Bacterial and parasitic pathogens in cultured common dentex, Dentex dentexL.

A bacteriological and parasitological study on cultured common dentex, Dent ex dentex L., was conducted in a 2-year survey. Two different groups of fis h were studied: (1) sampled only when mortalities occurred; and (2) sampled periodically from 10 days post-hatch until the juvenile stage. In both gro ups, peaks of mortalities coincided with high water temperatures. The same parasites were detected in both groups, except Ichthyophonus sp., which was identified only in the trunk kidney of fish from group 1. Two myxosporeans , Ceratomyxa sp. and lepthotheca sp., were found in the bile and the trunk kidney, respectively. Epitheliocystis infection was also very frequent in t he gills. An unidentified microsporidium, which was found in the liver, occ urred very infrequently. Vibrio harveyi was dominant in samples from diseas ed animals (79%) and clearly associated with mortalities. It was not detect ed in water or larval homogenates. A high percentage (60%) of the isolates of this species were sorbitol positive. Other less frequently occurring bac teria were V. alginolyticus and Photobacterium (V.) damselae. The disease c onditions found in common dentex were considered to be multifactorial in or igin.