Author： Nalepa Thomas Pothoven Steven Fanslow David
Publisher： Taylor & Francis Ltd
ISSN： 1463-4988
Source： Aquatic Ecosystem Health & Management, Vol.12, Iss.1, 2009-01, pp. : 2-10
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Abstract
Surveys of the benthic macroinvertebrate community were conducted in the main basin of Lake Huron in 2000 and 2003, and corresponding studies of lake whitefish diets were conducted in 2002-2004. Populations of three major benthic taxa, Diporeia spp., Sphaeriidae, and Chironomidae, declined dramatically between 2000 and 2003, with densities declining 57%, 74%, and 75% over this 3-year period. By 2003, Diporeia, an important food source for lake whitefish, was gone or rare at depths < 50="" m="" except="" in="" the="" far="" northeastern="" portion="" of="" the="" lake.="" in="" contrast,="" densities="" of="" the="" dreissena="" bugensis="" (quagga="" mussel)="" increased="" between="" 2000="" and="" 2003,="" particularly="" at="" the="" 31-50="" m="" depth="" interval,="" while="" densities="" of="" the="" zebra="" mussel="" dreissena="" polymorpha="" remained="" stable.="" as="" expected,="" the="" diet="" of="" lake="" whitefish="" varied="" with="" fish="" size.="" age-0="" lake="" whitefish="" fed="" mainly="" zooplankton,="" most="" of="" which="" were="" daphnia="" (98%).="" medium="" lake="" whitefish="">< 350="" mm="" excluding="" age-0="" fish)="" fed="" mainly="" on="" zooplankton,="" chironomidae,="" and="" dreissena="" bugensis,="" and="" large="" lake="" whitefish="" (350="" to="" 688="" mm)="" fed="" mainly="" on="" d.="" bugensis="" and="" gastropoda.="" the="" diet="" of="" medium="" and="" large="" lake="" whitefish="" reflected="" the="" changing="" nature="" of="" the="" benthic="" community;="" that="" is,="" diporeia="" was="" rarely="" found="" in="" the="" diet="" while="" d.="" bugensis="" played="" a="" prominent="" role.="" since="" diporeia="" has="" a="" much="" higher="" energy="" content="" than="" d.="" bugensis,="" contrasting="" density="" trends="" in="" the="" two="" organisms="" will="" have="" long="" term="" consequences="" to="" the="" relative="" health="" of="" lake="" whitefish="" populations="" in="" the="" lake.="">
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