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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Wetlands I
SALMON ON A SMALLER SCALE: MAYFLY LARVAL MIGRATION LINKS LAKE MICHIGAN TO A TEMPORARY WOODLAND POND (DOOR COUNTY, WISCONSIN, USA).
J.D. Hoekstra1,2 and D.A. Soluk1,2. 1Department of Animal Biology, University of Illinois, Urbana, IL 61801 USA, 2Center for Aquatic Ecology, Illinois Natural History Survey, Champaign, IL 61820 USA
Larvae of several Leptophlebiid mayfly species are known to migrate from larger streams into tributaries and fringing wetlands after snowmelt. In mid-April 2001, we observed larval migration by Leptophlebia sp. mayflies from Lake Michigan to a temporary woodland pond complex. Mayflies aggregated along the lake margin in the late evening and moved 78 m up an outlet stream to the pond complex. Larvae were abundant in connected ponds up to 300 m away from the outlet, but were absent from adjacent isolated wetlands. We censused larvae as they moved across a spillway. 5-minute counts were taken every 2-6 hours for 3 days. Over that period, we estimate that > 155,000 larvae moved from Lake Michigan into the temporary wetland (mean total dry biomass flux: 48 g d-1). By mid-May, the wetland was isolated from Lake Michigan but Leptophlebia larvae remained abundant and many had reached the final instar. Our observations, made at an undisturbed coastal preserve, illustrate how animal movements and material fluxes may link Great Lake littoral zones with adjacent wetlands. Throughout the region, many similar linkages have likely been disrupted by shoreline development.
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