EFFECTS OF ZATARIA MULTIFLORA ESSENTIAL OIL ON RAINBOW TROUT (ONCORHYNCHUS MYKISS) EGG HATCHABILITY AND SURVIVAL OF LARVAE COMPARED WITH HYDROGEN PEROXIDE AND MALACHITE GREEN

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Zataria multiflora essential oil, hydrogen peroxide(H2o2) and malachite green (MG) were used to assess their effects on rainbow trout egg hatchability and survival of larvae up to 1-1.2 g body weight using spring water at 12.5 °C, dissovled oxygen 8-9 mg/L, carbon dioxide 7±2 mg/L, ammunia <0.01 and total hardness about 170 mg/L . Zataria was used at 70 mg/L for 30 minutes per day , at 500 mg/L for 35 minutes per day with a reducing in the time treatment to 5 minutes during 70-140 degree-day and MG as the positive control at 2mg/L for 20 minutes per day. Normal control without any treatment was also included. Each treatment trial was provided in three replicates. The treatment trials started 36 hours post-incubation and were continued until the eyed-egg stage. The obtained results showed that the mortality level in normal control was significantly higher than other groups (p<0.05). Also, the mortality rate in eggs treated with Zataria was significantly higher than both MG and H2o2 groups (p<0.05). No significant different was seen between MG and H2o2 groups until the eyed-egg stage (p>0.05). Level of mortality in egg treated with Zataria was significantly higher than MG from eyed-egg stage until the hatching stage (p<0.05). In addition, the mortality rate of the produced larvae kept to 1-1.2 g body weight was significantly higher in both Zataria group and normal control groups than other two groups (p<0.05), while no significant difference was seen in weight of the produced larvae among all examined groups (p>0.05).The results showed that use of Zataria at 70 mg/L is incomparable with H2o2 and MG , although it is able to significantly improve the survival rate of rainbow trout eggs and larvae during incubation period.

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