Freshwater Mussels—Economics and Declining Populations
From Pearls to Pottery
Do mussels have eyes?No, they don't need them. They live buried in the bottom of a river and don't need to see.
Americans have used freshwater mussels many ways. They were used by Native Americans for utensils, tools, jewelry, and for tempering pottery. Native Americans even ate freshwater mussels in years past, but they are no longer considered edible. Because they are filter feeders, they concentrate chemicals and other pollutants from the streams. Also, freshwater mussels are now reported to be unappetizing (their taste has been compared to the mud where they live!). Despite this, mussels are a food source for other animals such as otters, raccoon, and some birds. One may find the remnants of a meal, a pile of cleaned mussels called a midden, along the bank of a stream.
In the mid-1800s, a large pearl was discovered in a freshwater mussel and mussel pearl fever began. However, one may have to open hundreds of thousands of mussels before finding a single pearl—many millions were opened to search for the valuable pearls.
Some mussels have a very pearly inside, and in the late 1800s and early 1900s many millions of pounds were harvested to make buttons. The first US pearl button factory was opened in Iowa in 1891. Only 30 years later the industry began its decline as plastic buttons were introduced.
Today, freshwater mussel shells are harvested from southern US to be exported to Japan where they are used as nuclei for pearls. Small round pieces of shell are placed in Pearl Oysters where they are coated with iridescent nacre from the oyster to form a pearl.
Mussels are very sensitive to the quality of their river habitat and are often thought of as good indicators of the health of a stream. Because they have to filter the water where they land as larvae, they ingest whatever is around them. They can't choose what they eat and are therefore sensitive to toxins and pollutants in the stream. Mussels need the same clean, cool, oxygenated water that our salmon need and, actually, they need the salmon themselves to survive. There are four primary threats to mussel survival:
1. Runoff from land development:
- Chemical and nutrient contaminants degrade the water quality—not only is it the mussels' home, but it is also their foods' home
- Sediment can smother stream bottoms—and the mussels
2. Water diversions for industrial, domestic, and agricultural uses:
- Flow and temperature can become inappropriate for mussel survival
- Physical barriers such as dams and impassable culverts prevent fish from reaching the mussel beds—then there is no host for the young glochidia (if the fish disappear, the mussels disappear)
3. Non-native invasions: Non-native zebra mussels are outcompeting the natives in the midwest and southwestern US (it is believed that it is merely a matter of time before zebra mussels appear in the northwest—see below)
4. Habitat loss: Channelizing, dredging and otherwise altering streams and buffer zones threaten, and may even remove, the homes of mussels.