ML12184A302

Fws 2011 Sheepnose Fact Sheet Jan 2011

ML12184A302
Person / Time
Site:	Watts Bar
Issue date:	03/28/2011
From:	US Dept of Interior, Fish & Wildlife Service
To:	Watts Bar Special Projects Branch
Poole J C
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Download: ML12184A302 (2)

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U.S. Fish & Wildlife Service Sheepnose (a freshwater mussel)

Plethobasus cyphyus P hoto by USFWS; Kristen Lundh The sheepnose is a freshwatermussel that the U.S. Fish and Wildlife Service has proposed to list

as an endangered species

.Endangered species are animals and

plants that are in danger of becoming

extinct. Threatened species are animals and plants that are likely to

become endangered in the

foreseeable future. Identifying, protecting, and restoring

endangered and threatened species

are primary objectives of the U.S.

Fish and Wildlife Service's

endangered species program.

What is a sheepnose mussel?

Appearance:

The sheepnose is a medium-sized mussel that grows to about 5 inches in length. The shell is

thick and solid, with the overall

shape slightly longer than wide and

somewhat inflated.The sheepnose shell is smooth,shiny, and light yellow to a dull

yellowish brown and without lines or

rays but with dark concentric ridges. The ridges result from

periods when growth stops or slows.

Range: The sheepnose is found across the Midwest and Southeast.

However, it has been eliminated from

two-thirds of the total number of

streams from which it was

historically known (24 streams are

currently occupied compared with 77 streams historically), and it has also been eliminated from hundreds of miles of rivers in the Illinois and

Cumberland River basins, and from

several reaches of the Mississippi and Tennessee Rivers. The

sheepnose is currently found in

Alabama, Illinois, Indiana, Iowa, Kentucky, Minnesota, Mississippi,Missouri, Ohio, Pennsylvania,Tennessee, Virginia, West Virginia, and Wisconsin.Reproduction:

The life cycle of the sheepnose, like most freshwater

mussels, is complex and includes a

stage that is parasitic on fish.

Initially, males release sperm into the water current. As female

mussels siphon water for food and

respiration, they also siphon sperm

that fertilizes their eggs. Within

special gill chambers, fertilized eggs develop into microscopic larvae called glochidia. Female mussels

expel the mature glochidia, which

then must attach to gills or fins of a

specific host fish species to complete

development into a juvenile mussel.

Sheepnose expel glochidia in conglutinates, a jellylike mass of

mucus and glochidia, that mimic fishfood in appearance. Theseconglutinates are narrow, red or

pink, and discharged in unbroken

form so that they look like small

worms. When a fish eats a

conglutinate, glochidia are exposed

to and can attach to the fish's gills.

If glochidia successfully attach to a host fish, they mature into juvenile

mussels within a few weeks and then drop off. The sauger (Stizostedion canadense) is the sheepnosemussel's only known host, but others may be available. After dropping off, glochidia continue to grow and

mature if they land in suitable areas.

Using fish as hosts allows the

sheepnose to move upstream and populate habitats it could otherwise

not reach.

As a group, mussels are long-lived, with individuals living up to severalThe shell of the sheepnose is extremely hard, so much so that clammers on the Cumberland River called it "clear profit" because they were "the only ones who get

anything out of it" as it was too hard for making buttons.

U.S. Fish & Wildlife Service1 Federal Drive Fort Snelling, Minnesota 55111

612/713-5350 http://www.fws.gov/midwest/endangered

January 2011 decades, and possibly up to 100, and even200 years. Sheepnose, especially thick-shelled individuals from large rivers, are thought to live longer than other mussel species, however, we have no age

information.

Habitat: Sheepnose mussels live in larger rivers and streams where they are usually

found in shallow areas with moderate to

swift currents flowing over coarse sand and gravel. Sheepnose have also been found in

mud, cobble, and boulders. In larger rivers

they may be found in deep runs.Feeding Habits: Adults are suspension-feeders, siphoning in water and

feeding on the suspended algae, bacteria, detritus, microscopic animals, and dissolved organic material. Adult mussels

spend their entire lives partially or

completely buried within the substrate.

What are threats to the

sheepnose mussel?Dams: Dams affect both upstream and downstream mussel populations by

disrupting natural river flow patterns, scouring river bottoms, changing water

temperatures, and eliminating habitat.

Large rivers throughout most of the

sheepnose mussel's range have been

impounded; leaving short, isolated patches of habitat below dams.

The sheepnose also depends on host fish to move upstream. Because dams block fish passage, mussels are also prevented

from moving upstream, which isolates

upstream from downstream populations, leading to small, unstable populations, which are more likely to die out.

Sedimentation: Poor land use practices, dredging, intensive timber harvests, road construction, and other activities may

accelerate erosion and increase

sedimentation. Sedimentation that results

in blanketing a river bottom may

suffocate mussels because they cannot

move fast enough to avoid the impact.

Also, increased sedimentation reduces the ability of mussels to remove food and oxygen from the water, which can lead to

decreased growth, reproduction, and

survival.Pollution: Adult mussels are easilyharmed by toxins and degraded water quality from pollution because they are

sedentary (they tend to stay in one place).Pollution may come from specific, identifiable sources such as accidental

spills, factory discharges, sewage

treatment plants, and solid waste disposal sites. Pollution also comes from diffuse

sources like runoff from fields, feedlots, mines, construction sites, private wastewater discharges, and roads.

Contaminants may directly kill mussels, but they may also indirectly harm sheepnose by reducing water quality, which reduces survival and reproduction, and lowers the numbers of host fish. Channelization:

Dredging and channelization have profoundly changed

rivers nationwide. Channelization

physically alters rivers by accelerating

erosion, reducing depths, decreasing habitat diversity, destabilizing stream

bottoms, and removing riparian vegetation.Small Population Size and Fragmentation: Most populations of sheepnose are small and geographically isolated. These small populations, which

live in short sections of rivers, are

susceptible to extirpation from single catastrophic events, such as toxic spills.

Also, isolation makes natural repopulation

impossible without human assistance.

Nonnative Species: The invasion of the nonnative zebra mussel into the United

States poses a serious threat. Zebra

mussels proliferate to such an extent

that they deplete food resources and

they attach to native mussel shells in

such large numbers that the native

mussel cannot open its shell to eat or

breath.What is being done to conserve

and restore sheepnose mussels?

Listing:

The sheepnose mussel was designated by the U.S. Fish and Wildlife

Service as a candidate species for listing as

threatened or endangered under the Endangered Species Act. The Service is now proposing to list it as endangered. If

listed, the sheepnose will receive the full

protection of the Endangered Species Act, which provides protection against certain

practices and would require planning for recovery.Prevent or Slow Spread of ZebraMussels: States and Tribes are working to prevent the spread of zebra mussels to

areas such as the northern portions of the St. Croix River, by enforcing aquaticnuisance species laws, monitoring, and providing information for boaters at water

access sites.

Monitoring and Research:

Many states with sheepnose populations and some federal agencies are conducting surveys

and funding research to find out about the

sheepnose mussel's specific life history

requirements and threats to its survival.

What can I do to help prevent

the extinction of species?

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.

Help improve water quality in your local streams by minimizing use of lawn-care

chemicals and properly disposing of or

recycling hazardous materials found in

your home, like batteries, paint, car oil, and pesticides.

When boating, please follow rulesestablished to prevent the spread of exotic pests like the zebra mussel.

Join a conservation group or volunteer ata local nature center, zoo, or wildlife refuge.