Cooperative Fish and Wildlife Research Units Program: Iowa
Education, Research and Technical Assistance for Managing Our Natural Resources

Iowa Project

Effects of Introduced Common Carp and Invading Zebra Mussels on Water Quality and the Native Biological Community of Clear Lake, Iowa

May 2007 - June 2012


Participating Agencies

  • Iowa Department of Natural Resources

Goals and Objectives: o Quantify major ecosystem components, including common carp, zebra mussels, and the native fish and macroinvertebrate communities. o Compilation and organization of existing data. o Assembly of empirical relationships from the literature and compiled data. o Construction of several component models describing portions of the ecosystem. o Combining component models into a single ecosystem-level simulation model. Progress: The project has had four field seasons completed during 2007-2010. The adult carp population was estimated to be 35,738 (95% C.I.= 29,756-41,694), 59330 (95% C.I. = 50,072-68,588) and 32615 (95% C.I. = 25889-39342), 62003 (95% C.I.= 54134-69872) individuals in 2007, 2008, 2009, and 2010 respectively based on mark-recapture population estimates. Estimated biomass per hectare was 92.62 (95% C.I. = 86-99) and 211.89 (95% C.I.= 203-221) and 126.85 (95% C.I.= 100.7-153.0) in 2007, 2008 and 2009 respectively. The fish assemblage has been dominated by walleye, yellow bass, and common carp on estimated densities and biomass of nearshore and offshore fish species. The age 1+ fish assemblage was generally similar in 2009 compared to 2007 and 2008, but few bullhead were captured in 2009 and 2010, reflecting a major decrease in black bullhead abundance. Age 0+ seine catches of yellow bass, yellow perch, and forage fish (e.g., spottail shiners, fathead minnows) in 2009 and 2010 were dramatically increased relative to 2007 and 2008. Benthic invertebrates assemblages were dominated by chironomidae in mud and muck benthic substrates and zebra mussels on rocky substrates. Zebra mussel densities on rock substrates was 1,032,508 individuals meter-2 in 2009, a 7.8 fold increase from 2007. Settlement of zebra mussels on colonization plates and benthic surveys indicate that the zebra mussel population was more abundant in 2010 than 2007 and have colonized the majority of suitable habitat in the lake. Zebra mussel (>2mm) densities on colonizaton plates was overall lower in 2009 and 2010 compared to previous years. A preliminary ECOPATH model of the system has been completed and in the prosess of being written up for publication (target journal: Ecological Modeling). Additional submodels (e.g., sediment resuspenstion, water quality) of the overall ecosystem model are in stages of development, parameterization, and integration with the ECOPATH model. Several presentations were made at various meetings at the state, region and national level. Check out the project web site at: Check reports on Clay Pierce's website ( for a complete version of this report. Questions about this project should be directed to Mike Colvin ( or Clay Pierce (, 515-294-3159). Future Plans: Synthesis of field results and model development and evaluation will continue. Processing of field samples will continue in the laboratory. Many more presentations of preliminary findings are planned.