LONG-TERM QUANTITATIVE ECOLOGICAL ASSESSMENT OF INSECTICIDES TREATMENTS IN 4 AFRICAN RIVERS - A METHODOLOGICAL APPROACH

In West Africa different insecticides had been applied in selected riv er areas for the reduction of the blackfly populations vectors of Onch ocerca volvulus, a parasite causing blindness. To evaluate the possibl e long term effects of the larvicides on the non target fauna an aquat ic monitoring programme has been up from the initial phase of the proj ect. Addressing the attention to the invertebrates data collected in f our countries during a maximum period ranging from 1977 to 1996, this paper shows and discusses the data analysis strategy for the measure a nd interpretation of the biological variation. In particular the appli cation of quantitative ecological analysis methods: Principal Componen t Analysis, rank abundance models and the community diversity indexes, is critically discussed and comments are given to the ecological inte rpretation of the results. (C) 1998 Elsevier Science Ltd. AII rights r eserved.