A study on the possible association of copper pollution with vibriosis in eel.

In this study, eel from a locality where the bacterium Vibrio anguillarim was common were transferred to copper-contaminated freshwater and brackish water (10%) under laboratory conditions. In one experiment (experiment I) 9 out of 20 eel died and bacteria (in six cases V. anguillarum and in two cases Aeromonas sp.) were isolated from the kidneys, and one was found to be sterile. In this experiment copper did not seem to be an initating factor in developing bacterial infection. In two other experiments (II and III) eel were exposed to copper-concentrations up to approx. 25 times as high as the level which is stated as critical in a infection context in a Norwegian work. With the exception of one case no bacteria were isolated from the kidneys and the mortality seemed to be caused by the direct toxic effect of the contaminent. Therefore, some unspecified factors would appear to have been the cause of the results obtained in the Norwegian work.