Mercury methylation by fish intestinal contents

Abstract

A new radiochemical method was applied to the examination of Hg methylation in fish intestinal contents. Intestinal contents of freshwater fish [Esox lucius, Stizostedion vitreum vitreum, S. canadense, Perca flavescens, Coregonus clupeaformis, Coregonus sp. Catostomus sp.] were capable of converting 203Hg2+ to CH3203Hg+. This activity was observed in fish from 5 of 6 lakes tested whether or not there was Hg pollution. Bacterial activity in the intestinal contents is most likely responsible for this methylation. Methylating activity of piscivors increased with decreasing quantity of intestinal contents. Generally, pike and walleye intestinal contents methylated a larger fraction of 203Hg2+ than those of whitefish and suckers. These data contradict the previous general conclusion that there is no Hg methylation in fish.