Abstract:
The toxicity of cadmium, copper and zinc to rainbow trout, Salmo gairdneri
Richardson, during early development was investigated. In addition the
synthesis of cadmium-binding protein by the perfused rainbow trout liver
was studied. It was concluded that;
1) Cadmium is extremely toxic to rainbow trout during early development. A continuous cadmium exposure during embryonic development resulted in almost complete mortality of eggs at 1.0 mgCdl *. Some sublethal effects were also observed in hatched alevins.
2) Embryonic sensitivity was not uniform throughout egg development.
The fertilisation process was particularly sensitive to cadmium
viexe,
exposure. Reductions in the fertilisation of eggs was obtained as a result of exposure to 1.0 mgCdl * and higher. The results also indicated that the period of axiation was sensitive to cadmium exposure as shown by a high mortality rate of eggs in continuous exposure tests.
3) Embryonic sensitivity to cadmium and zinc differed from sensitivity to copper indicating possible differences in toxic actions between these metals.
4) The toxicity of mixtures of cadmium, copper and zinc indicated that the toxicity of these metals to trout eggs and fry could be assessed
by the additive toxic unit method to give the total toxicity of the mixture. However sublethal effects and metal uptake studies showed possible departures from additive joint action.
5) Post exposure mortalities may result from brief exposure of fish to cadmium even after restoration to clean water. These results highlight the inadequacy of a standard toxicity test in predicting the consequences of brief exposure to a pollutant.
