By the 1960s, the Japanese cultured pearl industry had expanded. Today, thousands of mussels are legally harvested from North American rivers for this multi-million dollar enterprise. Illegal harvesting is on the rise in the United States and may be contributing to the decline of certain species. Mussels are extremely important to freshwater ecosystems because they form a critical link in the food chain. Mussels nearly continuously siphon water from their surroundings, filtering from it phytoplankton and other microscopic organisms for food.
Mussels are excellent biological indicators in part because of their key position in energy cycling.
By filtering contaminants, sediments, and nutrients from the water column, mussels help maintain water quality. Special-status mussels that are being monitored in the Mississippi River. Their shells can be analyzed to determine whether and when toxic chemicals were accumulated. The presence and abundance or absence of mussels in a historical range usually reflect habitat quality in a watershed. As such, mussels are an important ecological component of many of the nation's rivers and lakes and represent the foundation of a healthy river or lake.