Comparative study antifungal effect of garlic extract and malachite green on eggs and larvae during incubation of in rainbow trout (oncorhynchus mykiss)

The use of chemical materials such as malachite green to disinfect fish eggs is banned in many countries due to its reversed environmentaleffects. The purpose of this study was to investigate the effect of garlic extract as antifungal agent on eggs of oncorhynchus mykiss during the incubation period and to compare its effects with malachite green.24 hours after fertilization, eggs were treated with three concentrations of garlic extract (50, 100, 200 mg/L) and three replicates per concentration using static bath method every other day for 30 min and 2 mg/L malachite green using the same method every other day for 30 min. The control group didn’t have any antifungal agent. The results of study showed that the highest eye egg mortality rate of control group was 1477±6.94 (33.35±0.14%) (P<0.05). Also, the mortality rate of eye egg 200 ppm of  garlic extract treatment was (576±5.60 egg, 13.11±0.09%) which was significantly lower than the other treatments (P<0.05). the mortality rate of eggs between eye egg stage and hatching stage in the 200 ppm of garlic extract treatment was 335/6±9.88 egg (7.62±0.21%); however, it was 666±7% egg in the control group . malachite green (with 207±4.2 dead eggs, 5.74±18%),  and 200 mg/l garlic extract (11.82±.25%, 270.3±7.3) treatments had lowest mortality rate between hatching stage up to 1 gr weight (P<0.05) . However, in this stage, the control group showed the highest rate of egg mortality among all treatments. Since no apparent deformities and abnormalities were observed in hatched larvae, suggested garlic extract with 200 mg/l concentration, as an environmental friendly matter, can be used for disinfection of O. mykiss eggs during incubation period.