Researchers heading to deepest part of Lake Superior to investigate 'zombie' siscowet lake trout

Researchers from Michigan’s Department of Natural Resources and Michigan State University will journey to the deepest point of Lake Superior to study emaciated siscowet lake trout nicknamed 'zombie' fish. The team, part of a fisheries research effort, made the initial observation during recent deepwater surveys and plans to return to collect additional specimens for testing. They aim to rule out a fish pathogen as the cause of the extreme thinning and to understand the broader health of the lake’s deepwater population. The expedition centers on Superior Maximus, the lake’s deepest trench, and represents a coordinated scientific response to a visible ecological anomaly.

Officials note the condition appears linked to low food resources rather than a pathogen, suggesting a natural ecological phenomenon. The long-term trend shows the incidence of emaciated siscowet rising from roughly 3% in 2015 to about 20% in 2024-25. In 2024, 11 of the siscowet captured at Superior Maximus were categorized as zombies (37%), and in 2025, 15 of those captured (54%) fell into the same category. Michigan DNR fisheries research biologist Shawn Sitar characterized the trend as noteworthy but not alarming, highlighting the need for further data to determine causes and potential ecosystem implications.