Off-flavor detection in tilapia reared in cages in tropical lakes

Aquaculture activity in the aquatic ecosystem can intensify the presence of the semi-volatile compounds geosmin (GSM) and 2-methylisoborneol (MIB). These metabolites are the leading cause of off-flavor in fish from aquaculture facilities, even at small concentrations. Thus, this study aimed at evaluating the influence of tilapia production in cages on the availability and production of the metabolites GSM and MIB in water and sediment. Samples were obtained from two Brazilian natural tropical lakes (Palmas and Palminhas) in alternate months, in both dry and rainy periods. The physicochemical parameters of water and sediment samples were measured in situ and in the laboratory. Water samples were collected for quantitative analysis of the phytoplankton community, and fresh tissue samples from ten tilapia (Oreochromis niloticus) to analyze semi-volatile compounds (GSM, MIB, and beta-ionone). Samples from fish farms in Palminhas Lake present higher aqueous concentrations of phosphorus and ammonia, a higher abundance of Cyanophyceae, and the presence of GSM and MIB in sediment and fish flesh. Conversely, Palmas Lake presented low nutrients and a higher abundance of Chlorophyceae, with GSM presence and MIB absence. Therefore, eutrophication caused by fish farming in these tropical lakes with long water retention time coupled with inadequate governmental policies leads to negative feedback that leads to off-flavors in fish products.