Beschreibung:
<jats:p> A complete ecosystem analysis may be possible from the point of view of optimal control theory. Such an analysis has three parts: </jats:p><jats:p> (1) Determination of model structure </jats:p><jats:p> (2) Determination of coefficients for a given model </jats:p><jats:p> (3) Determination of optimal management programs for the model obtained by (1) and (2). </jats:p><jats:p> The methods of optimal control theory are suitable for examining these three parts separately. The essential ingredients for each part is an optimization concept. </jats:p><jats:p> Only the second and third parts are examined in detail here. For concreteness, a specific model structure for a prey-predator system is used. It is then shown that certain coefficients of this model are determined directly, given that the predator feeds in such a way as to maximize his caloric intake. By adding man's external controls to the model, the system can then be managed in a fashion to minimize some cost criterion. </jats:p><jats:p> To illustrate this latter point, the methods of optimal control theory are used to determine a manage ment program for controlling water quality in a natural lake at minimum cost. Man's control is re presented by the application of an algacide on the phytoplankton-zooplankton (prey-predator) system in the lake. The introduction of temperature dependence as a driving force in a simple dynamical model appears to be adequate for the determination of the optimal control program. </jats:p>