Enzymatic GST levels and overall health of mullets from contaminated Brazilian Lagoons

► Enzymatic GST assays are usually conducted inappropriately, with no previous standardizations. ► Extensive standardization assays were conducted with mullet liver to compare seasonal GST levels in contaminated lagoons. ► Overall mullet health condition was also investigated, using the Fulton Condition Factor and macroscopic abnormalities. ► Results corroborated the differences in enzymatic levels from the different study areas. ► GST levels are good indicators of environmental contamination and should be further studied using standardized assays.