Microcystin-LR contamination in Nile tilapia (Oreochromis niloticus) in some water bodies in Sri Lanka

Microcystin-LR (MC-LR) is a cyanotoxin produced by certain cyanobacteria species. It is toxic to humans and animals. Several studies have demonstrated that cyanotoxins accumulate throughout the food chain, eventually reaching high levels in freshwater fish. The Nile tilapia (Oreochromis niloticus) is the most popular freshwater fish in Sri Lanka and in most Asian countries. The current study sought to determine MC-LR concentration in Nile tilapia collected from thirteen freshwater reservoirs; Nallachchiya, Galkulama, Anakattiya, Padaviya, Nachchaduwa and Kalawewa in Anuradhapura District, Parakrama Samudraya, Halmilla, Kaudulla and Ambagaswewa in Polonnaruwa District, Muwapatigewela in Ampara District, and Ulhitiya and Rathkinda in Badulla District. The fish and water samples were collected, transported, and analyzed following standard procedures, and MC-LR was determined using a BEACON ELISA kit. To determine the MC-LR and Tolerable Daily Intake (TDI) levels in fish, samples of the fish skin, flesh, and head were collected and analyzed according to World Health Organization (WHO) guidelines. A comparison was made between the MC-LR levels of fish in different reservoirs and the WHO TDI standards (0.04 μgkg-1day^-1). From the Padaviya, the highest mean concentrations of MC-LR were found in fish skin (3004.25 ± 30 μg kg^-1), following head (836.25±18 μg kg^-1) and flesh (41.67±8 μg kg^-1). The average daily intake of MC-LR in the skin and head of all samples exceeded the WHO's TDI (0.04 μg kg-1 day^-1). According to the findings of this study, consumption of fish heads and skin increases the risk of MC-LR accumulation in the human body by a significant amount.