2024 Great Lakes fisheries surveys wrap-up: Highlights from annual assessments on Michigan Great Lakes

Every year from April to November, the Michigan Department of Natural Resources is on the Great Lakes, surveying the important and diverse Great Lakes fisheries. Crews from research stations in Marquette, Charlevoix, Alpena and Harrison Township gather data on fish populations, fish health and the presence and effects of invasive species. It’s vital information that directly informs fisheries management decisions — such as stocking levels or regulated catch limits — and provides data to help gauge the success of past actions.

With surveying for 2024 wrapped up, DNR fisheries biologists are now synthesizing the findings and preparing for next year’s surveys. Interested in what the surveys found? Check out highlights from each research station’s survey efforts.

• Lake Superior and northern Lake Michigan (Marquette Fisheries Research Station)
• Lake Michigan (Charlevoix Fisheries Research Station)
• Lake Huron (Alpena Fisheries Research Station)
• St. Clair-Detroit River System (Lake St. Clair Fisheries Research Station)

Lake Superior and northern Lake Michigan

The crew of the research vessel (RV) Lake Char began work on Lake Superior as soon as the ice melted and continued through early November. The Marquette Fisheries Research Station’s work focuses on lake trout, though species studied this year also included lake whitefish and burbot.

Data from the spring 2024 Lake Superior surveys showed a slight increase in adult lake trout populations in nearly all areas. The summer juvenile lake trout survey indicated slight increases in recruitment (reproduction and survival) on the west side of the Keweenaw and Munising areas and a slight decline in all other locations, with stable populations overall. During the field season, 257,100 feet (48.7 miles) of assessment gill net was deployed for these surveys at 123 sampling stations across the lake.

The RV Lake Char surveyed waters around Isle Royale in spring to assess the status of lake trout populations around the island. The crew also conducted surveys in the deepest waters of Lake Superior (and all the Great Lakes) — about 1,320 feet — to survey siscowet lake trout populations. The RV Lake Char crew finished the survey season with lake trout survey work at Klondike Reef, a remote location 40 miles from shore, in October and then surveyed nearshore lake trout spawning reefs near Munising in early November.

Nearshore Great Lakes fisheries assessment work from Upper Peninsula ports involved 10 miles of trawling in Lake Michigan’s Little Bay de Noc and Big Bay de Noc. In addition, over 25,000 feet of survey gill net was used in four locations in northern Lake Michigan (Big Bay de Noc, Little Bay de Noc, Naubinway and Manistique) and two locations in southern Lake Superior (Keweenaw Bay and Huron Bay). Catch data from these fall surveys provide useful metrics for assessing fish community change and populations of species including walleye, yellow perch, smallmouth bass, northern pike, lake sturgeon and invasive Eurasian ruffe.

This winter, the Marquette Fisheries Research Station staff will perform maintenance in preparation for the 2025 field season and process the samples and data collected during 2024. These surveys provided data for collaborations with researchers from Purdue University, University of Wisconsin-Milwaukee, State University of New York-Brockport, Michigan Technological University and Michigan State University.

Lake Michigan

Three surveys accounted for the majority of the Great Lakes survey work for the Charlevoix Fisheries Research Station staff and the survey vessel (SV) Steelhead in 2024.

Spring gill net survey

Since 1997, the DNR has participated in a spring gill net survey, in collaboration with other Lake Michigan agencies. The objective is to assess recreationally, commercially and ecologically important fish populations, with a focus on lake trout, burbot, lake whitefish and yellow perch in Michigan waters. The information collected is used to inform ongoing research and management efforts for multiple species in Lake Michigan. Due to the broad area covered and multispecies focus, this survey provides the most comprehensive information on the status of adult Lake Michigan fish populations.

The spring gill net survey was conducted at eight ports this year: St. Joseph, South Haven, Saugatuck, Grand Haven, Arcadia, Leland, Elk Rapids and Charlevoix. Across all ports, more than 100,000 feet of experimental bottom gill net was deployed and provided data on more than 5,000 fish.

Lakewide acoustic (forage fish) survey

From late August to early September, the SV Steelhead and crew conducted the prey fish survey, a multiagency effort measuring the abundance of alewife, rainbow smelt, bloaters and other prey fish throughout Lake Michigan. This survey uses hydroacoustic (high-precision, recordable fish finder) gear. Results inform research and interjurisdictional trout and salmon management around predator/prey balance and lower food web changes in Lake Michigan, including the lakewide “predator-prey ratio” analysis to ensure prey fish can support the lake’s salmon and trout populations.

The hydroacoustic survey comprised 25 sections spanning nearshore and offshore regions around the basin. Areas surveyed this season by the SV Steelhead stretched from waters offshore of Beaver Island in the north around the Michigan shore to St. Joseph in the south.

Strong offshore winds Aug. 2–21 resulted in persistent coldwater upwelling along the eastern shoreline. These environmental conditions likely changed normal fish distributions and abundance estimates relative to previous survey years. Despite this challenge, preliminary results suggest relatively similar densities of age-1 (1+ years old) alewife and higher abundances of bloaters compared to previous years. However, young-of-year alewife abundance was estimated to be very low in 2024.

Bottom trawl survey

The SV Steelhead crew completed the annual bottom trawl survey in September and October at three of the ports sampled during the spring gill net survey (Saugatuck, South Haven and Grand Haven), as well as at the port of Pentwater. Ten trawl samples were collected at each port, covering a range of water depths from 25 feet to 120 feet. This survey provides information on the overall status of the nearshore fish community, including the presence, range expansion and effects of invasive species, and the status of yellow perch recruitment.

Other assessments

Charlevoix Fisheries Research Station staff also used small vessels for targeted surveys in 2024. Staff assisted Central Michigan University researchers with scuba surveys of mussel populations in large rivers and continued a multiyear assessment of spawning reefs in northern Lake Michigan. Reef assessments included characterization of habitat quality, deployment and collection of egg-sampling gear, and tagging of lake whitefish with acoustic tags to assess movement and spawning site use.

Lake Huron

The 2024 field season for the Alpena Fisheries Research Station and research vessel (RV) Tanner began in April with the annual spring lake trout assessment. The crew surveyed 14 locations in U.S. waters of Lake Huron from Drummond Island to Port Sanilac to determine the abundance and distribution of both young and adult lake trout. The catch rate of adult lake trout was similar to that of recent years, and most young lake trout (both hatchery-reared and wild-born) continue to be collected in northern Lake Huron.

Following the conclusion of the lake trout survey in late May, commercial fishery sampling in June, and tending Great Lakes Acoustic Telemetry Observation System, or GLATOS, receivers for fish movement studies in July, the RV Tanner completed a sonar and trawl survey of outer Saginaw Bay that targeted cisco. Cisco are important Great Lakes species that help maintain healthy predator species and provide fishing opportunities, as well as serve as an indicator of ecosystem health. Because of this, cisco are a focus of ongoing restoration efforts by multiple natural resource agencies around Lake Huron.

In the fall, the RV Tanner crew completed the annual Saginaw Bay fish community survey. This survey is done each September in partnership with the Lake St. Clair Fisheries Research Station and RV Channel Cat, and the 2024 Saginaw Bay assessment covered 16 net stations and 24 trawl sites. Survey catches showed a high abundance of young-of-year walleye in the bay (the second highest on record!), and adult walleye gill net catch rates that were similar to recent years’ numbers. However, both gill net and trawl catch rates of adult yellow perch in Saginaw Bay remained very low. A highlight of the survey was an encounter with two juvenile lake sturgeon, confirming their survival from ongoing stocking efforts in the Saginaw River system.

Soon after departing Saginaw Bay, the RV Tanner once again made its way to the eastern Upper Peninsula for an annual fish community survey in the Les Cheneaux Islands, where the gill net catch rate of yellow perch increased, and other indicators of perch population health were within sustainable ranges.

St. Clair-Detroit River System

The field season in Great Lakes waters of southeast Michigan kicked off with northern pike, mooneye and smallmouth bass tagging in Lake St. Clair and tributaries during March, April and May. The tags, which are surgically implanted into fish and send a signal to receivers in GLATOS, allow scientists to track movement of fish throughout the region and the Great Lakes as a whole. While data from northern pike and mooneye tagging is still coming in, the results from smallmouth bass tagging suggest that Lake St. Clair smallmouth bass exist in multiple, smaller subpopulations rather than one large lakewide population. These subpopulations occupy well-known areas of the lake such as Anchor Bay and the Mile Roads and appear to mix very little with smallmouth bass from other locations.

The annual lake sturgeon assessment in the North Channel of the St. Clair River showed continued recruitment of young lake sturgeon into the adult population—which means that young lake sturgeon are surviving into adulthood. The North Channel sampling location is considered a “hot spot” for young lake sturgeon, and this is supported by DNR survey data. During the past 27 years, survey crews have encountered individual fish from each year class born between 1997 (the year the survey began) and 2019 (the most recent year class that, because of their age and size, can effectively be caught by the sampling gear). In 2024, the DNR tagged 24 juvenile lake sturgeon in the North Channel with tags that are detected by GLATOS (like the northern pike, mooneye and smallmouth bass mentioned above) and more will be learned about the specific movements and habitat use by these fish in the coming years. New molecular analysis of fin clips from captured lake sturgeon shows that most fish larger than 63 inches are females, while those less than 63 inches long are evenly split between males and females.

Since 2021, DNR staff have completed lakewide surveys on Lake St. Clair in partnership with the Ontario Ministry of Natural Resources and the U.S. Fish and Wildlife Service. The partnership completed a netting survey that targeted larger-bodied fish in offshore areas of the lake in 2024, complementing other netting and electrofishing surveys completed in 2021 through 2023. These surveys will be conducted on a rotational basis to monitor any changes that occur in Lake St. Clair and inform future fisheries management decisions.

The 56-year-old RV Channel Cat made a weeklong trip to Lake Erie in early August to conduct a bottom trawl survey that documented walleye and yellow perch reproduction and an abundance of 8-inch and larger yellow perch. The RV Channel Cat and crew then returned to Lake St. Clair to collect lake sturgeon using 35 individual trawl tows. The individual sturgeon captured in this survey, which sometimes exceed 100 pounds, are rarely encountered in the North Channel survey efforts described earlier. August concluded for the crew with a micro-mesh gill net survey to describe the Lake St. Clair forage fish community. Micro-mesh gill nets were deployed at six locations and commonly captured logperch, yellow perch and round goby.

The RV Channel Cat closed out the year with a trip to Lake Erie in early October for the annual walleye assessment. Catch rates in the survey gill nets were the third highest observed since 1992, and the catch included many year classes (ages) of fish, which represents strong walleye reproduction in Lake Erie since 2015.

To learn more about how the DNR manages Michigan’s fisheries for current and future generations, visit Michigan.gov/Fishing.

The accompanying photos are available below for download. Caption information follows.

• Isle Royale lake trout: Research tech Lydia Doerr with a large lake trout caught during survey at Isle Royale, June 2024.
• Survey gill netting: Experimental bottom gill netting aboard the SV Steelhead in 2024.
• Saginaw Bay survey: DNR fisheries research biologist Dave Fielder holds a young lake sturgeon captured during the 2024 Saginaw Bay fish community survey.
• Sturgeon survey: During the annual Lake St. Clair lake sturgeon survey in 2024, the crew caught a 75.2-inch, 125-pound sturgeon, the largest caught in the history of that survey.