PATHWAYS OF BACTERIAL-CONTAMINATION DURING EGG INCUBATION AND LARVAL REARING OF TURBOT, SCOPHTHALMUS-MAXIMUS

Overall microbial levels in the water system of a turbot farm were sim ilar to those found in regular seawater. At the end of an incubation p eriod, however, the numbers of colony-forming units (CFU) in Artemia c ultures and turbot egg incubation jars were up to four orders of magni tude higher than seawater level. Rinsing of the food organisms (rotife rs) prior to feeding them to turbot larvae, however, significantly red uced bacterial numbers, thus reducing the number of cross-contaminatio ns. Several species of Aeromonas, Pseudomonas and Vibrio among others, were identified in the eggs and larvae, or in the water in which thes e were incubated. Scanning electron microscopy shows that the surface of unfertilized turbot eggs is a breeding ground for bacteria; the rem oval of these eggs from incubation jars is therefore recommended. The epidermis of turbot larvae was virtually free of microorganisms.