Mussels important in birth of Shoals

Mussels important in birth of Shoals

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.

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