The impact of ozonation of Atlantic cod, Atlantic salmon and rainbow trout eggs on hatching success, larval growth and survival

Fry, Jessica S. (2014) The impact of ozonation of Atlantic cod, Atlantic salmon and rainbow trout eggs on hatching success, larval growth and survival. Masters thesis, Memorial University of Newfoundland.

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Abstract

The direct exposure of eggs to ozonated water has generated interest as a means of ensuring pathogen-free eggs without the use of harsh chemicals. However, there are numerous knowledge gaps including safe contact times, exposure levels in both fresh water and sea water, and as potential long-term effects on aquaculture species such as Atlantic cod, Atlantic salmon, and rainbow trout. The effect of different ozone doses (0.5- 1.0, 1.5- 2.0 and 2.5- 3.0 mg O3 L⁻¹ for 1.5 min) was tested on recently fertilized Atlantic cod and eyed salmonid eggs vis-à-vis the commercial disinfectant Perosan™ (0.004 mg L⁻¹) and Ovadine (100 mg L⁻¹) as well as an untreated control (similar handling and husbandry). The impact of ozone application was evaluated based on larval nucleic acid concentration, hatching success, larval growth, and survival. Overall, the study showed no negative effect of ozonation at < 3.0 mg O3 L⁻¹ for 1.5 min on cod eggs, cod larvae (up to 30 dph), and Atlantic salmon and rainbow trout eggs monitored until 85% yolk sac depletion. The ability of ozone to eradicate Saprolegnia diclina infection on salmonid eggs as well the impact of ozone disinfection on S. diclina in the absence of salmonid eggs were also investigated. Results suggest that ozonation of S. diclina hyphal mats can reduce the growth of the fungus, with the level of impact being dependent on volume of S. diclina initially present.

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