hose and instructed him to sweep in the opposite direction. The 

 diver sent mussels to the surface in collection bags. 



On the boat, both valves of unmarked mussels were engraved 

 with an identification number. To engrave shells we used a Dremel 

 hand-held grinding tool powered by a 110-volt AC, gasoline- 

 powered generator. Some dead shells were also engraved to 

 determine whether dead shells would be washed out of the study 

 area. After engraving, the mussels were identified to species, 

 inspected for damage, and measured. Marked mussels were returned 

 to corrals by the diver, with no more than 2 5 live mussels placed 

 in a single enclosure. Additional marked mussels were placed 

 outside the corrals by dumping them into the water from the 

 surface or by the diver scattering them along the bottom. 



SPECIES STUDIED 



Mussels could respond to fleeting in different ways because 

 of interspecific differences in physiology, morphology, and 

 behavior. We intended to use one relatively thick-shelled 

 species, Amblema plicata (the three-ridge) , and one thin-shelled 

 species, Leptodea fragilis (the fragile papershell) . We were 

 unable to collect sufficient numbers of Leptodea fragilis , so we 

 supplemented them with another fragile-shelled species Proptera 

 laevissima (the fragile heelsplitter) . We also collected and 

 marked other species as time permitted. A list of scientific and 



13 



