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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Life Histories
PREDICTING MASS EMERGENCE OF MAYFLY (HEXAGENIA) ADULTS IN LAKE ERIE.
L.D. Corkum1, J.J.H. Ciborowski1, D.M. Dolan2, and M.J. Roy2. 1Department of Biological Sciences, University of Windsor, Windsor, Ontario, Canada N9B 3P4, 2Natural and Applied Sciences, University of Wisconsin at Green Bay, Green Bay, Wisconsin, USA 54311
Improved water quality in Lake Erie has resulted in the re-appearance and expansion of burrowing mayflies in the lake. Mayflies are good water quality indicators, but the mass emergence of adults attracted to lights in cities and at power plants creates traffic problems and electrical brownouts. To assess which abiotic factors best predict mass emergence within the typical eight week emergence span, we recorded meteorological data and censused adult Hexagenia in randomly placed quadrats (n=5) at Colchester Harbour (NW Lake Erie) during June and July 2000. We used stepwise discriminant function analysis (SAS) to determine which abiotic factors (air temperature, wind speed, wind direction, wind chill, barometric pressure, humidity, dew point, rain, and moon phase) best predicted the peak emergence (June 18 to July 2) from early June until late July. Mean (SE) density during the largest nighttime swarm was 24,740 (8,757) adults per m2. Wind chill, air temperature, wind direction and moon phase (full moon) were most successful in predicting the density of adult Hexagenia. The number of dates on which mass emergence was correctly predicted varied with life history stage (subimagos, 68%; imagos, 76%), and sex (males, 60%; females, 76%).
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