This report of Ichthyophonus in common sport-caught fishes throughout the marine waters of southcentral Alaska represents the first documentation of natural Ichthyophonus infections in lingcod Ophiodon elongates and yelloweye rockfish Sebastes ruberrimus. In addition, the known geographic range of Ichthyophonus in black rockfish S. melanops has been expanded northward to include southcentral Alaska. Among all species surveyed, the infection prevalence was highest (35%, n = 334) in Pacific halibut Hippoglossus stenolepis. There were no gross indications of high-level infections or clinically diseased individuals. These results support the hypothesis that under typical conditions Ichthyophonus can occur at high infection prevalence accompanied with low-level infection among a variety of fishes throughout the eastern North Pacific Ocean, including southcentral Alaska.

The ecological mechanisms driving an observed decline in the mean size-at-age of adult Pacific halibut (Hippoglossus stenolepis) in the eastern North Pacific Ocean have yet to be defined. Here, we present the results of a study designed to investigate the relationship between one potential mechanism — diet — and size-at-age using carbon and nitrogen stable isotope analysis. Our results indicate significant differences in the skeletal muscle δ13C and δ15N values between size-at-age categories for each sex, with larger-size-at-age fish consuming diets with higher δ15N values, indicating higher trophic level feeding. Analysis of Bayesian standard ellipse areas showed that for females, intermediate size-at-age categories have the largest dietary range. For males, the largest dietary range was observed in the largest size-at-age category. Our results suggest a size-based stratification in dietary strategy for Pacific halibut with implications for observed declines in size-at-age.