A successful Great Lakes fisheries survey year

The Michigan Department of Natural Resources has completed its annual Great Lakes survey season, conducted on all of our Great Lakes waters from April to November 2021. The data from these surveys directly informs fisheries management decisions and future actions on Great Lakes waters.

Survey highlights from the DNR’s four Great Lakes fisheries research stations, as arranged from north to south, include:

Lake Superior and Northern Lake Michigan – Marquette Fisheries Research Station

The research vessel Lake Char, which surveys Lake Superior and focuses on lake trout, began work as soon as the ice was gone. The R/V Lake Char had a full season that included a trip to Isle Royale in June to document lake trout spawning in deep water and outside the expected fall spawning period, and the crew used a deep-water remotely operated vehicle that deployed video recording and a vacuum sampler. The sampling confirmed lake trout spawning in June and the deepest ever documented lake trout spawning in water over 300 feet deep. These surprising observations will be used with other survey data to further improve lake trout management in Lake Superior.

Lake Michigan – Charlevoix Fisheries Research Station

Two surveys accounted for the majority of the Great Lakes survey work for the Charlevoix Fisheries Research Station staff and the survey vessel Steelhead in 2021.

Spring gill net survey

The spring gill net survey was conducted at seven ports this year: St. Joseph, South Haven, Saugatuck, Grand Haven, Arcadia, Leland and Charlevoix. Across all ports, more than 100,000 feet of experimental, bottom gill net were deployed with catches of more than 5,000 fish.

The objective of this survey 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, and to use the information collected to inform ongoing research and management efforts for multiple Lake Michigan species. This is a collaborative assessment with other Lake Michigan agencies that has been conducted since 1997; due to the broad spatial coverage and multispecies focus, this survey provides us with our most comprehensive picture of the status of adult Lake Michigan fish populations.

Lakewide acoustic (forage fish) survey

For most of the month of August, the S/V Steelhead and crew were conducting the forage fish survey, a multiagency effort measuring the abundance of alewife, rainbow smelt, bloater chub and other prey fish throughout Lake Michigan, using hydroacoustic (high-tech, recordable fish finder) gear. This year’s prey fish assessment included an added element: a calibration study that used two U.S. Geological Survey “saildrones” that measured prey fish acoustically, but without vessel motor interference. Results from this survey continue to inform research and interjurisdiction trout and salmon management concerning predator/prey balance and lower food web changes in Lake Michigan including the lakewide “predator-prey ratio” analysis.

Bottom trawl survey

In addition to these two major surveys, the S/V Steelhead and crew completed the annual bottom trawl survey in September at four of the ports sampled during the spring gill net survey. This lakewide survey provides information on the overall status of the nearshore fish community, including the presence, range expansion and effects of exotic species and the status of yellow perch recruitment.

Other assessments

Small survey vessels were used by Charlevoix Fisheries Research Station staff for targeted surveys during fall 2021, with assessments of northern Lake Michigan reef fish populations being completed from August through November. Assessments included deployment and collection of egg-sampling gear, along with numerous acoustic telemetry projects examining lake trout, lake whitefish and cisco movements and spawning site use. Staff, who are members of the DNR Fisheries Division dive team, also assisted with mussel surveys in the Detroit River, as well as reef monitoring work in Saginaw Bay.

Lake Huron – Alpena Fisheries Research Station

The R/V Tanner and its crew from the Alpena Fisheries Research Station completed a full suite of fisheries assessments across Lake Huron during 2021, traveling from the Les Cheneaux Islands in the north to the Thumb Coast in the south, with many stops in between. Fieldwork began in April, with an annual lake trout survey that samples more than a dozen stations across the main basin through the month of May. The findings from the spring gill net survey continue to show strong natural reproduction of lake trout in the northern part of the lake, but declining recruitment of stocked lake trout in the south.

In early and mid-summer, the R/V Tanner and its crew conducted exploratory sampling and provided assistance to science partners including: remotely operated vehicle and water chemistry work at the Middle Island sinkhole, deploying of dissolved oxygen loggers in Saginaw Bay, and completing the second Outer Saginaw Bay hydroacoustics and midwater trawling survey in support of a multiagency evaluation to determine the success of recent cisco rehabilitation efforts.

By late August, the R/V Tanner again was deployed to Saginaw Bay for the annual September fish community survey. While data for the gill net portion of this survey are still being examined, preliminary results indicate the highest gill net catch rate for walleye since 1994, with yellow perch catch rates being similar to recent years. Of special note, two juvenile lake sturgeon stocked as part of recent restoration efforts in the Saginaw River watershed were captured and released.

Immediately after the conclusion of the Saginaw Bay survey, the R/V Tanner traveled north to the Les Cheneaux Islands, where an early October fish community survey revealed an increase in yellow perch gill net catch rates and a record smallmouth bass catch rate, which topped all previous data collected since 1969. The data collected throughout the entire 2021 survey season are being examined, shared with partners, and used to update models and decision tools that help inform fisheries managers on the status of lake trout, walleye, yellow perch and other important species across Lake Huron.

St. Clair River – Lake Erie Corridor – Lake St. Clair Fisheries Research Station

The 2021 field season for the R/V Channel Cat and crew began in April 2021 with a spring trap net survey in Anchor Bay of Lake St. Clair. New for this year’s survey was the surgical insertion of acoustic telemetry tags in smallmouth bass, which will allow biologists to track their movements and habitat use throughout the St. Clair-Detroit River System and beyond. After removing the trap nets in May, survey effort moved to the North Channel of the St. Clair River with the annual June setline survey for lake sturgeon. A total of 112 lake sturgeon were caught and tagged, including 37 fish that were captured in previous survey efforts.

In July, the first-ever binational Lake St. Clair-wide small fish survey was conducted in cooperation with the Ontario Ministry of Northern Development, Mines, Natural Resources, and Forestry and the U.S. Fish and Wildlife Service. Catch rates of forage fish and juvenile sport fish in the nearshore waters of the lake were sampled with similar survey gear to ensure results from U.S. and Canadian waters were comparable. Interestingly, catch rates were 10 times higher in Canadian waters where natural, undisturbed shorelines are much more common than in U.S. waters where hardened seawalls prevail.

In August, assessment efforts shifted to trawling with the eighth annual Lake Erie trawl survey and the annual Lake St. Clair lake sturgeon trawl survey. The Lake Erie survey, which is used to assess the abundance of forage fish and young-of-year walleye and yellow perch in Michigan waters of the west basin, continued to document strong reproduction for both species, including a record-high catch rate of juvenile yellow perch.

The Lake St. Clair survey resulted in the captured of 35 lake sturgeon (33 first-time captures and two fish that were captured in previous surveys) that were tagged and released. The largest lake sturgeon was a 73-inch fish that tipped the scales at 104 pounds. Trawling work continued into September, when the R/V Channel Cat joined the R/V Tanner for the annual Saginaw Bay fish community survey. The catch rates of young-of-year walleye and yellow perch in the Saginaw Bay trawls were high, and forage abundance was the second-highest measured in the past 10 years.

The survey season for the R/V Channel Cat concluded the first week of October with the Lake Erie walleye index survey, which measures the abundance of yearling and older walleyes. Walleye catch rates were up from 2020, with a substantial proportion of the fish likely representing the strong 2019 year class.

The year’s field work concluded with a Lake St. Clair nearshore assessment from the R/V Mooneye, the station’s electrofishing boat. Preliminary results indicate a diverse fish community comprised of both sport and nongame fish. Final data analysis from all 2021 surveys is ongoing, and results will be shared with partners to promote sound, scientific fisheries management in the international waters of the region.

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