Mercury Concentrations in the Fish Community from Indrawati River, Nepal

This study quantified concentrations of mercury (Hg) and its trophic transfer along the fish community in the Indrawati River, Nepal. Stable isotope ratios of nitrogen (δ¹⁵N) and carbon (δ¹³C), complemented by stomach contents data were used to assess the food web structure and trophic transfer of Hg in 54 fishes; 43 Shizothorax richardsonii and 11 Barilius spp. [B. bendelisis (1), B. vagra (3) and B. barila (7)]. Sixty-one muscle samples (including six replicates) were used for the analysis of total mercury (THg) and stable isotopes. Mean THg concentrations in B. spp. and the more common species S. richardsonii was observed to be 218.23 (ng/g, ww) and 90.82 (ng/g, ww), respectively. THg versus total length in both S. richardsonii and B. spp. showed a decreasing tendency with an increase in age. Regression of logTHg versus δ¹⁵N among the fish species showed a significant positive correlation only in S. richardsonii indicating biomagnification along the trophic level in this species.