Eggs and larvae are pelagic, being dispersed by currents. Larvae settle to the substrate primarily between early spring and summer. The primary spawning season in Oregon for gaper clams is from late January through April, and for butter clams from February to July. The primary spawning season in Oregon for native littlenecks from March through August. Softshells spawn between March and September, earlier in California and later in Washington.
Males normally spawn first, producing pheromones and sperm which stimulates females to spawn.
Fecundity is estimated between 120,000 to 3 million eggs per female per year. Food and Growth Bay clams feed by filtering plankton from the water. Predators include worms, boring snails, fishes, crustaceans, octopus, birds, sea stars, and humans. Important predators of adult softshell clams include raccoons and otters. Aging of bay clams can be done by counting the annuli on shells.