Viral Nervous Necrosis (VNN) of Striped Jack: Effects of Plasma Antibody Level of Spawners and Spawning Conditions on the Occurrence of the Disease in their Offsprings

Abstract

Plasma antibodies against striped jack nervous necrosis virus (SJNNV), the causative agent of viral nervous necrosis (VNN) in larvae of striped jack, Pseudocaranx dentex were monitored in spawners reared at the Komame Station of Japan Sea-Farming Association for about 2 years. There were no apparent seasonal changes in the antibody titer level, though it tended to decrease towards July.
In 1991, VNN occurred not only in the larvae from antibody-positive spawners but also in the larvae from antibody-negative spawners, both were induced to spawn continuously at higher temperature (22 °C) . On the other hand, VNN did not occur in 1992, when the antibody detection became negative in many spawners and they were induced to spawn intermittently to minimize the stress effects. These results suggest that VNN could be controlled by selection of spawners and improvement of spawning induction method.