The effect of disinfection with ozone in restocking brown trout farm in north Italy

Since new EU aquaculture rules prevent the use of traditional chemical disinfectants because of their environmental impact, researchers are looking at alternative disinfection methods and ozone seems to be an interesting candidate. This experimentation was conducted at a brown trout (Salmo trutta) restocking farm. The experimental plan was bifactorial balanced with randomized groups and the tested experimental factors were: disinfection method and density of eggs, with 8 replicates per treatments. Two densities of eggs were utilised: 1.2 eggs per cm2 (corresponding to a mono stratified layer of eggs) and 2.5 eggs per cm2 (corresponding to a bi-stratified layer of eggs) and 4 disinfection treatments: 0.1 mg/L ozone (10 min/day), 0.4 mg/L ozone (10 min/day), Detarox (10 min/day) and a control group without disinfection were studied. The daily egg survival rate was measured 6 days per week in each tank. The hampseed trapping technique was utilised to collect Saprolegnia fungi directly from the aquatic habitat. Observing the results obtained from the final egg survival rate, it is possible to see that in this experimentation the higher concentration of ozone obtained the best results, but there is only a little more than 2% difference between the highest and lowest results.