Effect of iodine disinfection on the bacterial flora and hatching rate of grouper, Epinephelus coioides eggs at the cleavage and eyed stages

Abstract

In this study, the effect of iodine disinfection on the bacterial flora and hatching rate of grouper egg at two different stages of development were investigated. The eggs (at cleavage and eyed stages) were soaked for 10 min in sterile seawater (control) and at different free iodine concentrations- 2.5, 5, 10, 15 and 20 ppm. Total bacterial and presumptive Vibrio count, as well as the hatching rate of the treated eggs were determined. Results showed that Vibrios are eliminated by iodine disinfection (2.5-20 ppm) but not by rinsing with sterile seawater. The total bacterial load and hatching rate of eggs decreased as the iodine concentration increased. Iodine concentrations of 15 and 20 ppm were effective in significantly reducing the total bacterial load of grouper egg at both the cleavage and eyed stages. However, at these concentrations the hatching rates were also significantly lower. Results also showed that grouper, Epinephelus coioides, eggs tolerate stress better at the eyed stage than at the cleavage stage.