Cadmium toxicity and accumulation in eggs and alevins of Atlantic salmon Salmo salar

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Abstract
Embryos and alevins of Atlantic salmon (Salmo salar) were exposed to cadmium concentrations of between 0.47 μg Cd/L and 27 mg Cd/L from fertilization to near complete yolk absorption. The most sensitive indicator of cadmium toxicity was the inhibition of growth in alevins, with significant reduction occurring in 0.47 μg Cd/L. The LC50 for the interval from fertilization to viable hatch was estimated to lie between 300 and 800 μg Cd/L. Newly hatched alevins had a 24-day LC50 of between 1.5 and 2.7 mg Cd/L. Sensitivity increased sharply in late alevins and significant mortality was recorded in concentrations as low as 8.2 μg Cd/L. Cadmium uptake by eggs was rapid, with dose-dependent saturation levels reached within 24 h and maintained until hatch. Although the total cadmium content of eggs increased with ambient concentration, the degree of bioaccumulation declined. The cadmium contents of newly hatched alevins were much lower but directly proportional to those of eggs. Uptake by alevins was logarithmic, independent of ambient concentration above about 1 μg Cd/L, and did not reach equilibrium during the exposure period (46 days).