Kinetic Analysis of Cadmium Toxicity to Red Sea Bream, Pagrus major

The sensitivity of red sea bream (Pagrus major) at various body sizes to Cd was investigated. The LC50 values for juvenile fish weighing over 0.16 g increased disproportionately with body weight and varied as the reciprocal of the rate of Cd accumulation in the body. The rate of accumulation and Cd concentration were much higher in the viscera than in the gills and remaining tissue. Cd elimination from the tissues was biphasic. Gel filtration studies revealed that metallothionein induction in the viscera of red sea bream was detected not after 4 hr, but after 24 hr postintoxication. This indicates that smaller juvenile fish with a higher rate of accumulation concentrate a larger amount of Cd before metallothionein synthesis and suffer more severe toxic effects.