Monitoring occurrence and prevalence of Ichthyophthirius multifiliis (Ich), Loma salmonae (Loma), and infectious hematopoietic necrosis virus (IHNV) in Skeena River sockeye stocks

Babine sockeye are the single largest sockeye stock in the northern boundary area. The stock currently provides approximately 90% of the Skeena sockeye. Recent returns have generally been below average, and the 2013 return in the range of 400,000 was one of the lowest since the early 1950’s. Although the specific causes for reduced productivity in recent years are unknown; one potential contributing factor may be losses due to infectious or parasitic disease. For instance, disease outbreaks of Ich and Loma in the Fulton River spawning channels in 1994 and 1995 resulted in exceedingly high prespawn mortalities (PSM) that ultimately lead to an estimated 154 million fewer sockeye salmon fry than the historical average. More recently in 2009 and 2013, Ich and Loma were found in association with upwards of 40% PSM in the largest channel at Fulton, resulting in sharp decreases in production from those two brood years. Another pathogen known to cause significant mortality in British Columbian and Alaskan Sockeye salmon populations is IHNV. Despite the potential impact that these pathogens may have on the productivity of Skeena sockeye stocks, our knowledge concerning the basic epidemiology (i.e. prevalence and distribution) of these agents is limited to that obtained through opportunistic sampling by DFO stock assessment and science staff.

Consequently the objective of this project is to conduct routine monitoring of Babine Sockeye stocks to better understand the disease epidemiology of deadly pathogens (Ich, Loma, and IHNV) with the goal of acquiring information to aid management in developing strategies to reduce disease impacts.