Mercury in muscle and brain of catfish from the Madeira river, Amazon, Brazil.

Abstract The central nervous system is a critical target for Hg toxicity in all living organisms. Total Hg (THg) was determined in brain and muscle samples of 165 specimens of eight species of catfish ( Brachyplatystoma filamentosum; Brachyplatystoma platynemum ; Brachyplatystoma rousseauxii ; Brachyplatystoma vaillantii ; Phractocephalus hemiliopterus ; Pseudoplatystoma punctifer; Pseudoplatystoma tigrinum ; Zungaro zungaro ) from the Madeira River, Brazilian Amazon. Despite the narrow range of Fishbase trophic level (4.2–4.6) the median THg concentrations ranged from 0.39 to 1.99 mg/kg and from 0.03 to 0.29 mg/kg respectively in muscle and brain from the studied species. Overall, the median concentration for all samples analyzed was 0.93 mg/kg and 0.16 mg/kg respectively in muscle and brain; most samples (76%) showed muscle Hg concentrations >0.5 mg/kg. There were statistically significant THg differences between sex (female>males). The correlation between THg concentrations in muscle and brain was statistically significant ( r =0.9170; p r =0.3163; p =0.0001) and brain ( r =0.3039; p =0.0003) THg; however, fish age was negatively and significantly correlated ( r =−0.2991; p =0.0012) with THg in muscle but not with THg in brain ( r =−0.0190; p =0.8492). Amazonian catfish accumulate high levels of Hg in muscle and brain; however, brain-THg concentrations can be predicted from muscle-THg. Muscle-Hg in catfish can be a tool to detect brain-Hg concentrations associated with environmental Hg.