The Naiades (Bivalvia: Unionoidea) of the Delmarva Peninsula Clement L. Counts, III1, Thomas S. Handwerker2 and Roman V. Jesien3 Coastal Ecology Research Laboratory, Department of Natural Sciences, University of Maryland Eastern Shore, Princess Anne, Maryland 21853, U. S. A. 2Small Farms Institute, Department of Agriculture, University of Maryland Eastern Shore, Princess Anne, Maryland 21853, U. S. A. 3Center for Estuarine and Environmental Studies, University of Maryland System, Cambridge, Maryland 21613, U. S. A. Abstract. Asurvey comprising307 stationsofthe freshwatersofthe DelmarvaPeninsulaofDelaware, Maryland, andVirginiawasconducted todeter- mine the species diversity and zoogeographic distribution ofunionid bivalves. The unionid fauna included Elliptic)fisheriana (Lea, 1838), E. complanata (Lightfoot, 1786), Lampsilis radiata (Gmelin, 1791), Leptodea ochracea (Say, 1817), Anodonta cataracta Say, 1817, A. implicate! Say, 1829, Ligumia nasuta (Say, 1817), Strophitusundulatus (Say, 1817), Alasmidonta undulata (Say, 1817), andthe rare and endangeredA. heterodon (Lea, 1830). Although a review ofthe literature and a survey ofmuseum collections revealed records forE. dilatata (Rafinesque, 1820), L. cariosa (Say, 1817) andA. varicosa (Lamarck, 1819), these species were not found during the field survey. No populations offreshwater unionids were found south ofthe Maryland/Virginia state line. Comparisons ofcollections in this study with those reported in the literature and in museums indicate a general decline in diversity. The federally listed rareandendangeredA. heterodon isreported fromtheChoptankdrainage inMaryland. Nopopulationsofthezebramussel, Dreissenapolymorpha (Pallas, 1771) were found. Rhoads (1904), inabriefexaminationofthe molluscan shoreofChesapeake Bay. He (Johnson, 1970) made reference fauna of Delaware, remarked that the literature on the to only E. fisheriana (Lea, 1838), which he considered a molluscanfaunaofDelawarewaspractically nonexistent. This junior synonym ofE. lanceolata, as having its type locality was true in 1904 and is still true nearly 80 years later, not attheheadoftheChesterRiverin Kent Co., Maryland. Davis only for Delaware but for the entire Delmarva Peninsula. and Fuller (1981) reported Lampilis radiata (Gmelin, 1791) Rhoads (1904), after collecting at three localities, reported from Sussex Co., Delaware, without more precise locality the presence often unionid species: Lampilis nasutus (Say, data. Davis (1984) reported E. fisheriana and E. dilatata 1817) [= Ligumia nasuta (Say, 1817)], L. radiatus (Gmelin, (Rafinesque, 1819) from Concord Pond, Sussex Co., 1791) [= L. radiata (Gmelin, 1791)], L. cariosus (Say, 1817) Delaware, E. complanata from Deep Creek, Sussex Co., [= L. cariosa (Say, 1817)], L. ochraceus (Say, 1817) [= L. Delaware, and the Sassafras River, Kent Co., and Chester ochracea (Say, 1817)], Unio complanatus CSolander' River, Queen Anne's Co., Maryland. Clarke (1981) noted the Dillwyn, 1817) [= Elliptiocomplanata (Lightfoot, 1786)], U. presenceofAlasmidontaundulataat "ChoptankMills," Kent fisherianus Lea, 1838 [= E. fisheriana (Lea, 1838)], Co., and A. varicosa at the head of Red Clay Creek, New Anodontacataracta Say, 1817, Strophitusedentulus (Say, 1829) Castle Co., Delaware. [= S. undulata (Say, 1817)], S. undulatus, andAlasmidonta These few reports constitute the published informa- marginata varicosa (Lamarck, 1819) [= A. varicosa tion available on the freshwater naiades of the Delmarva (Lamarck, 1819)]. This list remainsthemostcomplete faunal Peninsula. Given this paucity of information, the potential record for the naiades of the entire Delmarva peninsula. threat of exotic species introductions, e.g. Dreissena poly- Since the report ofRhoads, several other works have morpha (Pallas, 1771) (Counts etal. 1991; Handwerker and , mentioned the unionid fauna ofthe peninsula only in pass- Counts, 1991), and the geographic features unique to the ing (Ortmann, 1919; Johnson, 1970; Davis and Fuller, 1981; peninsula, thepresent study was undertaken to provide a re- Davis etal, 1981; Clarke, 1981; Davis, 1984). Ortmann(1919) cent baseline study of species diversity and zoogeographic mentionedElliptiofisheriana from the Chester River system distribution of the freshwater unionids indigenous to the of Maryland. Johnson (1970), in his treatment of the Delmarva Peninsula. The distribution ofthe Asianclam, Cor- freshwater bivalves ofthe Atlantic Slope, documented only biculafluminea (Miiller, 1774) on the Delmarva Peninsula theunionid species inhabitingthe watersdrainingthewestern is discussed in Handwerker et al. (1991). American Malacological Bulletin, Vol. 9(1) (1991):27-37 27 28 AMER. MALAC. BULL. 9(1) (1991) DESCRIPTION OF THE STUDY AREA agricultural region are little more than drainage ditches between cultivated fields, particularly those ofthe Virginia TheDelmarvaPeninsula, asdefinedhere, extendsfrom counties. Cecil Co. Maryland, eastoftheSusquehannaRiver, andNew , CastleCo. Delaware, andincludesall thatlandlyingbetween , METHODS the SusquehannaRiverand Chesapeake Bay onthe westand the Delaware Riverand Bay andAtlantic Ocean on the east, A review of the literature (Rhoads, 1904; Ortmann, south to Cape Charles, Virginia. The peninsula is bisected 1919; Clarke, 1981; DavisandFuller, 1981; Davis, 1984) was on an east-west axis by the brackish waters of the Chesa- conducted in conjunction with a survey of the unionid col- peake-Delaware Canal. Hence, the lowerportionofthepenin- lectionsofthe Academy ofNatural Sciences ofPhiladelphia sula is an island. The study area included the entire state of (ANSP) and Delaware MuseumofNatural History(DMNH) Delaware, the nine EasternShorecountiesofMaryland (from for collections made on the Delmarva Peninsula. This Cecil Co. in the north to Somerset - Worcester counties in museum survey was conducted to verify published records the south) and Virginia (Accomack and Northampton coun- and to record and consolidate any unpublished records ties). Geologically, the Delmarva Peninsula is composed of reflected by these collections. These records were collated deposits ranging from the Late Cretaceous Potomac Group and localities listed were then surveyed for the presence of in the north to the Pleistocene sands ofthe southern halfof species historically reported or collected. the peninsula (Stephenson et al., 1933). A survey ofmajor drainage systems ofthe Delmarva The freshwaters ofthe Delmarva Peninsula drain into Peninsula (Appendix, Fig. 1) was conducted from August the Chesapeake Bay on the west or into the Delaware Bay 1989through August 1990. The survey included 307 stations. or Atlantic Ocean on the east. River systems draining into A descriptionofall stationssurveyedisonfileattheAcademy Chesapeake Bay are generally longer and wide than those of Natural Sciences of Philadelphia. Stations were defined of the eastern portions of the peninsula that drain into the m asthe sectionofthe stream 100 aboveandbelowthepoint Atlantic Ocean, eitherdirectly or viathe Delaware Riverand Bay. Regardlessofthedrainage, the streamsofthe peninsula are tidal and saline for major portions of their length. The transition from brackish to freshwater is usually abrupt and occurs at mill dams. In some cases (e.g. the Sassafras River) thetidal, brackish portionofthe stream is substantially longer than the freshwater. The freshwaterdrainagesofthe Maryland portion of the peninsula have been described by Carpenter (1983). Generally, streams flow at a slow rate (0.25 - 3.74 m3/sec) and havea maximumdischarge rate rangingbetween 30.0 - 212.25 m3/sec and minimum discharge rates ranging between 0-0.37 m3/sec (Carpenter, 1983). All ponds ofthe Delmarva Peninsula were originally impounded to store water for livestock and to power grain millsor, inthecaseofthoseontheupperpeninsula, manufac- turing facilities. While noneofthe millsarenowoperational, the ponds have been preserved and many are maintained as recreational areas. The Delmarva Peninsula is also the northern-most point at which cypress swamps occur on the Atlantic coast. Many of the streams of southern Delaware and Somerset, Wicomico, andWorcestercounties, Maryland (e.g. Nanticoke River, PocomokeRiver, DividingCreek), draintheseswamps and these streams are typical "blackwater" systems. Many ofthe freshwater streams ofthe peninsula are channelizedandcharacterizedby steepbanksthat lackvegeta- tionotherthangrasses. These streams, andtheirheadwaters, serve to drain cultivated fields. Because of the intense agricultural development ofthe peninsula, freshwaters show a high degree of eutrophication south of the Chesapeake- Fig. 1. Station locations at which naiades were collected in the northern Delaware Canal. Most of the stream systems in this halfofthe Delmarva Peninsula (Delaware and Maryland). COUNTS ETAL. DELMARVA NAIADES 29 : at which the stream was entered. Stream surveys included 1984). An additional record was published for the Chester MD tidal andbrackish waterportionsofstreams wherethesecon- River, Queen Annes Co., (Davis, 1984). ditionsoccurred, alongtheChesapeakeBayandthe Delaware Museum Materials Examined. Stations 3, 4, 12 - 14, 17, 18, River estuary. Bivalves were collected by hand and small 21, 22 - 24, 28, 43, 46. Additional specimens: Elk River, dredgeandby screening substrata. Representative specimens Sandy Cove, Cecil Co., MD (DMNH 75226); an unnamed were placed in the collections held at the Coastal Ecology ditch, Petersburg, KentCo., DE, No Date, (DMNH 131124); Research Laboratory at the University ofMaryland Eastern Christmas Creek, Newark, New Castle Co., DE (ANSP Shore (UMES). 366090); Small Creek, Kent Co., DE (ANSP 358279). Collections made at sites reported in the literature or Records from Present Study. Stations 1, 6, 9, 10, 12, 13, whichwere represented inthe ANSPand DMNH werecom- 17 - 19, 21, 22, 25 - 27, 30 - 32, 34, 37, 48, 49, 53, 54, 59, paredtodeterminechanges in speciesdiversity. All localities 61, 63. reportedfromthosesources were surveyedwhenlocalitydata Elliptio complanata can demonstrate local morpho- were sufficient to relocate the original site. logical variability inboth shell shape andcoloration. Further, the specieshasthe widest zoogeographicdistributionofthose unionid bivalves indigenous to the Atlantic Slope, ranging RESULTS from the Apalachicola River drainage of Florida to the St. LawrencedrainageandInteriorBasinofCanada(Burch, 1973; Ten species of unionids were found in the waters of Clarke, 1973). Perhaps it is because ofthis wide variability theDelmarvaPeninsula. Historicrecordswerefoundforthree and zoogeographic distribution that numerous synoyms ex- additional species. Station numbers from the present study ist forthe species [124 inJohnson (1970)]. Softtissue anatomy are given in parentheses for surveys conducted at localities has been described by Ortmann (1911) and Reardon (1929). listed in published works and the museum records. Station Elliptio complanata is reported to breed from April localities are provided in the appendix. throughJuly or August. The host species is the anadromous yellow perch, Percaflavescens (Mitchill) (Lefevre and Cur- Elliptiofisheriana (Lea, 1838) tis, 1912; Matteson, 1948). E. complanata is the most com- Published Records. Chester River System: Head of the mon species offreshwaterbivalve encountered in the Atlan- MD Chester River (Kent Co.) [Type Locality (Lea, 1838)]; tic drainage (Clarke and Berg, 1959) and is typically found Stations5 (Ortmann, 1919), 8 (Ortmann, 1919), 15 (Rhoads, in lakes, ponds, rivers, and small streams on all types of 1904), 23 (Davis, 1984), 28 (Rhoads, 1904). substrata except very soft mud. Clarke and Berg (1959) Museum Materials Examined. Stations 5, 13, 17, 18, 23, 24, reported that often this is the only species found in a par- 28. Also examined were specimens from an unnamed body ticular locality and, ifother species ofunionids are present, ofwater, Chestertown, Kent Co., MD (DMNH 174253) and it is the most abundant. Our survey confirms this finding. from Sussex Co., DE (ANSP 345052). Records from Present Study. Stations 11, 17, 29, 30, 31, 34, Elliptio dilatata (Rafinesque, 1820) 35 - 39. Published Records. Chesapeake Bay drainage. Nanticoke There has been confusion as to the systematic posi- RiverSystem: Concord Pond, Sussex Co., DE (Davis, 1984) tionofElliptiofisheriana Ortmann (1919) noted that a close . Station 23). morphological similarity existsbetweenE.fisheriana andE. Elliptiodilatata is anInteriorBasin species that closely cupreus and believed that E. fisheriana could be a lowland resemblesE. complanata and is commonthroughout its range raceofE. cupreus. However, he also noted that hecould not (Clarke and Berg, 1959) in large and small rivers in either detect intergradesbetweenthetwo species. He furthernoted rapid or slow-flowing reaches, as well as in lakes on rocky, that specimens collected in White Clay Creek, Chester Co., gravel, sand, or mud substrata (Clarke andBerg, 1959) Soft Pennsylvania (Hartman and Michener, 1874), could in fact tissue anatomy was described by Ortmann (1911). Reproduc- havebeencollected in Delaware. Johnson (1970) reportedE. tion occurs in the spring although Ortmann (1919) reported fisherianatobeasynonymofE. lanceolata (Lea, 1828) which gravid females were found in Pennsylvania from May through he considered to be a highly variable species (25 synonyms August. Glochidiaare retainedinthemarsupiumuntil August listed for E. lanceolata); however, Davis (1984) found E. (Ortmann, 1919; Clarke and Berg, 1959). The host fish in fisheriana to be genetically distinct from E. lanceolata. No unknown. published reports exist regarding the glochidia, soft tissue No specimens ofElliptio dilatata were found during anatomy, or breeding season of E. fisheriana. the present study but a single published record is reported. Since the voucher specimen for this record was not found Elliptio complanata (Lightfoot, 1786) in the collections of the Academy of Natural Sciences of Published Records. Stations 4 (Davis, 1984), 24 (Davis, Philadelphia, it is believedthat the specimens were late iden- 30 AMER. MALAC. BULL. 9(1) (1991) tified as E. complanata. An examination of the collection pears to be locally abundant. A second population, which locality failedto reveal thepresenceofthis species. Therefore, we were unable to locate, was reported from Long Marsh no verified specimen ofE. dilatata has been taken from the Ditch (pers. comm., Maryland Nature Conservancy, 1991). Delmarva Peninsula. Becauseofits rareandendangeredstatus, nocollections were made. Alasmidonta undulata (Say, 1817) Alasmidonta heterodon has been described as in- conspicuous with adisjunctive distribution along the Atlan- Published Record. Chesapeake Bay Drainage. (Station 15) ticcoast (ClarkeandBerg, 1959; Clarke, 1981). The species (Clarke, 1981). is bradytictic and Clarke and Berg (1959) noted that its Museum Materials Examined. Stations 15 and 17. breeding season is not well known with gravid females be- Record from Present Study: Station 17. ing reported inFebruary andApril. Clarke(1981) notedgravid Clarke (1981) published a single locality for Alasmi- females havebeen found inJune and, in theTarRiver, North donta undulataonthe Delmarva Peninsula, andtwo lots from Carolina, inlateAugust. The fishhost species isnotknown. the Choptank Riversystemareat ANSP. We located asingle Detailsofsofttissue anatomy arepresented inClarke (1981). specimen during our survey. The reported habitats include medium-sized riversor rather Ortmann (1919) noted that Alasmidonta undulata is slow-moving rivers of varying size on substrata of gravel, gravid from July to the following June and Clarke (1981) sand, or muddy sand, and sometimes among submerged reported collecting gravid females between August and Oc- aquatic vegetation (Clarke and Berg, 1959; Johnson, 1970; tober. The host fish is unknown. A. undulata is reported to Clarke, 1981). The populationat NorwichCreek (Station 17) occur in moderately flowing streams, from rivers to creeks, is living in slow-moving water over a sandy substratum. and is most abundant ongravel and sand substrata, beingab- Clarke and Berg (1959) also noted that A. heterodon was sent from mud (Ortmann, 1919; Clarke and Berg, 1959; associatedcommonly withElliptiocomplanata andStrophitus Clarke, 1981). The species isalso found in lakeson sandand undulatus in central New York. Although we found neither gravel substrata (butgrowth canbe stunted inthese habitats) of these species in direct association with A. heterodon at and reaches its maximum size in streamoutletslocateddown- NorwichCreek, contemporaneoushistoricalcollectionsfrom stream of lakes (Clarke and Berg, 1959). The species is this locality indicated the presence ofE. complanata, S. un- reportedtobecommonly associatedwithElliptiocomplanata dulatus, as well as Anodonta cataracta, E. fisheriana, and and secondarily withStrophitus undulatus (Clarkeand Berg, A. undulata. 1959; Clarke, 1981). Ortmann (1911) describedthe soft tissue anatomy. Anodonta cataracta Say, 1817 Alasmidonta varicosa (Lamarck, 1819) Published Record. Seaford, SussexCo., DE(Rhoads, 1904). Museum Materials Examined. Stations 8, 11, 15, 17, 24, 55, Published Record. Station 47 (Clarke, 1981). 61. Other materials examined: Leonards Brick Pond, Chop- Museum Materials Examined. Station 47. tank River System, Cambridge, Dorchester Co., MD. (col- Clarke (1981) published a single locality for Alasmi- lections made before 1930, a note with the lot states that the donta varicosaonthe Delmarva Peninsula. However, we were locality now has dwellings) (DMNH 87400): Tributary of unabletolocatethespeciesandasurveyoftheClarke'slocal- Brandywine Creek, ChristinaRiverSystem, Greenville, New ity failed to reveal the presence of the species. Castle Co., DE (ANSP 182963). OnelotfromCambridge, DorchesterCo., MD. (ANSP Alasmidonta heterodon (Lea, 1830) 132477) is from a fish pond, with no outlets to streams. Museum Materials Examined. Station 17. One lot (ANSP Anotherlot (ANSP355544) gives a locality of"Wye Mills, 174899) collected by G. A. Coventry, August 1939, Norwich Creek, Talbot Co., MD." Wye Mills is located in "Delaware." Queen Anne's Co. and Norwich Creek is in Talbot Co. ap- Although Alasmidonta heterodon has been reported proximately 8 km east of Wye Mills. from streams to areas adjacent to the Delmarva Peninsula Records from PresentStudy. Stations 1 - 3, 6, 11, 20, 24, 29, (ClarkeandBerg, 1959; Johnson, 1970; Clarke, 1981), it has 30, 32, 34, 35, 38, 40 - 42, 51, 52, 55 - 63, 65. neverbeendescribed fromthe watersofthepeninsula-proper. Thiswasthe secondmostcommonly foundfreshwater The species was first collected on the peninsula in August bivalve on the Delmarva Peninsula. Clarke and Berg (1959) 1939by G. A. Coventry without specificcollectiondataother report the species to be common in lakes and ponds and than "Delaware." Onepopulationwas foundduringthisstudy streams varying in size from large rivers to small creeks, it in (Station 17) NorwichCreek, atributaryofTuckahoeCreek, is most abundant on substrata ofsand or mud. They further Choptank River system, near Hillsboro, Maryland. The noted that it was theonly species found in softand substrata population is locatedjust within the Talbot Co. line and ap- ofponds andbackwaterareas. OnDelmarva, the specieshas COUNTS ETAL. DELMARVA NAIADES 31 : been collected historically from small streams but our col- The host fish is unknown but these authors suggested that lections wereentirely fromthe small mill ponds, usually from many of the species serving as hosts for L. siliquoidea sand-silt substrata. (Barnes, 1823)alsoserveashosts forglochidiaofL. r. radiata Anodonta cataracta is reportedtobreedfromthemid- [bluegill, Pomoxis annularis Rafinesque; black crappie, P. dle ofJuly to the following April or May (Clarke and Berg, nigromaculatus (LeSueur); largemouth bass, Micropterus 1959). The host fish species isunknown. Detailsofsofttissue salmoides (Lacepede); smallmouth bass, M. dolomieui anatomy are presented in Reardon (1929). dolomieui Lacepede); white bass, Roccus chrysops (Rafinesque); yellow perch, Perca flavescens (Mitchill); eastern sauger, Stizostedion canadense (Smith); and yellow Anodonta implicata Say, 1829 pikeperch, S. vitreum (Mitchill)]. Museum Materials Examined. Stations 4, 5, 11, 13. Lampsilis r. radiata is foundtypicallyongravel orsand One lot (ANSP 355543) gives a locality of "Wye substrata and occasionally on mud. It occurs in lakes and Mills, NorwichCreek, TalbotCo., MD." WyeMills islocated rivers ofall sizes but can be absent from smaller ponds and in Queen Anne's Co. and Norwich Creek is in Talbot Co. creeks (Clarke and Berg, 1959). approximately 8 km east of Wye Mills. Records from Present Study. Stations 12, 13, 16, 31, 49, 50, Lampsilis cariosa (Say, 1817) 60. Anodonta implicata is found most commonly in sand Published Record. Seaford, Sussex Co., DE (Rhoades, orgravel substrataand, very rarely, inmud(ClarkeandBerg, 1904). 1959; Johnson, 1970). Johnson (1970) notes that the species Museum Materials Examined. Stations 24, 28. seems to prefer stream habitat although it can be found in The anatomy ofLampsilis cariosa was described by coastal ponds with an unobstructed outlet to the ocean. A. Lea (1838). Ortmann (1911) found it to be similar to that of implicata was foundduringour study in ponds without such L. ventricosa (Barnes, 1823). The length of the breeding direct access to the ocean in the Delaware River and Bay season is unknown but Clarke and Berg (1959) believed the drainage (Stations 49, 50, 60). species to be bradytictic. The host species is unknown. L. Ortmann (1919) reported Anodonta implicata to be cariosa is found in rifflesand shoalsoflargetomedium-sized bradytictic (winterbreeders) with larvaepresent inthe mar- streams in finetocoarsegravel, usually in sand bars (Clarke supiumbetweenJuly and September. Johnson(1970) reported and Berg, 1959; Johnson, 1970). gravid females in Massachusetts in early May and June. There are only three records for Lampsilis cariosa Larvaearereleasedthefollowiongspringandthehost species from the Delmarva Peninsula, all from the Nanticoke River is the anadromous alewife, Alosapseudoharengus (Wilson, system. The species was not encountered during our study 1811) (Clarke and Berg, 1959). No report of soft tissue even though collections were made at the same stations as anatomy isknown. TheglochidiaweredescribedbyJohnson the historic records. This absence ofL. cariosa could not (1946). Unionidsmostcommonly associatedwithA. implicata be explained on the basis of misidentification. are/1, cataracta, Lampsilis radiata radiata, L. ochracea, and Elliptio complanata (Clarke and Berg, 1959). There are no published records for A. implicata on the Delmarva Leptodea ochracea (Say, 1817) Peninsula. PublishedRecord. Seaford, SussexCo., DE (Rhoads, 1904). Museum Materials Examined. Stations 5, 24, 28, 55. Collections from Present Study. Stations 1, 2, 60, 61. Lampsilis radiata radiata (Gmelin, 1791) Ortmann (1919) reported Leptodea ochracea to be Published Record. Sussex Co., DE (Davis and Fuller, restrictedtothe tidal portionsofthe Delaware River. Clarke 1981). and Berg (1959) noted the species occurs in ponds, canals, Museum Materials Examined. Stations 3, 5, 11 - 13, 24. Ad- and slow-flowing portions ofrivers. The soft tissue anatomy ditional materials were examined from Grays Branch, Chop- was described by Reardon (1929). Very little is known con- tank River System, near Denton, Caroline Co., MD (ANSP cerning the glochidia, breeding season, or host species (Ort- 106007). mann, 1919; Johnson, 1947; ClarkeandBerg, 1959) although CollectionsfromPresent Study. Stations 1, 2, 12, 13, 33,44. Johnson (1970) reported findinggravid females in early May Lampsilis r. radiata is distributed widely over the at Plymouth, Massachusetts, and thought the species was Atlantic Slope (Johnson, 1970). Clarke andBerg (1959) noted bradytictic. Johnson (1970) also believed that the glochidia that the breeding seasonappears tobegin in August and end probably parasitize migratory fish because L. ochracea is the following August. It is not known if this implies con- restricted generally to the lower reaches of streams having tinuousbreedingor ifahiatusoccursbetweenbreedingyears. direct connections with the Atlantic Slope. AMER. MALAC. BULL. 32 9(1) (1991) Ligumia nasuta (Say, 1817) presentata single locality was5 (Station 17) followedbyone PublishedRecords. Station 15 andSeaford, Nanticoke River station (Station 2) with 4 species, 8 stations with 3 species, System, Sussex Co., DE (Rhoads, 1904). 10stationswith2 species, and36stationswithasinglespecies Museum Materials Examined. Stations 15, 24, 28. Additional present (Table 1). Whenthese dataare compared with those materials: Ditch, Choptank River System, near Petersburg, for the 21 historically identifiable stations represented in KentCo., DE, 1939 (ANSP 175862); headwatersoftheChop- museumcollectionsorpublished inthe literatureonly 2 sta- tank River, Medford, Mills, Sussex Co., DE, 1939 (ANSP tions show no change in species composition. Additionally, 14 stations show adecline in the numberofspecies present, 174904). Record from Present Study. Station 45. 2 stations show an increase in species diversity, and 3 sta- Whilethereare historical collectionsthat have placed tions have lost species but gained new ones. Therefore, the Ligumia nasuta in various streams and ponds of Delmarva, trend is towards a decrease in unionid species diversity. it was encountered at only a single station (45) during our A review ofhistorical collections revealed that Ellip- tio complanata was associated commonly with Anodonta study. cataracta and E. fisheriana and E. fisheriana with A. Clarkeand Berg (1959) reportLigumianasuta tobreed from August to the following June. The host fish species is cataracta (Table 1). Collections fromour survey indicatethat unknown. The preferred habitat appears to be ponds, lakes, E. complanata is commonly associated with E. fisheriana and slack water portions ofstreams and canals on sand and and E. fisheriana with A. cataracta but that E. complanata mud substrata (Clarke andBerg, 1959). The species isusually now is associated closely with Lampsilis radiata (Table 1). The three most commonly encountered unionids on associated with Elliptio complanata and Lampsilis radiata. the Delmarva Peninsula, bothhistorically andat present, are Anodonta cataracta, Elliptio complanata and E. fisheriana Strophitus undulatus (Say, 1817) (Table 2). Neither E. dilatata, Lampsilis cariosa nor Published Record. Station 15 (Rhoads, 1904). Alasmidonta varicosa were found during our survey. Table Museum Materials Examined. Stations 13, 17, 47. 2 summarizes species composition changes for all historical Record from Present Study: Station 17. and present collections of unionids on the Delmarva There is some debate as to the life-cycle ofStrophitus Peninsula. undulatus. Lefevre and Curtis (1912) and Clarke and Berg (1959) report that the species can complete its development DISCUSSION in parental marsupia but note that Baker (1928) reported glochidia completed development after attachment to The unionid fauna ofDelmarva is composed entirely largemouth bass, Micropterus salmoides (Lacepede, 1802), of species associated with the greater Atlantic Slope fauna and the northern creek chub, Semotilus atwmaculatus (Ortmann, 1919; Clarke and Berg, 1959; Johnson, 1970; (Mitchill, 1818). Both of these species are found in waters Clarke, 1981). Theoriginationofthis faunaprobablyoccurred draining into Chesapeake Bay (Lee, 1980; Lee and Platania, in much the same manner as that ofthe freshwater fishes of 1980; Hocutt et al, 1986). the peninsula. In view of the need for a fish host for the The habitats reported forStrophitusundulatus include bivalvestocompletetheirdevelopment, thepopulationofthe small rivers and creeks on substrata of mud, sand, or fine peninsulabythesetwogroups shouldhavebeensimultaneous. gravel (Clarke and Berg, 1959; Johnson, 1970). S. undulatus Hocuttetal. (1986) notedthatChesapeakeBay isthedrowned is reported in association with Elliptio complanata and channeloftheSusquehannaRiverandthatthelowersealevels Alasmidonta undulata (Clarke and Berg, 1959). Con- associated with interglacial periods facilitated the dispersal temporaneous collections at ANSP confirm this association ofseveral upland fish species to the peninsula. This process in Andover Creek, Maryland, as do our own collections in ofrisingand fallingsealevels inthebay occurred manytimes Norwich Creek, Talbot Co., Maryland. These collections (Flint, 1957) with the lowest level occurring during the furtherindicateassociationswithLampsilisradiata, Anodonta Wisconsonianglaciation(Lougee, 1953). Thus, withthefree cataracta, A. implicata, E. fisheriana, and Alasmidonta movement offishes and unionids during these periods, it is heterodon. not surprising that Delmarva's unionid fauna is like that of the rest of the Atlantic Slope. DIVERSITY Once established, some isolation ofunionid popula- tions in the major drainages of the peninsula could have Unionid bivalves were found at 56 (18.2%) ofthe 307 occurred (Sepkowski and Rex, 1974). Further, extinction of stations examined (Table 1). Of the 13 species of unionids local populations can occur and, given the disjunct popula- historically reported from watersofthe DelmarvaPeninsula, tionsofsuch speciesasAlasmidonta heterodon, this has un- 10are now present (Table 1). The highest numberofspecies doubtedly occurred. Given the life cycle and physiological COUNTS ETAL. DELMARVA NAIADES : Table1. Speciespresentatallstations(A, Specieshistoricallypresentbutnowabsent; B, Specieshistoricallypresentandnow present; C, New record for the species)2. 3456789 Station Number Taxon 1 10 11 12 13 Elliptiofisheriana — — — — A —CC— A —CC— C —BBA E. complanata —C — —A —A — — _ _ _ — — — — E. dilatata — — — — — — — — — — — — — Alasmidonta undulata — — — — — — — — — — — — — A. varicosa —CC— C— — — — — — — — — — — A. heterodon Anodonta cataracta CCA C — A — — AB BB A. implicata — — — A A — — — — — A C B Lampsilis r. radiata — — — —— —A —— —— _— —_ —_ — — — LL.epctaordieoasaochracea —C —C —— —— —A —— —— —— —— —— —— —— —— Ligumia nasuta — — — — — — — — — — — — A Strophitus undulatus Station Number 14 15 16 17 18 19 20 2B1 B22 A23 A24 C25C26 Elliptiofisheriana _— _A _— _BB_BA C_— _— _— _—AA A E. complanata A - — — AE.ladsimliadtoatnata undulata —— —A —— —B —— —— —— —— —— —— —— —— —— AAAALLL....aenmpopchitvdsameaooriptrdnillieetoiicraascsooaasdotcaro.caanhtrraaardaciceatataa —————— —————A —————C ————AB —————— —————— —————C —————— ——————__—————— _——AAAB —————— —————— Ligumia nasuta — A — — — — — — — — A — — Strophitus undulatus — A — B — — — — — — ACCC Station NumberCCCCCC 27 28 29 30 31 32 33 34 35 36 37 38 39 CCC — ____ Elliptiofisheriana E. complanata —C —A — _ _ _ — C C — — E. dilatata — — — — — — — — — — — — — Alasmidonta undulata — — — — — — — — — — — — A. varicosa — — — — — — — — — — — — A. heterodon ______£_ Anodonta cataracta C C C C C C A. implicata — — — — C — — — — — — — — — — — LLL.aempcptasoridileoiassaor.chrraadcieaata —— —A —— —A —— —— —— —— —— —— —— —— Ligumia nasuta —— —A —— —— —— —— —— —— —— —— —— —— — Strophitus undulatus Station Number 40 41 42 43 44 45 46 47 48 49 50 51 52 — — — — — — — _ _CC_ _ — — EEl.licpotimoplfiasnhaetraiana —— —— —— —C —— —— —A — — — —— —— —— E. dilatata — — — — — — — — — — — — — Alasmidonta undulata A. varicosa —CC— C— — — — — A — — — — — — — — — — — — — — — — —CC— A. heterodon Anodonta cataracta — — — C — — — — AL.ampismiplliicsatr.aradiata ———__——— _——— _———___——C __——— __———a_——— ———__——C _——C _——— ——— L. cariosa — —__— __ — — — — — Leptodea ochracea __ — Ligumia nasuta — — — — — — — Strophitus undulatus (continued) 34 AMER. MALAC. BULL. 9(1) (1991) Table 1. (Continued) Station Number Taxon 53 54 55 56 57 58 59 60 61 62 63 64 65 —CC— — — — — — — — — — — — EEl.licptoimc)plfiasnhaetraiana C — C — C — — — — — — — — — — — — — — — E. dilatata — — — — — — — — — — — — — Alasmidonta undulata — — —BC— C— C— C— C— B— C— C—A—C— A. varicosa — — — — — — — — — — — — — A. heterodon Anodonta cataracta A. implicata _— _— _— _— — — — C — — — — — — — — — — — — — — — — — — Lampsilis r. radiata — — — — — — — — — LL.epctaordieoasaochracea ___A _— _—_— — C C — — — — — — — — — — — — — — — — — Ligumia nasuta — _ — _ — — — Strophitus undulatus requirements of unionids, opportunities for expansion of tissues. It seems more likely that the usual mode of move- zoogeographic ranges are limited in these habitats and thus, ment ofunionid species on fish hosts occurred during times the observed pattern of distribution of unionids in coastal of high freshwater input into the system (e.g. rains, etc.). rivers is not explained easily. These events would dilute the saltwater barriers between Sepkowski and Rex (1974) offered three hypothesesto drainages and this seems to agree with the third hypothesis explain thedistributionofunionid faunaalongcoastal rivers. ofSepkowski and Rex (1974) that streamcapture andflooding The firstproposesthatgravid musselscouldattachtothefeet could play a role in dispersal. ofaquatic birds and are thence transported into neighboring This dispersal mechanism could also explain the systems. They noted that van der Schalie (1945) rejected this absence ofunionids onthe Virginiaportionofthe Delmarva particular statement ofthe hypothesis but noted that predatory Peninsula. These streams are shortand shallowandmostare birdscan carry the tissues ofglochidial-parasitized fish from tidal andbrackish. Furthermore, the watersoftheChesapeake one stream to another. This form of the hypothesis seems Bay on the west side of the peninsula are more saline [22 more reasonablegiven the sizeand weightofunionidbivalves -28ppt(BashoreandKelly, 1987)] thanthoseobservedfarther althoughthe size, depth, anddegreeofcanopy coverofmost north in Maryland. The extensive use ofmill dams that act Delmarva Peninsula streams do not lendthemselves to large- to sharplydemarcate freshandsalt watersareessentially ab- scale use by predatory birds. sent from the Virginia portion of the peninsula. Thus, the The second hypothesis hingesonparasitism ofsecon- movement of unionids from one drainage to another in the daryandperipheral fishes. Myers(1938, 1951)classifiedfishes southern end ofthe peninsula, even while attached to a host on the basis oftheir salinity tolerance. Primary fishes have fishspecies, requirestraversingwatersofevenhighersalinities little or no tolerance to sea water; secondary fishes are thanthose farthernorth. Evenmajorweathereventsthatresult restricted usually to freshwater but have a salinity tolerance in significantamountsofrainfallcouldnotdiluteappreciably sufficienttocross narrowbandsofsalt water. Thus, secondary watersofthesesalinitiestopermitthepassageofspeciesfrom fish hosts could move freely into the bay from one drainage one drainage to another. Another factor contributing to the and enteranother. Salinity tolerance studiesby Musick (1972) absenceofunionidspecies inthisregionisthefrequency with and Lee (1976) suggested that primary fishes can tolerate whichthe streamsdry upduring periodsofdrought. Should greater salinity concentrations than suggested by Myers. a unionid species become established in a southern penin- Because of this others (e.g. Hocutt et al., 1986) have sug- sula stream, itcould find itselfwithout waterduringthe sum- gested that the salinity tolerance classification scheme is in- mermonths. The absence ofspecies usually associated with valid. The presumed primary fish host ofLampsilis r. radiata ponds (Elliptio complanata, Anodonta cataracta, Lampsilis and Strophitus undulatus, Micropterus salmoides, tolerated r. radiata, Leptodea ochracea, Ligumia nasuta) is puzzling a salinity of 12.9 ppt and another primary fish host ofL. r. because many ofthe existing ponds have been stocked with radiata andElliptic) complanata, Percaflavescens, tolerated fish. a salinity of 13 ppt. Thus, these fishescouldmove more freely The collections made during our survey indicate a among the drainage systems of the peninsula than was general trendtowarddecline inspeciesdiversity. Whilethere suspected previously. Unionid glochidia, however, are in- has not beenahistorical trend towardsdevelopmentofheavy tolerantofsalineconditions (Cvancara, 1970) andtheirmove- industryonthe DelmarvaPeninsuladuringthepast 100years, ment on a fish host into saline conditions seems unlikely there has been an increase in population and an intensifica- unless physiological isolation occurs within the fish host's tion ofagricultural production. This has led to the channel- COUNTS ETAL. DELMARVA NAIADES 35 : izationofmany streams forboth floodcontrol and increased (Bivalvia) sibling species, convergence and cladistic relationships. drainageoffarm fields. This process couldhavecontributed Malacologia 25(2):629-648. to habitat loss for some species because several historical Davis, G. M. and S. L. H. Fuller. 1981. Genetic relationships among Re- cent Unionacea (Bivalvia) of North America. Malacologia localities are now channelized. Furthermore, the increased 20(2):217-253. applicationofagricultural chemicalscould haveplayedarole Davis, G. M., W. H. Heard, S. L. H. Fuller and C. Hesterman. 1981. indiversity declineby acting eitherdirectly uponthe mussels Molluscangeneticsandspeciation inElliptic)anditsrelationshipto or upon their fish hosts species. Because many of the fish other taxa of North American Unionidae (Bivalvia). Biological hosts for the species of unionids on Delmarva are as yet Journal ofthe Linnean Society 15:131-150. unknown, the extent of this factor is unknown. Flint, RN.eF.w1Y9o5r7k..Gl5a5c3iaplp.andPleistocene Geology. JohnWiley andSons, The zebra mussel, Dreissenapolymorpha, has yet to Handwerker, T. S., C. L. Counts, IIIandR. V. Jesien. 1991. Distribution be found along the Delmarva Peninsula. The point at which ofCorbiculafluminea (Bivalvia: Corbiculidae) in the Chesapeake direct introduction from abroad is likely to occur is the Baydrainageofthe DelmarvaPeninsulaand itsuse inaquaculture. ChesapeakeBay and Delaware Canal. The Maryland Depart- Proceedingsofthe 1990ChesapeakeResearchConference. Inpress. Hartman,W. D.andE. Michener. 1874. ConchologiaCestrica. Philadelphia. ment of Natural Resources is currently monitoring these 114 pp. waters for evidence of this exotic species. Hocutt, C. H., R. E. Jenkins and J. R. Stauffer. Jr. 1986. Zoogeography ofthefishesoftheCentralAppalachiansandCentralAtlanticCoastal Plain. In: TheZoogeographyofNorthAmericanFreshwaterFishes. ACKNOWLEDGMENTS C. H. HocuttandE. O.Wiley,eds.pp. 161-211.JohnWileyandSons, New York. The authors wish to thank Gene Handwerker and Nicholas Counts Johnson.R.I. 1946.Anodontaimplicate!Say. OccasionalPapersonMollusks. fortheirhelpduringsampling.ThanksarealsodueDavidO'Neill, University Museum ofComparative Zoology 1:109-116. ofMarylandEasternShore, forhishelpincollectingspecimens. Wewould Johnson, R. I. 1947. Lampsilis cariosa Say and Lampsilis ochracea Say. liketoalsothankDr. RudigerBieler, DelawareMuseumofNatural History OccasionalPaperson Mollusks, Museum ofComparativeZoology and Dr. Arthur E. Bogan, Academy ofNatural Sciences ofPhiladelphia, 1:145-156. and their respective staffs for assisting us in locating historical materials Johnson, R. 1. 1970. The systematics and zoogeography ofthe Unionidae described in this paper. The paper benefited from the comments of two (Mollusca: Bivalvia)ofthesouthernAtlanticSloperegion. Bulletin anonymous reveiwers whose assistance is gratefully acknowledged. ofthe Museum ofComparative Zoology 140(6):263-450. Lea, I. 1838. Descriptionsofnew freshwaterand landshells. Transactions oftheAmerican Philosophical Society, New Series, 6:1-154. Lee, D. S. 1976. Aquatic zoogeography of Maryland. Atlantic Naturalist LITERATURE CITED 31(4):147-158. Lee, D. S. 1980. Micropterus salmoides (Lacepede). In: Atlas ofNorth Baker,F.C. 1928.ThefreshwaterMolluscaofWisconsin. Part2. Pelecypoda. AmericanFreslrwaterFishes, D. S. Lee, C. R. Gilbert.C. H. Hocutt, Wisconsin GeologicalandNaturalHistory Survey, Bulletin 70(2). R. E. Jenkins, D. E. McAllisterandJ. R. Stauffer, Jr., eds. p. 608. 492 pp. North Carolina State Museum ofNatural History, Raleigh. Bashore,T. L.andK. L. Kelly. 1987. ChesapeakeBayMarineEnvironmental Lee, D. S. andS. P. Platania. 1980. Semotilusatromaculatus(Mitchill). In: AssessmentMarch 1986-August 1986. Chesapeake ResearchCon- AtlasofNorthAmericanFreshwaterFishes, D. S. Lee,C. R. Gilbert. sortium (Gloucester Point, Virginia) Publication 123. 51 pp. C. H. Hocutt, R. E. Jenkins, D. E. McAllisterand J. R. Stauffer, Burch, J. B. 1973. Freshwater Unionacean Clams (Mollusca: Pelecypoda). Jr., eds. p. 361. NorthCarolina State Museum ofNatural History, BiotaofFreshwaterEcosystemsIdentificationManual No. 11, United Raleigh. StatesEnvironmentalProtectionAgency(Washington.DC). 176pp. Lefevre, G. and W. C. Curtis. 1912. Studies on the reproduction andarti- Carpenter, D. H. 1983. CharacteristicsofstreamflowinMaryland. Depart- ficial propagation of freshwater mussels. United States Bureau of mentofNaturalResources, MarylandGeological Survey,Reportof Fisheries, Bulletin 30:105-201. Investigations No. 35. 237 pp. Lougee, R. J. 1953. A chronology of postglacial time in eastern North Clarke,A. H. 1973.ThefreshwatermolluscsoftheCanadianInteriorBasin. America. Science Monthly 76(5):259-276. Malacologia 13(1/2):1-509. Matteson, M. P. 1948. LifehistoryofElliptic)complanatus(Dillwyn, 1817). Clarke, A. H. 1981. ThetribeAlasmidontini(Unionidae: Anodontinae), Part American MidlandNaturalist 40:690-723. I: Pegias, Alasmidonta, andArcidens. Smithsonian Contributionsto Musick,J. A. 1972. FishesofChesapeakeBayandtheadjacentCoastalPlain. Zoology Number 326. 101 pp. Virginia Institute of Marine Science, Special Scientific Report Clarke,A. H. andC.O. Berg. 1959.ThefreshwatermusselsofCentralNew 65:175-212. York, with an illustrated key to the species ofnortheastern North Myers,C. S. 1938. Fresh-waterfishesandWestIndianzoogeography. Smith- America. CornellUniversityAgriculmralExperimentStationMemoir sonian Report 1937:339-364. 367:1-79. Myers, C. S. 1951. Freshwater fishesand East Indian zoogeography. Stan- Counts, C. L., Ill, T. S. Handwerkerand E. B. May. 1991. The potential fordIchthyologicalBulletin 4:11-24. for infestation ofChesapeake Bay by the zebra mussel, Dreissena Ortmann, A. E. 1911. AmonographofthenajadesofPennsylvania. Memoirs polymorpha (Bivalvia: Dreissenacea). Proceedings of the 1990 ofthe Carnegie Museum 4:279-347. Chesapeake Research Conference. In press. Ortmann, A. E. 1919. A monograph ofthe naiades ofPennsylvania. Part Cvancara,A. M. 1970. Mussels(Unionidae)oftheRedRiverValleyinNorth III. Systematic account ofthe genera and species. Memoirs ofthe Dakota and Minnesota, U.S.A. Malacologia 10:57-92. Carnegie Museum 8(1):1-384. Davis,G. M. 1984. GeneticrelationshipsamongNorthAmericanUnionidae Reardon, L. 1929. A contribution to the knowledge ofthe anatomy ofthe , 36 AMER. MALAC. BULL. 9(1) (1991) <resh-watermusselsoftheDistrictofColumbia. Proceedingsofthe Bay Region. InternationalGeologicalCongress,XVISession, United United States National Museum 75(11):1-12. States, 1933, Guidebook 5: Excursion A-5. 49 pp. Rhoads, S. N. 1904. A glimpse at the shell fauna of Delaware. Nautilus vanderSchalie,H. 1945.Thevalueofmusseldistributionintracingstream 43:63-67. confluence. Papers ofthe Michigan Academy ofArts and Letters Sepkowski,J.J.,Jr.andM. A. Rex. 1974. Distributionoffreshwatermussels: 20:355-373. coastal rivers as biogeographic islands. Systetnatic Zoology 23(2):165-188. Date ofmanuscript acceptance: 17 May 1991 Stephenson, L. W., C. W. CookeandW. C. Mansfield. 1933. Chesapeake APPENDIX. Collectionstation numbersand localitiesexamined forthe presence CHOPTANK RIVER SYSTEM ofunionid bivalves on the Delmarva Peninsula. The geographic locations 15. Choptank River, "Choptank Mills," RT207 at Mud Mill Pond, Kent ofstations are identified in figure 1 by station number. Stations are listed Co., DE (Rhoads, 1904; Clarke, 1981; ANSP 85224, 85226, 85264) from north to south first in the Chesapeake Bay drainage and secondly in 16. Tuckahoe Lake, Tuckahoe Creek, Tuckahoe State Park, Crouse Mill theDelawareBayAtlanticOceandrainage. Previouslyreportedstationsare Road bridge, Caroline-Queen Anne Cos., MD (UMES 2375) referencedinparentheses. (DMNH, DelawareMuseumofNaturalHistory; 17. NorwichCreek, RT404bridge,QueenAnne'sCo., MD(ANSPA9487, ANSP. Academy of Natural Sciences ofPhiladelphia; UMES, University A9488, A10261, A10262, 355556, 355802, 358285, 358286, 358287, ofMarylandEasternShore).Onlythosestationswhereunionidbivalveswere 358288, 358289, 358290; DMNH4U38; UMES2471,2472,2473,2474) foundarelisted.Acompletelistofallstationlocalities,includingthosewhere 18. MasonBranch, TuckahoeCreek, MDSR304 bridge, Caroline-Queen no naiades were found, is on file at ANSP. Anne's Cos., MD (ANSP 358294, 358295, 358296; UMES 2265) 19. Watts Creek, Legion Road bridge, Caroline Co., MD (UMES 2380) 20. Williston Lake at spillway, Denton Road, Caroline Co., MD (UMES 2400) Chesapeake Bay Drainage 21. UHoMgECSre2e4k,83H)ogCreekRoadbridge,CarolineCo.,MD(ANSP358306; SUSQUEHANNA RIVER 22. Beaverdam Branch, 1.5 km west ofMatthews at MDSR 328 bridge, 1. SusquehannaRiver, mudflatatVeterans Hospital, Perry Point, Perry- Talbot Co., MD (ANSP 358309; UMES 2484) ville, Cecil Co., MD (UMES 2258, 2259, 2260, 2261) NANTICOKE RIVER SYSTEM BOHEMIA RIVER SYSTEM 23. ConcordPond,justnorthofDESR20, CR516, 1.6kmeastofSeaford, 2. Little Bohemia Creek, Bohemia Mills, Bunker Hill Road, Cecil Co., Sussex Co., DE (Davis, 1984; ANSP 345054 352551, 358277) MD (UMES 2397, 2398, 2399) 24. "Deep Creek," just below Concord Pond spi,llway, RT 516, east of SASSAFRAS RIVER SYSTEM Seaford,SussexCo., DE(Davis, 1984;ANSP346863,346864,346865, 3. S3a5s8s3a0f2r,as3R5i8v3e0r,3,M3D5S83R042,9935b8r3id0g5e;,UCeMcEilS-Ke2n4t08C)o. line, MD (ANSP 334496383676,,334496383687,,35384277826,3,3538247738,6435,83247748,6355,8237467,86365,827384;78U67M,E3S492343736,) 4. S1a9s8s4a;frAasNSRiPver3,46u8n8d2e,rU3S46380819,br3i4dg7e8,68C)ecil-KentCo. line, MD(Davis, 25. GCroa.v,elDleEyB(rUanMcEh,SCo2l2l4i3n)sPond,justeastofCoverdaleCrossroads,Sussex 26. MarshyhopeCreek, DESR 16bridge,justeastofHickman, KentCo., CHESTER RIVER SYSTEM DE (UMES 2233) 5. RatcliffCreek, MDRT661,Chestertown,KentCo., MD(Ortmann, 1919; 27. NanticokeBranch, DESR 18bridge,justeastofjunctionwithCR533, ANSP 65093, 65095, 65096; DMNH 78556) Sussex Co., DE (UMES 2235) 6. Island Creek, MDSR 213 bridge, north ofCentreville Queen Anne's 28. NanticokeRiver,US 13bridge,Seaford,SussexCo.,DE(Rhoads, 1904; Co., MD (UMES 2402, 2403) ANSP 84837, 88219, 88370, 301003, 301004 345058; DMNH 75214) 7. Granny Finley Branch, MDSR 213 bridge. Queen Anne's Co., MD 29. TrapPond,TrapPondStatePark,SussexCo.,,DE(UMES2266,2267) (UMES 2409) 30. ChipmanPond,CR465bridgeatdam,SussexCo., DE(UMES2262, 8. Southeast Creek, MDSR213 crossing, Queen Anne's Co., MD (Ort- 2263, 2264) mann, 1919; ANSP 66311) 31. MeadowBranch,justdownstreamofHorsey'sPond,DESR24bridge, 9. RedLionBranch,DudleyCorseRoad,QueenAnne'sCo.,MD(UMES Laurel, Sussex Co., DE (UMES 2276, 2277, 2279) 2395) 32. Quantico Creek, Quantico Creek Road, east ofQuantico, Wicomico 10. Red Lion Branch, Red Lion Branch Road, Queen Anne's Co., MD Co., MD (UMES 2469, 2470) 11. (UnAiNcSoPrn3B5r8a2n9c9h,,3U5n8i3c0o0r,n3C5o83m0m1u;niUtMyELSake23,78Q,ue2e37n9)Anne's Co., MD 33. RMeDwas(tiUcMoEPSon2d2,5R2e)wasticoCreekatdam,AtholRoad,WicomicoCo. 12. ChesterRiver, MDSR313bridge, Millington, Kent-QueenAnne'sCos., 34. BarrenPond, BarrenCreekatdam,WicomicoCo., MD(UMES2249, MD(ANSPA9484,358297,358298,358308; UMES2307,2308,2309) 2250, 2451) 13. Andover Branch, Peacock Corner Road crossing, east ofMillington, 35. Tyndall Branch, Fleetwood Pond, CR 484 at dam, Sussex Co., DE Kent Co., MD (ANSP A9482, 355555, 355801, 358291, 358292, (UMES 2298, 2297) 358293; UMES 2480, 2481, 2482) 36. Record Pond, at dam, Laurel, Sussex Co., DE (UMES 2293) 14. Chester River, US 301 bridge, Kent-Queen Anne's Co. line (ANSP 37. Gales Creek, Galestown Pond, Galestown-Reliance Road at spillway, 346890) Galestown, Dorchester Co., MD (UMES 2287, 2289)