- Taxon: Freshwater mussel. Bivalve, Unionidae
- Range: Patuxent, Rappahannock, York, James, Chowan, Tar, and Neuse River basins in Maryland, Virginia, and North Carolina.
- Status: At-risk species, Proposed for listing as a threatened species.
The yellow lance is a bright yellow mussel with a shell more than twice as long as it is tall, reaching just over three inches in length. Its shell is composed of two hinged valves which are joined by a ligament. The outermost layer of the shell has a waxy appearance with brownish ridges known as “growth rests” that formed during an intermediate stage of growth when the ridge area was the edge of the shell. The lustrous inner layer is usually an iridescent blue color, and sometimes has white or salmon color on the shorter end of the shell from where the foot extends (the anterior). The longer end of the shell from where the siphons extend (the posterior) is distinctly rounded. Yellow lance has interlocking hinge “teeth” on the inside of the shell to help keep the two valves in proper alignment.
The yellow lance is a sand-loving species often found buried deep in clean, coarse to medium sand, although it can sometimes be found in gravel substrates. Yellow lances often are moved with shifting sand and eventually settle in sand at the downstream end of stable sand and gravel bars. This species depends on clean, moderate flowing water with high dissolved oxygen. This species is found in medium-sized rivers to smaller streams.
The life cycle of the yellow lance, like most freshwater mussels, is complex, relying on host fish for successful reproduction. Their eggs develop into microscopic larvae (glochidia) within the gills of the female mussel. The female expels its glochidia into the river where they must attach to gills or fins of a fish to continue developing. Each mussel species has specific fish species (host fish) that are needed by the glochidia to keep growing and transform into juveniles. After a few weeks, they drop off and land on the river bottom where they grow into adults.
Like many freshwater mussels, the yellow lance grows rapidly during the first few years of life and slows down with age. In the laboratory, the yellow lance reaches sexual maturity around three years old. Once the yellow lance reaches maturity, the female mussels release stringy clumps of glochidia in mucous. The clumps are likely eaten by minnows so the glochidia can attach to the minnow’s gills and fin scales. At least two species of minnow are confirmed to host yellow lance development in a laboratory setting, the white shiners (Luxilus albeolus) and pinewoods shiners (Lythrurus matuntinus). Biologists have developed ways to propagate Yellow Lance under controlled laboratory conditions.
Freshwater mussels are living filters, known as suspension feeders because they eat algae and other microscopic matter and other particles, such as leaf debris, they filter out of the water. Juveniles likely pedal-feed in the sediment, whereas adults filter-feed from the water column. A recent nutrition study found that probiotic bacteria (Bacillus subtilis) enhanced early juvenile growth and survival. When they feed, they help keep the water clean by removing pollutants that could potentially harm aquatic animals, birds, land-dwelling animals, and people who may drink the water.
Historically, the yellow lance ranged from the Patuxent River Basin in Maryland, to the Potomac River Basin in Maryland/Virginia, the Rappahannock, York, James, and Chowan River basins in Virginia, and the Tar and Neuse River basins in North Carolina.
Counties Where the Species has been Known to Occur
- Anne Arundel
- Prince George’s
- Prince Edward
- King George
The yellow lance is still found in seven of the eight river basins it used to occupy. No records exist of the species in the Potomac River in recent years and experts presume it extirpated from that river. Number and distribution of populations range occupying the remaining seven rivers have declined over the past 60 years.
Adult mussels are easily harmed by toxins and declines in water quality from pollution because they stay in one place. Pollution may come from specific, identifiable sources such as factories, sewage treatment plants and solid waste disposal sites or from diffuse sources (non-point pollution sources) like runoff from cultivated fields, pastures, cattle feedlots, poultry farms, mines, construction sites, private wastewater discharges, and road drainage. Pollutants can cause changes in water chemistry that seriously impact aquatic species by reducing water quality and may directly kill mussels, reduce the ability of surviving mussels to have young, or result in poor health or disappearance of host fish.
Sediment is material suspended in water that usually is moved as the result of erosion. Although sedimentation is a natural process, poor land use practices, dredging, impoundments, intensive timber harvesting, heavy recreational use, and other activities may accelerate erosion and increase sedimentation. A sudden or slow blanketing of the river bottom with sediment can suffocate freshwater mussels because it is difficult for them to move away from the threat. Increased sediment levels may also make it difficult for Yellow Lance to feed, which can lead to decreased growth, reproduction, and survival.
Dams affect both upstream and downstream mussel populations by disrupting natural flow patterns, scouring river bottoms, changing water temperatures, and eliminating habitat. The Yellow Lance, a mussel adapted to living in river currents, cannot survive in the still water impounded behind dams.
Yellow lance depend on their host fish as a means of moving upstream. Because dams are barriers that prevent fish from moving upstream they also prevent mussels from moving upstream. Upstream mussel populations then become isolated from downstream populations. This isolation leads to small unstable populations which are more likely to die out.
How You Can Help
Individuals can do a number of things to help protect freshwater species, including:
- Conserving water to allow more water to remain in streams.
- Using pesticides responsibly, especially around streams and lakes, to prevent runoff into mussel habitats.
- Controlling soil erosion by planting trees and plants to avoid runoff of sediments into freshwater areas.
- If you live near a stream, be careful not to disturb the stream bottom; you may be damaging a freshwater mussel’s home.
- Don’t pick up any mussels that you may see in a stream. It may be one of the last few members of its species on the planet.
- Help your family find ways to reduce the amount of chemicals that you pour down the drain in your home or possibly use on your lawn or garden.
- Check to see if the water draining off your roof or driveway flushes directly into a stream. Plant a garden to catch the water before it enters the stream. The garden will act like a filter and help purify the water.
- Recycle as much as you can to reduce the amount of waste you place in the garbage.
- Support conservation efforts that protect these unique animals and the habitats they live in.
- Become a biologist and discover new ways to help protect freshwater mussels and other wildlife.
- Learn more about how the destruction of habitat leads to loss of endangered and threatened species and our nation’s plant and animal diversity. Discuss with others what you have learned.
- Support local and State initiatives for watershed and water quality protection and improvement.
Subject Matter Experts
- Sarah McRae, Fish and Wildlife Biologist, Raleigh. Sarah_McRae@fws.gov
- Yellow lance species profile by the North Carolina Wildlife Resources Commission
- Freshwater Mussels & Endangered Fish Glossary by the North Carolina Wildlife Resources Commission
- Freshwater mussel activity book and learning resource
Federal Register Documents
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