THE RELATIONSHIP BETWEEN HABITAT AND UNIONID MUSSEL SHELL WEIGHT AND SIZE.

Cynthia D. Brownlee and Richard V. Anderson
Department of Biological Sciences, Western Illinois University, Macomb, IL  
61455

The effect of habitat on unionid mussel growth and shell morphometry has been 
document for some characteristics and habitat comparisons.  These relationships 
have usually found that shells were thinner in individual of a species from lake 
habitats than of that species from riverine systems and that grow differed 
between the habitats  It was suggested this was due to differences in the 
physical environment of these habitats.  However, within riverine systems there 
may be a wide range of physical conditions; different water velocities, 
substrates, and depths.  Invasive epizoites may also interrupt or limit the 
ability of mussels to obtain the needed dissolved salts and nutrients for grow.  
To examine the effect of habitat on shell growth in a riverine system mussels 
were collected from two distinct habitats, an adjacent channel border habitats 
and an area protected by aquatic macrophyte development in Pool 19, Mississippi 
River.  Growth curves, in terms of shell length verses total body weight, were 
similar for all species examined from the same habitat.  Fast growing species 
with thinner shells exhibited the same relationship as slower growing heavier 
species.  There was also no difference between  individuals of the same species 
found in different habitats in spite of differences in substrate, current 
velocity and  infestation by zebra mussels.  Growth was relatively constant 
between species and habitats.

Keywords:  Mississippi River, Pool 19, habitats, unionid mussels, growth