The effectiveness of biomarkers has been demonstrated in sev-eral studies on the toxicity of pesticides to fish [16,25,32]. Underphysiological conditions, reactive oxygen species (ROS) are contin-uously produced by O2metabolism. Antioxidant enzymes such assuperoxide dismutase (SOD), catalase (CAT), and glutathione per-oxidase (GPx) scavenge these free radicals to prevent oxidativedamage. The glutathione-S-transferase (GST) is a ohase II enzymethat mediates the conjugation of xenobiotics with reduced glu-tathione (GSH) in many organisms, including plants, mammals andfish [38]. ROS are commonly associated with cellular injuries, espe-cially with alterations to macromolecules, such as the DNA, lipids,and proteins. Several tests are known to quantify damage in thosemolecules, e.g., comet assay for DNA, lipid peroxidation (LPO) formembranes, and protein carbonylation (PCO) for proteins, and thushave high predictive value as effect biomarkers [28].