PARENT SESSION
6F Managing and communicating pesticide risks
9:00 AM to 7:00 PM, Tuesday, 08 May 2001
Session Chair:

(T/FF243) STUDIES ON THE ACUTE TOXICITY OF TEN COMMONLY USED RICE PESTICIDES TO NILE TILAPIA (Oreochromis niloticus L.).

Al-Arabi, Syed^1,2, Islam, Nargis³, ^{1 2 3}

ABSTRACT- The cumulative mortality of Oreochromis niloticus (L.) was studied by using ten widely used rice pesticides namely Basudin, Dimecron, Ekalux, Miral, Zithiol, Furadan, Padan, Cymbush, Decis and Sumicidin at varying exposures. The aim of the study was to assess the impact of these pesticides on rice-cum-fish farming in Bangladesh. LC50 values for 1, 3, 6, 12, 24, 48, 72 and 96 hours were determined using the OECD Guidelines For Testing Of Chemicals (1984). The water quality parameters of the test water showed little fluctuations. The 96-hours LC50 values of Basudin, Dimecron, Ekalux, Miral, Zithiol, Furadan, Padan, Cymbush, Decis and Sumicidin to Nile Tilapia were 1.46, 13.33, 0.95, 0.049, 9.03, 2.253, 0.84, 0.015, 0.014 qnd 0.007 ppm respectively. There were significant behavioural anomalies in the fish, like loss of equilibrium, erratic swimming, violent spasm, fast opercular activity, excess secretion of mucus, dark colouration on skin etc. due to the exposure of different pesticides at different concentrations were also observed in the 96-hours trial period. A 15 days long recuperative study was also performed to allow the assessment of the different levels of prolonged toxic effects of different pesticides. All the survivors from different concentrations of Miral, Cymbush, Decis and Sumicidin exposure died shortly after transfer to clean water, while survivors from all the concentrations of Dimecron and Zithiol treated and lower concentrations of Basudin and Furadan exposed fish remained all alive throughout the 15 days recuperation observations. Results show that permissible concentrations of Dimecron and Zithiol are almost non-toxic, while Furadan is less-toxic, Basudin and Ekalux are toxic and Padan, Miral, Cymbush, Decis and Sumicidin are extremely-toxic to this fish species.

Key words: Pesticides, Acute toxicity, (Oreochromis niloticus L.), Rice-cum-fish farming