Freshwater growth and survival in AYK Chinook salmon, maternal health, and the ultimate effects on stock productivity

This study focuses on the freshwater factors affecting Western Alaska Chinook salmon productivity through three complementary studies: a retrospective study of salmon scales examining the relationship between freshwater growth and survival to adulthood, a study of the persistent effects of infection of adults with the parasite Ichthyophonus on their offspring, and laboratory rearing experiments supporting the first two studies by validating scale and otolithbased indicators of growth and comparing growth and survival between offspring from Ichthyophonus-infected and Ichthyophonus-free parents. All project components are progressing, although there have been some delays due to weak Chinook returns in 2011 and a rearing-facility malfunction. In the retrospective study, scale growth measurements from stocks on both the Yukon and Kuskokwim Rivers have been taken, and these data are being analyzed to determine patterns in growth over time and the relationship of growth to survival. Ichthyophonus-infected and Ichthyophonus-free fish have been collected, samples analyzed and compared, and some preliminary results are included here. However, sample sizes are small because a weak Chinook return in 2011 precluded some of our anticipated sampling. Laboratory rearing experiments for validation of the relationship between scales, otoliths, ration, and freshwater growth were successfully concluded. Scales and otoliths will be read in the near future, and the experimental data statistically analyzed to quantify the growth relationships. Laboratory comparisons of growth and survival of offspring of infected and healthy parents were not possible because of an equipment failure in the first year and the unavailability of eggs in the second year. We anticipate requesting an extension of support to finish the Ichthyophonus-focused component of our project, which has been hampered by these unforeseen events. Component Title: Effect of Ichthyophonus infection on Yukon River Chinook salmon hatching success, growth, and survival PIs: Lara Horstmann-Dehn, Shannon Atkinson, Trent Sutton MS Student: Theresa Floyd