Tolerance of Penaeus (Marsupenaeus ) japonicus embryos to ozone disinfection Melony J. Sellars a, * , Greg J. Coman a , David T. Morehead b a CSIRO Marine Research, 233 Middle Street, Cleveland, Qld, 4163 Australia b Marine Research Laboratories, Tasmanian Aquaculture and Fisheries Institute and Aquafin Cooperative Research Centre (CRC), University of Tasmania, Nubeena Crescent, Taroona, Tasmania, 7053 Australia Received 8 September 2004; received in revised form 15 November 2004; accepted 22 November 2004 Abstract This study investigated the tolerance of Penaeus (Marsupenaeus ) japonicus embryos to ozone disinfection to establish a suitable treatment level that has no detrimental effect on embryo hatch rate. In a factorially design experiment, three families were exposed to four different ozone concentrations (C) (0, 0.5, 1 and 2 ppm), for five different exposure times (T) (0.5, 1, 2, 4 and 8 min), to give a total of eight ozone concentrationexposure time (CT) combinations, with an exception for family 1 which had no 8 min exposure time. This was conducted at 16, 120 and 480 min post-spawning for all three families. Embryos were least tolerant to ozonation 16 min post-spawning, with a CT value as low as 0.5 for family 1, and a CT value of 1 for families 2 and 3, significantly ( Pb0.05) affecting hatch rates relative to controls. For the 120 and 480 min post-spawning treatment times, CT values lower than 2 had no significant effect ( PN0.05) on hatch rate relative to controls in any of the three families. Families 1 and 2 mean hatch rate was not significantly ( Pb0.05) affected when treated at a CT of 4 at 480 min post- spawning, whilst a CT of 8 had no significant effect on mean hatch rate for family 2 when applied 120 min post-spawning. Based on our results, future studies towards developing disinfection protocols for P. japonicus embryos should utilise an ozone concentration of 2 ppm and exposure time of 1 min (CT of 2) applied 120 or 480 min post-spawning. D 2004 Elsevier B.V. All rights reserved. Keywords: Ozonation; Shrimp; Aquaculture; Biosecurity 1. Introduction Worldwide shrimp producers have suffered sub- stantial production losses over the last decade due to viral pathogens. One approach to minimize such losses is the elimination of viruses from culture organisms and systems through disinfection. Ozone is considered the most powerful viral deactivating agent available (Schuur, 2002; Emerson et al., 1982; Roy et al., 1981), and has proven an effective disinfectant for the removal of viral, bacterial and fungal pathogens in marine culture systems, while 0044-8486/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaculture.2004.11.042 * Corresponding author. Tel.: +61 7 3826 7359; fax: +61 7 3826 7222. E-mail address: Melony.Sellars@csiro.au (M.J. Sellars). Aquaculture 245 (2005) 111 – 119 www.elsevier.com/locate/aqua-online