An endangered mussel came home to a Tennessee river last week, a monumental reintroduction effort seven years in the making.
On Wednesday, federal and state biologists placed 103 winged mapleleaf mussels in the middle portion of the Duck River. The last time the species was seen in the river was more than two decades ago, when empty shells were collected in 1990 and 1991.
The freshwater mussel’s historical range, dating from the 1800s, is the Mississippi River and its tributaries from Minnesota to Arkansas. By the time the U.S. Fish and Wildlife Service listed the winged mapleleaf as endangered in 1991, its only known population was in the St. Croix River between Minnesota and Wisconsin. Since then, four additional populations were found in Arkansas, Oklahoma, and Missouri.
Partners in the reintroduction effort with the Service are the Tennessee Wildlife Resources Agency, Arkansas Game and Fish Commission, Missouri State University, and the Kansas City Zoo.
Service biologist Chris Davidson, the Southeast Regional lead for the winged mapleleaf mussel, said reintroducing the species to rivers within its historical range (such as the Duck River) is one of the recovery goals for the species.
“It took seven years to identify suitable fish hosts in the southern portion of the species’ range,” said Mr. Davidson. “Then we had to work out some kinks with propagation and ‘grow out’ techniques.”
One effort was an attempt to “grow out” the juvenile mussels in the Saline River (southern Arkansas), rather than a hatchery or zoo facility.
The young mussels – all about two and a half years old – have traveled more than some people. They were produced from fertilized females found in Arkansas’ Saline River, which were then brought to Missouri State University. At the university’s mussel propagation center, the female mussels expelled their larvae onto a channel catfish. The larvae have a parasitic stage where they must attach to catfish gills until they mature into tiny, juvenile mussels and drop off the host fish. Channel catfish and blue catfish are the only suitable fish hosts for winged mapleleaf.
The juvenile mussels remained at the university for about six months. They then were transferred to the Kansas City Zoo where they continued growing for another two years.
Mr. Davidson said the probability of survival is good because the mussels are more than two years old.
Future winged mapleleaf mussels for reintroduction in the Duck River will be grown at the Service’s Natchitoches National Fish Hatchery in Louisiana.
The Duck River was selected in part because it’s close to the Saline and Ouachita rivers in Arkansas, where two of the five populations of winged mapleleaf are found. The Duck River has high mussel density and diversity, plenty of channel and blue catfish, and no invasive zebra mussels, which have out-competed native species in other rivers.
One more good reason to pick the Duck River: Tennessee has long-term monitoring sites there, and will be able to track the mussels’ progress. Biologists tagged, or laser engraved, unique numbers to these mussels, which will help identify the mussels when they are later recaptured in the monitoring effort.
For more information about the winged mapleleaf mussel species, visit: http://www.fws.gov/midwest/endangered/clams/winge_fc.html.