58.FISH MEALS PLANT BUSINESS

Fishmeal is a generic term for a nutrient-rich feed ingredient used primarily in diets for domestic animals, sometimes used as a high-quality organic fertilizer. Fishmeal can be made from almost any type of seafood but is generally manufactured from wild-caught, small marine fish that contain a high percentage of bones and oil, and usually deemed not suitable for direct human consumption. These fishes are considered 'industrial' since most of them are caught for the sole purpose of fishmeal and fish oil production. A small percentage of fishmeal is rendered from the by-catch of other fisheries, and by-products or trimmings created during processing e.g., fish filleting and cannery operations of various seafood products destined for direct human consumption.

The fishmeal and fish oil industries are one of the few major animal industries existing today that still relies greatly on a "hunting-and-gathering" technique. Most fish rendered into meal and oil are captured at sea. Millions of tons of fishmeal are produced worldwide. Contrary to recent popular beliefs, most fishmeal and oil are produced from sustainable, managed, and monitored fish stocks, reducing the possibility of over-fishing. The supply is presently stable at 6.0 to 6.5 million tons annually. Approximately 4 to 5 tons of whole fish are required to produce 1 ton of dry fishmeal. Peru produces almost one-third of the total world fishmeal supply. Other principal fishmeal-producing countries are Chile, China, Thailand, U.S.A., Iceland, Norway, Denmark, and Japan (Table 1 ). Major groups of industrial fish rendered into fishmeal are anchovies, herrings, menhaden, sardines, shads, and smelts.

Cooking, pressing, drying and grinding the fish make fishmeal. There are several processing methods to produce good quality fishmeal, but the basic principle involves separation of the solids from the oil and water. When no oil needs to be removed, such as with lean fish, the pressing stage is often omitted. During cooking, the fish move through a long, steam-jacketed, screw conveyor cylinder, that coagulates the tissue proteins. This is a critical process, also responsible for sterilizing the product and preparing it for removal of the "liquor", which is a mixture of oil, water, and soluble protein. Once cooked, the liquor is removed by pressing, and the solid residue that remains is called "presscake". The liquor is centrifuged to remove the oil, which is often further refined before being transported to storage tanks. Prior to storage, it is essential to add an antioxidant to stabilize the oil, and the stored oil should not come into contact with air, heat or light to maintain its quality.

Balancing nutrients in diets by using the minimum amount of fishmeal to meet specific amino acid requirements for fast growth and reproduction and reducing feed costs constitute one of the principal objectives in formulation of fish feeds. Another important aim in feed formulation is to increase dietary nutrient density and digestibility of the feed to increase biological performance and to reduce nutrient leaching and water-quality degradation. The aquaculture industry must continue to seek out alternative sources of high-quality plant and animal-based protein ingredients for their feedstuffs. Presently, this is an active area of research in aquaculture nutrition.