Improved performance of gilthead sea bream, Sparus aurata , larvae after ozone disinfection of the eggs

Ozone (O 3 ) dissolved in seawater (ODS) was evaluated, as an egg disinfectant, on the spawn of captive gilthead sea bream, Sparus aurata , brood stock. Four contact times (CT) were tested (0.6, 1.2, 2.4 and 4.8 mg min L −1 ) where CT was calculated by multiplying the dissolved O 3 concentration (0.3 mg L −1 ) by different exposure periods (2, 4, 8, 16 min). There was also a disinfected seawater treatment that contained no O 3 or derived compounds (CT 0) and an untreated seawater control. All ODS treatments reduced egg surface bacterial counts to zero, which was significantly ( P <0.05) lower than the CT 0 and the control groups (194 and 1320 plate −1 respectively). Nevertheless, the hatching rate was high in the control and the CT treatments 0, 0.6 and 1.2 (88.7%, 87.3%, 89.5% and 83.7% respectively) while eggs exposed to a CT 2.4 and 4.8 hatched poorly (36.5% and 20.4% respectively), which was likely due, at least in part, to larvae unable to break the egg chorion successfully. Swim‐bladder inflation was significantly higher in the ODS groups (>97%) compared with the control and CT 0 treatments (ca. 70%). The results suggest that a 2‐min exposure of eggs to 0.3 mg O 3  L −1 of ODS (CT 0.6) would improve current protocols in marine larviculture.