Recent changes in benthic macroinvertebrate populations in Lake Huron and impact on the diet of lake whitefish (coregonus clupeaformis)

Abstract

Surveys of the benthic macroinvertebrate community were conducted in the main basin of Lake Huron in 2000 and 2003, and corresponding studies of lake whitefish diets were conducted in 2002-2004. Populations of three major benthic taxa, Diporeia spp., Sphaeriidae, and Chironomidae, declined dramatically between 2000 and 2003, with densities declining 57%, 74%, and 75% over this 3-year period. By 2003, Diporeia, an important food source for lake whitefish, was gone or rare at depths < 50 m except in the far northeastern portion of the lake. In contrast, densities of the Dreissena bugensis (quagga mussel) increased between 2000 and 2003, particularly at the 31-50 m depth interval, while densities of the zebra mussel Dreissena polymorpha remained stable. As expected, the diet of lake whitefish varied with fish size. Age-0 lake whitefish fed mainly zooplankton, most of which were Daphnia (98%). Medium lake whitefish (< 350 mm excluding age-0 fish) fed mainly on zooplankton, Chironomidae, and Dreissena bugensis, and large lake whitefish (350 to 688 mm) fed mainly on D. bugensis and Gastropoda. The diet of medium and large lake whitefish reflected the changing nature of the benthic community; that is, Diporeia was rarely found in the diet while D. bugensis played a prominent role. Since Diporeia has a much higher energy content than D. bugensis, contrasting density trends in the two organisms will have long term consequences to the relative health of lake whitefish populations in the lake.

Keywords:

• benthos
• Diporeia spp.
• Dreissena
• macroinvertebrate-fish interaction

Acknowledgements

We thank the crews of the R/V Laurentian and R/ V Lake Guardian for their help and assistance during field operations; the Great Lakes National Program Office, Environmental Protection Agency for use of the Lake Guardian and partial funding; the Michigan Great Lakes Protection Fund for partial funding; Michael Winnell for providing the unpublished 1972 data; Steve Lozano and Andrew Foley, III for assistance during field collections; and the many students that helped sort and process the samples. This is Great Lakes Environmental Research Laboratory Publication No. 1443.

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