Parasite infection and immune and health-state in wild fish exposed to marine pollution

Association between parasitism and immunity and health-state was investigated in wild Sebastes oculatus after having determined that pollution exposure is associated with altered immune and health-state parameters. Given the importance of the immune system in antiparasite defense we predicted: (i) parasite infection would be higher in pollution-exposed than in control fish and (ii) fish with lower immune and health-state parameters would show higher parasitism than fish in better condition. Metazoan parasite fauna was compared between pollution-exposed and non-exposed fish and parasitic indices were correlated with integrated measures of immunity and health-state. Results provided little support for the predictions; some parasite taxa increased, some decreased, and some were not affected in pollution-exposed fish despite their altered health and immunity. Furthermore, there was no link between individual immune and health-state parameters and parasitism. These findings highlight the complexity of host-parasite-environment interactions in relation to pollution in natural marine ecosystems.