The 53-mile stretch of the Tennessee River from west Decatur to below Seven-Mile Island in Florence once had the greatest diversity of freshwater mussel species of any place on Earth, according to Stuart McGregor, a Florence native and scientist who studies mussels and other mollusks for the U.S. Geological Survey in Tuscaloosa.

McGregor said some mussels like fast, flowing water, others prefer deep, still waters. Some live in rivers, others in small streams. Before dams were built along the Tennessee River, the Shoals provided every possible habitat for freshwater mussels.

“The Muscle Shoals was the perfect storm for freshwater mussels,” McGregor said. “Any habitat a freshwater mussel could want was available in the Muscle Shoals.”

Jeff Powell, a biologist for the U.S. Fish and Wildlife Service’s Daphne field office, said about 180 species of mussels once lived in the Shoals. He said the Shoals was the spot where mussel species typically found in Appalachian streams overlapped with species from the Ohio and Mississippi rivers.

Completion of Wilson, Pickwick and Wheeler dams in the 1920s and 1930s caused major changes in mussel habitats and caused many species to disappear from the area. Others were pushed to the brink of extinction. Pollution also has taken a toll on freshwater mussels around the Shoals.

In addition to altering habitats, the dams blocked the movement of fish that once swam freely up and down the Tennessee River. All mussels rely on fish to reproduce.

Freshwater mussel larvae attach themselves to fish, where they will live for two to five weeks. When a mussel larvae cyst forms on the fish’s body. When the mussel is capable of surviving on its own the cyst breaks free and falls to the bottom of the waterway where the mussel will spend the rest of its life.

Powell said each mussel species is dependant on specific fish. When the movement of that fish is restricted, the mussel species it is associated with can be affected.

Powell said about 50 to 60 species of freshwater mussels now live in the Tennessee River and its tributaries around the Shoals.

“There has been a significant loss of that fauna,” Powell said.

Shoals mussel hot spot

Many of the mussels that remain in the Shoals are rare and protected as endangered species.

Even with the losses, the Shoals is still home of the greatest concentration of freshwater mussel species in north America, Powell said.

“It’s still the hot spot for freshwater mussels,” Powell said.

Jeff Garner, a scientist for the Alabama Department of Conservation and Natural Resources, who studies mussels and other mollusks, said about 40 species live in the area of Pickwick Lake from O’Neal Bridge to Colbert Fossil Plant.

Garner said in some part of Pickwick Lake, 100 mussels can be found in a square meter of river bottom.

The abundance of mussels in the Shoals provided food for some of the earliest inhabitants of the region and later created jobs for residents who collected and sold the shells of the clam-like animals.

McGregor said large mounds of mussel shells along the Tennessee River in the Shoals were left by Native Americans who ate the shellfish.

McGregor suspects the name Muscle Shoals comes from the number of mussels that covered the river bottom around the Shoals. In a 2002 article published in “Alabama Heritage” magazine, McGregor wrote the shellfish were once called muscles. In the article, McGregor wrote the rocky, fast-moving section of the Tennessee River in the Shoals required strong muscles to paddle through, which also could be the origin of Muscle Shoals.

“There’s good arguments for both sides of the debate, but I personally suspect the name comes from the mussels, or muscles, that lived in the river,” he said.

Powell said Native Americans used mussel shells as hoes and other tools and as decorations.

McGregor said he is often asked what good is a mussel. The typically brown shellfish live on the bottom of a river, stream or lake and most people never see one alive. As a result, mussels get little respect, he said.

“Mussels are not cute and cuddly,” he said. “But they are extremely important animals. They are the canaries in the coal mine of a waterway. Because they are filter feeders, they are often the first animals to begin dying when water quality is compromised. If the mussel are dying, it can be a sign that the water is becoming polluted or you have other water quality issues.”

Industry affected

In the past, freshwater mussels have been a source of jobs for many Tennessee Valley residents.

Before the 1930s when early forms of plastic were developed, manufacturers cut circles from mussel shells to make buttons.

Even after plastic buttons replaced those made from mussel shells, collection of the shellfish continued in the Shoals.

Mussel shells from the Tennessee River were shipped to Asia where small pellets were used in making cultured pearls. Small pellets for mussel shells were implanted in oysters to become the core of a pearl.

Divers collected mussels from the bottom of the Tennessee River to supply the cultured pearl industry.

Mussel diving was a booming business around the Shoals in the 1990s when a 5-gallon bucket of shells from washboard or ebony shell mussels could earn a diver more than $300, Powell said.

Powell said plastic beads have replaced mussel shell pellets as the core of many cultured pearls.

Powell said the switch to plastic beads was a major blow to mussel divers in the Tennessee Valley.

Garner cannot recall the last time he saw a mussel diver on local lakes.

“Mussel divers used to be all over the place when I would be out on the lakes, but they are few and far between now,” he said.

Even when divers were harvest mussels en masse, the shellfish remained abundant in local lakes.

“Where they were collecting them, you would see fewer large shells because that’s what they were collecting, but there were still plenty of mussels left. As a diver would collect a large shell, a new shell would move take its place and begin to grow,” Garner said.

While many mussel species have disappeared from the Shoals, some new species have moved into the area.

Garner said Wabash pigtoe a species once found no further up the Tennessee River than Kentucky Lake has made its way into Pickwick Lake in recent years. He suspects fish traveling from Kentucky Lake into Pickwick Lake allowed the species to move upstream.

Dennis Sherer can be reached at 256-740-5746 or dennis.sherer@TimesDaily.com.