The relationships between fish heavy metal concentrations and fish size in the upper and middle reach of Yangtze River

Abstract

Heavy metal (Cd, Cr, Cu, Hg, Pb, Zn) concentrations identified in the muscle tissue of seven fish species (silver carp Hypophthalmichthys molitrix, grass carp Ctenopharyngodon idellus, crucian carp Carassius auratus, carp Cyprinus carpio, Coreius heterodom, catfish Silurus asotus, and yellow-head catfish Pelteobagrus fulvidraco) from the Yangtze River were measured. Additionally, the relationships between fish size (length and weight), condition factor, and metal concentrations were investigated by linear regression analysis. Metal concentrations (mg/kg wet w.) were found to be distributed differently amongst the different types of fish. The highest concentrations of Cu (1.22) and Zn (7.55) were measured in yellow-head catfish. The catfish also showed strikingly high Cd (0.115) and Hg (0.0304) concentrations. The crucian carp and common carp showed highest levels of Pb (0.811) and Cr (0.239), respectively. The results of comparisons made between metal concentrations and the fish size parameters demonstrated positive relationships between fish sizes and metal levels in most cases, with negative relationships found only between mercury and chromium levels in the size of catfish and yellow-head catfish. The variance observed in the relationships between metal concentration and fish size, as measured among different fish species, may be related to the differences in ecological needs, swimming behaviors, and metabolic activity.