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PLEASE NOTE: The schedule posted here is as of 1/25/16, and is subject to change. Please check back for updates.
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Monday, January 25 • 1:20pm - 1:40pm
Do Lake Huron Fish Prefer Hot Dogs or Potato Chips?

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AUTHORS: Patricia Armenio*, David "Bo" Bunnell, David Warner –USGS-GLSC

ABSTRACT: The Lake Huron food-web has undergone fundamental changes since 2002 from declines in primary production to the near collapse of the Chinook salmon fishery.  One native forage fish species, bloater Coregonus hoyi appears to have at least partially benefited from the changing ecosystem.  Bloater consumes both benthic invertebrates and zooplankton and has increased in abundance since the mid-2000s, although its growth and condition appears stunted.  Rainbow smelt Osmerus mordax, a nonnative forage fish, is another dominant prey fish in Lake Huron, although its population trends have trended downward since the 1980s and has been relatively stable in the 2000s.  One possible explanation for the changing fish community is a shift in zooplankton community composition and domination of the benthic invertebrate community by invasive dreissenid mussels (which bloater and smelt cannot consume).  To evaluate which prey species were important to bloater and rainbow smelt consumption, we calculated Vanderploeg’s W´ index of selectivity in Spring, Summer, and Autumn of 2012 at three depths (18 m, 46 m and 82 m) near Hammond Bay and Thunder Bay in northern Lake Huron.  Bloater greater than 90 mm total length (TL) selected mostly for chironomids, Mysis, and also Bythotrephes.  While Mysis is an energetically valuable prey item (i.e., hot dogs), chironomids and Bythotrephes are lower food quality (i.e., potato chips).  These diet selectivities could help explain the truncated size distribution and lower than expected physiological condition of bloater.  Rainbow smelt greater than 80 mm selected mostly for Senecella calanoides, a large calanoid copepod, in Spring and Bythotrephes in other seasons.  Rainbow smelt seem to be more opportunistic and generalist feeders than bloater.  Our research describing forage fish diet and selectivity patterns can be used in future research to better understand changes in growth and production of these two key species in Lake Huron.

Monday January 25, 2016 1:20pm - 1:40pm EST
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