ML12184A302
| 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 | |
| References | |
| Download: ML12184A302 (2) | |
Text
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.