Effects of Five Drugs on Hatchability of Fertilized Eggs in CASIIIStrain of Allogynogenetic Silver Crucian Carp

Fertilized egg adhesion on 5 cm×10 cm mesh patch of CASⅢstrain of allogynogenetic silver crucian carp Carassius auratus gibelio were incubated in a 5 L plastic bucket and exposed to five drugs Mei tingⅡ,Mei ling,Natamycin,oxadixyl mancozeb and potassium permanganate prepared by stock of 1000 mg/L by equal interval between logarithm at water temperature 21-23℃and pH 6.2-6.5 by using a semi-static test method to explore for the inhibition of water mold Saprolegnia and hatchability in fertilized eggs by the medicines.The results showed that all of 5 medicines had some inhibitory effects on the water mold of the fertilized eggs,with larger inhibition rate in Mei tingⅡthan in Mei ling and larger inhibition rate in Mei ling than in Natamycin,oxadixyl mancozeb and potassium permanganate.The toxicity and side effects of oxadixyl mancozeb were found to be significantly decreased in hatchability,with precautions utilization,and optimal dose of 4.90-6.50 mg/L in Mei tingⅡ,1.97-3.87 mg/L in Mei ling,1.50 mg/L in Natamycin and 2.50 mg/L in potassium permanganate in immersion.These findings suggest that Mei tingⅡ,Mei ling,Natamycin and potassium permanganate be effective for controlling Saprolegnia of fertilized eggs in allogynogenetic silver crucian carp CASⅢduring incubation.