Comparison of cadmium and chromium bioconcentration factors between scaled and scale less fish species: common carp and sutchi (striped) catfish

Water-borne, indissoluble heavy metals are bioaccumulated in fish (human food source). In this research, chromium (Cr) and cadmium (Cd) bioconcentration factors (BCFs) in the skin, gills, scales, livers and muscles of two widely-consumed fish species, scaled common carp Cyprinus carpio and scaleless catfish Pangasius hypophthalmus were compared. Lethal concentrations of Cd and Cr (64.89 & 7.46, and 84.8 & 17.05 mg/L for the catfish and carp, respectively) were determined during 96 hrs (96 h LC50), and the fishes were exposed for 15 days. Then the tissue samples were chemically digested and the contents of Cd and Cr were determined using atomic absorption. Total contents of Cr and Cd in the catfish's tissues were 2286.11 & 360.73, and those of Cr & Cd in carp were 734.71 & 725.67 μg/g.dw (excluding the scales), respectively. Metal concentrations in the water residues (day 15) revealed lower Cr and Cd (0.059 & 0.0036 mg/L) in the catfish than those in the carp media (0.1 & 0.0412 mg/L, respectively). In common carp, BCF of Cd was as liver > skin > gills > muscle > scales, and those in the catfish marked as liver>muscle >gills >skin. The BCF of Cr in common carp ranked as gills>liver>skin>scales>muscle, and the catfish showing a BCF pattern of Cr as liver> muscle>skin>gills. This study signifies that small amounts of cadmium and chromium with high BCFs especially in the muscles of scale less fish (catfish) threat consumers’ health.