Relations between some environmental parameters and the fish yield as a basis for a predictive model

Summary

Ponds may be a useful tool in the study of the interaction between the nutrients and the composition of the community of standing waters. The necessity of this type of study is justified by the impossibility to predict the metabolic change of the whole ecosystem if some of its levels are changed, even after a careful investigation of its single or paired levels. It has been demonstrated in particular with regard to the effect of the fish stock which, though contributing directly by a small fraction only to the metabolism of the whole community, induces when altered considerable changes both quantitative and qualitative ones. As the data on the fish production from ponds are much more reliable than are those from any other type of aquatic habitats, it is advantageous to use ponds for the assessment of the relations between the fish production and the other parameters of the environment. From the regression lines between different parameters and the fish production, it is possible to develop mathematical models describing the interaction between parameters and the fish yield.