Biologists in the United States are conducting research on the impact of a deadly parasite affecting Yukon River chinook salmon in the hopes that the findings will eventually play a role in decision-making on both sides of the border. Zachary Liller, from the Alaska Department of Fish and Game, explained that the current challenge lies in accounting for natural mortality associated with diseases like ichthyophonus, which can be fatal under certain conditions due to the extensive distances these vulnerable chinook travel to reach their spawning areas.
Liller emphasized the lack of ongoing monitoring for diseases and the absence of interpretation of disease metrics. To address this gap, researchers aim to compile relevant data and input it into a statistical tool for future population sampling, enabling formal estimates of disease-related chinook mortality. This information is not currently integrated into stock assessment programs or fisheries management decision-making frameworks, prompting the development of a new tool to rectify this gap and potentially impact decisions such as harvest closures.
Biologists in Seattle have been conducting experiments involving feeding young chinook infected fish flesh or inoculating them with the parasite, followed by rigorous monitoring for signs of infection. The parasitic infection primarily targets the heart before spreading to the muscles, impacting the fish’s movement and potentially leading to death. This parasite is believed to be a significant factor in the mortality of chinook en route to their spawning grounds, some traveling vast distances of around 3,200 kilometers.
The extent of ichthyophonus’s impact on chinook remains uncertain, prompting a collaborative effort between the Alaska Department of Fish and Game, the U.S. Geological Survey, and Alaska Pacific University to delve deeper into this issue and potentially expand their research in the future. Through special permits, biologists have extracted wild chinook for experimentation, studying the parasite’s response to different water temperatures to assess its adaptability to warming waters, possibly influenced by climate change.
Although the research was initially planned to continue through September, challenges arose, leading to potential delays. The team aims to increase infection prevalence in experimental fish to gather more comprehensive data. The research is crucial for understanding the implications on harvest regulations and overall fisheries management in the region.