Mechanism of oligochitosan improving non-specific immunity of Epinephelus fuscoguttatus (♀)× E. lanceolatu (♂)

Singapore grouper iridovirus (SGIV), one of the most important viral pathogens in grouper, has caused great economic losses to grouper industry. To evaluate the risk of iridovirus disease in grouper aquaculture, a risk assessment model of grouper iridovirus disease was established using Delphi method and Analytic Hierarchy Process (AHP) in this study. The evaluation index system consisted of 1 target level (risk of grouper iridovirus disease), 5 criterion layers (including water quality, grouper health status, feeding management, aquaculture mode and aquaculture environment), and 20 risk factors at the index level (including water temperature, pH, dissolved oxygen, ammonia nitrogen, iridovirus infection, bacterial infection, etc.). The weight values of 5 criterion-level risk factors was W= 0.1298, 0.3672, 0.1733, 0.0327, 0.2971. The higher weight values of risk factors, including virus infection(0.2485), incidence in neighboring areas(0.1384), water temperature(0.1123) and aquaculture density(0.1050), respectively, suggested that these factors might be crucial for the incidence of grouper iridovirus disease in aquaculture. Consistently, the infection experiments in laboratory confirmed that virus dose, density, and temperature all significantly affected the virus replication and the mortality of the fish. Thus, it was proposed that our risk assessment model could be used to assess the risk of iridovirus disease in grouper aquaculture.