First report of isolation and characterization ofPhotobacterium damselaesubsp.damselaefrom cage-farmed cobia (Rachycentron canadum)

Cobia (Rachycentron canadum) has been considered as a potential species for aquaculture because of its fast growth and commercial value. As a consequence of successful spawning and seed production, there has been a significant demand for cage farming of cobia in India (Philipose et al. 2013). Not many reports are available on diseases of cage-farmed cobia. Globally, mortality due to pasteurellosis in cage-cultured cobia caused by Photobacterium damselae subsp. piscicida has been reported (Liu, Lin & Lee 2003). Vibriosis caused by Vibrio alginolyticus, V. harveyi, V. parahemolyticus and V. vulnificus has also been responsible for mortalities in cage-cultured cobia (Rajan et al. 2001; Liu et al. 2004). Photobacterium damselae subsp. damselae was originally isolated from the skin lesions of damsel fish, Chromis punctipinnis (Love et al. 1981). Subsequently, diseases caused by this pathogen have been reported in several cultivable fish species like seabream (Vera, Navas & Fouz 1991), eel (Ketterer & Eaves 1992), turbot (Fouz et al. 1992), ovate pompano (Zhao et al. 2009) and Asian seabass (Kanchanopas-Barnette et al. 2009). Infection caused by P. damselae subsp. damselae has also been recorded in marine mammals like dolphins (Fujioka et al. 1988) and several wild fish species (Han et al. 2009). Pathogenicity of this bacterium in several marine fish species and humans has been reviewed (Rivas, Lemos & Osorio 2013a). There have been no reports on mortality caused by this pathogen in cobia. This study was envisaged with the objectives to describe the disease epizootic caused by P. damselae subsp. damselae in cage-farmed cobia and characterize the pathogen.