Triannual Unionid Report No. 11 March, 1997, continued

Author: Sue Bruenderman
Address: Missouri Department of Conservation
Fisheries and Wildlife Research Center
1110 S. College Ave.
Columbia, MO 65203
Phone: 573-882-9880 Ext. 3239
Fax: 573-882-4517

In September 1996, the Missouri Department of Conservation hired Sue Bruenderman to fill a newly-created malacologist position. First on the large slate of jobs to be done is a statewide survey to determine the current status and distribution of Missouri's mussel fauna. The survey will be conducted using a basin-by-basin approach and the Meramec River basin in eastern MO has been selected as the first to be examined (to begin in spring 1997). Another task to be completed in the spring is a search for the federally endangered Curtis' pearly mussel, Epioblasma florentina curtisi. The last known remaining population occurs in the upper Little Black River (of the Current River) in southeastern Missouri. Biologists from the United States Fish and Wildlife Service (USFWS) and Southwest Missouri State University (SMSU) will help MDC biologists search for this endangered species. If gravid individuals are found, glochidia will be collected and used by Dr. Chris Barnhart for use in laboratory experiments to hopefully identify fish hosts of this species. Dr. Barnhart has been actively conducting fish host and in vitro culture work for the past several years. Increased cooperation between SMSU, MDC and the USFWS over the past year has led to some positive changes that we hope will result in a relatively stable funding base for mussel conservation work in Missouri for years to come.

Greg Cope has joined the Department of Toxicology at North Carolina State University in Raleigh, North Carolina as the Department's Environmental and Extension Toxicologist. Greg will continue to conduct research related to the effects of anthropogenic stresses on aquatic organisms, with emphasis on fish and invertebrates, and the fate, bioavailability, and transport of contaminants in aquatic ecosystems. In addition, he will direct the Department's extension activities including county agent training and support, preparing extension-related literature, and conducting short courses and meetings. He will also be responsible for the College of Agricultural and Life Sciences' Agromedicine Program operated in conjunction with the Medical School at East Carolina University and other health-related organizations.

Greg has a Ph.D. with a Double Major in Toxicology and Fisheries Biology from Iowa State University, an M.S. in biology with emphasis in Aquatic Sciences from the University of Wisconsin-La Crosse, and a B.S. in Environmental Science from Lenoir-Rhyne College. He has worked as an ecotoxicologist at the U.S. Geological Survey's Upper Mississippi Science Center in La Crosse, Wisconsin for the past six years conducting research on the effects of waterborne and sediment-associated contaminants on fish and invertebrates, assessing various toxicant and nontoxicant methods for controlling zebra mussels, and developing methods for preserving the biodiversity of native unionid mussels. His new address is Department of Toxicology, North Carolina State University, Box 7633, Raleigh, NC 27695-7633 (phone 919-5155296; fax 919-515-7169; greg_cope@ncsu.edu).

The upper Tennessee River NAWQA study unit will be concentrating our sampling efforts this spring and summer in the French Broad River system (North Carolina) including the Nolichucky (Tennessee). Sampling will be conducted with TVA's French Broad River Action Team (RAT) and will include fish, benthic macroinvertebrates (mollusks), algae, and water quality. Streams selected for sampling are as follows:

In Virginia, we will continue our sampling in the Guest River, Copper Creek, and Middle Fork Holston River.

HAVLIK, MARIAN E., Malacological Consultants
1603 Mississippi Street, La Crosse, WI 54601-4969
Phone/Fax: 608-782-7958
E-mail: havlikme@aol.com

A pre-project survey at the T.H. 43 bridge, Mississippi River, Winona, MN/Wisconsin yielded a mean density of 11 unionids/m² (14 species) at nine piers that were to be enlarged. Dreissena polymorpha (Pallas 1771) were less numerous than at La Crosse, Wisconsin, 30 miles downstream (Triannual Unionid Report No. 10), because this side channel did not have direct commercial navigation impacts. A mussel translocation from 3-17 September 1996 yielded 6117 unionids (23 species) at a mean density of 2.0/m². No federally listed unionids were found but 2% represented seven Minnesota and Wisconsin endangered, threatened and special status species. Most of 80 Obovaria olivaria (Rafinesque 1820) were juveniles. Ellipsaria lineolata (Rafinesque 1820) (1), Pleurobema sintoxia (Raf. 1820) (4), Liqumia recta (Lamarck 1819) (12), and Utterbackia imbecillis (Say 1829) (11), were also represented by juveniles. Other special status species were Arcidens confragosus (Say 1829) (2), and Megalonaias nervosa (Rafinesque 1820) (2). At Pier 1 a mat of D. polymorpha 25-75 mm thick, carpeted the riprap, debris and mud substrata complicating recovery of 1371 unionids. Divers had difficulty determining if there were rocks or living unionids under the Dreissena. Although all special status species were at this site in depths up to 6 m, over 300 D. polymorpha were attached to most unionids Most unionids from Pier 1 were adults, but there were some juveniles. Overall the current was less than at La Crosse, WI. Many dead unionids were found, but few were fresh-dead. All visible D. polymorpha were removed by hand and both unionid valves were marked. The first Alasmidonta marginata Say 1818 (a threatened, small stream species) reported from the Minnesota portion of the Mississippi River since 1930 was found at the nearby translocation site which had a resident density of 4.0/m² (2 other special status species were found on the first dive). Special status mussels were hand planted 15 m offshore in a longitudinal transect.

At Piers 2-9 about 50% of the unionids were under 3 years of age and less than 35 mm long. Recovery of juveniles was the result of careful searching in sand substrata. There were fewer exotics, but up to 60 D. polymorpha, from 1-5 mm in length representing the August-September 1996 cohort, covered most of many small unionids. These findings have profound implications for juvenile unionids. Depths at Piers 2-9 ranged from 5 cm, but averaged 3-5 m, with a substrata of sand, mud, and dead trees. This site was a prime example of a patchy unionid distribution. Preliminary survey results from 45-0.25 m² quadrats had indicated a population of 32,000 mussels, but fewer were recovered even though 3100 m² were searched twice. A few young Corbicula fluminea (Muller 1774) were also found, but they were not considered problematic at the site.

J.L. Metcalfe-Smith¹, S.K Staton¹, G.L. Mackie², and N.M. Lane^1
1National Water Research Institute, Environment Canada, Canada Centre for Inland Waters.
867 Lakeshore Road, P.O. Box 5050, Burlington, Ontario, Canada L7R 4A6
Ph: (905) 336-4685 Fax: (905) 336-4420
²University of Guelph, Guelph, ON

Over the last 50 years, the freshwater mussel fauna of North America has been decimated. As a result. in the United States, mussels have been protected under endangered species legislation for many years. The U.S. Fish & Wildlife Service has drafted a national strategy for the conservation of native mussels, and recovery plans are in place for most endangered species. The plight of mussels in Canada has recently been recognized with the formation of the Mollusc Working Group (MWG) of the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in 1995. Since molluscs (which include mussels) are one of the most threatened groups, the MWG was formed to develop a national list of Canadian species at risk and to prepare status reports on these species. Two of the authors are members of the MWG, hence the impetus behind the project.

The study focused on the lower Great Lakes drainage basin because this area historically supported the most diverse mussel fauna in Canada (41 of the 53 Canadian species occur here and 22 are found only here). Recently, however, zebra mussels have virtually eliminated native mussels from the lakes themselves, leaving the rivers and streams as the last refuge for many species. The purpose of the project was to develop a computerized, GIS-linked database on the historical diversity of freshwater mussels in the study area in order to: develop biodiversity objectives for the various waterways, compare historical and recent data to determine if diversity is declining, identify the species most at risk and species-rich areas that should be protected, and identify data gaps. The database consists of data obtained from natural history museums within the basin, the primary literature, government reports, and university theses. Over 4000 records for 41 species of mussels collected from over 1500 sites between 1860 and 1996 have been entered to date. Each record represents the occurrence of a given species at a given site on a given date. The geographic distributions of the 41 species are a consequence of their post-glacial re-invasion routes; 36 species are southwestern in origin and only 5 are northeastern. Some species are widespread, but most have local distributions and this is significant because species with restricted ranges are very vulnerable.

Using the database, we attempted to derive biodiversity objectives for 10 waterbodies in the study area. The simplest objective is species richness which is the total number of species that a system has historically supported. The species richness objectives are as follows: Lake St. Clair & the Detroit River (33), Sydenham River (33), Thames River (32), Lake Erie (35), Grand River (34), Niagara/Welland Rivers (27), Lake Ontario (18), Moira River (16), Trent-Severn River (14), and Rideau River (13). Lake St. Clair and Lake Erie drainages historically supported a much more diverse mussel fauna than the Lake Ontario drainage (the last four waterbodies listed). All species have been found in the Lake Erie & Lake St. Clair drainage, but only 23 have been found in the Lake Ontario drainage. The database was also used to determine if species composition had changed over time. Data for the entire study area were divided into six time periods and examined for trends; the results showed that significant changes were beginning to take place around 1960. Major changes included a reverse in the order of dominance of the two most common species, with Lampsilis siliquoidea accounting for the greatest proportion of the records prior to 1960 and Pyganodon grandis accounting for the most records after 1960. L. siliquoidea was found at 30% of the sites in both time periods. However, P. grandis was found at 16% of the sites before and 45% after 1960, so it appears to have become more common. Two other species of Anodontinae, Strophitus undulatus and Lasmigona complanata also became much more common after 1960. It has recently been shown that all three of these species move into areas that have become deforested, suggesting that they may be general indicators of degraded conditions. As a number of less common species appeared to have become more rare since 1960, the data for each waterbody were examined for evidence of species losses. We found that losses had occurred in waterbodies of the Lake St. Clair and Lake Erie drainages and in Lake Ontario itself, but there were no losses in the three river systems draining into Lake Ontario. The Grand River is a large, well-studied tributary to Lake Erie with 900 unionid records available for the period 1885 to 1996. During this period, the structure of the mussel community changed from a community with a large number of well-represented species prior to 1960, to a community becoming increasingly dominated by fewer and fewer species and eventually resulting in a species loss of at least 30%. Eight species accounted for 50% of the records prior to 1960 vs. only six species in the period 1961-1983 and five species in the recent time period. Also, the community has become dominated by Anodontinae, i.e. P. grandis, S. undulatus, and A. ferussacianus ranked 7^th, 18^th, and 21^st in dominance prior to 196O, 1^st, 2^nd, and 10^th in the period 1961-1983 and 2^nd, 7^th and 1^st in the period 1984 to 1996.

To identify the species that should be recommended to COSEWIC for national status designation, the following factors were taken into account: recognized conservation status in Ontario, Canada, and North America, evidence of decline in the study area, restricted range, host specificity, and vulnerability to current threats, especially zebra mussels. It should be noted that Ontario's Natural Heritage Information Center has ranked the species in our study area, but have used only a subset of the data we now have available. Based on these considerations, the following species were deemed to be most at risk (threatened, endangered, or extirpated) and are proposed for consideration by COSEWIC: Cyclonaias tuberculata, Ligumia nasuta, Obovaria subrotunda, Pleurobema coccineum, Truncilla donaciformis, Utterbackia imbecillis, and Villosa fabalis. Several other species already presumed extirpated from Canada include: Epioblasma obliquata obliquata, Epioblasma triquetra, Epioblasma torulosa rangiana, Obliquaria reflexa, Obovaria olivaria, Simpsonaias ambigua, and Toxolasma parvus.

The mussel database provides the most complete picture possible of the historical distributions of mussels in the lower Great Lakes drainage basin and will be used as a resource to support the activities of the Mollusc Working Group of COSEWIC. This year we plan to focus our efforts on additional surveys at high diversity sites where priority species were found in the past. This information will be used to refine the conservation status rankings of species and to identify waterways in need of protection or rehabilitation.

The authors would like to thank Environment Canada's Ecological Monitoring Coordinating Office and Great Lakes 2000 Program for their financial support. We would also like to thank the curators of the following museums for their willing contributions to our project: Canadian Museum of Nature, Ohio State University Museum of Zoology, Royal Ontario Museum, University of Michigan Museum of Zoology, Buffalo Museum of Science, and the Rochester Museum and Science Center. A special thanks also goes out to the several biologists of the Ontario Ministry of Natural Resources who contributed to our project.

David L. Strayer and Andrew R. Fetterman

Institute of Ecosystem Studies
Box AB
Millbrook, NY 12545
(914) 677-5343 (phone)
(914) 677-5976 (fax)
dlstrayer@aol.com

Between 1955 and 1965, Arthur Clarke, Willard Harman, and Carol Stein surveyed the unionid communities at about 70 sites in the Susquehanna basin in New York. We are resurveying these sites and trying to correlate patterns of faunal change with water quality and land use. Because of unusually rainy weather, we were able to resurvey only 47 sites in 1996; the remaining sites will be examined in 1997.

Unionids are extremely patchy at most sites; it was not uncommon for us to spend over half an hour before finding our first living unionid. Nonetheless, faunas appear to have been very stable since 1955-65, with few changes in species lists at any site (see table below). Exceptions to this general statement are Alasmidonta varicosa, which seems to be declining in the upper Susquehanna basin, and possibly Lasmigona subviridis, which may show a decline in distribution.

Species Number of sites (1955-65) Number of sites (1966) a Number of living specimens (1966) Elliptio complanata 29 25 807 Lasmigona compressa 3 0 0 Lasmigona subviridis 6 3 7 Anodontoides ferussacianus 2 1 1 Pyganodon cataracta 16 11 41 Alasmidonta undulata 16 15 55 Alasmidonta marginata 14 12 101 Alasmidonta varicosa 12 3 19 Strophitus undulatus 22 22 238 Lampsilis radiata I 1 13 105 Lampsilis cariosa 14 20 108 a includes living or freshly dead shells only

U. S. GEOLOGICAL SURVEY
Biological Resources Division
Florida Caribbean Science Center
352-378-8181

Nonindigenous aquatic species have been and continue to be a major source of socio-economic benefits and costs to many sectors of American society and a significant threat to the maintenance of biological diversity. Despite this significance, nonindigenous species issues in general have been vastly under-recognized. Primarily in response to the introduction of zebra mussels into the Great Lakes, Congress enacted the Nonindigenous Aquatic Species Prevention and Control Act of 1990 (Act). The major focus of the Act was to set up a framework to reduce the risk of unintentional introductions and to monitor and control nonindigenous aquatic nuisance species. A core element of this framework was to create an Information Service to provide timely, reliable data about the presence and distribution of nonindigenous aquatic species.

In 1993, The National Nonindigenous Aquatic Species Geographic Information System was established at the USGS, Biological Resources Division research facility in Gainesville, Florida. This public access information system includes maps, fact sheets, data sets, general and scientific reports, and other related information regarding aquatic introductions reported since 1850. The current on-line data base contains over 35,000 geographically referenced accounts of over 680 species of fish, mammals, amphibians, reptiles, tunicates, bryozoans, sponges, coelenterates, annelids, mollusks, crustaceans, algae, ferns, monocot and dicot plants, diseases, and parasites. This service is routinely used by Department of Interior Bureaus, NOAA, Department of Agriculture, state agencies, universities, and numerous U.S. and Canadian private industries to monitor the distribution of these organisms and to enable regional and national assessments of important species for management and control. It has also been recognized as the model system for developing a joint US/Canada/Mexico system under the auspices of the North American Free Trade Agreement (NAFTA).

General accessibility is provided through a world-wide-web site (http://www.nfrcg.gov/nas) which was a pioneer in data serving on the internet. The information content and format has earned the site a '4-star' rating by the Magellan Internet Guide and was recognized by Discovery Communications, Inc., parent company of Discovery Channel and The Learning Channel who featured the site twice during the past 2 years. To date the site has been accessed by nearly 70,000 unique users from around the globe. Site content has been used within a variety of other information products including a CD-ROM demonstrating advanced capabilities of the Internet, school and university teaching aids (Canadian and U.S), and the new USGS Digital Atlas.

Additional services are provided by research staff who serve as a central contacts for national aquatic nuisance species information. Informal networks of regional and state contacts are maintained to encourage information exchange and bring new understanding to nonindigenous aquatic species issues. Radio and television interviews, extension service satellite teleconferences, scientific presentations and demonstrations, press releases, popular articles, reference books, map products, fact sheets, and scientific publications are all products prepared by the staff to provide broad-spectrum outreach and public service for this recognized information need.

Richard Levey and Steve Fiske
VT Dept. of Environmental Conservation-Biomonitoring and Aquatic Studies Section
103 South Main St., Waterbury, Vt. 05671
(802) 244-4520

The Lake Champlain Basin supports the most diverse freshwater mussel fauna in New England (14 species). Eight species are at or near their northeastern range limits in the drainage, of these, none are common in Vermont. In 1993 the exotic zebra mussel (Dreissena polymorpha) was discovered in Lake Champlain. The zebra mussel poses a very serious threat to the native unionid populations of Lake Champlain. By the summer of 1995 Dreissenid infestations were already causing significant native unionid mortality in southern Lake Champlain.

The greatest immediate threat is to those species that are found only in the Lake Champlain drainage, there are seven species - Potamilus alatus, Leptodea fragilis, Ligumia recta, Lampsilis ovate, Lasmigona costata, Anodontoides ferussacianus and Pyganodon grandis.

Lewis Creek delta supports a diverse and dense mussel population, that has recently become heavily colonized by zebra mussels. In the summer of 1995 native unionids had 1 - 6 zebra mussels attached to their shells, by the summer of 1996 attachment had increased to 40 - 100 zebra mussels per native unionid.

In an effort to conserve a small but diverse population of native unionids in the Lewis Creek delta a 60 meter by 30 meter area was designated for physically removing zebra mussels from the native unionids. Scuba divers working inside the designated area removed native unionids from the substrate, rubbed off the zebra mussels; crushing as many as possible in the process and replaced the native unionids into the substrate.

Rare native unionids encountered by scuba divers inside the designated area and outside the area by snorkelers (Leptodea fragilis, Potamilus alatus, Lampsilis ovata, and Pyganodon grandis) were collected, cleaned of zebra mussels and placed into a 5 meter by 10 meter area near the mouth of Lewis Creek for potential relocation next year. Between 100 and 150 rare native unionids were collected, cleaned and placed into the 5 by 10 meter area.

The effort to clean all native unionids inside the 30m by 60m area was impressive, but the size was a little more than the half dozen SCUBA divers could manage in one days effort. The following week, survey work was conducted inside and outside the maintained area to document zebra mussel attachment on the native unionids.

Results indicate that there had been some re-attachment of zebra mussels that had been removed from native unionids inside the maintained, presumably some clumps of zebra mussels that had been rubbed off the natives but not crushed had reattached to the native unionids inside the maintained area.

Work will be conducted in the summer of 1997 to document the survival of native unionids inside and outside of the maintained area; and zebra mussel attachment to native unionids. Future efforts to conserve native unionids most likely will focus on collecting and relocating as many rare native unionids from sites threatened by heavy Dressenid infestations.

Andrew D. Roberts, Ashley P. Farnsworth, Janet Sternburg
Missouri Department of Conservation
Jefferson City, MO 65102
573-751-4115

M. Christopher Barnhart
Department of Biology, Southwest Missouri State University,
Springfield, MO 65804
417-836-5166
E-mail mcbO95f@wpgate.smsu.edu

The lowlands of southeastern Missouri were once a vast, wooded flood plain, watered by the Mississippi, St. Francis, and Castor rivers. Since the turn of the century, enormous drainage and deforestation projects have converted the region to agriculture. Although the destruction of natural landscapes in the Bootheel is nearly complete, a surprisingly diverse aquatic fauna exists in the hundreds of miles of man-made waterways, including numbers of freshwater mussels (Unionidae).

We surveyed unionid mussels in the waterways of Dunklin and Pemiscott Counties in summer of 1996. Objectives were to determine diversity and abundance of unionids, and, in particular, to investigate the possible presence of the federally endangered fat pocketbook mussel, Potamilus capax. A total of 114 man-hours was spent in searching at 71 sites. A total of 1,708 individual live mussels of 28 species was examined. The ten most abundant species, in order of abundance, were Amblema plicata, Potamilus purpuratus, Quadrula nodulata, Pyganodon grandis, Quadrula pustulosa, Quadrula quadrula, Leptodea fragilis, Lampsilis cardium, Lampsilis teres, and Obliquaria reflexa.

Twenty-four living individuals of Potamilus capax were found along a 3-mile stretch of the Belle Fountain Ditch in southern Dunklin County. Significantly, 3 of these individuals were less than 3 years of age, indicating that the population is reproducing. Mussels are relatively long-lived and juveniles are often rare. Relatively large numbers of juveniles of other species were noted as well. Despite the effects of intense agriculture and periodic dredging impacting these waterways, it appears that they provide good habitat for a number of mussel species.

M. Christopher Barnhart and Andrew D. Roberts
Department of Biology, Southwest Missouri State University,
Springfield, MO 65804
417-836-5166
E-mail mcbO95f@wpgate.smsu.edu

Recent mussel surveys in southeast Missouri permitted investigation of the reproduction of the federally endangered fat pocketbook mussel. A total of 22 adult individuals were examined in the Belle Fountain waterway in Dunklin County, MO. Two of six individuals were gravid with mature glochidia on June 6-20. No further observations were made until August 13-22, at which time none of 16 individuals examined was gravid. Evidently, glochidia were released in July or August.

Twenty-eight species of fish were tested as possible hosts of the parasitic glochidia larvae. Glochidia successfully transformed to juveniles only on freshwater drum (Aplodinotus grunniens). Glochidia remained encysted for several days on white crappie (Pomoxis annularis) but died within the cysts without transformation. Other fish species tested generally shed attached glochidia within 24 hours. Preliminary attempts to culture the glochidia in vitro were unsuccessful.

Metamorphosis from glochidium to juvenile was completed in 15-26 days at 21 degrees C, with the peak of encystment at 20 days post-infection. Unlike most mussel species, the glochidia of Potamilus grow substantially during encystment. Shell length (anterior-posterior) of P. capax increased from 95 micrometers in glochidia to 334 micrometers in recently encysted juveniles (means of 5 individuals).

This study supports previous evidence that drum may be the primary natural host of Potamilus capax (Cummings & Mayer 1993). At least twelve other mussel species are also known to utilize drum as a host, including all members of the genus Potamilus that have been investigated (Watters 1994).

Literature Cited

Cummings, K.S. and C. Mayer 1993. Distribution and host species of the federally endangered freshwater mussel, Potamilus capax (Greene 1832), in the lower Wabash River, Illinois and Indiana. Illinois Natural History Survey, Center for Biodiversity Technical Report 1993(1): 1 -29.

Watters, G.T. 1994. An annotated bibliography of the reproduction and propagation of the Unionoidea (primarily of North America). Ohio Biological Survey Misc. Contrib. l :1 -158.

M. Christopher Barnhart
Department of Biology, Southwest Missouri State University,
Springfield, MO 65804
417-836-5166
E-mail: mcbO95f@wpgate.smsu.edu

Unfertilized or infertile eggs have been reported in a number of unionid species (Howard 1914). These undeveloped eggs have sometimes been interpreted as a failure of fertilization due to low population density and shortage of sperm (Downing et al. 1993). However, little attention has been given to the fact that, in many unionids, a large fraction of eggs normally do not develop, regardless of the availability of sperm. These sterile eggs occur in species that release cohesive masses (conglutinates) of sterile eggs and glochidia larvae. Conglutinates attract host fish, which then become infected with the parasitic glochidia larvae while attempting to ingest the conglutinates.

Sterile eggs appear to enhance conglutinate function in several ways. For example, in Fusconaia, Pleurobema, and Cyprogenia, sterile eggs provide color and opacity to conglutinates and thereby render them more visible to hosts. Mature eggs bearing glochidia are transparent. In Cyprogeniu aberti, sterile eggs comprise up to 85% of the conglutinate total and serve a structural role by providing a tough and elastic support upon which the developed glochidia are arrayed in a superficial layer. This support increases handling time by the host fish and ensures that the glochidia are easily shed when the conglutinate is bitten. Although evidence is scant, it appears that sterile eggs may also make conglutinates more attractive to the host through taste and scent.

Improved rates of host fish infection by conglutinates bearing sterile eggs presumably offset the consequent reduction in the number of larvae that are produced. The mechanisms that are responsible for the production and orderly placement of sterile eggs within the conglutinates are unknown. (Abstract submitted for 1997 annual meeting, North American Benthological Society)

Literature Cited

Downing, J.A., Y. Rochon, and M. Perusse. 1993. Spatial aggregation, body size, and reproductive success in the freshwater mussel Elliptio complanata.J. N. Am. Benthol. Soc. 12(2):148-156.

Howard, A.D. 1914. Experiments in propagation of freshwater mussels of the Quadrula group. Bureau of Fisheries Document 801 :1-51.

James B. Layzer, Acting Unit Leader
Telephone: 615/372-3032
E-mail: jbl2432@tntech.edu

Current Research Projects

Relationship between stream discharge and mussel recruitment. Dina J. Crawford, James B. Layzer, and Lesa M. Madison.

Reintroduction of freshwater mussels into the Tennessee River and its major tributaries (start: July 1997). Natalie Constantino and James B. Layzer.

The relation between mussel density and survival during quarantine. Robert D. Quinn and James B. Layzer.

Feasibility of reestablishing populations of eight federally listed mussel species and two federally listed fish species into Shoal Creek, Alabama and Tennessee. Lesa M. Madison and James B. Layzer.

Maintenance and production of Ohio River mussels. Jason R. Khym and James B. Layzer.

Zebra mussel impacts on unionids. Lesa M. Madison and James B. Layzer.

Olivia J. Westbrook and James B. Layzer

In April 1996, 64 fish of three known host species were infested with glochidia of L. cardium; 5 fish were held in laboratory aquaria and the remaining fish were released into a raceway at the Minor E. Clark Fish Hatchery. Juvenile mussels produced in the laboratory were transferred to petri dishes filled with substrate and suspended in a wire cage in the raceway. Survival was assessed at 60, 90 and 120 days by removing one or two petri dishes and examining the contents under a dissecting microscope (10X). Survival declined from 17% at 60 days to 3.5% at 120 days; however, mean length increased from 1.88 mm to 18.2 mm during this same period. Results of quantitative sampling in October indicated a juvenile density of 12.1/m² in the raceway. Mean length of juveniles in the raceway was 21.5 mm.

James B. Layzer, Lesa Madison, and Robert Quinn
Tennessee Cooperative Fishery Research Unit
Tennessee Technological University
PO Box 5114
Cookeville, Tennessee 38505

In 1994 we began to establish captive populations of unionids. As of December 1997, we are holding 7,017 mussels of 36 species at several locations in Tennessee and Kentucky. Some of these species are being held primarily for propagation studies.

Table 1. Numbers and Species of Mussels in Captivity

Species Number Species Number Actinonaias ligamentina 175 Megalonaias nervosa 115 Amblema plicata 554 Obliquaria reflexa 223 Arcidens confragosus 5 Obovaria olivaria 8 Cyclonaias tuberculata 251 Plethobasus cooperianus 5 Ellipsaria lineolata 126 Pleurobema coccineum 45 Elliptio crassidens 5 Pleurobema cordatum 336 Elliptio dilatata 385 Pleurobema pyramidatum 10 Epioblasma capsaeformis 20 Potamilus alatus 23 Fusconaia barnesiana 6 Ptychobranchus fasciolaris 130 Fusconaia ebena 3,725 Quadrula cylindrica 1 Fusconaia flava 143 Quadrula metanevra 60 Lampsilis cardium 11 Quadrula nodulata 146 Lampsilis fasciola 6 Quadrula pustulosa 272 Lampsilis siliquoidea 13 Quadrula quadrula 25 Lasmigona costata 39 Tritogonia verrucosa 86 Leptodea fragilis 8 Truncilla truncata 5 Lexingtonia dolabelloides 42 Villosa taeniata 4 Ligumia recta 6 Villosa vanuxemensis 3

Arthur E. Bogan, former Director of Freshwater Molluscan Research, Sewell, NJ has accepted the position of Curator of Aquatic Invertebrates at the North Carolina State Museum of Natural Sciences in Raleigh. He arrived 1 January, 1997, and will continue working on the systematics and zoogeography of freshwater bivalves, participating in workshops on freshwater mollusks, developing a morphological phylogeny of unionoid bivalves, and will begin to enhance the NCSM freshwater molluscan collections. The NCSM is in the process of building a new museum, with new exhibits due to open in 1999. The museum is also constructing a new collections and research facility. Since his arrival, he together with the Wayne Starnes, Curator of Fishes, completed the movement of the Institute of Marine Sciences Mollusk collection from Morehead City, NC to Raleigh. Hugh Porter built this collection, which contains about 12,000 lots of marine and brackish water mollusks with a healthy representation of freshwater mollusks.

THE RELATIONS BETWEEN COMPLEX HYDRAULICS AND MUSSEL DENSITY

Bart S. Hardison
Master of Science in Biology

The hydraulic conditions that are most relevant in determining mussel distribution are those that characterize flows near the substrate, because adult and juvenile mussels live in the substrate and encysting juveniles must settle onto the stream bottom. A stratified random sampling design was used to examine the relations between selected hydraulic variables and the density of mussels in the Green, Licking, and Rough Rivers of Kentucky. Strata were positioned to ensure that samples were collected over a wide range of hydraulic conditions at each site. Eight 0.25 m² quadrat samples were collected from each 25 m² stratum. Before collecting each sample, mean water column velocity, depth, and substrate roughness were measured in each quadrat. 'Fliesswasserstammtisch' hemispheres were used to estimate shear stress. Substrate roughness was positively correlated with mussel density for the Rough River. Depth was positively correlated with mussel density in the Green River, negatively correlated in the Rough River, and was not significantly correlated in the Licking River. Mean water column velocity, Froude number, shear velocity, and Hemisphere density were negatively correlated with mussel density for all rivers. Although mean water velocity was significantly correlated with mussel density, the relations between complex hydraulic variables (especially shear velocity and hemisphere density) and mussel density had higher correlation coefficients. Therefore, shear velocity and hemisphere density may be more useful for predicting the distributions of freshwater mussels.

AGE, GROWTH, AND STABILITY OF A MUSSEL ASSEMBLAGE IN HORSE LICK CREEK, KENTUCKY

Bradley S. Houslet
Master of Science in Biology

During the past 15 years, several studies have documented mussel distributions in Horse Lick Creek and how strip mining of coal in the lower watershed reduced the distributions of many species. Recent data indicated that mussel length in the lower portion of the creek were significantly less than those upstream of mine run-off. Forty-three Villosa taeniatawere collected at one site in the upper portion and 46 at one site in the lower portion to determine if the difference in mussel size was related to differences in growth or was indicative of colonization following possible post-mining improvements in water quality. Ages determined from thin-sections ranged from 11 to 27 years at the lower site, and from 6 to 44 years at the upper site. Length was highly correlated with age at the upper site but there was no significant correlation between these variables at the lower site. Results of analysis of covariance indicated that increases in width, height, and mass of shells per incremental increase in length were similar between sites. Tissue dry mass was 67% greater at the upper site. Apparently, mussels at the lower site were still being affected by the residual effects of strip-mining of coal. At the lower site, the lack of young (<11 yrs) and old (>27 yrs) mussels, their poor condition and lower density likely reflects the residual effects of past stripmining.

Community stability of the upper site musselbed in Horse Lick Creek, Kentucky, was assessed by comparing total mussel density, length frequency distributions, and relative abundance data with data collected in 1990 and 1991. Total mussel density increased from 4.88 mussels/m² in 1991 to 9.04 mussels/m² in 1995. However, juvenile density decreased from one juvenile in 4.3 m² to one juvenile in 10 m². Relative abundance remained unchanged or increased for 8 of 14 species, including an endangered mussel Pegias fabula. Although relative abundance decreased for three species, these were species considered rare (< 1% of the assemblage) and are thus more likely influenced by differences in normal sampling variance than actual causal effects of natural or anthropogenic perturbations. Average length decreased for 11 species, while minimum and maximum lengths of five species increased. The mussel community sampled in 1995 was 95.9% similar to the community sampled in 1990. Analyses of length frequency distributions and aging suggest that mussel populations do not necessarily need high annual reproductive success to maintain a stable population. The long-lived nature of Villosa taeniata and irregular length frequency distributions suggest that this particular musselbed is demonstrating regular stability.

REPRODUCTIVE ECOLOGY OF TWO SPECIES OF FRESHWATER MUSSELS IN TENNESSEE

Jackie R. Heinricher
Master of Science in Biology

The reproductive biology and age at sexual maturity were determined for Fusconaia ebena (Lea 1831) in Kentucky Lake, Tennessee, for a period of one year beginning October 1993. Fusconaia ebena is a short-term brooder (tachyticic) and is dioecious. Spawning began in April and continued into mid-August. Gonadal activity increased in the spring with increased water temperatures; the least amount of gonadal activity occurring during the winter months. Sex ratio of the sample population was 1:1. Only one of the 326 individuals examined histologically, was found to be a hermaphrodite. This hermaphrodite was considered to be functionally male with a majority of the gonadal tissue involved in spermatogenesis. Gonadal tissue color was dimorphic during the spawning season: testes were fleshtone, while ovaries ranged from pink to dark purple. Thinsectioning shells of F. ebena was a successful technique for accurately obtaining the ages of individuals of various sizes. Ninety-six percent agreement was reached in a double-blind reading of 53 thin-sections. Sagital sectioning of the hinge ligament was also a successful and efficient method for determining the age of F. ebena. Shell growth was determined to be annular for F. ebena with one new growth line occurring in April. Fusconaia ebena becomes sexually differentiated by age four. By age five F. ebena becomes sexually mature and begins active gametogenesis. Ages of the sample population ranged from two to eleven years. Retention of coded wire tags injected into the hinge ligament was 100% over a two year period. These tags are potentially an effective tool for enforcement and research purposes.

Reproduction of Megalonaias nervosa (Rafinesque 1820) has not been documented for over 20 years in much of the Cumberland River, where water temperature and flow regimes have been greatly altered by hypolimnetic discharges from impoundments. Studies in other streams have implicated altered temperature or discharge patterns as causative factors inhibiting reproduction. Megalonaias nervosa were collected from the Cumberland River, translocated to the Tennessee River, and held in an embayment of Kentucky Lake. After the first and second year, samples of M. nervosa were taken from the Cumberland River, an existing population in Kentucky Lake, and the translocated group. Histological examination indicated that translocated mussels had a high incidence of hermaphroditism, and like mussels originating in Kentucky Lake, had undergone an otherwise normal reproductive development. Individuals functioning successfully as females from the translocated group had mature glochidia in their marsupia. Females from the Kentucky Lake sample also had mature glochidia present. In contrast, there was no indication of reproductive activity in gonads or marsupia of individuals collected from the Cumberland River. These results suggest that the more natural temperature regime in Kentucky Lake reinstated reproduction in translocated mussels. This study suggests that the altered temperature regime may be disrupting the gametogenic cycle of all mussels including at least six federally-listed endangered species occurring in the Cumberland River. These relic populations will likely disappear unless they are translocated or the thermal regime returned to normal.

FEASIBILITY OF REINTRODUCING FRESHWATER MUSSELS INTO SHOAL CREEK, ALABAMA AND TENNESSEE

Annette Morgan
Master of Science in Biology

In 1991, a study was initiated to evaluate Shoal Creek as a possible location for reestablishing freshwater mussels. About 20 years earlier, nearly all mussels were extirpated from the creek by pollution. Shoal Creek may now provide a unique opportunity for reintroducing several rare mussels because of substantial improvements in water quality. Between 1992 and 1996, 29 species of mussels were introduced: 5,957 adults of 26 species, 7,472 juveniles of two species, and an estimated 15,000 juveniles of one species by infesting 174 host fish with glochidia and releasing them into the creek. During two qualitative searches, many of the located adult mussels had been transported downstream as much as 1.3 km during high flows. No glochidial infestations were detected on 2,365 fish, collected in 1995 and 1996, at the introduction sites.

Wally Holznagel, Kevin Roe, and I have a number of ongoing studies examining the conservation genetics and systematics of freshwater molluscs. Available reprints are listed below:

Lydeard, C., and R.L. Mayden. 1995. A diverse and endangered aquatic ecosystem of the Southeast United States. Conservation Biology 9:800-805.

Lydeard. C. 1996. U.S. Biodiversity Status Report. Conservation Biology 10:1480-1482.

Lydeard, C., M. Mulvey, and G.M. Davis. 1996. Molecular systematics and evolution of reproductive traits of North American freshwater unionacean mussels (Mollusca: Bivalvia) as inferred from 16S rRNA gene sequences. Phil. Trans. R. Soc. Lond. B 351:1593-1603.

Lydeard, C., W.E. Holznagel, J. Garner, P. Hartfield, and J. Malcolm Pierson. 1997. A molecular phylogeny of Mobile River drainage basin pleurocerid snails (Caenogastropoda: Cerithioidea). Molecular Phyl. Evol. 7:117-128.

ROBERT G. HOWELLS
Texas Parks and Wildlife Department, Heart of the Hills
Research Station, HC07, Box 62, Ingram, Texas 78025

Freshwater mussels of the genus Toxolasma, represent a unique, but taxonomically perplexing group. Intraspecific variability and interspecific similarity make classification difficult. At present, three species are recognized in Texas: lilliput, T. parvus (Barnes 1823); Texas lilliput, T. texasensis (Lea 1857); and western lilliput, T. mearnsi (Simpson 1900).In the past, both texasensis and mearnsi have been given as subspecies of T. parvusT. texasensis and T. mearnsi has led some to question the validity of the latter and Howells et al. (1996) did not distinguish between them. During statewide surveys of freshwater mussel populations by Texas Parks and Wildlife Department's Heart of the Hills Research Station 1992-1995, tissue samples from all three lilliputs were obtained for subsequent electrophoretic examination. Horizontal starch gel electrophoresis following the methods, buffers, and enzyme designations of Morizot and Schmidt (1990) was used. Specimens of T. parvus from Falcon Reservoir on the Rio Grande, T. mearnsi from the Nueces-Frio System, and T. texasensis from the Colorado, Brazos, Angelina, and Buffalo Bayou Systems were examined(Table 1). Results indicated T. parvus from the Rio Grande possessed several unique or rarely-shared alleles which designate it as different from T. mearnsi and T. texasensis. However, none of the enzyme-system loci examined produced alleles unique to T. mearnsi; it and T. texasensis were distinguishable electrophoretically. Unfortunately the T. parvusspecimens examined were from the extreme southwestern limit of its range; other populations further to the northeast or from the Mississippi River valley need to be examined. Further, a freezer malfunction resulted in the loss of the original tissue samples and a drought in 1996 confunded ability to obtain additional T. parvus specimens. Although the numbers of specimens and enzyme systems examined has been limited, these preliminary data suggest T. parvus and T. texasensis are clearly distinct, but T. mearnsi has yet to display genetic differences to distinguish it from T. texasensis. If the genetic patterns seen here are maintained at other loci and among other populations, it would be difficult to justify maintaining T. mearnsi as a distinct species.

Literature Cited

Howells, R.G., R.W. Neck, and H.D. Murray. 1996. Freshwater Mussels of Texas. Texas Parks and Wildlife Press, Austin.

Morizot, D.C., and M.E. Schmidt. 1990. Starch gel electrophoresis and histochemical visualization of proteins. Pages 23-80 in D.H. Whitmore. Electrophoretic and isoelectric focusing techniques in fisheries management. CRC Press, Ann Arbor, Michigan.

Strecker, J. 1931. The distribution of the naiades or pearly fresh-water mussels of Texas. Baylor University Museum Bulletin 2, Waco.

Turgeon, D.D., and nine co-authors. 1988. Common and scientific names of aquatic invertebrates from the United States and Canada mollusks. American Fisheries Society Special Publication 16, Bethesda, Maryland.

Table 1. Results of horizontal starch gel electrophoresis used to examine specimens of Toxolasma at Heart of the Hills Research Station 1994-1995. Allele frequencies represent percentage of migration distance based upon the most common allele for T. texasensis.

                                                                        Allele Frequency by Enzyme System

Species Water Body (Drainage Basin)   N  TPI (-) GPI (TEB) GPI (TC) MDH ME IDH HK PGM SOD parvus Falcon Reservoir (Rio Grande)   4  90 95 95 90 - - - - - mearnsi San Miguel Creek (Frio River)   4  100 100 100 100 100 100 100 100 100 mearnsi L. Corpus Christi (Nueces River)   4  100 100 100 100 95 90 100 95 100 100 100 100 texasensis Giddings Lake (Colorado River)   6  100 100 100 100 95 90 100 95 90 100 100 100 100 texasensis L. Nacogdoches (Angelina River)   1  100 100 100 100 100 100 100 100 100 texasensis Flat Bank Creek (Brazos River)   1  100 100 100 100 100 100 100 100 100 texasensis Buffalo Bayou   1  100 100 100 100 100 100 100 100 100

Author: Richard J. Neves
Address: Virginia Cooperative Fish & Wildlife Research Unit
Department of Fisheries and Wildlife
Virginia Tech
Blacksburg, VA 24061-0321
Phone Number: (540) 231-5927
Email: mussel@vt.edu

The Virginia Department of Transportation (VDOT) proposed replacement of the Route 40 bridge over the Nottoway River, Nottoway/Lunenburg counties, Virginia in 1993. Because the Nottoway River is home to the federally endangered dwarf wedgemussel (Alasmidonta heterodon), a mussel survey was requested by the U.S. Fish and Wildlife Service (FWS) in September 1993, from 200 m upstream to 800 m downstream of the existing bridge. This piedmont river is characterized by slow flow, 15-20 m width, and sand substratum at the bridge site. Five dwarf wedgemussels were collected during the survey in 1993; hence, FWS issued a Biological Opinion in July 1994, placing several requirements on VDOT to ensure protection of the endangered dwarf wedgemussel. Two of the requirements included: 1) the removal of all dwarf wedgemussels and other mussel species each year from the construction area (40 m upstream to 40 m downstream), and 2) a resurvey of the 1000 m each year during and after construction to record possible changes in the unionid assemblage resulting from the project. In September, 1994 and 1995, mussel surveys were conducted during bridge replacement, and again in September 1996 following completion of the project. Thus, 4 years of survey data were collected to compare pre- and post-construction impacts as well as impacts to unionids during the bridge replacement.

Results of these surveys documented the presence of 8 unionid species, and compared number of live mussels collected per hour, or catch-per-unit-effort (CPUE), and species richness among years. Overall, the abundance of mussels and species composition did not change appreciably among sampled river reaches (upstream, downstream) and years. CPUE among years was nearly identical (Table 1). The apparent increase in mussel abundance in 1996 was attributed to a more experienced survey crew in the downstream reach (lower 800 m). Presence of the endangered dwarf wedgemussel in various reaches during 1994-1996 indicated that its occurrence at the site had not changed during the project period. The comparability of CPUE among years, continuous presence of dwarf wedgemussels, and limited habitat disturbance in the survey reach indicated that environmental safeguards were effectively maintained on this project. Thus, this study demonstrated that a bridge replacement project can be compatible with unionid conservation, at least in piedmont rivers. I attribute the success of this project to planning and cooperation between VDOT and FWS, adequate environmental safeguards (erosion and silt control structures, etc.), scrutiny by the VDOT project inspector, and adherence to contract requirements by the construction firm. Kudos to VDOT and the construction firm for maintaining the biological integrity of this reach of the Nottoway River.

Table 1. Summary of total number of mussels and sampling effort at the Route 40 bridge crossing, 1993- 1996.

Year Number of Mussels Effort (man-hr) CPUE 1993 724 29.0 25 1994 1273 54.5 23 1995 973 37.7 26 1996 1122 27.9 40

Commercial Musseling: In August 1996, the Tennessee Wildlife Resources Commission (TWRC) voted to remove three species (Cyclonaias tuberculata, Quadrula pustulosa and Quadrula nodulata) from the TWRA list of commercially harvestable mussels. This action was taken after two years of documented incidental harvest of the federally endangered orange-foot pimpleback mussel (Plethobasus cooperianus). Between 1994 and 1995, seven P. cooperianus (five fresh dead, two live) were taken from musselers working the Kentucky Reservoir reach of the Tennessee River in Perry and Hardin counties, TN; or from shell containers at Borden's Shell Co., Crump, Hardin Co., TN. Although this action posed no significant economic burden on the mussel harvesters or buyers, considerable opposition was encountered from some shell companies who feared further restrictions might follow. However, faced with the choice of closing all commercial mussel harvest within the historical range of P. cooperianus or possibly having the three similar species listed as endangered based on their similarity of appearance, the TWRC removed them from the list of commercially harvestable species.

In 1995, Tennessee mussel buyers reported purchasing 3,881 tons of shell form State waters worth an estimated $14.7 million (wholesale). Then, after more than ten years of increasing demand and prices, Tennessee's commercial shell industry experienced a declining market in 1996. Wholesale shell prices began falling in March 1996 and continued to drop through the fourth quarter, some shell prices dropped as much as 76%. In October, some companies stopped buying shells and by mid-January 1997, none were purchasing from local harvesters. Shell company representatives blame diseased oyster beds in Japan, Chinese competition and altered jewelry consumer purchases for the current depressed market for U.S mussel shells. They also expect total U.S. mussel shell exports to be 60 to 70% lower in 1997 than 1996, when approximately 4,500 tons were shipped. The current market condition is expected to extend through 1997 and possibly 1998. Regardless of the cause for the decline, Tennessee's commercial mussel stocks could benefit from reduced harvest pressure. Recent survey data on Kentucky Reservoir indicate that 98% of some commercial mussel populations are under legal size limits (Hubbs and Jones 1995).

Hubbs, D., and A. Jones. 1995. 1995 Statewide commercial mussel report. Tennessee Wildlife Resources Agency, Fish Management, Nashville, Tennessee. Report Number 96-15. 49p.

1. New publication

Watters, G.T. & S.H. O'Dee. 1996. Shedding of untransformed glochidia by fishes parasitized by Lampsilis fasciola Rafinesque, 1820 (Mollusca: Bivalvia: Unionidae): evidence of acquired immunity in the field? Journal of Freshwater Ecology 11: 383-389.

ABSTRACT - Fifteen fish species were exposed to glochidia from the freshwater mussel Lampsilis fasciola. Mussels and fishes were collected in the Big Darby Creek system in Ohio. All fishes began shedding untransformed glochidia within 24 hrs of exposure and continued for approximately eight days. On Day 19, after two weeks of inactivity, rosefin shiner began to shed numerous untransformed glochidia again. This release lasted 24 days. Rainbow darter began shedding untransformed glochidia on Day 25 and continued to do so for 14 days. No transformation occurred on either fish species. We believe this reaction was due to an acquired immunity and may represent the first report of this phenomenon in wild-caught fishes.

2. Surrogate hosts: transformation on exotic and non-piscine hosts

As part of a search for surrogate hosts, funded by the Ohio Chapter of The Nature Conservancy, the following hosts were identified for Lampsilis cardium and Utterbackia imbecillis.

Lampsilis cardium Painted sword Panchax killifish Guppy Lavender gourami Flame gourami Siamese fighting fish Larval tiger salamander       Utterbackia imbecillis Zebra Malawi cichlid Marbled cichlid Peacock cichlid Angelfish Giant danio Goldfish Blue danio Golden barb Brilliant rasbora Red-eye tetra Von Rio tetra Silver tip tetra Glowlight tetra Silver dollar Panchax killifish Painted sword Guppy Lavender gourami Pearl gourami Flame gourami Siamese fighting fish Australian rainbow fish Black loach Pangasius catfish Chinese algae-eater Glass knifefish Northern leopard frog (tadpole) Bullfrog (tadpole) African clawed frog (adult) Larval tiger salamander

3. Prolong^TM and glochidial transformation

Prolong^TM (Argent Chemicals) is a commonly administered product for reducing stress and removing parasites from fishes. We found that at the recommended dosage, the medication did not affect encysted glochidia, or delay or decrease transformation. Largemouth bass, and Lampsilis cardium were the test subjects.

Karen J. Couch
12 Ventura Lane, Olathe, Kansas 66061
(913) 829-3981

Published accounts of the occurrence of Arcidens confragosus in Kansas are as sparse as the species itself. Reference is often made to the 1962 Kansas Unionid book by Murray and Leonard which indicates its presence in the state. In the 35 years since this book was written, shells are still found, demonstrating to us that the Rock Pocketbook is apparently holding its own, even though water quality in Kansas has deteriorated.

In the early 1980's, Charles H. Cope collected several shells while sampling Pottawatomie Creek in Anderson County. Employees of the Kansas Department of Health and Environment have also acquired specimens in the same creek. Brian K. Obermeyer found one large fresh dead shell in the Marais des Cygnes River west of Osawatomie, Miami County, in August, 1994. He also surveyed an area of Big Sugar Creek in Linn County and a portion of the Little Osage River in Bourbon County without locating additional specimens. The author collected three shells of different size classes in the Marais des Cygnes River within the city limits of Ottawa, Franklin County, in March, 1996. This site is above the city's wastewater treatment plant and is the westernmost locality the species has been found (in Kansas) to date. Two of the shells were fre.sh dead; the smallest measured 5.6 cm. It appeared to have succumbed to predation. Drought conditions had been occurring for a period of approxunately eight months, and the extremely low water leveLs were causing other mussel species in the riffles to become stranded.

The latest Marais des Cygnes site, and areas adjacent to it, were revisited in the Fall of 1996. Further specimens of Arcidens were not seen, although Dr. Robert Angelo (KDHE) encountered a living specimen of Acffnonaias ligamentina, which was believed extirpated in the state. Future plans are to again investigate this length of river between a low-head dam and the wastewater treatment plant.

Due to its rarity and its being restricted to a single drainage in the state, Arcidens confragosus is listed as "threatened" by the Kansas Department of Wildlife and Parks; this species is considered "currently stable" in some states. Species diversity in the Marais des Cygnes River was once greater than at present, although the short stretch of river intersecting the city of Ottawa provides a good variety of mussels even now.

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15 May 2001 cam