Long-Term Heavy Metal Mixture Toxicity to Embryos and Alevins of Rainbow Trout (Oncorhynchus mykiss)

Abstract

Possible effects of heavy metal mixture (HMM) on hatching, survival and growth have been tested on the early-life-history stages of rainbow trout. The eggs of rainbow trout were exposed to HMM concentrations of between 12.5% and 200% from fertilisation to near complete yolk absorption, for 70 days. Water hardness and pH were approximately 250 mg/l CaCO3 and 7.5, respectively. The following concentrations of metals in the model mixture tested were taken as 100%: Cu – 0.02, Cr – 0.02, Ni – 0.05, Zn – 0.06, Pb – 0.03, Fe – 0.3, Cd – 0.003, Mn – 0.09 mg/l. The HM concentrations in 100% mixture were close to the mean annual levels of HM found in the discharges from Vilnius City into the Neris River. Hatching was the most sensitive indicator of HMM toxicity. The MATC for the period from fertilisation to viable hatch was estimated to 70.7% HMM. The alevin stage was a less sensitive early life stage to HMM. Significant reduction in viability and growth of alevins was apparent in 200% HMM concentration after 70-da...