PARENT SESSION
Contributed Oral Session 35: Invasive Species: Great Lakes Area
Monday, August 8, 1:30 PM - 5:00 PM, Meeting Room 524 B, Level 5, Palais des congrès de Montréal
Zebra mussels (Dreissena polymorpha) increase the growth rates of adult bluegill sunfish (Lepomis macrochirus) in inland Michigan lakes.
Scheele, Carrie*,1, Knoll, Lesley2, Hall, Donald1, 1 Michigan State University, East Lansing, MI2 Miami University, Oxford, OH
ABSTRACT- The invasive zebra mussel (Dreissena polymorpha) has rapidly spread throughout freshwater systems in the United States and has recently overcome terrestrial dispersal barriers, colonizing smaller inland lakes. We conducted an extensive survey of inland Michigan warm-water lakes to examine the indirect impacts of zebra mussels on the growth rates of adult bluegill sunfish (Lepomis macrochirus), the dominant fish species. Sixty lakes with similar morphometries and nutrient concentrations were sampled in 2002-2003. Half were infested with zebra mussels (invaded), while the zebra mussel free (uninvaded) lakes served as controls. Preliminary results show zebra mussels lowered chlorophyll a by 30% and thus significantly increased the water clarity of invaded lakes. Growth rates of young-of-the-year bluegill did not differ between invaded and uninvaded lakes, while growth rates of adult bluegill were significantly higher in invaded lakes. On average, adult bluegill in invaded lakes grew 2mm more each year compared to adult bluegill in uninvaded lakes and these effects became much greater in older, longer fish. Possible mechanisms for increased adult bluegill growth rates include greater foraging efficiency on zooplankton (Daphnia) due to improved water clarity and diet supplementation with benthic invertebrates that are promoted by zebra mussel presence in lakes. Increased understanding of zebra mussel effects on diet and growth of bluegills will expand our knowledge of the food web consequences of this invasive species and help lake managers determine important recreational fish management decisions in Midwestern lakes.
Key words: zebra mussels, bluegill sunfish, invasive species, food web interactions