Perseverance paying off for La. pearlshell

The Margaritifera hembeli is not a new adult frozen beverage consumed to waste away summer happy hours, as the name might imply; it is an animal once commonly found in small waterways that is struggling with a one in 100 million shot at survival each time a female Louisiana pearlshell mussel releases its young into a stream.

More than 30 years ago, scientists recognized the tenuous hold on life for the rare freshwater mussel. Since that time, biologists with the U.S. Forest Service (USFS), U.S. Fish and Wildlife Service (USFWS) and the Louisiana Wildlife Diversity Program (originally Louisiana Natural Heritage Program) of the Louisiana Department of Wildlife and Fisheries have worked diligently to understand the life cycle of this creature and how they could help it from disappearing off the face of the earth.

After years of studying the secrets of the mussel, about 900 young mussels raised at the Natchitoches National Fish Hatchery were placed into streams on the Kisatchie National Forest in July. It was a monumental feat to reintroduce the mussel.

The Louisiana pearlshell was first placed on the Endangered Species List in 1988 and was believed to be found in only a few streams in Rapides Parish in the Bayou Boeuf watershed. However, new populations were discovered in the 1990s in Red River drainage watershed streams in Grant Parish and the species was downlisted to threatened in 1993. Many of the streams where the Louisiana pearlshell were found are on the Kisatchie National Forest, so the USFS began issuing management initiatives to help protect this rare species.

No longer were beavers allowed to dam up creeks and streams the mussel was known to inhabit. Off-road vehicle traffic was also restricted as well as the establishment of streamside zones to minimize sedimentation during logging operations.

Biologists from federal and state agencies, as well as various university students, began in 1985 to conduct surveys every few years, painstakingly counting (by hand) the number of pearlshell mussels on federal and private lands.

Freshwater mussels are bivalve (two calcium carbonate shells attached at a hinge) mollusks. You may be familiar with their close cousins — clams, oysters and scallops.

Like their cousins, mussels are filter feeders, wedged into the bottom of streams and rivers, filtering food particles out of the water. Dirty water — from pollutants or increased sedimentation and silt — can harm mussels. However, loss and degradation of habitat from a variety of land uses are the main reasons why the Louisiana pearlshell is struggling to survive.

Mussels do not have legs (although they have one foot — that’s a great riddle!) so they can’t pick up and move when things get rough.