BENTHIC PRODUCTIVITY AND LIFE-HISTORY OF FINGERNAIL CLAMS OF POOL 9, UPPER 
MISSISSIPPI RIVER

Jim Eckblad,  Matt Hoegh,  Dan McAdam,  Ben Reynolds,  Betsy Evans,  Michael 
Swenson,  Karl Swenson,  David Schultz,  Melissa Howie,  Trish Young,  Nick 
Leslein,  Bret Powell,  Leah Doerr,  Katie McVey
Department of Biology, Luther College, Decorah, Iowa 52101

      Over a 4-year period (2003 - 2006, May to October) studies were conducted 
on benthic macroinvertebrate populations of Big Lake, along with 9 other 
backwater lakes of  Pool 9.  Thirteen abiotic parameters were estimated to help 
characterize differences in the 10 lakes.  Greater water depth, higher bottom 
oxygen, greater Secchi depth, higher pore water percentage, higher silt or clay 
percentage were variables associated with greater numbers of macroinvertebrates.  
Life-history data for fingernail clams (Musculium transversum) was used to 
estimate reproductive contribution during the months of May to October.  This 
provided additional realism to population models for these populations. 
 
Keywords: backwater lakes, Mississippi River, macroinvertebrate, life-history, 
fingernail clam