Comparison of Neutral Anolyte solution and Malachite green efficiency on fungal contamination control of Rainbow trout (Oncorhynchusmykiss) eggs in incubation stage
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AbstractOne of the important problems in Rainbow trout production industry is egg fungal infection especially saprolegniasis which is the most important mortality factor in Rainbow trout hatcheries. Controlling saprolegniasis in hatcheries was done using green malachite in the past years, which is a very effective fungicide. Nowadays, due to the prohibition of using green malachite, effort is done to replace it with other materials as an effective fungicide. Some of the most important materials which have been examined are formalin, sodium chloride and hydrogen peroxide etc. The aim of this study was to evaluate the effects of neutral anolyte on the mortality percent of rainbow trout eggs and produced larvae in point of view of growth indices and survival until yolk sac absorption and larvae active feeding in incubation phase comparing with green malachite to be able to introduce a suitable alternative. This study was carried out in a complete randomly plan with 7 treatments and 3 replications (21 troughs in general), in 20*35*70 cm (length*width*depth) Californian troughs containing an incubator. Treatments included anolyte solutions constant bathing with 0.5 and 0.25 ppm concentrations and periodic anolyte treatments with 2 ppm concentrations (every 2 days), positive control infected with fungus without any disinfectant and negative control without any infection or disinfectant. 300 grams of newly propagated green eggs of rainbow trout which were provided from one of the fish hatcheries in Haraz Road and acclimated with the trough’s water temperature, were distributed in one layer at the bottom of the trough basket. All treatments, except negative control, were infected with saprolegnia, taken from infected eggs of rainbow trout which were previously provided from one of the fish hatcheries of 2000 Road in Tonekabon. The treatments took one month to complete. The studied variables included hatching percent, percent of eyed eggs, abnormality percent and percent of unfertilized eggs, from which percent of eyed eggs was calculated and recorded in the middle and the rest of the variables at the end of the test. In this study Paired-sample T-student test, Levene’s test, one-way ANOVA and Bonferroni’s test was used. For examining egg abnormality, hatching, fungus infection and eyed eggs, first the percent of the variables were specified and then for comparing the rate of abnormality in one of the anolyte treatments (which had the least abnormality) and green malachite, Mann-Whitney test was carried out. This comparison was done to analyze the rate of hatching, fungus infections, eyed eggs, resulting from the materials used in different treatments, using one-way ANOVA Bonferroni’s tests. Results showed that in lower anolyte concentrations (0.5 and 0.25 ppm), the number of fungal colonies of hatchery water and the percent of egg fungus infection were significantly higher than higher concentrations of anolyte (100 ppm and 30 ppm) and green malachite. In other words with concentration increase, the fungicidal effect has also increased. In evaluating the percent of eyed eggs, statistical results showed that eyed eggs percent in 0.25 ppm treatment and green malachite treatment were significantly higher than the other three anolyte treatments. This result can explain egg hatching in 0.25 ppm concentrations and not seeing hatching in the (other) remaining three doses. Between the treatments of 0.25 ppm and green malachite, the group of 0.25 ppm anolyte can be a better disinfectant for rainbow trout eggs compared to green malachite, for fish farmers, due to the high percent of eyed eggs and the low total count of fungus. The results of this study showed that the amount of abnormality in 0.25 ppm treatment has been higher compared to the green malachite group. Because this study was the first research on using anolyte as a fungicide in rainbow trout hatcheries, therefore for more specific study of the concentrations, the timing of usage and the factors affecting these two, more vast and general research is needed.
Publisher or UniversityIranian Fisheries Science Research Institute
Series : Nr47505;