Methyl mercury bioaccumulation in long-finned eels, Anguilla dieffenbachii, from three rivers in Otago, New Zealand

This research focuses on mercury (Hg) bioaccumulation in New Zealand long-f inned eels (Anguilla dieffenbachii) from the aquatic environment. Total Hg (Hg-T) and methyl mercury (MeHg) concentrations were determined in muscle t issue from eels living in three South Island rivers dominated respectively by urban, native bush and agricultural land-uses. Most of the Hg in eels wa s MeHg(> 84%) and the MeHg concentrations increased linearly with both leng th and eel age for a given river habitat. The annual growth rates for eels from the urban and agricultural streams were greater than for eels from the native bush stream. The average MeHg accumulation rate was significantly h igher for the eels in the agricultural stream compared with either the urba n or native bush catchments. These results are probably due to a combinatio n of factors and further investigations in the lower food web are necessary to elucidate the exact mechanisms of MeHg bioaccumulation in these creatur es. (C) 2000 Published by Elsevier Science B.V. All rights reserved.