Why mercury concentration increases with fish size? Biokinetic explanation

Abstract

In field-collected juvenile blackhead seabream Acanthopagrus schlegeli schlegeli, measured total mercury (THg) and methylmercury (MeHg) concentrations were related to 0.19 and 0.33 power of fish mass over a wide size range (more than 50-fold). The causative factors remain unclear. In this study, size-dependent biokinetic parameters for both inorganic mercury [Hg(II)] and MeHg were estimated, and their relative contributions to size-related Hg accumulation were further assessed. Except for the MeHg dietary assimilation efficiency (AE), which was not affected by the fish size, other examined biokinetic parameters showed either positive (Hg(II) AE) or negative correlations (growth rate constant-g, dissolved uptake rate constant-ku and efflux rate constant-ke) with fish size. The biokinetic variation explained the observed allometric pattern of Hg accumulation in juveniles. Especially, both size-related g and ke were the key drivers. The current study addressed the importance of size-related biokinetics, in particular the ke and g, which have important implications to manage Hg contamination in fisheries.