Abstract: The invention involves the immunizing of fish against Enteric Redmouth by immersing the fish in a vaccine prepared from killed organisms of Y. ruckeri.

Abstract: A large, generally rectangular tank with an open top is divided into an inlet chamber and a shower chamber by an adjustable gate. The floor of the inlet chamber is grate raised above the floor of the tank so that the fish may be dewatered. The fish then flap themselves along the grate under the gate and into the shower chamber where they are subjected to a shower of vaccination solution introduced through shower nozzles supported across the top of the shower chamber. The floor of the shower chamber is solid and not a grate so that a quantity of vaccination solution stays on the floor of the shower chamber so that one is assured that both sides of the fish will be exposed to the vaccine solution. The floor of the shower chamber is also raised above the floor of the tank but stops short of the tank end wall so that the fish fall off onto the tank floor and are then flushed through an outlet into a holding pool.