2011 NORTHEASTERN NATURALIST 18(3):357–369 A Multi-taxa Biological Survey of Passage Creek, Virginia Michael B. Duncan1,2,*, Sarah E. DuRant1, Brett J.K. Ostby1, James H. Roberts1, and John D. Willson3,1 Abstract - Identifying and conserving functioning headwater ecosystems is essential for ensuring the structure and function of natural ecosystem processes. The Passage Creek watershed (PCW) in Virginia is an upland tributary system of the North Fork Shenandoah River, which is found within the Potomac River basin. The PCW appears to maintain an array of terrestrial and fluvial habitats now uncommon in many adjacent watersheds because of human disturbance. We assessed the biotic condition of the PCW by sampling the fish, mollusk, and salamander assemblages throughout the watershed. We observed 29 fish, 9 salamander, and 4 aquatic mollusk species representing a variety of life histories and functional groups. Furthermore, we found that due to spatial differences in abundance and species richness, each assemblage offered unique insight into the condition of the PCW. The fish assemblage was indicative of those found in least disturbed areas within the Potomac basin, while salamander abundance and richness indicated areas of habitat degradation. Though we observed only one mussel species, the presence of native mussels suggested the PCW has maintained sufficient ecological condition to support long-lived animals potentially sensitive to low-level, additive, and compounding long-term disturbances, while neighboring watershed assemblages have collapsed. Given the relatively high species richness found within PCW, this watershed may be pivotal to the overall persistence of aquatic species in the Potomac basin and should receive high priority for future conservation efforts. Introduction Headwater ecosystems are vital for maintaining the biological health of downstream environments and directly provide unique habitats and refuge for a diverse community of terrestrial and aquatic species (Meyer et al. 2007). These environments support multiple life histories of many species, such as resident and migratory fish, that help to sustain larger populations (Campbell Grant et al. 2007). However, many headwater ecosystems within the Mid-Atlantic region are degraded by urbanization, agriculture, and logging. Development and population growth have altered the landscape, leading to drastic changes to the natural structure, function, and biodiversity of many watersheds within the region (Benz and Collins 1997). Passage Creek is a headwater tributary to the Potomac River basin, a system that has experienced widespread anthropogenic disturbance throughout the 1Department of Fisheries and Wildlife Sciences, Virginia Polytechnic Institute and State University, 106 Cheatham Hall (0321), Blacksburg, VA 24061. 2Ecology Department, Montana Cooperative Fishery Research Unit, Montana State University, PO Box 173460, Bozeman, MT 59717-3460. 3Savannah River Ecology Laboratory, University of Georgia, PO Drawer E, Aiken, SC 29802. *Corresponding author - michaelduncan12@hotmail.com. 358 Northeastern Naturalist Vol. 18, No. 3 last century (Eggleston 2009, Elmore and Guinn 2010, Potomac Conservancy 2010). Unlike the remainder of the basin, the Passage Creek watershed (PCW) appears to maintain an array of high-quality terrestrial and fluvial habitats now uncommon in many adjacent watersheds (Potomac Conservancy 2008). Its proximity and connectivity to the greater Potomac River valley make the PCW a potential source and refuge for a variety of fluvial and terrestrial organisms, including regionally and globally rare species. However, little is known about general patterns of biological diversity within the PCW. We sampled the fish, salamander, and aquatic mollusk assemblages of the PCW as part of a multi-faunal ecosystem assessment of the PCW. Our specific objectives were to describe the fish, salamander, and mollusk assemblages of the PCW and to explore the spatial variation in biodiversity within the PCW. Methods Site and study description Passage Creek flows approximately 61 km northeast before converging with the North Fork Shenandoah River near Strasburg, VA. Elevation ranges from 141 m to 852 m. Annual precipitation for the watershed is 92.7 cm, resulting in an annual mean stream discharge of 73 m3 s-1 (1932–2007; USGS 01635500 Passage Creek near Buckton, VA). We conducted surveys during summer and fall 2007. For each taxonomic group, we distributed survey sites throughout the PCW, attempting to sample a broad range of habitats and to characterize longitudinal gradients within the watershed. We determined site coordinates and elevations using a handheld GPS unit. Site locations, sampling dates, and survey methods varied among taxonomic groups, and are described separately below. Fish sampling We sampled the fish assemblages at each of six sites that were evenly distributed between the headwaters and confluence with the Shenandoah River (Table 1; Fig. 1). We sampled Sites 1–5 on 18 and 19 June 2007 and Site 6 on 19 August 2007. Sites included all channel-unit types (i.e., riffles, runs, and pools), ranged in length from 160 to 200 m (i.e., approximately 45 x mean stream width), and were delineated by natural habitat discontinuities (i.e., riffles). At each site, we collected all fish observed using a single upstream pass with a direct-current backpack electrofisher (Smith-Root, Inc., Shaw Island, WA) and 4.9-mm-mesh dipnets. Following electrofishing, we identified fish to species and examined them for external anomalies before we released them back to the site. Specimens that could not be identified in the field (e.g., Cyprinella and Cottus spp.) were preserved in formalin and identified in the laboratory using taxonomic keys in Jenkins and Burkhead (1994). We used these data to determine species richness and the relative abundances of each species at each site. Using Jenkins and Burkhead (1994), we categorized 2011 M.B. Duncan, S.E. DuRant, B.J.K. Ostby, J.H. Roberts, and J.D. Willson 359 species into ecological guilds to assess the structural and functional traits of the fish assemblage. We used personal judgment in instances when Jenkins and Burkhead (1994) had insufficient data for classification. Salamander sampling We selected 18 salamander survey sites along the length of Passage Creek (Fig. 1, Table 1). We sampled six sites on 28 June 2007 and the remaining 12 sites on 5 and 6 October 2007, avoiding the hot summer months when salamander surface activity is reduced. Sites were approximately 15 m long and represented a variety of habitat types, including low-elevation forested areas near the confluence of Passage Creek and the North Fork Shenandoah River (Sites S1–S3), sites in the middle reaches of the watershed characterized by agricultural land-use (Sites S4–S6), and high-elevation sites in the creek’s forested headwaters (Sites S7–S18) (Table 1, Fig. 1). We placed particular emphasis on headwater sites, given that small, high-elevation streams generally support the highest abundances and diversities of salamanders (Corn et al. 2003). We surveyed each site for 30 min between 0700 and 1800 h. Each survey consisted of 10 min turning cover objects (e.g., rocks and logs) within the stream, 10 min turning cover objects along the stream banks but out of the water, and 10 min turning cover objects in the adjacent terrestrial habitats within 50 m of the stream. All salamanders were captured, identified to species, and released at the end of each 30-min survey. We used criteria proposed by Southerland et al. (2004) to classify species as “tolerant” or “intolerant”. We pooled salamander captures at the site level for all Figure 1. Map and satellite imagery of sampling sites within Passage Creek watershed. Samples were taken at sites representing the range of stream size and habitats available: FM = combined fish and mollusk site, M = only mollusk site, S = salamander site. 360 Northeastern Naturalist Vol. 18, No. 3 analyses. We also noted any other amphibians or reptiles that were incidentally encountered while sampling. Mollusk sampling We surveyed mollusks on 17–19 June 2007 at eight sites in Passage Creek, six of which overlapped with sites sampled for fishes (Table 1, Fig. 1). Our primary objective was to detect all mussel species present, and secondarily to document all other aquatic mollusks present. Snorkeling was our preferred sampling method; however, we used water scopes in shallow waters ≤ 30 cm deep or unaided visual inspection in waters ≤ 15 cm deep. We surveyed all habitat types encountered within sites, but focused our efforts on run and riffle habitats and in habitats near stream banks. We also searched adjacent stream banks and gravel bars for mussel shells and muskrat middens. Sites ranged in length from 125 to 575 m, and sampling effort ranged from 2.25 to 6.00 person-hours. We identified, measured, and returned all mussels to the exact location from which they were collected. We noted other mollusks as present or absent and qualitatively classifi ed them as rare, common, or abundant. Table 1. Summary of sampling sites for Passage Creek survey (FM = fish and mussel; M = mussel only; S = salamander). Site length refers to length of fish and mussel sites, respectively. Effort represents only mussel and salamander surveys. Site Date UTM (N, E)* Length (m) Effort (person/hrs) Elevation (m) FM1 6/18/07 0736680, 4317595 160, 275 3.0 151 M2 6/20/07 0736862, 4315978 NA, 275 6.0 162 FM3 6/18/07 0731933, 4312471 180, 525 3.75 224 M4 6/20/07 0730563, 4311281 NA, 270 6.0 230 FM5 6/19/07 0727510, 4307499 200, 575 4.0 243 FM6 6/19/07 0725387, 4304113 196, 475 2.0 246 FM7 6/19/07 0721458, 4299056 175, 360 3.0 270 FM8 8/19/07 0715781, 4290362 192, 125 2.25 356 S1 6/28/07 0733567, 4314123 NA 0.5 193 S2 10/5/07 0732392, 4313222 NA 0.5 210 S3 10/5/07 0731409, 4311448 NA 0.5 219 S4 6/28/07 0727435, 4307823 NA 0.5 256 S5 10/5/07 0724957, 4301959 NA 0.5 256 S6 10/5/07 0721391, 4299011 NA 0.5 278 S7 6/28/07 0718189, 4293767 NA 0.5 234 S8 6/28/07 0713773, 4288807 NA 0.5 388 S9 10/5/07 0712776, 4287747 NA 0.5 491 S10 6/28/07 0712418, 4287376 NA 0.5 445 S11 10/5/07 0712411, 4287358 NA 0.5 512 S12 10/5/07 0711356, 4286529 NA 0.5 541 S13 6/28/07 0711292, 4286516 NA 0.5 514 S14 10/5/07 0710738, 4285859 NA 0.5 564 S15 10/6/07 0710617, 4285540 NA 0.5 534 S16 10/5/07 0710401, 4285208 NA 0.5 559 S17 10/5/07 0710333, 4285185 NA 0.5 507 S18 10/6/07 0710338, 4285114 NA 0.5 569 *WGS84, Zone 17S 2011 M.B. Duncan, S.E. DuRant, B.J.K. Ostby, J.H. Roberts, and J.D. Willson 361 Results Fish sampling Jenkins and Burkhead (1994), the most recent ichthyological compilation for Virginia, recognized a total of 88 fish species that occupy upland and/or montane habitats within the Virginia portion of the Potomac basin; 60 of these species (68%) were described as native to the basin. Our survey of the PCW captured 19 of these 60 presumably native species (32%), 9 of the 28 presumably non-native species (32%), and one presumably non-native species that had not previously been observed in the Potomac basin (Lythrurus ardens [Rosefin Shiner]; Table 2). Five of the 19 native fish species that we captured (Cyprinella analostana [Satinfin Shiner], Nocomis leptocephalus [Bluehead Chub], Notropis amoenus [Comely Shiner], Ameiurus natalis [Yellow Bullhead], and Noturus insignis [Margined Madtom]) had not previously been observed within the PCW. Conversely, we did not capture five native species previously observed within the PCW (Anguilla rostrata Lesueur [American Eel], Semotilus atromaculatus Mitchill [Creek Chub], Nocomis micropogon Cope [River Chub], Cyprinella spiloptera Cope [Spotfin Shiner], and Cottus bairdi Girard [Mottled Sculpin]). If our PCW capture records are combined with those reported in Jenkins and Burkhead (1994), 40% of the native fish species (24 of 60) and 40% of all fish species (35 of 88) known from upland regions of the Potomac basin have been captured within the PCW. We captured 10 fish species that were presumed by Jenkins and Burkhead (1994) to be non-native to the Potomac basin. Of these, four species (Phoxinus oreas [Mountain Redbelly Dace], Salmo trutta [Brown Trout], Lepomis cyanellus [Green Sunfish], and Etheostoma blennioides [Greenside Darter]) had previously been observed in the Potomac basin but not in the PCW, whereas Rosefin Shiner had previously not been observed in the Potomac basin. Only one non-native species observed previously in the PCW (Micropterus salmoides Lacepède [Largemouth Bass]) was not collected by us. Species richness increased in a downstream direction, ranging from 6 to 22 species. Throughout the stream, samples were numerically dominated by Campostoma anomalum (Central Stoneroller) and Cottus girardi (Potomac Sculpin), which together comprised over 50% of the fish collected. Six species were captured at all sites: Bluehead Chub, Luxilus cornutus (Common Shiner), Etheostoma flabellare (Fantail Darter), Hypentelium nigricans (Northern Hogsucker), Potomac Sculpin, and Ambloplites rupestris (Rock Bass). Six other species were captured at only one site each: Oncorhynchus mykiss (Rainbow Trout), Brown Trout, Lepomis gibbosus (Pumpkinseed), Comely Shiner, Catostomus commersoni (White Sucker), and Yellow Bullhead. Salamander sampling Salamander surveys yielded a total of 351 individuals representing 9 of the 15 salamander species recorded previously from Shenandoah or Page counties, VA (Table 3; Mitchell and Reay 1999, Petranka 1998). Overall, salamanders were most abundant at headwater sites. Salamander richness and abundance was 362 Northeastern Naturalist Vol. 18, No. 3 Table 2. Species traits, collection records (x = collected), and total relative abundance across all sites (%) of fish collected at the six Passage Creek sites. Species traits were assigned based on species accounts in Jenkins and Burkhead (1994) and expert judgment. Trait codes are as follows: tolerant (T), intolerant (I), native (N), introduced (I), algivore (AL), omnivore (OM), insectivore (IS), invertivore (IV), generalist (GE), top predator (TP), yes (Y), and no (N). Tolerant/ Native/ Feeding Lithophilic Site Relative Family/species Common name intolerant introduced category spawner FM1 FM3 FM5 FM6 FM7 FM8 Abundance Catostomidae Suckers Catostomus commersoni Lacepède White Sucker T N OM Y x 0.1 Hypentelium nigricans Lesueur Northern Hogsucker N OM Y x x x x x x 0.5 Centrarchidae Sunfishes Ambloplites rupestris Rafinesque Rock Bass I GE Y x x x x x x 1.6 Lepomis auritus L. Redbreast Sunfish N GE Y x x x 0.4 Lepomis cyanellus Rafinesque Green Sunfish T I GE N x x x x x 1.2 Lepomis gibbosus L. Pumpkinseed T N IV N x 0.2 Lepomis macrochirus Rafinesque Bluegill T I IV N x x 0.2 Micropterus dolomieu Lacepède Smallmouth Bass I TP Y x x 0.2 Cottidae Sculpins Cottus girardi Robins Potomac Sculpin I N IS Y x x x x x x 28.1 Cyprinidae Minnows Campostoma anomalum Rafinesque Central Stoneroller T N AL Y x x x x x 24.2 Cyprinella analostana Girard Satinfin Shiner N OM N x x x 0.5 Exoglossum maxillingua Lesueur Cutlips Minnow I N IS Y x x 0.1 Luxilus cornutus Mitchill Common Shiner N OM Y x x x x x x 5.4 Lythrurus ardens Cope Rosefin Shiner I OM Y x x x x 2.1 2011 M.B. Duncan, S.E. DuRant, B.J.K. Ostby, J.H. Roberts, and J.D. Willson 363 Table 2, continued. Tolerant/ Native/ Feeding Lithophilic Site Relative Family/species Common name intolerant introduced category spawner FM1 FM3 FM5 FM6 FM7 FM8 Abundance Nocomis leptocephalus Girard Bluehead Chub T N OM Y x x x x x x 6.5 Notropis amoenus Abott Comely Shiner N IV Y x 0.2 Notropis hudsonius Clinton Spottail Shiner N IV N x x 2.1 Notropis rubellus Agassiz Rosyface Shiner N IV Y x x x 0.3 Phoxinus oreas Cope Mountain Redbelly Dace I AL Y x x 0.2 Pimephales notatus Rafinesque Bluntnose Minnow I OM N x x x x x 0.7 Rhinichthys atratulus Hermann Blacknose Dace T N IV Y x x x x 3.4 Rhinichthys cataractae Valenciennes Longnose Dace N IV Y x x x x x 5.1 Semotilus corporalis Mitchill Fallfish N GE Y x x x x x 3.0 Ictaluridae Bullhead Catfishes Ameiurus natalis Lesueur Yellow Bullhead T N GE N x 0.7 Noturus insignis Richardson Margined Madtom I N IV N x x x x x 2.0 Percidae Perches Etheostoma blennioides Rafinesque Greenside Darter I I IV Y x x x x 1.6 Etheostoma flabellare Rafinesque Fantail Darter N IS N x x x x x x 9.5 Salmonidae Trout Oncorhynchus mykiss Walbaum Rainbow Trout I I TP Y x 0.2 Salmo trutta L. Brown Trout I I TP Y x 0.1 Total species richness 22 19 18 19 17 8 364 Northeastern Naturalist Vol. 18, No. 3 Table 3. Summary of salamander captures by site within Passage Creek watershed. Site # Species Common name S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13 S14 S15 S16 S17 S18 Total Ambystoma maculatum Shaw Spotted Salamander 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 Notophthalmus viridescens Rafinesque Eastern Newt 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 Hemidactylium scutatum Temminck Four-toed Salamander 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 and Schlegel Eurycea bislineata Green Northern Two-lined Salamander 0 6 0 2 3 1 4 9 12 10 12 15 16 13 32 8 7 13 163 Eurycea longicauda Green Longtail Salamander 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 Desmognathus fuscus Rafinesque Northern Dusky Salamander 0 0 0 0 0 0 3 4 1 3 1 6 3 11 8 15 16 9 80 Pseudotriton ruber Latreille Red Salamander 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 Plethodon cinereus Green Eastern Redback Salamander 0 6 1 0 0 0 0 0 5 0 2 19 0 6 26 6 0 3 74 Plethodon cylindraceus Harlan White-spotted Slimy Salamander 0 1 0 0 0 0 2 1 2 1 0 2 1 2 8 3 5 1 29 Total 0 13 3 2 3 1 9 14 20 14 15 42 20 32 75 34 28 26 351 2011 M.B. Duncan, S.E. DuRant, B.J.K. Ostby, J.H. Roberts, and J.D. Willson 365 particularly low in middle sections of Passage Creek (between S4 and S6). Capture rates ranged from 50 to 150 salamanders per person-hour at many headwater sites, which equates to one or more salamanders under most cover objects overturned. Eurycea bislineata (Northern Two-lined Salamander), Desmognathus fuscus (Northern Dusky Salamander), Plethodon cinereus (Eastern Red-backed Salamander), and Plethodon cylindraceus (White-spotted Slimy Salamander), were all abundant and accounted for 99% of the individual salamanders observed (Table 3). The five other species we observed, Ambystoma maculatum (Spotted Salamander), Notophthalmus viridescens (Eastern Newt), Hemidactylium scutatum (Four-toed Salamander), Eurycea longicauda (Long-tailed Salamander), and Pseudotriton ruber (Red Salamander), each were represented by a single specimen from a single site. In addition to salamanders, we collected or observed one species of turtle (Terrapene carolina L. [Eastern Box Turtle]), one lizard (Sceloporus undulatus Bosc and Daudin [Eastern Fence Lizard]), four anurans (Lithobates catesbeianus (Shaw) [American Bullfrog], Rana clamitans Latreille [Green Frog], Rana palustris LeConte [Pickerel Frog], Pseudacris crucifer Wied-Neuweid [Spring Peeper]), and five snake species (Nerodia sipedon L. [Northern Watersnake], Regina septemvittata Say [Queensnake], Thamnophis sirtalis L. [Eastern Gartersnake], Lampropeltis triangulum Lacépède [Eastern Milksnake], Diadophis punctatus L. [Ring-necked Snake]). Mollusk sampling The native Elliptio complanata Lightfoot (Eastern Elliptio) was the only mussel species that we collected in Passage Creek (Table 4). Of the eight sites surveyed, Eastern Elliptio was observed at the middle four sites (Sites FM3, M4, FM5, and FM6), but not at the downstream- or upstream-most sites (Sites FM1, M2, FM7, and FM8). Mussel catch-per-unit-effort (CPUE) ranged from 3.0 to 13.5 mussels per person-hour among occupied sites. The greatest mussel density was recorded at Site 7, where we observed more than 50 individuals in Table 4. Mollusk species encountered in Passage Creek and catch per unit effort at each site (average number of individuals observed per person-hour effort). Elliptio Campeloma Leptoxis Site complanata Mussel/person-hour decisum carinata FM1 - - - Abundant M2 - - Rare Abundant FM3 31 8.27 Shell Abundant M4 81 13.5 Rare Abundant FM5 14 3.5 Rare Abundant FM6 6 3 Shell Abundant FM7 - - - Common FM8 - - - Common 366 Northeastern Naturalist Vol. 18, No. 3 an approximately 2-m2 area. Mussels were most abundant along sandbars near vegetation, large woody debris, and stream banks. We also observed two species of native aquatic snails, Campeloma decisum Say (Pointed Campeloma) and Leptoxis carinata Bruguiére (Crested Mudalia), and one non-native bivalve, Corbicula fluminea Müller (Asian Clam). Crested Mudalia and Asian Clams occurred in riffle and run habitats, whereas Pointed Campeloma occurred in low-velocity pools along the stream banks and channel margins. Discussion Overall, the PCW appears to support fish and salamander assemblages structurally and functionally consistent with watersheds that exhibit high biological condition in the region (McCormick et al. 2001, Southerland et al. 2004), and may serve as an important center of biodiversity in a largely degraded region experiencing rapid human population growth (Elmore and Guinn 2010, Masek et al. 2000) and degraded water quality (Eggleston 2009). Fish assemblages, for example, were relatively speciose compared to similar-sized watersheds in the region (Roth et al. 2000) and included regionally uncommon species (e.g., Cutlips Minnow, Margined Madtom). Fish assemblages also contained an abundance of benthic species (e.g., Potomac Sculpin, Fantail Darter, Longnose Dace) and herbivores (Central Stoneroller), indicating a low impact of siltation in Passage Creek (Berkman and Rabeni 1987). We estimated that 40% of the overall fish species diversity of the Potomac basin is present in the PCW. The Potomac River basin has experienced widespread anthropogenic disturbances, which have threatened fish diversity throughout the river system (Starnes 2002). The PCW therefore may serve a vital role as a refuge and/or source of colonists for the larger Potomac basin. Fish species richness in PCW peaked in the most downstream site, indicating the potential for a migratory connection (sensu Roberts and Hitt 2010) between Passage Creek and its much-larger receiving river, the North Fork Shenandoah River. Like fishes, salamanders were relatively speciose in the PCW. We observed nearly all of the stream-dwelling salamander species potentially occurring in the PCW (Mitchell and Reay 1999). Most of the salamander species that we did not document either use habitats that were not surveyed (e.g., vernal pools) or are generally associated with higher elevations than are present in the PCW. Those species include two pond-breeding species not targeted with our surveys (Ambystoma opacum Grayenhorst [Marbled Salamander] and Ambystoma jeffersonianum Green [Jefferson Salamander]), two terrestrial species that are generally restricted to high elevations of the Ridge and Valley physiographic region (Plethodon hoffmani Highton [Valley and Ridge Salamander] and Plethodon punctatus Highton [Cow Knob Salamander]), and two streamdwelling species (D. monticola Dunn [Seal Salamander] and Gyrinophilus porphyriticus Green [Spring Salamander]). Our surveys within the PCW 2011 M.B. Duncan, S.E. DuRant, B.J.K. Ostby, J.H. Roberts, and J.D. Willson 367 revealed that the stream headwaters supported high salamander abundances, including many individuals of “intolerant” species, e.g., the Northern Dusky Salamander, indicating high overall stream health. In contrast, at three low-elevation sites (S4–S6) located in the middle of the PCW, no intolerant species were found, and only a few of the tolerant species were detected. We collected only small numbers of Northern Two-lined Salamander, a highly tolerant species at these sites. Low densities of “tolerant” salamanders also suggest that these sites may be somewhat degraded. Although the most downstream sections of Passage Creek (Sites S1–S3) are of higher order than streams that typically have high salamander abundance, the presence of two “intolerant” species that were not recorded elsewhere in the watershed (Red Salamander and Long-tailed Salamander) indicates that this portion of the watershed maintains relatively high habitat and water quality. In the Appalachian region of the eastern United States, salamanders are diverse and exhibit a variety of trophic and life-history strategies. Assessment of salamander assemblages can provide information about stream health that is complementary to information provided by fish (Moyle et al. 1986). For example, whereas fish assemblages tend to reach greater diversity in downstream areas of watersheds, salamander assemblages tend to be more abundant and diverse in stream headwaters (Corn et al. 2003). Unlike fish and mussel taxonomic and functional diversity, which provide a poor indicator of headwater stream health (Fausch et al. 1984), amphibian diversity holds a stronger potential in lower order streams (Southerland et al. 2004). Furthermore, many amphibians, including salamanders, use both terrestrial and aquatic habitats and are particularly sensitive to loss of connectivity between the two environments (Becker et al. 2007, Corn et al. 2003, Willson and Dorcas 2003), which often results from degraded riparian corridors. Much attention has recently been placed on the importance of headwater streams and their terrestrial linkages to water quality and biodiversity (Lowe et al. 2006, Meyer et al. 2007, Nakano et al. 1999), indicating the value of properly assessing these areas of a watershed. We collected only one mussel species, the Eastern Elliptio, in the PCW. A recent museum and literature search suggests that Passage Creek may have supported at least two additional mussel species in the recent past, Alasmidonta undulata Say (Triangle Floater) and Lasmigona subviridis Conrad (Green Floater) (Chazal 2009). Chazal (2009) also found evidence that a total of seven species once inhabited the North Fork Shenandoah River watershed. Although we only detected one mussel species, the presence of any mussels is noteworthy given their extensive decline throughout the Shenandoah watershed (Chazal 2009). Mussel species richness in the PCW does not appear to be limited by a lack of fish hosts, given the diverse assemblage of known fish hosts we captured, so another cause, such as past human disturbances, are likely responsible for the decreased species richness. To our knowledge, this survey is the most comprehensive conducted in Passage Creek. The limited species richness we observed reflects the collapse of the mussel fauna of the greater Shenandoah River watershed 368 Northeastern Naturalist Vol. 18, No. 3 (Chazal 2009); however, at one site we observed a relatively high density of mussels as compared to the observations reported by Chazal (2009). This observation of high mussel density indicates the PCW maintains a greater level of ecological condition than surrounding watersheds. Our survey of the PCW indicated that this watershed supports a diverse group of organisms, some of which are rare in the Potomac basin. The broad taxonomic focus of our survey of biodiversity in the PCW provides greater insight than if we had limited our inventory to a single taxonomic group. Species richness varied spatially among taxa: fish richness peaked in downstream sites, whereas salamander richness peaked at upstream sites and mussels were captured only in middle sites. The presence and relative richness of rare and native species within the watershed indicate that the PCW provides critical habitat for many species that have experienced declines elsewhere in the Potomac basin and that this watershed is a good candidate for future conservation efforts (e.g., Potomac Conservancy 2008). Acknowledgments This study was funded by the Potomac Conservancy as part of a larger project aimed at increasing public awareness of biodiversity and initiating conservation efforts within the watershed. We thank Seth Coffman for considerable logistical assistance with field work; and Dan Dutton, Seth Coffman, Megan Bradley, Amy Bush, and Daniel Weaver for assistance with sampling. E. Rosi-Marshall and two anonymous reviewers provided valuable comments on a draft of the manuscript. Literature Cited Becker, C.G., C.R. Fonseca, C.F.B. Haddad, R.F. Batista, and P.I. Prado. 2007. Habitat split and the global decline of amphibians. Science 318:1775–1777. Benz, G.W., and D.E. Collins. 1997. Aquatic Fauna in Peril: The Southeastern Perspective. Special publication 1, Southeast Aquatic Research Institute. Lenz Design and Communications, Decatur, GA. 554 pp. Berkman, H.E., and C.F. Rabeni. 1987. Effect of siltation on stream fish communities. Environmental Biology of Fishes 18:285–294. 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