Expert Advisory Committee twelfth session, Ouagadougou 10-14 June 1991: monitoring of aquatic environment

OCP/EAC.LZlBriefing Paper no. 5 Expert Advisory Committee Twelfth session Ouagadougou. 10-14 June 1991 ,1 . Briefing session B June 1991 * a,L MONITORING OF THE AQUANC ENVIRONMENT n I * f t As in previous years, the aquatic monitoring activities comprised four main aspects:\l '- L the screening of new larvicides, long-term monitoring, coordination of aquatic monitoring activities and the training of national hydrobiologists. Screening of new larvicides Since chlorphoxim is no longer being marketed, gutter tests carried out on two phoxim formulations (40Vo EC and 50Vo E,C) showed that they are less toxic than chlorphoxim and comparable with each other. The Ecological Group has therefore authorized the operational use of this larvicide (50Vo EC formulation). As regards OMS 3050 (a pyrethroid), its gutter impact on the non-target invertebrates is less than that of phoxim but diluted solutions conserved in cold storage for several weeks seem to be 100 times more active on S. damnosum. Tests are therefore being continued with this product so as to better evaluate its toxicity level both on fishes and on invertebrates. Other pyrethroids (OMS 3055, OMS 3056, Bioresmethrin and Betacyfluthrin) have also been tested on aquatic invertebrates and the samples are currently being processed. It should however be noted that OMS 3055 and OMS 3056 had no sufficient efficacy on S. damnosum at the doses tested. On the other hand, Bioresmethrin gave satisfactory results on the vector with an impact on the non-target fauna that is comparable to that of.chlorphoxim. L.ong-term monitoring In most cases, the long-term use of the larvicides has not caused serious and irreversible disruptions of the ecosystems. Changes have been recorded in the abundance and relative composition of the benthic invertebrate communities but they do not seem to be definitive since they vary from one year to another according to the type of larvicide used and the extent of the pressure exerted. The more the recommendations of the Ecological Group concerning the use of permethrin and carbosulfan are respected the more minimal these changes will be. With regard to pyraclofos, the medium-term treatment data confirm the acceptable impact of the product on the non-target fauna. Coordination of monitoring activities All the monitoring results have been centralized in Ouagadougou, checked and analysed and tables and graphs produced for the national teams and the Ecological Group. The OCP hydrobiologist, who is the coordinator of the monitoring of the aquatic environment, sees to the proper implementation of the monitoring programme and the observance of the work protocols, serves as the liaison with the OCP Administration and organizes the annual hydrobiologists' meeting. Hydrobiologists have been trained for Sierra lrone. They will become operational after receiving the technical equipment ordered by the Programme. At the moment, the monitoring continues to be undertaken by the Programme team.