Conducting superior Great Lakes research: RV Lake Char beginning spring surveys on Lake Superior

Covering a surface area of roughly 31,700 square miles, holding 10% of the Earth’s surface fresh water and housing more than 177 species of fish, Lake Superior is a fascinating site for exploration, research and discovery. This spring, the Michigan Department of Natural Resources research vessel Lake Char will launch from Marquette to conduct essential lake trout research in Lake Superior.

The spring surveys will collect data on adult lake trout populations across the nearshore areas of Michigan, including the west side of the Keweenaw Peninsula near Ontonagon, Isle Royale, outer Keweenaw Bay from Bete Grise to the Huron Islands, Big Bay, Marquette, Au Train, Munising and Grand Marais. Anglers and boaters in those areas in late April through May are advised stay at least 500 feet from survey nets marked with black and orange flagged buoys and to avoid traveling between buoys.

These surveys occur during a narrow seasonal window when lake trout can be most accurately assessed, forming the foundation for long-term management of the species across Michigan waters.

“This long-term research is what allows us to track population trends, evaluate management actions and ensure the sustainability of these fisheries for future generations,” said Shawn Sitar, DNR fisheries research biologist and science officer of the RV Lake Char.

‘Mobile, floating laboratories’

From its home port in Marquette, the RV Lake Char monitors Michigan’s portion of Lake Superior — which is 50% of the largest freshwater lake on Earth. This work directly informs fisheries management decisions, supports co-management with tribal governments and underpins the long-term sustainability of one of the region’s most important natural resources. Exploration like this on Superior, or any of the other Great Lakes, would not be possible without research vessels.

“These vessels are essentially mobile, floating laboratories,” said Sitar. “The Great Lakes function like inland oceans, and these platforms allow crews to safely reach remote offshore locations, collect high-quality scientific samples and conduct research that would otherwise be impossible from shore or smaller boats.”

He added that the work conducted from the RV Lake Char has greatly advanced understanding of Lake Superior and management of key fish populations, such as lake whitefish, salmon and lake trout. The program has been central to the recovery of lake trout in Lake Superior, one of the Great Lakes’ biggest restoration successes.

Since its commissioning in 2007, the RV Lake Char has enabled scientists to access remote and offshore waters — including Isle Royale, Stannard Rock and Klondike Reef — and has contributed to major discoveries, such as documenting fish at Superior Maximus, the deepest point in the Great Lakes (1,320 feet) and recording the oldest known lake trout in the Great Lakes (62 years old). More recently, the program has also documented and presented findings on the occurrence of “zombie fish” — emaciated deepwater siscowet lake trout in offshore habitats, which the team will continue to investigate this June as part of its monitoring work in deep areas of Lake Superior.

A better home base

The Marquette Fisheries Research Station serves as the operational hub for the RV Lake Char. The station is located approximately 7 miles inland at the Marquette State Fish Hatchery in Harvey, which requires transporting the crew and sampling gear to Marquette Harbor for vessel deployment. The vessel is currently overwintered at a facility designed for small recreational boats, which limits pre-season maintenance, equipment staging and efficient field preparation. The DNR is exploring development of a dedicated research station and vessel base on Lake Superior at a location with existing deep-water dockage and industrial infrastructure, the former site of a decommissioned Marquette Board of Light and Power plant.

Though the vessel was scheduled to begin its 2026 work April 27, unexpected issues at its current storage facility have delayed launch, affecting this year’s survey schedule. In past seasons, similar constraints have contributed to delayed or shortened surveys, limiting data collection for important research. However, staff are working hard to get repairs done at the site to safely launch as soon as possible.

Want to dig deeper?

Learn more about the DNR’s research vessels by checking out highlights from last year’s Great Lakes fisheries surveys or by visiting Michigan.gov/FishResearch.

The RV Lake Char’s spring surveys will use nets deployed overnight, marked with black and orange flagged buoys. See Michigan Sea Grant’s Nets of the Great Lakes page for additional net safety information and best practices and the US Coast Guard Local Notice to Mariners site for the RV Lake Char sampling schedule and locations.