Use of phytophagous fish to control aquatic plants

Abstract

Effectiveness of grass carp in control of water weeds depends on a number of factors, the most important being water temperature species composition of plants, individual weight of fish and stock density. Under thermal conditions of Northern and Middle Europe an effective control of water weeds requires very dense stocks with a high initial weight of fish. Such dense stocks are not always economically justified. However, grass carp used as a supplement to mechanical and chemical methods applied so far, may contribute to the limitation of water overgrowth stimulating at the same time additional resources for fisheries. Under the same climatic conditions grass carp proved to be very effective in controlling water weeds in water bodies heated by effluents from thermal power stations. Stocking of water in tropical climates as well as in Southern Europe, may solve that problem of overgrowth of water bodies without using the traditional methods. In addition to reduction of aquatic plants phytophagous fish may cause considerable changes in biocenosis. Controlling of water blossoms with use of silver carp ( Hypophthalmichthys molitrix Val.) has been discussed. Application of this species for controlling the phytoplankton requires further study.