The overall goal of this proposed work is to quantify and analyze ichthyophonus infections from four sample locations on the mainstem yukon river, including fort yukon, and allow for opportunistic…

The overall goal of this proposed work is to quantify and analyze ichthyophonus infections from four sample locations on the mainstem yukon river, including fort yukon, and allow for opportunistic evaluation of multiple life stages of chinook, chum, and prey fish species captured in the northern bering sea (NBS). Funds would be used to directly test samples collected from the fourth location, fort yukon, and marine fish in the NBS. The first objective is to use qpcr and statistics to assess for differences in ichthyophonus infections of yukon river chinook salmon sampled from pilot station, rapids, fort yukon, and eagle in 2023. We hypothesize that ichthyophonus infection prevalence and severity will vary by location consistent with the disease progression within the host species and disease-associated mortality between locations. The second objective is to use qpcr to screen for ichthyophonus and quantify infections in chinook and chum salmon, walleye pollock and forage fish species opportunistically captured in the 2023 NBS survey. Qpcr positive samples will be confirmed with histopathology. Funding will support continued assessment of ichthyophonus infections in chinook salmon from the NBS survey and expanded testing to chum salmon from this platform. We hypothesize that ichthyophonus infections will occur in chinook and chum salmon at an unknown level that may differ by host age, size, or SEX and that infections will occur in walleye pollock and forage fish species at an unknown level that may provide insight into infection sources for yukon river chinook and chum salmon. The vision of this project beyond this current funding year is to support the intended long-term annual monitoring program for ichthyophonus in yukon chinook salmon collected from the pilot station test fishery performed inseason to assist managers with estimating EN route mortality for their management decisions. Research is needed to develop this program by comparing infections from different river locations. Monitoring infections from marine samples collected from the NBS survey complements this work by providing information on infections in salmon used for future run forecasts as heavily infected fish may indicate a source of variation in estimates for forecasting. This could be extended to the key prey species if determined from this research. Anticipated outcomes include: 1) vital information about infection and parasite-associated mortality by testing fish upriver (i.e., fort yukon) where survivors will be compared to infections lower in the river, 2) determining infection levels in salmon from the NBS survey to provide managers with infection and disease information that may be qualitatively considered in the context of preseason run forecasts, and 3) an initial determination of key prey species that infect NBS salmon. The work will benefit the U.S. Fish and wildlife service, alaska department of fish and game (ADF g), and department of fisheries and oceans canada tasked with assessing population abundance and fishing opportunities. IT will also directly benefit the subsistence fishery via better informed management and may aid in postseason assessment canadian-origin chinook salmon fates, as required to address U.S. Canada treaty obligations. ADF g intends to continue operating an ichthyophonus monitoring project for the foreseeable future if sufficiently funded. Laboratory reports and any peer-reviewed manuscripts will be available to agency staff and the public. This project involves a partnership with local fishers and yukon river residents contracted to collect fish with opportunities to learn about fish anatomy, necropsy, and disease during sample collection. All sampled fish from the yukon river will be provided back to the communities were sampled so residents can use them for cultural and food security needs. This work is of interest to both alaskans and canadians.