Thanks, Harry and Wesley!!  This is useful information.

I am wondering if this species might be an "indicator species", that
indicate when an ecosystem is starting to become unbalanced or unhealthy
- like the proverbial canary in the mine?   Does anyone know of other
molluscs that are species quite sensitive to ecosystem disturbance, and
whose dissapearance or dramatic reduction in numbers might be taken as
an Early Warning sign of developing problems?   I know many Unionids
fall into this category, but what about marine species or fresh water gastropods?

From Canada with curiosity,
Ross M.