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A dark colored mussel embedded in a stream bed, open filtering water.
Information icon Carolina heelsplitter. Photo by USFWS.

Carolina heelsplitter

Lasmigona decorata

Appearance

The Carolina heelsplitter freshwater mussel was first described in 1852. It has an egg-shaped shell. The outer surface of the shell varies from greenish brown to dark brown in color. Shells from younger specimens have faint greenish brown or black rays. The nacre (inside surface) is often pearly white to bluish white, grading to orange in the deepest part of the shell. In older specimens, the entire nacre may be a mottled pale orange. The shell of the largest known Carolina heelsplitter specimen measures 4.6 inches in length.

An illustration of a mussel lifecycle going from spat to a host fish to an adult mussel
Each year fresh water mussels reproduce as males release sperm into the water column. As the sperm passively drift with the water currents, it may enter females as they are siphoning and fertilize her eggs. Adapted from NCWRC, Life Cycle of a Freshwater Mussel.

The reproductive cycle of this freshwater mussel is similar to other native mussels. Males release sperm into the water, and the eggs are fertilized when the sperm are taken in by the females through their siphons during feeding and respiration. Females retain the fertilized eggs in their gills until the larvae (glochidia) fully develop. The glochidia are released into the water and must attach to the gills or fins of an appropriate fish species or “fish host”. The larvae remain attached to their fish host for several weeks, drawing nourishment from the fish while they develop into juvenile mussels. They do not hurt their fish host.

A striated mussel on a rock with bluish green and brown coloring.
Carolina heelsplitter. Photo by USFWS.

The juvenile mussels then detach from the fish host and drop to the bottom of the stream where they continue to develop, provided they land in a suitable place with good water conditions. This dependence on a certain species of fish increases the mussels’ vulnerability to habitat disturbances. If the fish host is driven off or eliminated because of habitat or water quality problems, the mussels can’t reproduce and will eventually die out.

A line of mussels next to a ruler in decreasing size from 2cm down to 1cm in width.
Subadult Carolina heelsplitter subadults. Photo by USFWS.

Habitat

The Carolina heelsplitter requires cool, clean, well-oxygenated water. Stable, silt-free stream bottoms appear to be critical to the species. Typically stable areas occur where the stream banks are well-vegetated with trees and shrubs.

Diet

Like other freshwater mussels, the Carolina heelsplitter feeds by siphoning and filtering food particles from the water column.

Historic range

Historically the Carolina heelsplitter occurred in several locations within the Catawba and Pee Dee River systems in North Carolina and the Catawba, Pee Dee, Saluda, and Savannah River systems in South Carolina. Today, only 11 populations are known to survive.

Current range

The species still occurs in three small streams in North Carolina – one in the Catawba River system and two in the Pee Dee River systems. In South Carolina there are 10 remaining populations, one in the Pee Dee; five in the Catawba; two in the Saluda and two in the Savannah River system.

A map highlighting populations in northern South Carolina, just south of Charlotte, NC and in southwestern South Carolina, south east of Greenville, SC.
South Carolina watersheds containing Carolina heelsplitter. Map by USFWS.

Conservation challenges

Poor water quality and habitat conditions have led to the decline and loss of populations of the Carolina heelsplitter and threaten the remaining populations. Studies have shown that freshwater mussels, especially in their early life stages, are extremely sensitive to many of the pollutants (chlorine, ammonia, heavy metals, etc.) commonly found in municipal and industrial wastewater releases. Impoundments (dams), channelization projects, and in-stream dredging operations directly eliminate habitat. These activities also alter the quality and stability of remaining stream reaches by affecting the water flow, temperature, and chemistry. Agriculture (both crop and livestock) and forestry operations, roads, residential areas, golf courses, and other construction activities that do not adequately control soil erosion and water runoff contribute excessive amounts of silt, pesticides, fertilizers, heavy metals, and other pollutants that suffocate and poison freshwater mussels. The alteration of floodplains or the removal of forested stream buffers can be especially detrimental. Flood plains and forested stream buffers help maintain water quality and stream stability by absorbing, filtering, and slowly releasing rainwater. This also helps recharge groundwater levels and maintain flows during the dry months.

Recovery plan

Establish four distinct viable populations that are protected from present and foreseeable threats, with at least one population each in the Catawba, Pee Dee, and Savannah River systems, to downlist.

Establish six distinct viable populations that are protected from present and foreseeable threats, with at least one population each in the Catawba, Pee Dee, and Savannah River systems, to delist.

Actions needed

  • Use existing legislation/regulations to protect the species.
  • Elicit support for recovery efforts through the development and utilization of an information/education program.
  • Search for new populations and monitor existing populations.
  • Determine the species’ life history, habitat requirements, and threats.
  • Implement management and alleviate threats to the species’ existence.
  • Through augmentation, reintroduction, and protection, establish six viable populations.
  • Develop and implement cryopreservation of the species.

Download the 1997 recovery plan.

Five-year review

Download the 2012 five year review, which recommends no change from endangered status.

Partnerships, research and projects

Surviving heelsplitter populations are found on land representing the full spectrum of types of ownership and management. In the Savannah Basin, federal ownership (U.S. Forest Service) controls a major proportion of occupied habitat, while in the Catawba and Pee Dee River Basins, private ownership dominates, interspersed with a smattering of non-profit, for profit, and state ownership. Not surprisingly, recovery efforts have required assembling diverse stakeholders.

Although partners have come and gone over the years since listing, the Service is now privileged to have, among others, the following entities as strong, engaged and committed partners in heelsplitter restoration across its range:

  • South Carolina Department of Natural Resources
  • North Carolina Wildlife Resources Commission
  • U.S. Forest Service
  • Federal Highway Administration
  • U.S. Army Corps of Engineers
  • North and South Carolina Departments of Transportation
  • Lancaster County, South Carolina
  • The Catawba Indian Nation
  • The Nature Conservancy
  • Katawba Valley Land Trust
  • The South Carolina Aquarium
  • Private Citizens
A Brownish red mussel with shades of blue on rocky substrate.
Carolina heelsplitter. Photo by USFWS.

Although core restoration planning generally takes place between federal and state partners, every partner is critical to the success of the heelsplitter recovery program. Over the years, examples of partner support have included providing funding, allowing access to survey sites, aiding in host fish collection and survey efforts, state and federal permit coordination, property acquisition, management and restoration, information sharing and scientific expertise.

Propagation

In fall 2006 North Carolina State University collected heelsplitters from Duck Creek. Adults were taken to Table Rock Fish Hatchery for holding. In 2007, two of the animals from Duck Creek were found to be gravid. An additional gravid heelsplitter from Six Mile Creek was brought in to the hatchery by Tim Savidge (Chris Eads and Jason Mays, pers. comm., 2017). These animals were used for host trials.

Dozens of tiny, semi-transluscent mussels as seen through a microscope.
Juvenile Carolina heelsplitter mussels under a microscope. Photo by USFWS.

Propagated animals from host trials went initially to Table Rock Hatchery, but did not do well and were subsequently moved to NCWRC’s Marion facility in August 2008, where they grew well and exhibited decent survivorship. From 2008 onward, Marion has been responsible for most heelsplitter propagation efforts in the state.

A service biologist and student intern inspect mussels under a microscope.
Carolina heelsplitter inventory. Photo by USFWS.

Beginning in the spring of 2015, the Service initiated propagation and augmentation efforts for the heelsplitter in South Carolina, at Orangeburg National Fish Hatchery’s Mussel Conservation Center (OMCC). Containing 10 of the species’ 11 surviving populations, South Carolina is now the recovery stronghold for the species, playing a critical role in maintaining species abundance and genetic viability into the future. The heelsplitter is currently found in four river basins in South Carolina, including the Pee Dee, Catawba, Saluda, and Savannah.

How you can help

  • Establish and maintain forested stream-side buffers. Several federal, state, and private programs are available to assist landowners, both technically and financially, with restoring and protecting stream-side buffers and eroding streams.
  • Implement and maintain measures for controlling erosion and stormwater during and after land-clearing and disturbance activities. Excess soil in our streams from erosion is one of the greatest water pollution problems we have today.
  • Be careful with the use and disposal of fertilizers, pesticides, and other chemicals. Remember, what you put on your land or dump down the drain may eventually wind up in nearby water.
  • Support local, state and national clean water legislation.
  • Report illegal dumping activities, erosion, and sedimentation problems. These activities affect the quality of our water, for drinking, fishing, and swimming.
  • Participate in the protection of our remaining wild lands and the restoration of damaged ecosystems.

Subject matter experts

  • Morgan Wolf (national lead), South Carolina Ecological Services Field Office, morgan_wolf@fws.gov, (843) 727-4707 ext. 219
  • Jay Mays, Asheville Ecological Services Field Office, jason_mays@fws.gov, (828) 258-3939, ext. 226
A biologist holding about a dozen small mussels in her hand.
Carolina heelsplitter subadults from the Catawba River. Photo by USFWS.

Designated critical habitat

Designated September 2, 2002.

A biologist with USFWS hat and shirt uses super glue to affix a small plate with an ID on a mussel.
Marking Carolina heelsplitter mussels before returning them to a stream. Photo by USFWS.

Federal Register notices

The following Federal Register documents were automatically gathered by searching the Federal Register Official API with this species’ scientific name ordered by relevance. You can conduct your own search on the Federal Register website.

  • We're sorry but an error occurred. Visit the Federal Register to conduct your own search.

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