Enhanced vulnerability of rainbow trout ( Salmo gairdneri) to Saprolegnia infection, following treatment of the fish with an androgen

Abstract

The retention of zoospores of Saprolegnia diclina on the external surfaces of rainbow trout was enhanced if the experimentally challenged fish had previously been implanted with the androgen 11-ketotestosterone. Saprolegnia infections, developing as a result of experimental challenges, appeared as crescentic patterns on the fish surfaces. Possible interpretations of the observations are discussed, with particular reference to the susceptibility of wild salmonid fish to saprolegniasis.