USGS science for a changing world

WHAT MAKES A HEALTHY ENVIRONMENT FOR NATIVE FRESHWATER MUSSELS?

What are freshwater mussels, and what makes them special?

Freshwater mussels are mollusks-close relatives of clams, oysters, and saltwater mussels. Many species of freshwater mussels can live for 20 to 30 years, and individuals of some species live for more than 100 years. Freshwater mussels have been valued by humans throughout history. They can produce pearls, and their shells can be used to make buttons for clothing or to serve as seedstock for Figure 1 . Life cycle of freshwater mussels. After fertilization of eggs (lower right corner), glochidia, or larvae, are released. Those glochidia that successfully attach to fish hosts transform into the cultured pearl industry. In past times, juvenile mussels, which detach and burrow into the streambed. (Diagram by G.T. Walters, Ohio freshwater mussels also were food for State University.) Native Americans. Attempts are being made to restore the stream bottom and along the edge of Freshwater mussels are sensitive to native-mussel populations in areas where water, especially if predators such as contamination of sediment that they reintroduction has a chance for success. muskrats, otters, and raccoons are feeding inhabit and to the water that they filter, The success of these attempts, however, in the area. making the presence of live, adult mus­ will depend on whether physical habitat sels an excellent indicator of ecosystem and other environmental factors are favor­ health and stability. Freshwater mussels able for the mussels to survive and repro­ What is the life cycle of are relatively immobile, imbedded in the duce. As yet, researchers and biological- freshwater mussels? streambed with part of their shell sticking resource managers know little about up into the water so that they can filter which environmental factors have the The life cycle of North American fresh­ water to obtain oxygen and food. This most significant effects on mussel com­ water mussels is unusual among aquatic lack of mobility makes them particularly munities or how various environmental animals because it usually requires fish as vulnerable to water and sediment contam­ factors interact to support or harm intermediate hosts for mussel larvae ination, changes in sedimentation, or pro­ mussels at various stages of life. (fig. 1). Freshwater mussels are conceived longed drought. Thus, ecosystem health when male mussels release sperm into the water and the eggs of nearby females are and stability are critical for their fertilized. The fertilized eggs of the reproduction and survival. Where are freshwater mussels found? female develop into larvae (glochidia), which are released into the water in ways Freshwater mussels are among the Although freshwater mussels are found that have evolved to attract host fish most endangered groups of animals in throughout much of the world, the highest (fig. 2). If a larva attaches to a fish, it will North America. Human influences such freshwater-mussel diversity on Earth is in ingest cell fluid of the fish for nutrition; as agricultural practices, construction of North America (Stansbery, 1970). For after a period of several hours to several dams, and urban sprawl have altered example, a single stream Big Darby weeks (depending on water temperature river flows, water quality, fish popula­ Creek, in central Ohio historically and species), the larva will transform to a tions, and other environmental factors contained 42 species of unionid mussels, juvenile, drop off the fish, and burrow that are essential for the survival of fresh­ more species than in all of Australia and into streambed sediment with its foot (fig. water mussels. These influences have Europe combined. Live freshwater mus­ 1). The proportion of released larvae that contributed to the continuing decline of sels are not often seen because they are actually attach to host fish and survive to freshwater mussels throughout the United partly buried in the sediments of creeks, inhabit the streambed is minute, estimated States (National Native Mussel rivers, and lakes. The empty shells of at anywhere from 1 in a million to 1 in Conservation Committee, 1998). dead mussels, however, can be found on 100 million (Waiters, 1995)

U.S. Geological Survey USGS Fact Sheet 124-00 U.S. Department of the Interior October 2000 charge helps to moderate seasonal changes in streamflow and water temper­ ature, dilute contaminants in surface- water runoff, and help mussels survive drought. Base flow can be determined by analyzing long-term streamflow records, if available, and/or by making special streamflow measurements during a dry- weather period.

Water and sediment quality. Because adult mussels are filter feeders, they are Figure 2. Female mussel displaying mantle to attract a fish host. Predator fish lured by the sensitive to waterborne contaminants prey-like appearance of the mantle come close to where glochidia are released, and some such as those carried in agricultural runoff glochidia may successfully attach. (Photo by G.T. Walters, Ohio State University.) and in municipal and industrial wastewa- ter. Juvenile mussels, on the other hand, What factors influence For example, the U.S. Geological may be particularly sensitive to the chem­ success during life stages Survey (USGS)-in cooperation with the istry of the sediments in which they live of freshwater mussels? U.S. Environmental Protection Agency, and feed. Thus, possible influences on Ohio Environmental Protection Agency mussel communities include not only the Each life stage for freshwater mussels has (Ohio EPA), Indiana Department of chemical quality of streamwater but also specific environmental requirements: Natural Resources (IDNR), Alien County the chemical quality of streambed sedi­ (Indiana) Soil and Water Conservation ments, which are particularly prone to Adults Adequate water quantity and District (SWCD), The Nature Conser­ storing trace metals and organic chemical quality, a stable stream channel, ade­ vancy, Ohio Department of Natural compounds. Water and sediment quality quate sediment quality, food, protec­ Resources (ODNR), and The Ohio State can be evaluated from a combination of tion from predators, and sufficient University did a study of this kind in the onsite measurements of water quality and population densities for fertilization. St. Joseph River Watershed in Indiana, collection of water and sediment samples Michigan, and Ohio. (See inset box for laboratory analyses. Larvae (Glochidia) Availability offish describing this study.) The purpose of this host upon which to attach, for study was to gather information on mus­ Stream-channel stability. A stable nourishment and dispersal. sel-population viability and suitability of stream channel is favorable for freshwater Juveniles Same as adults; however, stream sites for mussels, information that mussels because it provides a secure dwelling area and promotes water clarity. because a juvenile gathers food par­ could potentially help in efforts to restore In unstable channels, movement of stre­ ticles by extending its foot into the native-mussel populations in this water­ ambed sediment due to high flows often streambed, it is more sensitive to shed and perhaps elsewhere in the United leaves mussels either buried too deeply in sediment contamination than the States. Thirty-six species of freshwater adults that feed by filtering the mussels had previously been found in the sediment or stranded on sand or gravel bars, exposing the mussels to air and surrounding water. St. Joseph River Watershed, 30 of them occurring in Fish Creek, including the predators when streamflows are low. One approach toward clarifying the Federally endangered white catspaw Moreover, unstable channels are prone to relations between environmental factors (fig. 3), clubshell, and northern riffleshell producing excessive suspended sediment and healthy native-mussel communities is (Walters, 1988, 1995, 1998). A composite that can clog the mussels' gills (Strayer, to locate a particular stream where native- view of a site on Fish Creek is shown in mussel populations are known to exist, figure 4. then The following paragraphs list some compile an inventory of native fresh­ of the environmental factors that can be water-mussel species that have been studied; results from work in the St. found previously, Joseph Watershed are given in the inset section. follow with an evaluation of current populations, and Water quantity. For a particular stream collect data on possible positive and site or reach to be suitable habitat for negative factors contributing to the mussels, the stream bottom must not go Figure 3. Specimens of white catspaw mussel, Epio- survival of native freshwater dry. Thus, an adequate amount of base flow-that part of streamflow that is sus­ blasma obliquata perobliqua (Conrad, 1836). This mussels, using conventional water- very rare mussel species is on the Federal endan­ and sediment-quality analyses and tained by ground-water discharge to the gered species list. (Photo by G. T. Walters, Ohio ecological-assessment tools. stream-is crucial. Ground-water dis­ State University.) Figure 4. Composite view of surface and subsurface characteristics, Fish Creek near Alvarado, Ind. (site 8 on fig. 5). Environmental factors favorable for native freshwater mussels include a forested buffer along the streambanks and a gravel streambed with a moderate cover of silt.

1999a). Stream channels can be example, is native to Europe and Asia. In effects of wastewater discharges described by means of stream-habitat North America, it attaches and grows (contributing to the elevated assessment procedures, such as the Qual­ over the freshwater mussels, competing concentrations of phosphorus, algal itative Habitat Evaluation Index (QHEI) for food and oxygen. The presence of chlorophyll a, and bacteria), developed by Ohio EPA (Rankin, 1989). exotic mussel species can be identified by examination of the streambed and stream- the possibility of future habitat Fish. Although fish can be a banks. degradation, and negative influence on mussel communi­ ties because of predation (see next the presence of sufficient numbers of healthy adult mussels for successful paragraph), host species offish must be How can information on reproduction. present for most mussels to be able to these environmental factors reproduce and disperse. Known or The factors and tools listed in this suspected fish hosts can be inventoried at help in protecting and restor­ fact sheet would be a logical starting a site by way of electrofishing surveys or ing mussel populations? point for studies elsewhere. Additional other means of fish-population factors and tools could be added to this assessment. If potential positive and negative environmental factors of a current or approach as knowledge of native freshwa­ ter-mussel species increases (specifically, Predation. Humans have caused a potential mussel habitat can be identified what exactly serves as food sources, and dramatic decline in mussel populations by by means of scientific study, then how tolerant are mussels of contaminants harvesting them for natural pearls, but­ biological-resource managers can begin in water and sediments). Also beneficial tons, and seed stock for the cultured pearl to evaluate management strategies for would be collection of sediment-quality industry. Other predators include musk- trying to preserve or restore native-mussel data and microbiological data at each site rats, raccoons, some duck species, and populations. where other environmental factors are some fish species. Predation can be measured. assessed only indirectly, by examining In the St. Joseph River Watershed, records of poaching (humans) or looking for example, study results indicate that Protecting and restoring native- for piles of empty shells on the stream- the strong environmental qualities of the mussel populations is difficult if knowl­ bank, especially in the spaces between watershed (adequate dry-weather stream- edge of their environmental requirements roots of large trees (animals). flow, stable stream channels, and presence of host fish) should be incorpo­ is lacking. Studies like the one done in the St. Joseph Watershed begin to build an Exotic species. Species that invade rated in a preservation/restoration design information base that can be used to pre­ from outside their original ranges have to minimize or reduce environmental- serve a healthy native-mussel population strongly affected the distribution and quality concerns. Specific environmental- or to restore a community in a place abundance of native freshwater mussels quality concerns for preservation and where native mussels have disappeared. and their native mollusk relatives in North restoration include America (National Native Mussel uncertainty about survival rates of Conservation Committee, 1998). The young mussels in contaminated zebra mussel (Dreissenapolymorpha), for sediments,

Julie A. Hambrook and Michael Eberle St. Joseph Watershed study

Three tributaries in the St. Joseph River Watershed were chosen to characterize mussel habitat because this watershed serves as a refuge for mussel biodiversity in the Great Lakes region (Nature Conser­ vancy, 1994). Twelve locations were stud­ ied, four on each of the three tributary streams that flow into the St. Joseph River Cedar Creek, Fish Creek, and the West Branch of the St. Joseph River (fig. 5). The rich diversity of mussels (30 spe­ cies) in such a small watershed as Fish Creek (109 square miles) has received considerable attention from those inter­ ested in preserving biological diversity in the region (Nature Conservancy, 1994). EXPLANATION Cedar Creek, a State Scenic River in Indi­ Subwatersheds ana, once had a much greater diversity of Gaging Stations mussels (27 species) than it does today Study-Site Locations (1-12) (table 1). The West Branch headwater stream was included because of its simi­ larity in size to the Fish Creek Watershed, the number of live mussel species found

(20), and the fact that it has undergone 10 KILOMETERS little urban or industrial development

Number of mussels found. The Figure 5. Location of St. Joseph Watershed and s'tudy sites. (Site names and data in table 1.) number of native-mussel species found Although Cedar Creek and Fish mussels tended to be lowest (table 1). either alive or freshly dead ranged from Creek had nearly identical flow rates, Phytoplankton chlorophyll a, a measure zero (at two sites on Cedar Creek) to 16 numbers of mussel species differed of the concentration of algae in streamwa- (site 6, on Fish Creek). As an indicator of greatly. ter, also was highest at Cedar Creek sites mussel-diversity decline, the number of In contrast, West Branch and Fish (table 1), likely in response to the high mussels found at each of the 12 study Creek had considerably different flow nutrient concentrations. In addition, con­ sites was compared to records of native- rates, but numbers of mussel species were centrations of Escherichia coli (E. coif) mussel species recorded at that site during similar (table I). These findings indicate bacteria tended to be substantially higher comprehensive surveys of mussels in the that base flows throughout the watershed in Cedar Creek than in the other two trib­ 1980's and 1990's (Hoggarth, 1987; were probably adequate to sustain mussel utaries (data from the Alien County Waiters, 1988, 1996, 1998; table 1). populations and that other factors were SWCD, 1998; not shown). The relatively Base flow. For the St. Joseph responsible for the varying numbers of high nutrient, chlorophyll a, and E. coli Watershed study, a preliminary analysis mussel species found. concentrations raise a concern about ani­ of the long-term records of streamflows at Water and sediment quality. Con­ mal waste, sewage, and other associated gaging stations on Cedar and Fish Creeks centrations of common ions, nutrients wastes-such as laundry detergents and (fig. 5) indicated that more than half of (nitrogen and phosphorus compounds), pharmaceuticals-that make their way to the annual streamflow came from ground and pesticides were determined at base these streams, particularly Cedar Creek. water (57 and 67 percent of annual flow, flow to compare differences in water Overall, the pattern in the data indicates respectively). Because no previous quality among sites (Shindel and others, that sewage and (or) animal waste may be streamflow information was available for 1999). In addition, data on trace metals influencing Cedar Creek more than the West Branch, a low-flow (base-flow) and organic-chemical compounds in the other two streams and may be a major study was done during a summer dry- streambed sediments were examined for factor affecting mussel-community health weather period to compare the amount of two sites in the watershed, one each on in the St. Joseph River Watershed. streamflow in the three tributaries. Cedar and Fish Creeks. Because juvenile freshwater mus­ West Branch on average had three Concentrations of common ions sels live in and get their food from aquatic times the amount of ground water drain­ were similar among the 12 sites (Shindel sediments, they are particularly vulnera­ ing into the channel per unit area of sub- and others, 1999); however, nutrient con­ ble to contaminants in sediment. For that watershed-about 0.46 cubic foot per -5 fy centrations in particular, phosphorus reason, data collected on streambed sedi­ second per square mile (ft /s/mi )-than were highest at the Cedar Creek sites, ments from one site each on Cedar and Fish or Cedar Creek (about 0.15 ft3/s/ Fish Creeks were examined for 29 con- .mi2). where the numbers of live or freshly dead higher means excellent habitat. In the I Table 1. Selected mussel and environmental data collected in the St. Joseph River Watershed lower part of Fish Creek, site 5 scored [Sites listed for each tributary are in order from downstream to upstream; , no data] 59.5 because of fine-clay sediment deposition. In the upper part of Cedar T * . .. Plankton Creek, sites 3 and 4 had little riparian Map number and site Mussel Total phos- . . BasefloW3 ,__ c chloro- QHEIe vegetation and considerable bank erosion, location species" phorusc . .. d phyll a reducing habitat scores to 49.5 and 45, Cedar Creek respectively. The lack of correlation between the 1 Near Cedarville 4 of 26 0.187 0.119 9.4 72 number of mussel species and QHEI 2 Near Robinson Chapel Oof 14 ,202 .105 6.9 83 scores suggests that a minimally suitable and stable channel may be necessary for 3 Near Auburn Oof 11 .095 .211 4.2 49.5 freshwater-mussel survival but that good 4 Near Waterloo 6 of 11 .087 .062 43.7 45 or excellent channel conditions are no guarantee of mussel-community health. Fish Creek

5 At Edgerton 8 of 12 .185 .062 3.4 59.5 Fish. Fish surveys during 1997 and 1998 (by Ohio EPA, IDNR, and USGS) 6 Near Edgerton 16 of 22 .174 .072 2.1 76 determined the availability of potential 7 Near Edon 10 of 15 .117 .064 2.1 68.5 host fish living in the three St. Joseph 8 NearAlvarado 6 of 11 .097 .051 1.7 73.5 River tributaries. Each tributary had 20 or more host fish species. Some fish species West Branch known to serve as hosts to the greatest 9 Near Pioneer 5 of 7 .580 ... number of mussels (8-10 mussel species) in this study were bluegill, white crappie, 10 Near Nettle Lake 15 of 17 .464 .068 3.9 75.5 largemouth bass, green sunfish, and 1 1 Near Austin 6 of 12 .395 .083 3.2 76 yellow perch. Because of this diversity, host-fish availability does not appear to 1 2 At Austin 5 of 10 .415 .030 1.9 72.5 be a limiting factor at least for common a. Number of examples of live or freshly dead native-mussel species compared with total num­ native freshwater mussels in the St. ber of native-mussel species recorded during comprehensive surveys in the 1980's. Source: Walters Joseph Watershed whose fish-host (1988, 1998), plus data from this study. requirements are known. b. Cubic feet per second per square mile of area contributing flow to each site. Source: Data col­ lected for this study during a period of low flow, August 18-19, 1998. L c. Concentrations in milligrams per liter. Source: Shindel and others (1999). I Predation. The decline in mussels d. Concentrations, in micrograms per liter, of chlorophyll a in phytoplankton in the water col­ in Cedar Creek (table 1) does not appear umn (free-floating algae). Source: Linda Roberts, U.S. Geological Survey, Iowa City, Iowa; extraction to be due to widespread poaching or ani­ in September 1998, analysis in November 1998. mal predation. Legislation in Indiana, e. Composite scores from the Qualitative Habitat Evaluation Index (as described in Rankin, 1989). Scale is 1 to 100. Source: Data collected for this study, August 18-19, 1998. Michigan, and Ohio make it illegal to col­ lect any species of freshwater mussels taminants (trace elements and organic Although the TEL guidelines do not apply either alive or dead even with a fishing chemicals) known or suspected to specifically to mussels, the high propor­ license. Ohio has now closed its water­ be detrimental to organisms dwelling on tion of contaminants exceeding effect- ways to all commercial musseling, and stream bottoms (U.S. Geological Survey, level guidelines raises concern, particu­ collecting for scientific purposes is 1997). larly with regard to long-term exposure to allowed only under special permit Almost one-half of the 29 contami­ multiple contaminants on juvenile fresh­ through the Ohio Department of Natural nants in sediments in Cedar and Fish water mussels. Resources. I Creeks were present at concentrations Stream-channel stability. The exceeding the Threshold Effect Levels QHEI developed by Ohio EPA (Rankin, Exotic species. Although zebra (TEL), guidelines based on toxicity tests 1989) was used to measure substrate sta­ mussels are documented in the St. Joseph with selected streambed-dwelling organ­ bility, channel morphology, and to evalu­ River Watershed, they are not yet consid­ isms (Ingersoll and others, 1996; Smith ate the overall quality of habitat structure. ered to be a problem. They could eventu­ and others, 1996; U.S. Geological Survey, All locations in the study area ally become a problem in the watershed 1997). The high concentrations of some except three sites (3, 4, and 5, fig. 3; and because control of exotic aquatic species of these contaminants could be due to past table 1) had QHEI scores above 60 (on a in North America has been difficult, and, industrial and municipal discharges in this scale of 1 to 100), where less than 45 attempts at control have largely been area (Ohio Department of Health and means poor habitat, 45-60 means gener­ ineffective (Strayer, 1999b). others, 1953). ally good, 60-75 means good, and 75 and Selected references Ohio Department of Health; Indiana I999b, Effects of alien species on Stream Pollution Control Board; and freshwater mollusks in North Amer­ Havlik, M.E., and Marking, L.L., 1987, U.S. Department of Health, Educa­ ica: Journal of North American Effects of contaminants on naiad tion, and Welfare, Public Health Ser­ Benthological Society, v. 18, no. 1, mollusks (Unionidae) A review: vice, 1953, Report of water pollution p. 74-98. U.S. Fish Wildlife Service Resource study of Maumee River Basin 1950- Publication 164, 20 p. 1951: Ohio-Tennessee Drainage U.S. Geological Survey, 1997, Analyses Basins Office, 90 p. of samples collected at water-qual­ Hoggarth, M.A., 1987, The freshwater ity partial-record stations: National mussels (Unionidae) of the upper St. Rankin, E.T., 1989, The Qualitative Habi­ Water-Quality Assessment, Lake Joseph River basin within Ohio: tat Evaluation Index [QHEI] Erie-Lake St. Clair Study Unit, Final report to the Division of Wild­ Rationale, methods, and application: available at URL http://www- life, Ohio Department of Natural Ohio Environmental Protection oh.er.usgs.gov/nawqa/. Resources, 73 p. Agency, Division of Water Quality Monitoring and Assessment, Surface Waiters, G.T., 1988, A survey of the fresh­ Ingersoll, C.G., Haverland, P.S., Brunson, Water Section, 54 p. plus appendix. water mussels of the St. Joseph River E.L., Canfield, T.J., Dwyer, F.J., system, with emphasis on the feder­ Henke, C.E., Kemble, N.E., Mount, Shindel, H.L., Mangus, J.P., and Trimble, ally endangered white cat's paw D.R., and Fox, R.G., 1996, Calcula­ L.E., 1999, Water resources data, pearly mussel: West Lafayette, Ind., tion and evaluation of sediment Ohio, water year 1998: U.S. Geolog­ Indiana Department of Natural effect concentrations for the amphi- ical Survey Water-Data Report OH- Resources, 127 p. pod Hyalella azteca and the midge 98-2, p. 436-449. Chironomus riparius: Journal of 1995, A guide to the freshwater Great Lakes Research, v. 22, no. 3, p. Smith, S.L., MacDonald, D.D., Keenley- mussels of Ohio (revised 3d ed.): 602-623. side, K.A., Ingersoll, C.G., and Field, Ohio Department of Natural L. J., 1996, A preliminary evaluation Resources, Division of Wildlife, 122 National Native Mussel Conservation of sediment quality assessment val­ P- Committee, 1998, National strategy ues for freshwater ecosystems: Jour­ for the conservation of native fresh­ nal of Great Lakes Research, v. 22, 1996, 1996 survey of the mussels water mussels: Journal of Shellfish no. 3, p. 624-638. of the Fish Creek drainage: Final Research, v. 17, no. 5, p. 1419-1428. report to the Indiana Chapter of The Stansbery, D.H., 1970, Eastern freshwater Nature Conservancy [unpaginated]. Nature Conservancy, 1994, The conserva­ mollusks (1) the Mississippi and the tion of biological diversity in the St. Lawrence River systems. Mala- 1998, Freshwater mussel survey Great Lakes ecosystem Issues and cologia, v. 10, no. 1, p. 9-22. of the St. Joseph River drainage, opportunities: Chicago, 111., The exclusive of Fish Creek: Indiana Nature Conservancy Great Lakes Strayer, D.L., I999a, Use of flow refuges Chapter of The Nature Conservancy, Program, 118 p. by unionid mussels in rivers: Journal appendixes A-D. of North American Benthological Society, v. 18, no. 4, p. 468-476.

Additional Information Selected Web sites on freshwater mussels

For additional information about the Illinois Natural History Survey Mollusk Collection USGS and its programs, contact http://www.inhs.uiuc.edu/cbd/collections/mollusk.html U.S. Geological Survey District Chief America's Mussels: Silent Sentinels 6480 Doubletree Ave. http://www.fws.gov/r3pao/eco_serv/endangrd/clams/mussels.html Columbus, OH 43229-1111 Email: [email protected] American Freshwater Mussels (by Tom Watters) http://erato.acnatsci.org/conchnet/uniowhat.html Phone: (614) 430-7700 Fax: (614) 430-7777