Bioaccumulation of priority trace metals in edible muscles of West African lungfish (Protopterus annectens Owen, 1839) from Nyabarongo River, Rwanda

Abstract Heavy metal pollution and accumulation in aquatic ecosystems present serious threats to sustainability. In the current study, the heavy metal content of water and edible muscles of a piscivorous fish (Protopterus annectens) as well as bioaccumulation of the heavy metals in fish tissues were evaluated. Samples of water (n = 6) and fish (n = 6) were taken from Kirinda bridge and Ruliba station on Nyabarongo river and analyzed by UV spectroscopy and atomic absorption spectrometry, respectively. The heavy metal concentrations in water were: iron (0.63 ± 0.02 and 1.61 ± 0.03 mg/kg), manganese (0.53 ± 0.002 mg/kg at Ruliba station), chromium (0.06 ± 0.002 mg/kg at Kirinda bridge), cadmium (0.106 ± 0.002 mg/kg at Ruliba station) and lead (0.75 ± 0.02 and 0.051 ± 0.01 mg/kg). Edible muscles of Protopterus annectens contained 336.0 ± 0.70, 302.6 ± 1.22, 6.4 ± 0.26, 44.7 ± 0.20, 138.2 ± 0.17 and 302.4 ± 1.50 mg/kg of iron, manganese, copper, zinc, chromium and lead at Kirinda bridge and 272.8 ± 0.36, 292.2 ± 0.25, 8.8 ± 0.36, 135.2 ± 0.15, 148.0 ± 0.21 and 432. 0 ± 0.50 mg/kg of iron, manganese, copper, zinc, chromium and lead, respectively, at Ruliba station. Most of the heavy metal contents were above the recommended levels. Bioaccumulation factors recorded in Protopterus annectens ranged from 403.2 to 15,130 L/kg, implying that consumption of this fish could pose deleterious health risks. The study suggested that P. annectens could be used as a sentinel organism for biomonitoring of aquatic ecosystems.