Download 3.6 Freshwater Mussels - North Carolina Wildlife Resources

3.6 Freshwater Mussels
Freshwater bivalve molluscs, or mussels, are filter-feeders with a diet that varies across habitats
and among species but primarily consists of microscopic particular matter such as
phytoplankton, zooplankton, bacteria, and organic detritus (Vaughn and Hakenkamp2001; Haag 2012).
North America has the richest mussel fauna with more than 300 species distributed among
approximately 50 genera that are members of the family Unionidae (Haag 2012).
Mussels live most of their lives burrowed in the bottom of a stream or lake and depending on
species and season they may be closer to the substrate surface (warm seasons) or burrow more
deeply during colder seasons (Amyot and Downing 1991, 1997; Watters et al. 2001; Schwalb and Pusch2007; Haag
2012). When population density is high mussels can be the dominant biomass and exert control
over the structure of an aquatic community (Vaughn and Hakenkamp 2001) as demonstrated in
locations which have large populations of the non-native Asian Clam.
Most mussel species have a complex life
history that includes a reproductive process
dependent on an obligate larva parasite on fish
called a glochidium, which has important
ramifications for many aspects of mussel
ecology and conservation (Layzer and Scott 2006).
Recolonization success is dependent on the
successful parasitizing of a host fish and
subsequent movement of the infected host
fish into water that provides suitable habitat
for the mussel (Layzer and Scott 2006). Many
freshwater mussels have undergone drastic
declines and many are predicted to go extinct
in the next few decades (Eckblad and Lehtinen1991;
Bogan 1993; Neves 1993; Shannon et al. 1993; Wilson et al.
1995; Neveset al. 1997; Vaughn and Taylor 1999; Vaughn and
Brook Floater (Brena Jones NCWRC)
Hakenkamp 2001).
A list of freshwater mussels considered Species of Greatest Conservation Need (SGCN) is
provided in Table 3.6.1 and the Taxa Team evaluation results can be found in Appendix#. River
basin and habitat associations for these species can be found in Appendix#.
Table 3.6.1 Conservation Concern SGCN priority freshwater mussel species.
Family
Unionidae
Unionidae
Unionidae
Scientific Name
Alasmidonta heterodon
Alasmidonta raveneliana
Alasmidonta sp. 2
Common Name
Dwarf Wedgemussel
Appalachian Elktoe
A freshwater bivalve
Federal/
State
Listing*
E/E
E/E
Family
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Unionidae
Scientific Name
Alasmidonta undulata
Alasmidonta varicosa
Alasmidonta viridis
Anodonta couperiana
Anodonta implicata
Cyclonaias tuberculata
Elliptio dilatata
Elliptio lanceolata
Elliptio marsupiobesa
Elliptio steinstansana
Elliptio waccamawensis
Fusconaia masoni
Fusconaia subrotunda
Lampsilis cariosa
Lampsilis fullerkati
Lampsilis sp. 2
Lasmigona decorata
Lasmigona subviridis
Pegias fabula
Pleurobema collina
Pleurobema oviforme
Pleuronaia barnesiana
Toxolasma pullus
Villosa constricta
Villosa delumbis
Villosa iris
Villosa modioliformis
Villosa vaughaniana
Common Name
Triangle Floater
Brook Floater
Slippershell Mussel
Barrel Floater
Alewife Floater
Purple Wartyback
Spike
Yellow Lance
Cape Fear Spike
Tar River Spinymussel
Waccamaw Spike
Atlantic Pigtoe
Longsolid
Yellow Lampmussel
Waccamaw Fatmucket
Chameleon Lampmussel
Carolina Heelsplitter
Green Floater
Littlewing Pearlymussel
James Spinymussel
Tennessee Clubshell
Tennessee Pigtoe
Savannah Lilliput
Notched Rainbow
Eastern Creekshell
Rainbow
Eastern Rainbow
Carolina Creekshell
Federal/
State
Listing*
- /T
- /E
- /E
- /E
- /T
- /E
- /SC
- /E
- /SC
E/E
- /T
- /E
- /E
- /T
E/E
- /E
E/E
E/E
- /E
- /E
- /E
- /SC
- /SC
- /E
*Federal Listing Status:
E – Endangered; a taxon which is in danger of extinction throughout all or a significant portion of its range.
T – Threatened; a taxon which is likely to become an endangered species within the foreseeable future throughout
all or a significant portion of its range.
C – Candidate; taxa for which the [Fish and Wildlife] Service has on file enough substantial information on
biological vulnerability and threat(s) to support proposals to list them as endangered or threatened.
FSC – Federal Species of Concern; an informal term not defined in the federal Endangered Species Act. Defined as
those species that appear to be in decline or otherwise in need of conservation and are under consideration for
listing or for which there is insufficient information to support listing at this time.
State Listing Status:
E – Endangered; any native or once-native species of wild animal whose continued existence as a viable
component of the State’s fauna is determined to be in jeopardy or listed as a federal endangered species.
T – Threatened; any native or once-native species of wild animal which is likely to become an endangered species
Family
Scientific Name
Common Name
Federal/
State
Listing*
within the foreseeable future throughout all or a significant portion of its range or listed as a federal
threatened species.
SC – Special Concern; any species of wild animal native or once-native to North Carolina which is determined to
require monitoring but which may be taken under regulations adopted under State laws.
3.6.1 Comparison of 2005 - 2015 Priority Species
The 2015 evaluation identified 31 species as SGCN; 27 species as knowledge gap priorities; and
30 species as management concern or need priorities. Some species may be considered a
priority in more than one of the evaluation categories. The 2005 WAP listed 43 freshwater
mussel species as SGCN priority species but did not provide separate evaluation categories to
identify knowledge gap or management concern priorities.
Table 3.6.2 provides a list of species included on the 2005 priority list that were not ranked by
the Taxa Team as a priority for conservation concern and are therefore not included on the
2015 SGCN priority list.
Table 3.6.2 2005 priority species that are not included on the 2015 SGCN priority list.
Scientific Name
Common Name
Alasmidonta robusta
Elliptio cistellaeformis
Carolina Elktoe
Box Spike
Fusconaia barnesiana
Lampsilis radiata conspicua
Lasmigona holstonia
Villosa trabalis
Villosa vanuxemensis
Tennessee Pigtoe
Carolina Fatmucket
Tennessee Heelsplitter
Cumberland Bean
Mountain Creekshell
3.6.2 Conservation Concern
Haag (2012) notes that because the conservation status of many species remains poorly known,
high conservation concern stems from expecting the potential for future imperilment will
exceed current imperilment. Freshwater mussels are among the most globally imperiled
freshwater organisms, with about 75% of those historically found in the Southeastern U.S.
thought to now be extinct or at risk of extinction (Williams et al. 1993; Bogan, 1996; Neves et al. 1997; Gangloff
et al. 2009). The synergistic effects of numerous point and nonpoint source impacts that affect
water and habitat quality are likely causes of these declines, with changes to the physical and
chemical variables in a stream believed to be principle factors for this decline (Neves et al. 1997;
Brim-Box and Williams 2000; Gillies et al. 2003; Lydeard et al. 2004; Gangleoff et al. 2009).
3.6.3 Knowledge Gaps
Progress toward species recovery depends on knowledge about species distribution patterns as
well as a clear understanding of habitat and life history requirements of species (Flebbe and Herrig
2000). Compared to other taxa, we have limited knowledge levels and data regarding freshwater
mussels. Accurate distribution information is still lacking for many species, as is work related to
fish host identification, ecology (both of individual species and among communities of
organisms), and basic systematics (genetics, taxonomy, and morphology). Extensive monitoring
of populations is generally lacking.
There are endemism concerns associated with many species, both throughout the Tennessee
River Basin tributaries, as well as concerns about the distribution of some species with rather
restricted ranges within South Atlantic river systems. Taxonomic difficulties have yet to be
resolved for several genera, most notably Elliptio. There is an extreme knowledge deficit
regarding the pea clams; attaining information on their distributions should be pursued
whenever possible.
A rigorous phylogenetic study based on quantifiable, heritable attributes such as DNA sequence
data for scientifically defensible estimates of North American mussel diversity is needed (Lydeard
and Roe 1998). Such efforts have already yielded surprising departures from traditional
classifications. Because mussel dispersal occurs primarily by transport of glochidia on fish hosts,
cryptic variation may be high for mussels (Haag 2012). Molecular studies have uncovered a high
degree of cryptic variation not reflected by shell morphology. These studies show that several
currently recognized species include multiple evolutionary units (Mulvey et al. 1997; Roe
andLydeard1998; King et al. 1999; Jones et al. 2006; Serb 2006), suggesting that diversity of North American
mussels has been underestimated.
Protecting a rich fauna of mussels (about 50 species of mussels in North Carolina) from
environmental contamination requires an understanding of mussel sensitivity to diverse
toxicants. The vast majority of mussel species remain untested for most toxicants, and
estimating safe environmental concentrations is a critical need, especially for the protection of
rare, threatened, or endangered species. Freshwater mussel toxicology still lacks full
identification of pollutants that may limit mussel survival, recruitment and recovery. Few of the
compounds that mussels encounter in the wild have been evaluated in the lab. Also, toxicity
tests seldom address mussel reproduction, and tests are still short relative to mussel lifespans.
In particular, there is a need to test previously unevaluated contaminants of emerging concern,
using long-term exposures which more closely mimic natural conditions, and to evaluate more
ecologically relevant endpoints such as mussel health and recruitment.
Several publication over the last decade have noted the absence or under-protectiveness of
national water quality criteria for particular pollutants to which mussels are known to be
sensitive (Augspurger et al. 2003, Wang et al. 2010, Stokstad 2012, Haag 2012). To facilitate habitat evaluation,
work is needed to better characterize chemical and contaminated sediment exposure and
provide benchmarks to define acceptable pollutant concentrations. Researchers at N.C. State
University, University of Georgia, and U.S. Geological Survey have started work on testing
additional classes of chemicals (Bringolf et al. 2010, Hazelton et al. 2012, 2013, Wang et al. 2012), and the U.S.
Environmental Protection Agency has been an active participant in design and funding these
studies but more are needed. Publication of recommended benchmarks for pollutants of
concern (e.g., metals, major ions) will be useful in developing water quality regulations.
In the wild, almost all mussels require a fish host for the transformation of the larval glochidia
stage into the free-living juvenile stage. Transformation on a host fish is referred to as in vivo
transformation. In the lab, artificial growth media has been used to transform glochidia to
juveniles in vitro with increasing success (as measured by % transformation) as mussel
nutritional needs are better understood and with improvements in artificial media (Lima et al.
2012). There is a need to better define the relative health of in vivo and in vitro transformed
juveniles by other measures such as reproductive fitness and tolerance to environmental
stressors, including pollutants (Augspurger pers.comm.).
There are 27 species identified as research priorities because there are knowledge gaps, of
which 15 are also considered SGCN (see Table 3.6.1). Table 3.8.3 represents only those species
considered a knowledge gap priority.
Table 3.6.3 Knowledge Gap priority freshwater mussel species.
Scientific Name
Corbicula fluminea
Strophitus undulatus
Pyganodon cataracta
Lampsilis radiata
Ligumia nasuta
Uniomerus carolinianus
Pyganodon grandis
Taxolasma parvum (parvus)
Elliptio fisheriana
Utterbackia imbecillis
Elliptio roanokensis
Elliptio icterina
Common Name (Population)
Asian Clam
Creeper
Eastern Floater
Eastern Lampmussel
Eastern Pondmussel
Florida Pondhorn
Giant Floater
Lilliput
Northern lance
Paper Pondshell
Roanoke Slabshell
Variable Spike
Federal/
State
Listing
Status*
- /T
- /T
- /T
- /T
3.6.4 Management Needs
Restoring mussels into areas where they have been extirpated but the habitat is now suitable is
a high priority. Propagation and release of mussels to augment existing populations will help
reduce risk of extinction and may increase genetic diversity of small populations. Removing
barriers and other impediments to host fish movement will allow natural recolonization of
suitable habitats and facilitate gene flow between populations.
Waters important for mussels must be monitored for water quality use support ratings. Rating
of water quality (poor to excellent) by the N.C. Division of Water Resources (NCDWR)
Environmental Sciences Section informs several other aspects of state water quality programs.
For example, some waters with excellent quality can be petitioned for additional protection,
and waters rated as poor may be listed as impaired thereby making them subject to restoration
planning. Not all waters are monitored, so having important mussel habitat included in a longterm monitoring program is an important step in having access to other water quality
management tools.
Waters rated as Excellent and which have outstanding resources values (defined in water
quality statutes) can be petitioned for Outstanding Resource Waters (ORW) or High Quality
Waters (HQW) designations. Those designations afford additional protections to ensure that
water quality and associated resources are maintained. The process is not automatic and starts
when NCDWR is petitioned to provide the additional designation and associated protections.
Resource agencies should identify the waters important for mussel conservation which are
eligible for ORW or HQW designations and petition for those protections.
Cooperation between NCDWR and others is needed to develop site-specific water quality
restoration plans under N.C. Administrative Code (see 15A NCAC 02B 0.0110) which outlines
rules for considerations for federally-listed threatened or endangered aquatic species. Through
collaborative efforts, NCWRC along with NCNHP, USFWS, and NCDWR developed the technical
basis for a site-specific water quality management plan for Goose Creek (Yadkin – Pee Dee River
Basin), and there are other waters with federally-listed aquatic species and water quality
concerns in need of additional site-specific restoration plans.
3.6.5 Threats and Problems
Invasive and non-native species can create competitive pressures on food resources and their
burrowing activity can uproot native mussels in sandy sediments (Vaughn and Hakenkamp 2001; Bogan et
al. 2011). The first location in the state of the non-native Lilliput was first discovered in 2007 at
Falls Lake in Wake County and was confirmed through DNA analysis (Bogan et al. 2011). Asian Clam
can be found throughout the state, often in such large quantities they create high levels of
ammonia in streams that can negatively affect native mussels.
Contaminants and water pollution are a significant threat to all aquatic species and especially to
mussels. Point source discharges from municipal wastewater that contains monochloroamine
and unionized ammonia compounds are acutely toxic to freshwater mussels and may be
responsible for glochidial mortality that results in local extirpation of mussels (Goudreau et al. 1993;
Gangloff et al. 2009). However, given the transient nature of flowing systems (e.g., a water
continuum) and potential for dilution at
any point along the system it is especially
difficult to detect not only origination
points but also concentration levels in
the water column (Fleming et al. 1995). A dieoff event affecting Tar River Spinymussel
populations was detected in the Swift
Creek watershed (Nash County) as it
occurred and was attributed to
anticholinesterase poisoning related to
organophosphorus and carbamate
pesticides used in agricultural
applications (Hill and Fleming 1982; Fleming et al.
Tar River Spinymussel (NCWRC)
1995).
Since the publication of Kolpin et al. (2002) on the extent and diversity of chemicals present in
the nation’s waters, there has been increased concern about the biological relevance of the mix
of chemicals to which mussels and other aquatic organisms are exposed, including
pharmaceuticals, personal care products, and agrochemicals. Many pollutants detected in
streams have never been evaluated for their impacts to mussels (Augspurger pers.comm.).
Given their burrowing nature and consumption of detritus and particulate matter mussels may
be more susceptible to trace metal exposure and uptake of contaminants than other aquatic
animals (Wilson 2008; Jarvis 2011). Sediments from upstream locales, especially hydroelectric
impoundments, can be a source of sediments laden with trace metals (Jarvis 2011). A decline in
Appalachian Elktoe populations in the Upper Little Tennessee River watershed may be related
to trace metals concentrations, especially copper and zinc, found in stream sediments (Jarvis
2011). In urbanized areas, a lack of riparian vegetation and increased impervious areas
contributes to higher sediment loads from erosion that carry fertilizers, pesticides, herbicides,
and many other chemical compounds (Gangloff et al. 2009).
Lab studies indicate freshwater mussels are more sensitive than most other aquatic animals to
toxicity from sodium chloride and potassium chloride (Gillis 2011, Wang et al. 2012). As sea levels rise
and salt water moves upstream into freshwater habitats, it could be predicted that mussels
would be particularly vulnerable. Field conformation of the estimated limits of tolerance
predicted by the lab tests is important in determining the significance of this threat and in
design of ameliorative measures (Augspurger pers.comm.).
Climate change, mining, hydraulic fracturing, and other energy development will bring
additional stressors that need to be evaluated for mussels. In addition to specific pollutants that
may be introduced into the aquatic environment, the interactions of pollutants and
temperature (from climate change), salinity (related to sea level rise), and lower dilution (from
altered flows) will need to be considered (Augspurger pers.comm.).
Impervious areas in urbanized watersheds contribute to high water levels, even during short
rainfall events, which can result in flash flooding. These high or flashy flow events contribute to
increased sediment loads, turbidity throughout the water column, and stream bed movement
that stress mussel populations (Gangloff et al. 2009).
3.6.6 Additional Information
The Southern Appalachian Man and the Biosphere program, in partnership with several federal
and state agencies, conducted the Southern Appalachian Assessment which was designed to be
a regional assessment of all resources in 132 counties in mountain areas of North and South
Carolina, Georgia, Alabama, Tennessee, and Virginia (Flebbe et al. 1996).
3.6.7 Recommendations
 
In general, protection and restoration of natural community composition and function and
protection of surrounding natural areas under current conditions are the best ways to ensure
suitable habitats are available for this species. Measures that protect a large and diverse pool of
populations are the best way to ensure that species are able to survive future stresses and
adapt to changing climate conditions.
Distributional and status surveys. Priorities for conducting distributional and status surveys
need to focus on species believed to be declining or mainly dependent on at-risk natural
communities. 

Continue species distribution surveys for all SGCN and priority species.
Monitoring. Long-term monitoring is critical to assessing species and ecosystem health and in
gauging resiliency of organisms to a changing climate. These efforts will inform future decisions
on how to manage species and their habitats. Long-term monitoring is needed to identify
population trends and to assess performance of conservation actions. Monitoring plans should
be coordinated with other existing monitoring programs where feasible. We will

Conduct long-term monitoring to identify population trends for SGCN and priority
species.
Research. Research to facilitate appropriate conservation actions includes habitat
use/preferences, spawning location and timing, fecundity, population dynamics, population
genetics, feeding, competition, and predation. Research must also be conducted to determine
vulnerability of SGCN and other priority species to specific threats and studies should provide
recommendations for mitigation and restoration. Specific research needs are to











Support taxonomic resolution with completion of species descriptions for undescribed
taxa and resolution of species complexes using DNA research.
Conduct research to facilitate appropriate conservation actions. Research should focus
on life history studies of priority species. Specific questions to be addressed include:
habitat use/preferences, spawning location and timing, fecundity, population dynamics,
mortality and other demographic parameters, feeding, competition, predation.
Pea clam species are a research priority because there is little knowledge about them in
North Carolina.
Determine appropriate areas of suitable habitat for augmentation or restoration
activities.
Develop propagation techniques and protocols.
Investigate host fish relationships for all SGCN and priority species.
Research into the impact of chemicals, especially pharmaceuticals, personal care
products and agrochemicals and their interaction, to all mussel life stages. Test chemical
selection should be guided by chemical occurrence and class (representative
compounds from various classes of pharmaceuticals, for example) (Augspurger pers.comm).
Histological and toxicological assessments to help understand health of mussel cellular
and tissue fitness will improve ability to investigate mussel die-off events (Augspurger
pers.comm).
Field conformation of the estimated limits of tolerance for sodium chloride and
potassium chloride concentrations (Augspurger pers.comm).
The influence of suspended sediment and its associated contaminants, especially
metals, on mussels needs to be evaluated. Development and application of a standard
test method for evaluating the quality of sediment on mussel survival, growth and
reproduction is needed (Augspurger pers.comm).
The interactions of pollutants and temperature (climate change), salinity (sea level rise),
and lower dilution (altered flows) need to be investigated (Augspurger pers.comm.).
Management Practices and Conservation Programs. Management practices that reduce
impacts and work synergistically with other conservation actions are needed to enhance the
resilience of natural resources. Particular needs include preserving biodiversity, protecting
native populations and their habitats, and improving degraded habitats.


Conduct population augmentations and restorations using hatchery reared and
translocated mussels.
Promote best management practices on Commission-owned game lands and other state
lands (parks, forests, preserves).
Cooperative Efforts and Partnerships. Conservation programs and incentives and partnerships
should be utilized to the extent possible to preserve high quality resources and protect
important natural communities. Protection measures that utilize existing regulatory
frameworks to protect habitats and species should be incorporated where applicable. Land
conservation or preservation can serve numerous purposes in the face of anticipated climate
change but overall, promotes ecosystem resilience.


Continue to work with partners such as N.C. State University and propagation facilities
from other states to facilitate a robust production and augmentation program.
Riparian buffers are recognized as important in maintaining suitable instream physical
and chemical habitat quality. Not all waters of the state have buffer rules, so voluntary
approaches or local, regional, state land use ordinances which encourage riparian
buffers should be pursued.
References will be cited at the end of the chapter
Amyot, J. P. and Downing, J. A. 1991. Endo-and epibenthic distribution of the unionid mollusk
Elliptio complanata. Journal of the North American Benthological Society, 280-285.
Augspurger pers.comm. Personal communication June 2015 with Tom Augspurger, USFWS
regarding freshwater mussels, water quality, research, and management needs.
Bogan AE, Smith JM, and Raley ME. 2011. The Lilliput (Toxolasma parvum) (Mollusca: Bivalvia:
Unionidae) introduced into North Carolina. Journal of the North Carolina Academy of Science
127(2): 192-193.
Bogan AE. 1996. Decline and decimation: the extirpation of the unionid bivalves in North
America. Journal of Shellfish Research 15: 484.
Brim-Box J and Williams JD. 2000. Unionid mollusks of the Apalachicola Basin in Alabama,
Florida, and Georgia. Bulletin of the Alabama Museum of Natural History 21: 1–143.
Dillon, R. T. 2000. The ecology of freshwater molluscs. Cambridge University Press. pp 434-498
http://dx.doi.org/10.1017/CBO9780511542008.011.
Eckblad J.W. and Lehtinen S.F. 1991. Decline in fingernail clam populations (Family Sphaeriidae)
from backwater lakes of the Upper Mississippi River. Journal of Freshwater Ecology 6, 353-362.
Flebbe PA and Herrig JA. 2000. Environmental Auditing. Patters of aquatic species imperilment
in the Southern Appalachians: an evaluation of regional databases. Environmental Management
25(6): 681-694.
Flebbe PA, Harrison J, Kappesser G, Melgaard D, Riley J, and Swift, Jr. LW. 1996. Status of
aquatic resources. Pages 15–63 in The Southern Appalachian Assessment aquatic technical
report. US Forest Service, Southern Region, Atlanta, GA.
Fleming WJ, Augspurger TP, and Alderman JA. 1995. Freshwater mussel die-off attributed to
anticholinesterase poisoning. Environmental Toxicology and Chemistry 14(5): 877-879.
Gangloff MM, Siefferman L, Seesock W, and Webber EC. 2009. Influence of urban tributaries on
freshwater mussel populations in a biologically diverse piedmont (USA) stream. Hydrobiologia
636: 191-201.
Goudreau SE, Neves RJ and Sheehan RJ. 1993. Effects of wastewater treatment plan effluents
on freshwater mollusks in the upper Clinch River, Virginia, USA. Hydrobiologia 252: 211–230.
Haag WR. 2012. North American freshwater mussels. Cambridge University Press. 505 pp.
Hall EF and Fleming WJ. 1982. Anticholinesterase poisoning of birds, field monitoring and
diagnosis of acute poisoning. Environmental Toxicology and Chemistry 1: 27-38.
Jarvis JD. 2011. Water quality in the Upper Little Tennessee River and its potential effects on
the Appalachian Elktoe mussel (Alasmidonta raveneliana). Thesis, Western Carolina University,
Department of Geosciences and Natural Resources. 88 pp.
Layzer JB and Scott EM. 2006. Restoration and colonization of freshwater mussels and fish in a
southeastern United States tailwater. River Research and Applications 22: 476-491.
Moore, J. 2006. An introduction to the invertebrates. Cambridge University Press. Pp. 120-134.
Neves RJ, Bogan AE, Williams JD, Ahlstedt SA and Hartfield PW. 1997. Status of the aquatic
mollusks in the southeastern United States: a downward spiral of diversity. In: Aquatic Fauna in
Peril: the Southeastern Perspective. Eds. G.W. Benz & D.E. Collins, pp. 43-86. Special Publication
1, Southeast Aquatic Research Institute. Decatur, GA. 554 pp.
Neves RJ. 1993. A state-of-the-unionids address. In: Conservation and Management of
Freshwater Mussels, Proceedings of a UMRC Symposium, 12±14. October, 1992, St Louis, MO.
Eds. K.W. Cummings, A.C. Buchanan and L.M. Koch, pp. 1-10. Upper Mississippi River
Conservation Committee. Rock Island, IL.
[NCAC] North Carolina Administrative Code 15A Subchapter 2B Surface Water and Wetland
Standards. Section .0100 Procedures for Assignment of Water Quality Standards.
http://ncrules.state.nc.us/ncac/title%2015a%20%20environment%20and%20natural%20resources/chapter%2002%20%20environmental%20management/subchapter%20b/subchapter%20b%20rules.pdf
Shannon L., Biggins R.G. and Hylton R.E. 1993. Freshwater mussels in peril: perspectives of the
U.S. Fish and Wildlife Service. In: Conservation and Management of Freshwater Mussels. Eds.
K.S. Cummings, A.C. Buchanan and L.M. Koch, pp. 66-68. Proceedings of a UMRCC symposium,
12-14 October, 1992, St Louis, Missouri. Upper Mississippi River Conservation Committee, Rock
Island, IL, USA, pp. 117-122.
Vaughn C.C. and Taylor C.M. 1999. Impoundments and the decline of freshwater mussels: a
case study of an extinction gradient. Conservation Biology (13): 912-920.
Vaughn CC and Hakenkamp CC. 2001. The functional role of burrowing bivalves in freshwater
ecosystems. Freshwater Biology 46: 1431–1446.
Vaughn CC. 2010. Biodiversity losses and ecosystem function in freshwaters: emerging
conclusions and research directions. BioScience 60(1): 25-35.
Vaughn CC. and Hakenkamp, C. C. 2001. The functional role of burrowing bivalves in freshwater
ecosystems. Freshwater Biology 46: 1431-1446.
Williams JD, Warren Jr. ML, Cummings KS, Harris JL, and Neves RL, 1993.Conservation status of
freshwater mussels of the United States and Canada. Fisheries 18: 6–22.
Wilson DM, Naimo TJ, Wiener JG, Anderson RV, Sandheinrich MB and Sparks RE. 1995.
Declining populations of the fingernail clam Musculium transversum in the upper Mississippi
River. Hydrobiologia (34): 209-220.
Wilson WAS. 2008. Bioaccumulation of Trace Elements by Bivalves in the Altamaha River
System. Dissertation at the University of Georgia. Athens, GA.