Mercury concentrations of five species of Antarctic fish collected from CCAMLR Subareas 88.1 and 88.2

The mean mercury level for the D. eleginoides 1998 sample was 0.43 mg/kg-1, which is slightly lower than the permissible level of 0.5 mg/kg-1 set by the New Zealand Food Safety Authority (NZFSA). In contrast, mean levels of mercury for D. mawsoni were 0.10 mg/kg-1 in the 1998 samples and 0.16 mg/kg-1 in the 2006 samples, both of which are well below the permissible level.
Mercury levels were highly variable both within and between the five species studied. Once the factors length and year had been accounted for, the mercury levels in D. eleginoides were over four times greater than in D. mawsoni. The three prey species had intermediate mercury levels, with Whitson’s grenadier (Macrourus whitsoni) being only slightly lower than D. eleginoides, whilst the levels of ice fish (Chionobathyscus dewitti) and blue antimora (Antimora rostrata) were at low levels, similar to that of D. mawsoni. Mercury levels were positively correlated with fish length in four of the species. Mercury levels also showed positive trends with depth for D. eleginoides and C. dewitti, and with area for A. rostrata. Mercury levels showed no trends with any factors for M. whitsoni.
The low levels of mercury in D. mawsoni relative to its prey species and the four-fold difference in mercury concentrations between it and D. eleginoides were unexpected. Reasons for these different levels of bioaccumulation were explored including differences in diet, growth and longevity, and location. We conclude that these results can only be explained by a lower rate of mercury assimilation and/or a higher rate of mercury elimination by D. mawsoni.