Species composition of planktonic Rotifera, Cladocera and Copepoda in the littoral zone of Lake Ladoga

In Mexico, more than 40 000 ha of dams, lakes, canals and drains are infested with waterhyacinth (Eichhornia crassipes). To prevail over the problems resulting from this infestation, specific management programs are needed. Under a national program to control the waterhyacinth, guidelines to deal with the related ecological, social, technical and economic factors, and specific strategies to reduce coverage were developed. The ecological factors which were noted include the identification of the most affected areas and the consequences of proposed treatments. The social aspects embraced the stimulation of user awareness as to the importance of water quality, the creation of organizations to coordinate user-sponsored control activities, and the awakening of a community identity. Basic to all are the technical and economic aspects which make the activities feasible and operational. Examples are given of control by means of water level management, mechanical controls using trituration, and the application of chemical and biological agents, all of which may be combined in an integral program.