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MDNR Report

Salmon Forage BaseSalmon Forage Base

Michigan’s DNR’s survey vessel Steelhead and vessels from two other agencies cooperatively plied the waters of Lake Michigan in August, sampling key forage fish populations critical to the health of salmon, steelhead and lake trout, and found forage fish numbers to be improving in Michigan waters.

The 2022 hydro acoustic survey comprised 26 transects spanning nearshore and offshore regions around Lake Michigan. A transect essentially is a predetermined line, from point A to point B, that determines the survey route.

The S/V Steelhead completed 13 of these transects in cooperation with the U.S. Geological Survey research vessel Sturgeon (eight transects) and the U.S. Fish and Wildlife Service R/V Baird (five transects).

“The work was completed in late summer in spite of midseason shipyard repair delays that gave the S/V Steelhead a later-than-normal start,” said Dave Clapp, Charlevoix Fisheries Research Station manager. “Thanks to the crew’s hard work and favorable weather, though, the S/V Steelhead was able to complete the largest number of annual survey transects since this survey began in 2004.”

Transects completed by the S/V Steelhead this season stretched from waters offshore of Chicago in the south, around the Michigan shore, to Platte Bay in the north. At roughly the same time, the R/V Sturgeon completed transects along the Illinois and Wisconsin shore in the west, while the R/V Baird completed transects along the Wisconsin and Michigan shore in the north.

While final survey results have not yet been compiled, several noteworthy observations emerged:

  • As expected in recent years, forage fish abundance was much greater in nearshore areas than further offshore. However, unlike previous years, midwater trawl catches and apparent fish densities were higher in the northeast nearshore than in the southeast nearshore where fish abundance is nearly always greatest.
  • Largest catches in midwater trawls were yearling and older rainbow smelt, alewife and bloater. Yearling and older rainbow smelt have rarely been encountered in recent years, so the large catches this year mark a sharp departure from recent surveys.

The size distribution of the alewives captured in 2022 was also very different than recent years. Typically, smaller size groups have dominated the catch, but this year’s alewife catches included a much broader range of sizes from 4-8 inches and included some large individuals greater than 8 inches in length. Moreover, very few young-of-year (< 4 inches) alewives were captured at any transect location. These results may indicate that 2022 was a low recruitment year for alewives, but also that predation and other mortality was low, allowing some to survive to larger sizes.

Finally, acoustic density estimates and midwater trawl catches of bloater have been increasing in recent years; 2022 survey results suggest that densities of bloater continue to remain high and may be increasing regionally in Lake Michigan.

Overall, the forage community is showing signs of improvement that bodes well for future fishing on Lake Michigan.