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GLIN==> UPCOMING SEMINAR

Dr. Steve Pothoven from the NOAA Great Lakes Environmental Research Laboratory, will be giving a seminar on Wednesday, April 12 as a part of the NOAA/ University of Michigan Great Lakes Seminar Series. Please find details of his talk listed below.

Title: Condition and Diet of Lake Whitefish in Lakes Michigan and Huron

Speaker: *Steve Pothoven*, Fishery Biologist, Lake Michigan Field Station, NOAA/GLERL

Date: Wednesday, April 12

Time: 1030 AM

Location: NOAA/ GLERL
              2205 Commonwealth Blvd., Ann Arbor, MI, 48105

Abstract:
Fishery managers and commercial fishermen have expressed concern about recent declines in lake whitefish body condition in the Great Lakes. We evaluated the diets of lake whitefish throughout Lake Michigan during 1998-2004 and Lake Huron during 2002-04 to determine what prey types are currently eaten following dreissenid invasions and /Diporeia/ declines. Results from both lakes confirm that /Diporeia/ are a major prey source when available. In the absence of /Diporeia/, lake whitefish tend to eat more /Mysis/, /Chironomidae/, zooplankton, or dreissenid mussels, depending on geographic location and fish size. These prey either contain little energy or are less abundant than /Diporeia/ were historically. Based on data from Lake Huron, the type of prey eaten affected the food and energy intake differently for different size classes of lake whitefish. Food weight in juvenile lake whitefish stomachs did not differ across prey groups, but energy in stomachs was highest for fish that ate mainly non-mollusc macro invertebrates. For large lake whitefish, there was no difference in food weight or energy in stomachs for different prey groups. The size of benthic prey (/Diporeia/, /Chironomidae/, and /Dreissena/ spp.) eaten increased with fish size and influenced the energetic content of prey for different size groups of fish. Energy density and body condition of lake whitefish was higher in Lake Michigan than Lake Huron. Differences in energy density between lakes were attributed to variation in diet and prey energy content as well as factors that affect feeding rates such as lake whitefish density and prey abundance.

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If you have any questions or concerns, please email me at kanika.suri@noaa.gov; or call 734-741-2147.

For more information about the seminar series, please visit our website at http://www.glerl.noaa.gov/news/seminars/

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Kanika Suri
Center of Excellence for Great Lakes and Human Health
2205 Commonwealth Blvd.,
Ann Arbor, MI
48105

734-741-2147


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