ABSTRACT
The mussel Anodontites trapesialis (Lam, 1819) was used as an indicator of organochloride pollutans in the Canoas River, located in the municpality of Mococa (21-25'08"S and 47W), State of Säo Paulo, Brazil. Biological monitoring was performed for one year at the site of an orange grove on the left bank of the river. Forty-five animals were placed in aluminum enclosures on the river bottom at this site and 4 animals were sacrificed for pesticide analysis at 3-month intevals, each corrsponding to one season of the year. Pesticides were extracted by the method of Bedford et al., (1968), modified, and the analyses were performed bay gas phase chromatography equipped with an elelctron capture detector. The aninals were found to have been exposed to DDT. Lindane and Heptachlor. Variation in Aldrin and Dieldrin levels was not significant enough to permit inferences. Endrin was not detected in any of the analyses