DETERMINATION OF MINERAL REQUIREMENTS OF FISH

The precise feeding of fish entails a mineral supply tailored to meet requirements. The aim is an optimal supply status, that manifests itse lf in excellent health and productivity, combined with minimal water p ollution. Having considered possible methods for determining requireme nts (i.e. factorial deduction or balance studies amongst others), the dose-response technique appears to be the best option. Sensitive indic ators that measure utilization should be given priority, even when the y have to be developed, and it is important to include as parameters b iochemical criteria as well as retention of the elements in organs or the whole body. Here, however, the extent of the knowledge on homeosta tic regulation of minerals will have to be extended. Work on availabil ity of minerals should be carried out, in the suboptimal part of the s upply range, under identical conditions. In estimating requirements, m any factors (productivity level, chemical form of the compound, diet c omposition, interactions with other minerals and with waterborne eleme nts) have all to be considered. Connections between these factors are presented in this paper, with examples given.