High prevalence and low intensity Ichthyophonus infections in Pacific Halibut (Hippoglossus stenolepis)

AbstractIchthyophonus occurred at high prevalence but low intensity in Pacific Halibut (Hippoglossus stenolepis) throughout the west coast of North America, ranging from coastal Oregon to the Bering Sea. Infection prevalence in adults was variable on spatial and temporal scales, with the lowest prevalence typically occurring on the edges of the geographic range and highest prevalence consistently occurring inside Prince William Sound, AK (58–77%). Additionally, intra-annual differences occurred at Albatross - Portlock, AK (71% versus 32% within 2012) and inter-annual differences occurred along coastal Oregon (50% versus 12% from 2012 to 2015). The infection prevalence was influenced by host age, increasing from ≤ 3% among the youngest cohorts (≤age 6) to 39–54% among age 9–17 cohorts, then decreasing to 27% among the oldest (age 18+) cohorts. There was little indication of significant disease impacts to Pacific Halibut, as the intensity of infection was uniformly low and length-at-age was similar between ...