Biocontrol of saprolegniosis in silver perch Bidyanus bidyanus (Mitchell) by Aeromonas media strain A199

The potential of Aeromonas media strain UTS A199 as a candidate for the biocontrol of winter saprolegniosis was tested during a winter outbreak in a farm and in a laboratory challenge trial on silver perch, Bidyanus bidyanus Mitchell. The daily addition of A199 to tanks during the winter outbreak of saprolegniosis resulted in a significant increase (p < 0.05) in fish survival. Close monitoring of fish revealed that A199 treatments halted the progress of the disease by inhibition of hyphal growth within lesions and cyst germination. In a laboratory-based challenge of perch by exposure to high numbers of cysts and zoospores of Saprolegnia parasitica, the presence of A199 in the tank water delayed the onset of the disease but, ultimately, could not protect the fish from the disease under these conditions. (C) 2003 Elsevier B.V. All rights reserved.