The world demand for sea food is increasing dramatically year by year, although an annual upper limit of 100 million tons is set so as not to exhaust reserves. It is for this reason that there is a considerable move towards modernizing and intensifying fish farming.
Tests prove the effect of potassium diformate on the quality of fish under tropical conditions. -- Almost one-third of the world fish harvest is not used for direct human consumption, but is converted into fish meal or fish oil for further application in animal feed. Of the 75 million tons of fish about 25 million tonnes is therefore handled and processed in other ways than fresh, frozen, smoked or canned (Balios, 2003).
Recording feed intake To be able to select directly for feed efficiency, feed intake of individual fish should be recorded. Until recently, difficulties in measuring individual feed intake on a large scale have prevented accurate genetic evaluation of feed utilization traits in farmed fish. To solve the recording challenges, we have applied the X-ray method to measure feed intake and feed efficiency of thousands of individuals in pedigreed populations of farmed rainbow trout (Oncorhynchus mykiss) and European whitefish (Coregonus lavaretus).
Most fish farmers and ornamental fish hobbyists buy the bulk of their feed from commercial manufacturers. However, small quantities of specialized feeds are often needed for experimental purposes, feeding difficult-to-maintain aquarium fishes, larval or small juvenile fishes, brood fish conditioning, or administering medication to sick fish. In particular, small ornamental fish farms with an assortment of fish require small amounts of various diets with particular ingredients. It is not cost effective for commercial manufacturers to produce very small quantities of specialized feeds. Most feed mills will only produce custom formulations in quantities of more than one ton and medicated feeds are usually sold in 50-pound bags.
In trout farming, the amount and suitability of feed used determines the profitability of production. Trout and other salmonids can efficiently digest foods that contain primarily protein (mostly from fish), and can obtain some of their energy from fats and, to a lesser extent, from carbohydrates. Fry and fingerling trout require a higher protein and energy content in their diets than larger fish. Fry and fingerling feed should contain approximately 50 percent protein and 15 to 20 percent fat. Feeds for larger fish typically contain 38 to 45 percent protein and 10 to 18 percent fat. The switch to lower protein formulations usually occurs at the transition from a "crumble" feed to a pelleted ration, called a "growout" or "production" diet. High energy diets may contain 45 to 50 percent protein and 18 to 24 percent fat. Several brands of high quality commercial trout diets are available, and although a farm could produce its own fish food, it is not usually economical to do so.