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First Evidence of Elliptio complanata (Bivalvia: Unionidae) from the Patapsco River, Maryland
William Harbold, Jay V. Kilian, Gerald Mack, Jenny Zimmerman, and Matthew J. Ashton

Northeastern Naturalist, Volume 21, Issue 3 (2014): N35–N40

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N35 2014 Northeastern Naturalist Notes Vol. 21, No. 3 W. Harbold, J.V. Kilian, G. Mack, J. Zimmerman, and M.J. Ashton First Evidence of Elliptio complanata (Bivalvia: Unionidae) from the Patapsco River, Maryland William Harbold1,*, Jay V. Kilian1, Gerald Mack2, Jenny Zimmerman1, and Matthew J. Ashton1 Abstract - In March 2012 and April–May 2013, we collected three dead specimens of Elliptio complanata (Eastern Elliptio) in the tidal, freshwater portion of the Patapsco River, providing the first evidence of this species from the river. Although these specimens do not definitively confirm the presence of an extant population, they indicate that a remnant population may well persist in the tidal, freshwater portion of the river. If it exists, this population could serve as a source for natural recolonization into the non-tidal reaches of the river where the species is believed to have once occurred but is now likely extirpated. Further mussel surveys are needed in the tidal, freshwater portion of the river to confirm the presence of an Eastern Elliptio population, and to determine its size, age structure, and distributional extent. Discovery of specimens. On 16 March 2012, during surveys for anadromous fishes, we observed a single valve of Elliptio complanata (Lightfoot) (Eastern Elliptio) from the Patapsco River approximately 250 m upstream of the Interstate 295 bridge (39°13'44.27''N, 76°38'51.24''W; Fig. 1). The periostracum and nacre of this specimen were heavily eroded. We could not make an accurate measurement because a portion of the valve was broken off; however, we estimate the specimen to be approximately 110 mm long and 60 mm tall, based on examination of other fully intact specimens of approximately the same size. During additional surveys for anadromous species the following year, we observed two additional Eastern Elliptio shells. We collected the first (75 mm length and 35 mm height) on 3 April 2013 from a sand/gravel bar approximately 150 m downstream of the Interstate 195 bridge (39°12'57.03''N 76°41'47.23''W) and a second (116 mm length and 63 mm height) on 6 May 2013 from a sand bar approximately 150 m upstream of the Maryland 295 bridge (39°13'45.63''N 77°20’45.38''W) (Fig.1). The first specimen was complete and relatively fresh with both valves still attached by the hinge ligament. The second was even fresher and contained decomposing soft tissue. We found all three specimens in a portion of the Patapsco River that is considered tidal freshwater, downstream of the head-of-tide near Elkridge, MD (Fig. 1), and upstream of brackish conditions near the river’s confluence with Chesapeake Bay. Significance of the discovery. Eastern Elliptio is a globally common freshwater mussel distributed throughout Atlantic and Great Lakes drainages in a variety of aquatic habitats (Matteson 1948, Williams et al. 1993). It is the most common freshwater mussel in Maryland and, prior to our discovery, was known from all major Chesapeake Bay tributaries in Maryland, with the exception of the Patapsco River (Fig. 2B). Our discovery of three Eastern Elliptio specimens represents the first documented evidence of this species from the Patapsco River. We obtained data from online databases or collection managers of the following: Academy of Natural Sciences (ANSP), Philadelphia, PA; American Museum of Natural History (AMNH), New York, NY; Canadian Museum of Nature (CMNML), 1Maryland Department of Natural Resources, Monitoring and Non-Tidal Assessment Division, 580 Taylor Avenue, C-2, Annapolis, MD 21401. 2 Montgomery County Department of Environmental Protection, Watershed Management Division, 255 Rockville Pike, Suite 120, Rockville, MD 20850. *Corresponding author - william.harbold@maryland.gov. Manuscript Editor:Robert Hershler Notes of the Northeastern Naturalist, Issue 21/3, 2014 2014 Northeastern Naturalist Notes Vol. 21, No. 3 N36 W. Harbold, J.V. Kilian, G. Mack, J. Zimmerman, and M.J. Ashton Ottawa, ON, Canada; Carnegie Museum of Natural History (CM), Pittsburgh, PA; Delaware Museum of Natural History (DMNH), Wilmington, DE; Florida Museum of Natural History (FLMNH), Gainesville, FL; Illinois Natural History Survey (INHS), Champaign, IL; Museum of Comparative Zoology (MCZ), Boston, MA; North Carolina Museum of Natural Science (NCSM), Raleigh, NC; Ohio State University Museum (OSUM), Columbus, OH; University of Michigan Museum of Zoology (UMMZ), Ann Arbor, MI; United States Natural History Museum (NMNH), Washington, DC; and Virginia Museum of Natural History Figure 1. Locations within the Patapsco River watershed where Eastern Elliptio specimens were collected (closed circles) in reference to local landmarks. N37 2014 Northeastern Naturalist Notes Vol. 21, No. 3 W. Harbold, J.V. Kilian, G. Mack, J. Zimmerman, and M.J. Ashton (VMNH), Martinsville, VA. We found no current or historical records of Eastern Elliptio from the Patapsco River, even though Maryland has been widely surveyed by malacologists since the mid-19th century (Bogan and Proch 1997). Figure 2. A) Sites in the Patapsco River watershed that have been surveyed for mussels since 1990 where no Eastern Elliptio were detected (open squares). B) Distribution of historic (pre-1990) and contemporary (1990–2012) records of Eastern Elliptio (crosshatched area) in Maryland watersheds draining to the Chesapeake Bay (MDNR Maryland Biological Stream Survey and J. McCann, MDNR Natural Heritage Program, unpubl. data). 2014 Northeastern Naturalist Notes Vol. 21, No. 3 N38 W. Harbold, J.V. Kilian, G. Mack, J. Zimmerman, and M.J. Ashton The Patapsco River is a large 5th-order tributary (Strahler 1957) located on the western shore of Chesapeake Bay near Baltimore City (Fig. 2A). Its 953-km2 watershed drains predominately agricultural and urban land in Baltimore, Carroll, Howard, and Anne Arundel counties and Baltimore City. Approximately 66 river kilometers (rkm) of the Patapsco River mainstem are non-tidal; the remaining 12 rkm are tidally influenced. Prior to our discovery, four species of freshwater mussels were known from the Patapsco River watershed. Anodonta implicata (Say) (Alewife Floater), Pyganodon cataracta (Say) (Eastern Floater), and Utterbackia imbecillis (Say) (Paper Pondshell) are known from reservoirs in the headwaters of the Patapsco River basin (J. McCann, Maryland Department of Natural Resources,Annapolis, MD, unpubl. data). Although these species are native to Maryland, they have not been recorded in the basin outside of the reservoirs. Their presence in these lentic habitats is likely the result of the stocking of game and bait fishes infected with their parasitic glochidia (e.g., Long 1983). The fourth species, Alasmidonta undulata (Say) (Triangle Floater), is currently known from approximately 11.2 rkm of the lotic, non-tidal portion of the Patapsco River (Harbold 2010). The fresh condition of the two dead specimens we found in 2013 suggests that a population of Eastern Elliptio persists in the tidal, freshwater Patapsco River. However, the scarcity of specimens from the area suggests that, if extant, this species is present in very low abundance. Although an Eastern Elliptio population in the non-tidal, freshwater portion of the Patapsco River has yet to be confirmed, the presence of robust populations in non-tidal portions of nearby rivers (Fig. 2B), historic records, and archaeological specimens (Johnson 1991) suggest that the species was likely historically present within the non-tidal Patapsco River as well. In recent years, there have been extensive mussel surveys (Harbold 2010) and numerous stream assessments (Harbold et al. 2013) throughout the non-tidal portion of the Patapsco River. Many of the sites sampled as part of these efforts have been annually surveyed since 2009. To date, these surveys have yielded no evidence of Eastern Elliptio (Fig. 2A). The methods used in these mussel surveys (e.g., Strayer and Smith 2003) routinely detected live Triangle Floater even at low abundance, and we frequently encountered valves of this species at biological monitoring sites where we sampled. Presumably, these methods would detect Eastern Elliptio if it were still present in the non-tidal portion of the Patapsco River. Although Eastern Elliptio remains the most common mussel in Maryland, its distribution has been reduced in numerous Chesapeake Bay tributaries, and many populations show little evidence of recruitment (e.g., Strayer and Fetterman 1999). This phenomenon appears to be related to disruption of mussel reproduction caused by the upstream exclusion of Anguilla rostrata (Lesueur) (American Eel) by river dams in the region; American Eels are the primary host fish of Eastern Elliptio in the Mid-Atlantic (Lellis et al. 2013, Wiley et al. 2004). The Patapsco River also has a long history of agricultural and industrial pollution (MDE 2005, 2009a, 2009b) and has been called one of the most dammed rivers in the US (Travers 1990). It is likely that the apparent extirpation of Eastern Elliptio from the non-tidal portion of the river resulted from the combined effects of degraded water quality, altered habitat, and disrupted mussel reproduction that has occurred over the past two hundred years. Conclusions/recommendations. The tidal portion of the Patapsco River—located downstream of historical dams and, thus, in an area historically accessible to American Eel—may have been the only refuge where Eastern Elliptio could persist while populations in the non-tidal reaches declined and were extirpated. Due to low conservation priority, poor water quality, and difficult access, the tidal, freshwater portion of the river has received little N39 2014 Northeastern Naturalist Notes Vol. 21, No. 3 W. Harbold, J.V. Kilian, G. Mack, J. Zimmerman, and M.J. Ashton attention in comparison to recent survey efforts focused in non-tidal reaches. Further mussel surveys are needed in the tidal, freshwater portion of the river to confirm the presence of an extant Eastern Elliptio population and determine the size, age structure, and distributional extent of the population if one can be detected. Our recent discovery is encouraging and suggests that a portion of the river may harbor a population that could serve as a potential source for the recolonization of Eastern Elliptio into upstream, non-tidal reaches. American Eel passage in the Patapsco River has seemingly improved with the addition of fish ladders, the removal or destruction of most historic dams (Travers 1990), and the recent removal of Union and Simkins Dams (Harbold et al. 2013). Plans are underway to remove Bloede Dam (the most downstream dam remaining in the river) and to build an eel ladder on Daniels Dam (J.Thompson, MD Department of Natural Resources Fisheries Service, Annapolis, MD, 2013 pers. comm.), the only other remaining instream blockage (Fig. 2 A). Additionally, water quality has improved in the Patapsco River since the implementation of the Clean Water Act of 1972 (Friedman 2009) and is now within the range Eastern Elliptio appears to tolerate (Ashton 2010, Harbold et al. 2013). An extant tidal, freshwater Eastern Elliptio population may facilitate the natural recolonization of this species into non-tidal reaches as American Eel passage is restored throughout the basin, although recolonization potential will ultimately be influenced by multiple factors, such as host dispersal and mussel-population size (Downing et al. 1993, Schwalb et al. 201 1). Acknowledgments. We would like to thank Arthur Bogan of the North Carolina Museum of Natural Sciences for verifying the identification of the Eastern Elliptio specimens. These specimens are currently stored at the Maryland Department of Natural Resources, Annapolis, MD. We would also like to thank Scott Stranko and Ron Klauda for their editorial advice and guidance in improving this manuscript. Literature Cited Ashton, M.J. 2010. Freshwater mussel records collected by the Maryland Department of Natural Resources’ (MDNR) Monitoring and Non-Tidal Assessment Division: Investigating environmental conditions and host fishes of select species. MDNR, Annapolis, MD. RAS-MANTA-AIM-10-01. 63 pp. Bogan A.E., and T. Proch. 1997. Manual of the freshwater bivalves of Maryland. Chesapeake Bay and Watershed Programs, Monitoring and Non-Tidal Assessment Division, MDNR, Annapolis, MD. CBWP-MANTA-EAP-96-3. 68 pp. Downing, J.A., Y. Rochon, M. Pérusse, and H. Harvey. 1993. Spatial aggregation, body size, and reproductive success in the freshwater mussel Elliptio complanata. Journal of the North American Benthological Society 12:148–156. Friedman, E.S. 2009. Benthic macroinvertebrate communities at Maryland’s CORE/TREND monitoring stations: Water quality status and trends. Monitoring and Non-tidal Assessment Division (MNAD), MDNR, Annapolis, MD. CBWP-MANTA-MN-09-01. 31 pp. Harbold, W. 2010. Patapsco River Dam Removal Study: Assessing changes in American eel distribution and aquatic communities. MDNR, MNAD, Annapolis, MD. 65 pp. Harbold, W., S. Stranko, J. Kilian, M. Ashton, and P. Graves. 2013. Patapsco River Dam Removal Study: Assessing changes in American Eel distribution and aquatic communities. MDNR, MNAD, Annapolis, MD. 115 pp. Johnson, M.F. 1991. Middle and Late Woodland settlement systems in the Interor Fall Zone of the Potomac Valley: Not a live oyster in site. North American Archaeologist 12(1):29–60. Lellis, W.A., B.S.J. White, J.C. Cole, C.S. Johnson, J.L. Devers, E.V.S. Gray, and H.S. Galbraith. 2013. Newly documented host fishes for the Eastern Elliptio Mussel ( Elliptio complanata). Journal of Fish and Wildlife Management 4(1):75–85. Long, G.A. 1983. The Unionids (Bivalvia) of Loch Raven Reservoir, Maryland. The Nautilus 97(3):114–116. 2014 Northeastern Naturalist Notes Vol. 21, No. 3 N40 W. Harbold, J.V. Kilian, G. Mack, J. Zimmerman, and M.J. 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Dispersal limitation of unionid mussels and implications for their conservation. Freshwater Bio logy 56:1509–1518. Strahler, A.N. 1957. Quantitative analysis of watershed geomorphology. Transactions of the American Geophysical Union 38:913–920. Strayer, D.L., and A.R. Fetterman. 1999. Changes in the distribution of freshwater mussels (Unionidae) in the Upper Susquehanna River basin, 1955–1965 to 1996–1997. American Midland Naturalist 142:328–339. Strayer, D.L., and D.R. Smith. 1999. A guide to sampling freshwater mussel populations. American Fisheries Society, Monograph 8, Bethesda, MD. 103 pp. Travers, P.J. 1990. The Patapsco: Baltimore’s River of History. Tidewater Publishers, Centreville, MD. 220 pp. Wiley, D.J., R.P. Morgan, R.H. Hilderbrand, R.L. Raesly, and D.L. Shumway. 2004. Relations between physical habitat and American Eel abundance in five river basins in Maryland. Transactions of the American Fisheries Society. 133:515–526. Williams, J.D., M.L. Warren, K.S. Cummings, J.L. Harris, and R.J. Neves. 1993. Conservation status of freshwater mussels of the United States and Canada. Fisherie s 18(9):6–22.