A. The calculated total biomass and relative TCA are shown below. During the trial, all groups received the same amount of feed; therefore, we can calculate the relative TCA (total fat content) for group A, as shown in the last column of Table 13. Groups fed feeds B, D, and E, where 6% of the tuna oil in feed A was replaced with 6% alkali metal salts of fatty acids, showed a 41% to 46% reduction in TCA compared to control group A. Group C, where 6% of the tuna oil in feed A was replaced with 9% alkali metal salts of fatty acids, achieved an outstanding 60% reduction in TCA compared to feed A. The survival percentage is shown in Table 14. As shown in Table 14, all feeds with a fatty acid alkali metal salt composition showed a significant increase in survival rate compared to standard feed A. These unexpected results from feeding shrimp larvae with feeds comprising fatty acid alkali metal salts may allow for a reduction in the use of Artemia naupii. 10. Post-larval shrimp growth trial. The three feeds in Table 8 (Feeds F, G, and H) were tested with approximately 3 grams of post-larval shrimp (Litopenaeus vannamei) at the start of the trial. Each diet was tested with three replicates, using a total of nine baskets. Each basket held 12 shrimp. All baskets were placed in a larger tank, thus maintaining the same water quality. Water quality in the larger tank was maintained with bioflocs. Each basket was equipped with an automatic feeder.The shrimp were fed continuously. Measurements during the trial: At baseline, after 2 weeks, after 4 weeks, and after 6 weeks, the shrimp were counted and weighed together to obtain the total weight or biomass production. Feed supply was adjusted daily according to an expected growth curve and the average weight of the initial and final measurements. At the end of the growth trial, total weight, feed conversion ratio (FCR), and survival rate were calculated. Results of the shrimp larvae growth trial (Tables 15, 16, 17, 18, and 19): As noted previously, the two diets containing alkali metal salts of fatty acids (FEED G and FEED H) resulted in a better survival rate than the standard feed, which did not contain alkali metal salts of fatty acids (FEED F, with 2.5% tuna oil). Total weight gain or biomass at the end of the trial was significantly higher for both diets containing alkali metal salts of fatty acids compared to standard feed F, and the feed conversion ratio of feeds G and H was significantly lower than that of feed F. These results demonstrate the superior performance of compositions containing alkali metal salts of fatty acids over oils and fats (triglycerides) in conventional shrimp diets. An unexpected result was observed: feed H performed equivalently to feed G.Both diets were formulated with foods containing alkaline salts of fatty acids, but food H used only alkaline salts of vegetable oil (flaxseed oil) instead of alkaline salts of fish oil (as in food G), resulting in a different omega-3 fatty acid profile. Table 18 below shows the content of the main omega-3 fatty acids in the three foods. Feed H, compared to feeds F and G, contained less than 50% of the total concentration of EPA and DHA, two essential fatty acids in shrimp diets. However, the use of the linseed oil-based composition of feed H, rich in alpha-linolenic acid (ALA) sodium salt, indicates that the use of marine oils could be reduced or even eliminated by using alkaline metal salts of ALA fatty acids (C18:3 n3). It appears that the alkaline metal salt form of ALA has superior bioavailability in shrimp diets, allowing for a reduction in the concentration of EPA and DHA in the formulation without negatively impacting biomass production, survival, or shrimp growth. On the contrary, it offers the key benefit of reducing the use of marine oils in favor of vegetable oils (such as alkaline metal salts of fatty acids).Finally, the fatty acid profile was analyzed in lipid extract samples from shrimp tails. The lipid content was 0.54%, 0.61%, and 0.59% for shrimp fed FEEDS F, G, and H, respectively. The EPA and DHA content in the lipids is shown in Table 19. As shown in Table 19, feed G incorporated a higher concentration of EPA and DHA into the lipids present in the shrimp tail meat. Therefore, the feeds of the present invention can incorporate higher concentrations of omega-3 fatty acids into the meat of aquatic animals than the standard oils and fats present in aquaculture feeds. Again, the results for feed H were unexpected. This feed showed the highest inclusion rate of EPA and DHA in the shrimp tail meat. 11. Pre-smolt salmon growth trial. Atlantic salmon fry (Salmo salar, n = 3,600) with an average initial weight of 2.3 ± 0.2 g were randomly assigned to 12 experimental tanks (300 fry per tank, 6 tanks per group) with fresh river water (100 L) and monitored for 240 days until smoltification. The water temperature, 13.1 ± 1.7 °C and oxygenation (>85%) remained constant.Particulate feed, previously sieved and fractionated into 0.3–0.5 mm, 0.5–0.8 mm, and 0.8–1.2 mm particles, was provided according to the average weight of the fish: <0.8 g, <1.5 g, and up to smolts or <5 g, respectively. At the end of the trial, all fish were counted. Table 20 below shows the effect on the average weight gain of the fish with the experimental diet in which tuna oil was replaced by alkali metal salts of the fatty acid composition of tuna oil. As shown in Table 20, salmon fed FEED II, which comprised alkali metal salts of fatty acids, produced greater biomass production compared to the group fed FEED I, which did not contain alkali metal salts of fatty acids but rather fish oil (tuna oil). 12. Salmon Smolt Growth Trial. Atlantic salmon smolts (Salmo salar, n = 450) with an initial weight of 51.3 ± 6.8 g and a total length of 17.0 ± 0.4 cm (mean ± SD) were randomly assigned to experimental tanks (200 L and 1 m deep). Water temperature (7.8 ± 0.1 °C), oxygenation (>85%), and a 24-h photoperiod were maintained. The fish were fed ad libitum for three months using an automated system twice a day. 30 minutes after ingestion, uneaten food and feces were removed, separated, and frozen for later analysis.After anesthesia, the fish were weighed and measured individually, and fecal matter was obtained by scraping. The results are shown in Table 21. FEED II, comprising alkali metal salts of fatty acids, resulted in higher biomass production efficiency compared to FEED I. 13. Post-larval shrimp growth test with different fatty acid derivatives. A sample of the tuna oil used in Example 1 was saponified and neutralized: In a 2-liter Erlenmeyer flask, 250 grams of tuna oil were contacted with a NaOH solution prepared with 200 grams of water, 200 grams of ethanol, and 40 grams of NaOH. The mixture was refluxed for 2 hours with magnetic stirring to saponify the oil. The saponified mixture was cooled to 50 °C and neutralized with 600 grams of a 40% aqueous citric acid solution. The neutralized mixture was transferred to a separatory funnel, and the aqueous phase was separated. The oil phase was washed twice with warm water and dried in a vacuum rotary evaporator to recover free fatty acids from tuna oil (AGL-AA).The analysis of free fatty acids recovered from tuna oil is shown in Table 22:. A new Food (J) was formulated with tuna oil free fatty acids (AGL-AA) using the same procedure as in example 7. (vitamins, minerals, cholesterol) Feed J was tested in conjunction with a sample of Feed F and Feed G (from Example 6) using approximately 3 grams of shrimp post-larvae (Litopenaeus vannamei) at baseline. Each diet was tested with three replicates, using a total of nine baskets. Each basket contained 12 shrimp. All baskets were placed in a larger tank, ensuring consistent water quality. Water quality in the larger tank was maintained using bioflocs. Each basket was equipped with an automatic feeder. The shrimp were fed continuously. Measurements during the trial: At baseline, after two weeks, after four weeks, and after six weeks, the shrimp were counted and weighed together to determine total weight or biomass production. Feed supply was adjusted daily based on a projected growth curve and the average weight of the initial and final measurements.At the end of the growth trial, total weight, TCA, and survival rate were calculated. Results of the shrimp larvae growth trial (Tables 24, 25, and 26): As shown in Table 24, the diet containing alkali metal salts of fatty acids (FEED G) resulted in a better survival rate than the two feeds without alkali metal salts of fatty acids (FEED F, with 2.5% tuna oil, and FEED J, with 2.5% free fatty acids). Total weight gain or biomass at the end of the trial was significantly higher in the diet with alkali metal salts of fatty acids (FEED G) compared to the standard Feed F and Feed J with free fatty acids. The feed conversion ratio of Feed G was significantly lower than that of the other two feeds. These results demonstrate the superior performance of alkali metal salts of fatty acids compared to oils and fats (triglycerides) and free fatty acids. 14.Salmon smolt pellet tests. Three tests were performed on the pellets analyzed in the smolt growth trial: oil leakage, settling time, and flotation. The results are shown in Table 27. a. Oil leakage was measured as the oil loss from 100 g of feed incubated at 40 °C for 24 h in a heating chamber. Initially (P1), a sheet of blotting paper folded into four parts and contained in a box was weighed, then after placing 100 g of granules or pellets on it (P2), and again after removing all pellets and dust at the end of the incubation period (P3). Oil leakage was recorded in 6 replicate samples, and its percentage was calculated as: [(P3–P1) / P2) x 100]. Oil leakage decreased significantly with FEED II diets compared to FEED I diets. b.Sedimentation time: For pelleted feeds, the time it took for 40 pieces of feed to sink in a tank filled with fresh river water one meter deep was measured. The average settling time of the sample was considered. c. Buoyancy %: The number of 40 pellet pieces that did not sink in 120 seconds in the previous sedimentation experiment was recorded. As can be seen in the table above, FEED II performed better than FEED I in the oil leakage, settling time, and flotation tests, demonstrating the improved performance of pellets made with alkali metal salts of fatty acids. 15. Oxidation Stability of Compositions Comprising Alkali Metal Salts of Fatty Acids Six Petri dishes were placed in an oven at 40 °C: three containing 10 grams each of a sample of the same tuna oil used in Example 1, and three containing 10 grams each of a sample of alkali metal salts of fatty acids from the tuna oil produced in Example 1. After 48 hours, the peroxide value of the samples was analyzed. The results are shown in Table 28. The alkali metal salt composition of fatty acids exhibits significantly greater oxidation stability compared to oil. This characteristic allows for a longer shelf life in formulations made with alkali metal salt compositions of fatty acids. 16. Pellet Stability Test Six 100 ml Erlenmeyer flasks were filled with 75 ml of distilled water. Three of the Erlenmeyer flasks were filled with 2 grams of 1.5 mm pellets of FEED A from Example 5. The remaining three Erlenmeyer flasks were filled with 2 grams of 1.5 mm pellets of FEED B from Example 6. The six Erlenmeyer flasks were placed in an Erlenmeyer shaker at room temperature for 240 minutes at 200 U / min. After the shaking time was complete, the contents of each Erlenmeyer flask were filtered, the remaining pellets were washed with water, and weighed.The recovered pellets were analyzed for the presence of non-volatile matter in a furnace at 105 °C for 24 hours. The results are shown in Table 29. As previously mentioned, the use of alkali metal salts with fatty acids reduces exudation or material loss from pellets. Furthermore, it improves feed stability in water, reduces disintegration and nutrient leaching into the water, acting as a binder. In summary, the examples above reveal the enhanced advantages of using feeds containing one or more alkali metal salts of fatty acids: - Improved efficiency in feed production with smaller particle sizes. - Improved bioavailability of fatty acids and nutrients, observed through better biomass production and a higher survival rate, resulting in greater biomass production efficiency. - Increased feed digestibility; alkali metal salts of fatty acids can act as emulsifying enhancers in the digestive system of aquatic animals. - Greater stability and shelf life of fatty acids.- Greater pellet stability and shelf life. - Greater water stability, reduced water pollution. - High-energy pellets: Alkali metal salts of fatty acids can be added to the feed formulation at high levels, resulting in a high-energy pellet for maximum aquaculture performance improvement. - Cost-effectiveness: Feeds containing alkali metal salts of fatty acids are easy to produce and eliminate the additional processing steps and cost of including standard oil in the pellets. - Better use of natural resources: Byproducts obtained during oil processing that were previously discarded can be transformed into valuable products. - Improved PUFA production in the meat of animals fed the feed of the invention. - Suitable matrix for additives such as minerals and vitamins, as well as for pharmaceuticals.- Improves the survival rate of aquaculture animals. - Improves the efficiency of biomass production in a hatchery or farm for aquatic animals such as fish and crustaceans.

Claims

CLAIMS 1. A method for feeding a crustacean or fish in a crustacean or fish hatchery or farm, CHARACTERIZED in that the fish or crustacean is fed a feed comprising one or more alkali metal salts of fatty acids.

2. The method of claim 1, CHARACTERIZED in that the alkali metal of the alkali metal salts of fatty acids is selected from the group consisting of sodium, potassium, and mixtures thereof.

3. The method of claim 1, CHARACTERIZED in that the crustacean is Pacific white shrimp, black tiger shrimp, Indian white shrimp, Kurume shrimp, northern white shrimp, banana shrimp, Chinese white shrimp or Kona shrimp, giant river shrimp, or giant tiger shrimp.

4. The method of claim 1, CHARACTERIZED in that the fish is carp, tilapia, goldfish, roho, trout, bream, salmon, shad, coho, or sea bass. 5.The method according to claim 1, CHARACTERIZED in that the one or more alkali metal salts of fatty acids comprise alkali metal salts of one or more monounsaturated or polyunsaturated fatty acids, in particular monounsaturated fatty acids or. polyunsaturated C16-C30 fatty acids, and wherein preferably the amount of alkali metal salts of monounsaturated or polyunsaturated fatty acids is 10% by weight or more, relative to all fatty acids forming alkali metal salts of fatty acids.

6. The method according to claim 1, CHARACTERIZED in that the fatty acids of the alkali metal salts of fatty acids are derived from a marine oil and comprise at least three fatty acids selected from palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, alpha-linolenic acid, arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid. 7.The method according to claim 5, CHARACTERIZED in that the weight percent of the alkali metal salts of fatty acids is as follows: alkali metal salts of palmitic acid between 0.1 and 80%, alkali metal salts of palmitoleic acid between 0.1 and 50%, alkali metal salts of stearic acid between 0.1 and 50%, alkali metal salts of oleic acid between 0.1 and 80%, alkali metal salts of linoleic acid between 0.1 and 80%, alkali metal salts of alpha-linolenic acid between 0.1 and 80%, alkali metal salts of arachidonic acid between 0.1 and 20%, alkali metal salts of eicosapentaenoic acid between 0.1 and 60%, alkali metal salts of docosahexaenoic acid between 0.1 and 60%, and between 1 and 25% of one or more salts of selected fatty acids from the group that alkali metals. consists of C14:0, C20:0, C22:0, C24:0, C26:0, C18:1 n-7, C20:1 n-9, C22:1 n-9, C22:1 n-11, C24:1 n-11, C18:4 n-3, C20:2 n-6, C20:4 n-3, C21:5: n-3, C22:5 n-6, C22:5 n-3, C24:4 n-3, C24:5 n-3, C24:6 n-3, C26:4 n-3, C26:5 n-3, C26:6 n-3, C26:7 n-3, C28:4 n-3, C28:5 n-3, C28:6 n-3, C28:7 n-3, C28:8 n-3, C30:5 n-3 and C30:6 n-3, and wherein the weight percent of the alkali metal salts of fatty acids is expressed relative to the total fatty acid salt content in the food.

8. The method according to claim 5, CHARACTERIZED in that the fatty acids forming the alkali metal salts of fatty acids are derived from a by-product obtained in a process for producing an EPA and / or DHA concentrate from a marine oil. 9.The method according to claim 1, CHARACTERIZED in that the fatty acids of the alkali metal salts of fatty acids are derived from vegetable oil, such as linseed oil, or mixtures of one or more vegetable oils and one or more marine oils or processed marine oil products, such as a mixture of linseed oil and a product or by-product of a process for producing EPA and DHA concentrates from marine oil, for example, the heavy fraction.

10. The method according to claim 1, CHARACTERIZED in that feeding is carried out continuously or intermittently several times a day, such as 2 to 12 times a day.

11. The method of claim 1, CHARACTERIZED in that the feed comprises between 0.5 and 40% by weight of alkali metal salts of fatty acids, relative to the total weight of the feed.

12. The method of claim 1, CHARACTERIZED in that it leads to an increase in biomass growth and / or survival rate and / or omega-3 fatty acid content of the crustacean or fish compared to a crustacean or fish receiving the same amount of feed containing the same amount (expressed in g / day) of oil instead of the alkali metal salts of fatty acids.

13. The method of claim 1, CHARACTERIZED in that the feed is in powder or granule form.

14. The method of claim 1, CHARACTERIZED in that the feed further comprises one or more components selected from the group consisting of animal protein, vegetable protein, carbohydrates, vitamins, minerals, cholesterol, and lecithin.

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