Effects of environmental and maternally derived methylmercury on the embryonic and larval stages of walleye (Stizostedion vitreum)

The effects of environmental and maternally derived methylmercury (MeHg) on the embryonic and larval stages of walleye (Stizostedion vitreum) were inv estigated using eggs collected during two successive spawning seasons. Eggs were collected from fish in a mercury (Hg)-polluted environment (Clay Lake , Ontario, Canada), and from fish in two relatively pristine lakes (Lakes M anitoba and Winnipeg, in the province of Manitoba). Both bioaccumulation of Hg into muscle and its mobilization into eggs was significantly higher in Clay Lake females. Maternal muscle MeHg concentration was positively correl ated with female length and egg MeHg was positively correlated with muscle MeHg concentration in all three populations. Hatching success of eggs from all three stocks declined significantly with increasing waterborne MeHg (0. 1-7.8 ng l(-1)). Hatching success was not significantly affected by egg MeH g concentration. Embryonic heart rate declined with increasing waterborne M eHg concentration, but larval growth was not affected.. Occurrence of larva l deformities was negatively correlated with size of female, but was not si gnificantly correlated with MeHg in either eggs or water. Larval MeHg was p ositively correlated with the concentrations of MeHg in eggs demonstrating transmission of MeHg from females. Uptake of ambient MeHg was higher in lar vae exposed to higher waterborne MeHg concentrations. (C) 2000 Elsevier Sci ence Ltd. All rights reserved.