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To return to the Midwest Fish & Wildlife Conference website, go to http://www.midwestfw.org/ The following schedule and room names are subject to change (as of February 1, 2017). Please check back for updates. 

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Tuesday, February 7 • 6:00pm - 9:00pm
Poster Display. Depth Distribution of Juvenile Bluegill Sunfish in an Oligotrophic Wisconsin Lake

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AUTHORS: David Lonzarich, University of Wisconsin - Eau Claire, Nate Sylte, University of Wisconsin - Eau Claire, Emma Donley, University of Wisconsin - Eau Claire

ABSTRACT: A large literature has accumulated on the factors affecting the distribution and abundance of lake-dwelling juvenile Bluegill (Lepomis macrochirus).  Among the factors most often linked to patterns of habitat use in this species are vegetation cover, predation risk and food availability.  In this study, conducted in a deep oligotrophic, warm-water Wisconsin lake, we used trapping surveys and underwater observation to document variability in bluegill densities along a depth gradient from 1 to 7 meters.  Pine Lake, located in northwestern Wisconsin is one of the deepest and clearest lakes in the state.  Secchi depths during summer routinely exceed 6 meters and the epiliminion extends to a depth of 7.5 meters.  Sampling waters at depths of 1, 3, 5 and 7 meters, we collected juvenile bluegill with minnow traps and estimated fish densities from dive surveys in late summer 2016.  We also measured zooplankton densities, and estimated vegetation type and cover from all depth strata. Minnow trap surveys revealed a dome-shaped distribution of fish with the highest numbers collected at 5 meters (10 fish/trap) and the lowest at 1 meter (2.8 fish/trap).  Dive surveys, however, revealed a linear relationship with depth, with the deepest locations containing the highest sunfish densities.  In fact, we often encountered extraordinarily large aggregations (10s of thousands) of Bluegill juveniles (and other species) at individual dive locations near 7 meters, just above the thermocline.  This depth also typically contained dense, uniform stands of vegetation and the highest zooplankton densities.  While supporting the conventional view concerning habitat selection in juvenile Bluegill, our findings suggest that lake trophic status (which affects the depth of the epilimnion and of vegetation) may help inform our understanding of distribution patterns of juvenile bluegill in lake ecosystems.

Tuesday February 7, 2017 6:00pm - 9:00pm
Lancaster Ballroom

Attendees (2)