Pyramid pigtoe
photo by Matthew Patterson, USFWS
Following more than a decade of advocacy by the Center for Biological Diversity and allies, the U.S. Fish and Wildlife Service today proposed to protect the pyramid pigtoe mussel as a threatened species under the Endangered Species Act.
Currently found in Alabama, Arkansas, Kentucky, Louisiana, Mississippi, Ohio, Oklahoma, Tennessee and Virginia, the freshwater mussel has lost nearly 80 percent of its range to the nation’s lack of regard for rivers. Historically there were 151 known populations. Today there are only 35.
“Freshwater mussels are irreplaceable treasures so it’s great that the pyramid pigtoe is getting a lifeline under the Endangered Species Act,” said Tierra Curry, a senior scientist at the Center. “We’ve already lost 38 kinds of mussels to extinction in North America. It’s time to draw a line in the sand and say we’re not going to lose one species more.”
Only four out of 28 surviving management units of the mussel are deemed to have a high chance of recovery. Nine units are in medium condition, and an additional nine are not expected to survive without intervention to improve water-quality conditions and connectivity.
The Center and allies petitioned for protection of the mussel in 2010 and won a lawsuit in 2019 to secure a date for a decision on its protection.
The pyramid pigtoe (Pleurobema rubrum) declined because of historical collection of shells to make buttons on an industrial scale followed by widespread damming of rivers, which cuts off the flowing water the mussels need to breathe, eat and reproduce. Pollution from suburban development, agriculture, mining and dredging have reduced water quality throughout its range.
The pigtoe is also threatened by a novel virus that is causing a die-off of mussels, and by the spread of zebra mussels and other invasive species.
The mussel has already disappeared from Illinois, Indiana, Iowa, Kansas, Minnesota, Missouri, Pennsylvania, West Virginia and Wisconsin. It is found in medium to large rivers and is still occurring in the Arkansas-White-Red, Lower Mississippi, Tennessee and Ohio River basins.
Freshwater mussels improve water quality for humans by filtering algae, bacteria and dead matter out of rivers. Their shells stabilize the river bottoms and provide housing for other animals.
The pyramid pigtoe, also known as the pink pigtoe, is reddish to chestnut brown with a smooth thick triangular shell that can grow to almost 4 inches. The mussel reproduces by releasing packets of fertilized eggs into the water where minnows try to eat them. The packets burst and the larvae attach to the fish’s gills to grow. Once the mussels develop tiny shells, they drop off onto the river bottom to begin life on their own. They may live up to 45 years in good habitat.
“The ongoing decline of mussels shows that we’ve got to do a better job of protecting rivers for people and wildlife,” said Ms. Curry. “We can save freshwater mussels from extinction if we can muster the political will to do it. There are literally hundreds of actions we could take to protect rivers but we’re not taking them seriously.”
The mussel needs better management or removal of locks and dams to ensure healthy flow regimes and to kill invasive species that spread on boat traffic. It also needs protective stream buffers to maintain vegetation and reduce pollution and erosion from logging, off-road vehicles and other activities. More monitoring is needed to ensure best management practices are actually followed to keep streams cleaned.