Hines, R.S., Fish and Aquaculture Research Station, Israel
Wohlfarth, G.W., Fish and Aquaculture Research Station, Israel
Moav, R., Department of Genetics, Hebrew University, Jerusalem, Israel
Hulata, G., Department of Genetics, Hebrew University, Jerusalem, Israel

In a test involving 5 inbred strains, and 9 strain crossbreds of the common carp, one inbred strain was found to be infected by Epidermal epithelioma disease and a second inbred strain was infected by a swim bladder inflammation. Crossbreds between these 2 strains, as well as between them and other strains did not show a single fish infected by either disease. It was concluded that susceptibility to both of these diseases is controlled by recessive genetic factors. It appears that the decreased incidence of Epidermal epithelioma in Israeli fish ponds in recent years has been due to the increased use of selected crossbred carp fry. The incidence of Epidermal epithelioma was twice as high in experimental ponds with a high stocking rate than in those with a lower stocking rate. The swim bladder inflammation was apparently due to a blockage of the pneumatic duct, with secondary infection by Aeromonas liquefaciens. © 1974.