MSU Extension Michigan Sea Grant

At the recent annual Ludington Regional Fishery Workshop, offered by Michigan Sea Grant and MSU Extension, presentations included recent findings on natural reproduction of Chinook salmon, steelhead, and lake trout along with new developments in prey fish monitoring techniques. Two of the presentations are highlighted below.

Lake Michigan Prey Fish Monitoring - Dave Warner, U.S. Geological Survey

Since 1973, USGS has been conducting annual fall bottom trawl surveys to assess the abundance of alewife and other forage fish in Lake Michigan. This valuable long-term data set came into question as water clarity increased following the invasion of zebra and quagga mussels. An annual acoustic survey and midwater trawling was initiated in 2004, which has proven particularly useful for monitoring young alewife not normally caught in bottom trawls. New technologies including autonomous underwater vehicles (AUVs) and saildrones are being used to ensure accurate assessments of Lake Michigan prey fish.

Highlights from the video include:

• Quiet saildrones did not produce different forage fish estimates than trawling vessels, suggesting that boat noise is not a factor.
• Traditional acoustic surveys can miss fish close to the surface and close to the bottom; ongoing AUV studies will be able to look at the potential impact of this in the future.
• Spring bottom trawls were conducted in 2022; alewife were closer to bottom in deeper water than expected in spring and 85% of alewife caught in spring were Age 1.
• The fall acoustic survey found a very low density of Age 0 alewife, suggesting a poor 2022 year-class.
• Yearling and older alewife abundance has flatlined since 2014 in the bottom trawl survey, but the fall acoustic survey suggests a moderate increase in 2022 relative to the past few years.
• Bloaters were extremely abundant in the 1980s and early ‘90s, but nearly disappeared by the mid-2000s. The 2021 bloater year-class appeared to be the strongest on record since acoustic surveys began in 2003, and adult bloater abundance is beginning to trend upward.
• Although bloaters are now the most abundant forage fish in Lake Michigan, there is no evidence of salmon and trout utilizing bloater as a food source.

Great Lakes Mass Marking Program - Chuck Bronte, U.S. Fish & Wildlife Service

The Great Lakes Mass Marking Program is a collaboration among federal, state and tribal agencies coordinated by the U.S. Fish and Wildlife Service. The program began marking and tagging salmon and trout in 2010 to address questions on their survival, natural reproduction, movement, and growth. Since its inception, the program has marked and/or tagged over 113 million hatchery fish destined for Lakes Michigan, Huron and Ontario. The program also collects biodata and tags from fish returning to sport fisheries, with records on over 146,000 angler-caught fish over ten years. Program biologists extract and read tags from this field survey as well as state creel and assessment surveys; estimate ages from wild fish; contribute data to fish population models used to make management decisions; and provide biological specimens to several partner-led research efforts, such as studies of fish diet.

Coded-wire tags (CWTs) are embedded into the snouts of fish in hatcheries and are etched with a unique code that provides information on the stocking location, genetic strain, and year class of a group of fish, and have been used on all lake trout stocked in US waters since 2010.  Chinook salmon stocked in lakes Michigan and Huron from 2011 – 2016 also received a coded-wire tag; but beginning in 2017, tagging shifted from Chinook salmon to steelhead. Most Chinook salmon continued to receive fin clips (but not CWTs) after 2016, but Chinook salmon and steelhead stocked in 2020 did not receive fin clips due Covid-19 safety protocols. Anglers may notice increased numbers of unmarked fish in their catches both due to this unmarked year-class and increasing natural reproduction.

Highlights from the video include:

• Most Chinook salmon caught in lakes Michigan and Huron are from wild reproduction, not hatcheries. 
• Wild Chinook salmon production has varied from year to year, occurs mostly in Michigan tributaries, and is trending upward.
• Chinook salmon move long distances, and where a fish is landed has little to do with where it was stocked except during the fall, when fish return to streams where they were stocked (hatchery fish) or produced (wild fish) to spawn.
• Most Chinook salmon stocked in Lake Huron move into Lake Michigan to feed before returning to Lake Huron to spawn.
• Wild Lake trout abundance in sport fisheries has increased in Lake Huron as well as southern and northern Lake Michigan.  These trends are encouraging but are not yet at management targets in many areas.
• Lake trout stocked offshore in fishing refuges have higher survival than lake trout stocked onshore, and offshore-stocked lake trout contribute substantially to nearshore sport fisheries.
• Most lake trout are landed within 60 miles of where they were stocked.
• About 30-45% of steelhead in Lake Michigan are from wild, natural reproduction, and wild production has ranged from 1.0 – 1.6 million steelhead per year during 2017 – 2019.
• Steelhead, like Chinook salmon, move long distances after stocking and where they are landed has little to do with where they were stocked except during spawning season.
• About 24% of steelhead stocked in Lake Huron have been caught in Lake Michigan, but like Chinook salmon, few fish stocked in Lake Michigan are caught in Lake Huron.
• Steelhead survival was generally higher from southern stocking locations than northern stocking locations.
• Survival and growth rate may also vary among different genetic strains of steelhead.

More workshops

Michigan Sea Grant will also hold other Regional Fisheries Workshops offered around the state in April. Registration and agendas are available online.

Michigan Sea Grant helps to foster economic growth and protect Michigan’s coastal, Great Lakes resources through education, research and outreach. A collaborative effort of the University of Michigan and Michigan State University and its MSU Extension, Michigan Sea Grant is part of the NOAA-National Sea Grant network of 34 university-based programs.

This article was prepared by Michigan Sea Grant under award NA180AR4170102 from the National Oceanic and Atmospheric Administration, U.S. Department of Commerce through the Regents of the University of Michigan. The statement, findings, conclusions, and recommendations are those of the author(s) and do not necessarily reflect the views of the National Oceanic and Atmospheric Administration, the Department of Commerce, or the Regents of the University of Michigan.