MANAGEMENT OF POND ECOSYSTEMS AND TROPHIC WEBS

The productivity of common carp (Cyprinus carpio L.) varies among cont inents according to current fish-pond management practices and variati ons in trophic conditions and/or fish-carrying capacity. ''Biomanipula tion'' as a management tool for aquatic communities is aimed at exploi ting ''top-down forces'' or the ''trophic cascade'' in order to influe nce the food-web and efficiency of energy transfer from primary produc ers to fish. The aim of food-web manipulation in fish-ponds has usuall y been in contrast to that in natural waters. This paper focusses on t he basic ecosystem processes and provides an overview of the efficienc y of energy transfer in various lakes, ponds and reservoirs which may be influenced by food-web manipulation using different approaches (fer tilization, stocking. chemical treatment. supplementary feeding). Seve ral sources of data have also been summarized illustrating the relatio nships between stocking rate and fish production in a variety of natur al and artificial ecosystems.