I have witnessed mussel die-offs on several occasions.  In South Alabama
during the winter months during flood events mussels apparently move toward
shallower water for shortly after a flood event I visited the streams to find
the mussels stranded in situ and in mass high upon the bank.  The species
observed this way were Margaritifera marrianae, Elliptio icterina, Villosa
vibex, Villosa lienosa and Uniomerus caroliniana.  Interestly, on the days I
visited live mussels were found only by digging in the substrate in streams
where during the summer months the mussels would have been exposed.  Also, in
South Georgia I witnessed a die-off after a dam broke on the Flint River near
Cordele.  For more than a year afterwards (until the dam was repaired) you
could walk out onto a dry lake bed and pick up choice specimens.  I actually
took the opportunity to do a quantitative survey of the lake during this time.
 
 
Doug Shelton
Alabama Malacological Research Center
2370-G Hillcrest Road #236
Mobile, AL 36695