Tolerance of Penaeus (Marsupenaeus) japonicus embryos to ozone disinfection

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 (P<0.05) 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 (P>0.05) on hatch rate relative to controls in any of the three families. Families 1 and 2 mean hatch rate was not significantly (P<0.05) 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.