Organochlorine pesticides residues in feed and muscle of farmed Nile tilapia from Brazilian fish farms.

Organochlorine pesticide (OCP) concentrations were determined in fish muscle and feed collected from four different fish farms in Brazil. Nile tilapia from two growth stages, juveniles and adults, collected at two intensive tanks farms (IT1 and IT2) and two net cage farms (NC1 and NC2), were analyzed by High Resolution Gas Chromatography/High Resolution Mass Spectrometry. Pesticides were detected in almost all samples, but no samples exceeded international maximum limits for safe fish consumption. ΣDDT was the predominant pesticide in fish muscle, found in all fish samples, and endosulfan was the most predominant pesticide in feed, found in all feed samples. No significant correlation (p>0.05) was observed between the different growth stages and OCP concentrations, although slightly higher OCP concentrations were observed in adults. Among the rearing systems, NC farmed fish presented higher lipid levels and, consequently, higher OCP concentrations than fish from IT farms. Some OCPs (ΣHCH, aldrin, dieldrin and endrin) presented strong positive correlations (p<0.05) between feed and fish muscle concentrations, while others (ΣDDT, mirex, chlordane, ΣHCB and endosulfan) presented no correlation. However, the low levels of the sum of contaminants found in most of the feed samples may explain the low contaminant levels in fish tissue.