Ichthyophonus ‐infected walleye pollock T heragra chalcogramma ( P allas) in the eastern B ering S ea: a potential reservoir of infections in the N orth P acific

• Published in: Journal of fish diseases 2014-07, Vol.37 (7), p.641-655
• Main Authors: White, V C, Morado, J F, Friedman, C S
• Format: Article
• Language: English
• ISSN: 0140-7775; 1365-2761
• DOI: 10.1111/jfd.12161

In 2003, the A laska walleye pollock industry reported product quality issues attributed to an unspecified parasite in fish muscle. Using molecular and histological methods, we identified the parasite in B ering S ea pollock as I chthyophonus . Infected pollock were identified throughout the study area, and prevalence was greater in adults than in juveniles. This study not only provides the first documented report of I chthyophonus in any fish species captured in the B ering S ea, but also reveals that the parasite has been present in this region for nearly 20 years and is not a recent introduction. Sequence analysis of 18 S r DNA from I chthyophonus in pollock revealed that consensus sequences were identical to published parasite sequences from P acific herring and Y ukon R iver C hinook salmon. Results from this study suggest potential for Ichthyophonus exposures from infected pollock via two trophic pathways; feeding on whole fish as prey and scavenging on industry‐discharged offal. Considering the notable I chthyophonus levels in pollock, the low host specificity of the parasite and the role of this host as a central prey item in the B ering S ea, pollock likely serve as a key I chthyophonus reservoir for other susceptible hosts in the N orth P acific.