An economical, efficacious vaccine delivery system for immunizing fish has been developed which employs a liquid spray apparatus operated at pressures up to 7.0 kg/cm2 (0 to 100 lb/in2). A bacterin consisting of formalin-killed Vibrio anguillarum culture was both antigenic and immunogenic when sprayed on coho salmon(Oncorhynchus kisutch)and rainbow trout(Salmo gairdneri). The technique, referred to as spray(shower)vaccination, was found to confer higher levels of immunity against virulent V. anguillarum than oral vaccination.