MINIMIZING WASTE THROUGH BIOENERGETICALLY AND BEHAVIORALLY BASED FEEDING STRATEGIES

Most species in aquaculture are new to cultivation and so behave like wild animals. They are products of evolution, with adaptations to spec ific habitat conditions. In the wild, food is not available uniformly throughout the day or the year, or in space, and rarely exceeds the fi shes needs. Competition is energetically expensive, reducing growth ef ficiency. Consequently, feeding activity patterns have evolved, implyi ng internal appetite rhythms, which optimise food intake under these v arious constraints. Salmonids can adapt quickly to short term variatio n in food availability, but show seasonal genetically determined anore xia. Rational feeding regimes in culture should take all such features into account When appetite is high naturally, food should be presente d so that it is economically indefensible - where every individual can eat, and where fighting does not pay. At periods of anorexia it will be prudent to offer no food. Manufacturers' feed tables are usually re gimes devised to meet the bioenergetic needs of fishes, as they are un derstood in a physico-chemical sense. While useful first approximation s, they do not take into account these evolutionary features of the fi shes, and can lead to waste. Methods of presentation are described whi ch allow the fish to determine when food shall be available, and in wa ys which, by diminishing the advantages of social dominance, ensure re latively even opportunities to feed for all individuals in the populat ion. Allowing the fish to set the time-table reduces the likelihood of waste.