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Bringing back the whitefishes

Today’s MI Environment story by Todd Wills, Edward Baker and Dave Clapp, of the Michigan Department of Natural Resources, is from the State of the Great Lakes report.

Great Lakes “coregonines” are an ecologically and economically important group of fishes within the trout and salmon family.

In Michigan, this group of fish in the genus Coregonus includes well-known species such as lake whitefish and cisco, as well as less-familiar fish such as shortjaw cisco, bloater and kiyi.

Implanting lake whitefish from Lake Michigan with acoustic tags. (Photo courtesy of DNR)

Implanting lake whitefish from Lake Michigan with acoustic tags. (Photo courtesy of DNR.)

Historically, these widespread and abundant species supported large commercial fisheries, created recreational fishing opportunities and provided a critical link in Great Lakes food webs between plankton and top predators such as lake trout and walleye.

Unfortunately, by the middle of the 20th century a number of factors – including over-fishing, loss of habitat and predation and competition from invasive species such as sea lamprey and rainbow smelt – caused many Great Lakes coregonid populations to collapse. This group continues to host some of the most imperiled native species in the Great Lakes, and much interest exists in rehabilitating their populations.

Many of the same pressures that caused coregonid populations to decline in the past century still exist and remain a concern today. While lake whitefish continue to be a highly-desired food fish in the Great Lakes, their populations have exhibited slow growth and poor body condition that correlate with the loss of Diporeia, a group of zooplankton species that has been in decline since the invasion of zebra and quagga mussels in the late 1980s.

Further, lake whitefish populations have experienced poor recruitment since the early 2000s, which is thought to be due to climate variability and resulting changes in water temperature, water levels and currents and ice cover as well as pressure from zebra and quagga mussels that continue to alter zooplankton communities (and their availability as a food source for young fish) and foul spawning habitat. Great Lakes cisco have experienced a loss of diversity and historical forms that bridged lower and upper trophic levels and are sending different population signals across the basin. Cisco populations are declining in Lake Superior, expanding in Lake Michigan and geographically isolated in Lake Huron despite opportunities to expand and fill an open niche in the food web.

These issues, combined with gaps in knowledge and information about environmental, behavioral and genetic factors that support existing coregonine fisheries, make fisheries management a challenge. To address these challenges, staff from state, federal and tribal natural resource agencies in Michigan are currently engaged in collaborative work, facilitated through the Great Lakes Fishery Commission’s lake committee structure, to address knowledge gaps and advance coregonine management, as detailed in the accompanying infographic on pages 28 and 29 in the State of the Great Lakes report.