Like other bivalves that live permanently attached to a substrate they filter small food particles from the water column. They are known to be fast-growing and to occur in very high numbers from time to time. Perhaps these population peaks are associated with extended periods of higher rainfall which flush nutrient into the Bay, triggering growth of tiny floating plants and animals?
Perhaps I was snoring and missed all the action, but unusually high numbers of Common Butterfly Shells Electroma georgiana reported on eastern bayside beaches over the past two weeks are evidence of recent stormy weather. This small, delicate, semi-transparent mollusc is often found on the high tide line attached to beachcast seagrasses and seaweeds.