Levels of environmental pollution are commonly assessed via biomarkers, one of which is the activity of the cholinesterase enzyme. This study analyzed activity of cholinesterase in muscles samples of Rineloricaria kronei fish in order to assess levels of anticholinesterasic pollution in coastal rivers of the Serra do Mar mountain range in southern Brazil. A total of 93 specimens were collected at six sites along the Caiuru, Pinto and Sambaqui rivers between August and November 2007. Specimens were collected via electrofishing, with a sampling effort of 50m/hour. Cholinesterase enzyme (ChE) activity was measured in extracted muscles in the laboratory and the results analyzed using one-factor ANOVA, followed by Dunnett’s test. ChE activity at sites 2, 3 and 4 was similar to that observed in control specimens. Mean activity was lower than the control (p<0.05) at Site 1 (4.6+1.5) and highest at Site 5 (98.7±16.2). Site 5 appears likely to be contaminated with heavy metals, based on the increased activity of the cholinesterase enzyme. This study suggests that the cholinesterase biomarker can be used not only to demonstrate the presence of organophosphate and carbamate pesticides, but also to indicate the presence of heavy metals
