Dwarf Wedgemussel - August Species of the Month
What type of animal is sandwiched between two shells,
has no backbone and no legs but one foot, a heart but no brain, teeth
but no mouth, and gills but no lungs?
This describes the Dwarf Wedgemussel, a type
of freshwater bivalve or mussel that resides in New Jersey. It was the
August Species of the Month in honor of the
30th Anniversary of the New Jersey Endangered Species Conservation
Act and the formation of DEP's Endangered
and Nongame Species Program (ENSP).
There are 12 native freshwater mussel species in New
Jersey, nine of which are listed as Endangered, Threatened or Special
Concern. Often referred to as nature's vacuum cleaners, they improve water
quality by straining particles and pollutants from water. They have a
low tolerance for water-borne pollutants and are excellent indicators
of water quality and stream health. The decline or extinction of New Jersey's
freshwater mussels is being attributed to several factors, including pollution
Since the early 1990s the DEP has conducted freshwater
mussel surveys to locate and monitor existing populations. Survey information
is now being used for recommending stream classification upgrades in critical,
high quality habitats.
In order to recover healthy populations of the dwarf
wedgemussel and other freshwater mussels, stronger management and clean
up of the state's waterways is required, along with increased research
and public understanding and involvement.
Dwarf wedgemussels on stream bottom
Photo courtesy of North Carolina Resources Commission
Dwarf wedgemussel habitat in the Pequest River
Dwarf wedgemussel habitat in the Paulins Kill
Photo courtesy of Allen Barlow
into New Jersey's Wildlife Protection Effort
- Freshwater mussels are among the most rapidly
declining animal groups on the continent. The dwarf wedgemussel
once existed in 70 locations within 15 major rivers draining
into the Atlantic, from Canada to North Carolina. Today, the
species exists in only 42 small sites within nine drainages.
In New Jersey they are found only in sections of the Paulins
Kill, the Pequest River, and a portion of the upper Delaware
- Primary threats to this species include
water pollution from urban, industrial and agricultural run-off;
erosion and sedimentation from construction and development;
habitat loss from damming; dredging; and, exotic species of
bivalves such as the Asiatic clam and zebra mussel.
- The dwarf wedgemussel is protected through
state and federal
Endangered Species Acts, state and federal
Clean Water Acts, rules related to flooding, and environmental
reviews of proposed development projects.
- Biologists conduct freshwater mussel surveys
by visiting historic locations, suitable habitats and areas
where host fishes are present. Viewing scopes and snorkeling
gear are often used when searching rivers, streams and ponds,
and shorelines are inspected for mussel shells. ENSP biologists
also receive funding through the Division
of Science, Research and Technology to survey for freshwater
mussels as part of the Integrated
Biological Aquatics Assessment Project (IBAA). The IBAA
is a collaborative effort that focuses on collecting species
and water quality information at existing DEP
Ambient Biomonitoring Network (AMNET) sites.
- Plans are under way to produce an atlas
of New Jersey's freshwater mussels, which will include life
history narratives, color plates of shells and maps.
Dwarf Wedgmussel Facts
- Freshwater mussels are filter feeders and
eat by filtering plankton from water. By doing so, they slowly
accumulate toxins within their bodies that were possibly in the
water. They are known to be sensitive to potassium, zinc, copper
and chlorine, as well as fertilizers and pesticides.
- All freshwater mussels have a bivalve shell
that is divided into a left and right half. It is made of calcium
carbonate and the color and texture of the shell's outer surface
is important for identification. The dwarf wedgemussel is known
for its "humpbacked" shell that rarely exceeds one and
a half inches long.
- The dwarf wedgemussel is usually found in
clear rivers, creeks, streams or ponds with slow to moderate current
and having a muddy sand to sand and gravel bottom.
- Mussels have a large, muscular foot that
extends from between the shells and functions in locomotion (pulling
it along) and anchorage (to the river bottom).
- Certain species of fish are important to
the dwarf wedgemussel. In mid-summer male mussels release sperm
into the water while females downstream siphon the sperm and fertilize
the eggs still stored in their bodies (gills). When the fertilized
eggs are ready in spring they are released into the water and
must attach to a specific host fish so that they can further develop.
Eventually the young mussels will drop from the host fish to the
- Young mussels are often eaten by ducks,
herons and fishes while mature mussels can be eaten by raccoons
- Although some freshwater mussels can live
in excess of a century, the average life span of a dwarf wedgemussel
is about 15 years.
Dwarf wedgemussels closed
Dwarf wedgemussels opened
Photos courtesy of
North Carolina Resources Commission
You Can Help
Conserve Wildlife special interest license plate for your vehicle. It's
tax-deductible, with 80% of the payment benefiting New Jersey's Endangered
and Nongame Species Program.
Want to volunteer? Enjoy giving presentations? Looking
for speakers? The Division of Fish and Wildlife offers two opportunities:The
Endangered and Nongame Species Program's Speakers
Bureau and the Division's Wildlife Conservation
Corps. Visit these sites for details.
Want to learn new information quickly about New Jersey
wildlife? The Division of Fish and Wildlife offers eight E-mail "mailing
list" choices to the public. Visit the E-mail
List Subscription Page to learn more about this free service and how
to sign up.