The Ecology, Distribution, Conservation, And

The Pennsylvania State University

The Graduate School

Intercollege Graduate Degree Program in Ecology

THE ECOLOGY, DISTRIBUTION, CONSERVATION,

AND MANAGEMENT OF PENNSYLVANIA’S SURFACE-DWELLING

CRAYFISH FAUNA WITH AN EMPHASIS ON THE EASTERN PART OF

THE STATE

A Dissertation in

Ecology

David Andrew Lieb

Submitted in Partial Fulfillment of the Requirements for the Degree of

Doctor of Philosophy

December 2011

The dissertation of David Andrew Lieb was reviewed and approved* by the following:

Robert F. Carline Retired Adjunct Professor of Wildlife and Fisheries Science Dissertation Advisor Co-Chair of Committee

Eric Post Professor of Biology Co-Chair of Committee

Hunter J. Carrick Professor of Aquatic Biology

James L. Rosenberger Professor of Statistics

Katriona Shea Professor of Ecology

David Eissenstat Professor of Woody Plant Physiology Chair of the Intercollege Graduate Degree Program in Ecology

*Signatures are on file in the Graduate School.

Abstract

Although crayfish have long been the object of scientific inquiry and where studied appear to be functionally (ecologically) important, much remains to be learned about their ecology, distribution, and conservation. Even the most basic information (presence/absence data) is lacking for the majority of species. The absence of adequate crayfish data is a major problem, because many species are thought to be imperiled across all or parts of their range and even species that were once widely distributed are rapidly disappearing. Anthropogenic disturbances, especially crayfish introductions, appear to be responsible for many of these losses. The replacement of native crayfish by introduced (exotic) crayfish represents a significant threat to aquatic communities because introduced crayfish often become extremely abundant and can destroy aquatic macrophyte beds, suppress benthic invertebrate communities, reduce fish abundance and biomass, and negatively affect amphibian populations.

At the turn of the 20th century, Arnold E. Ortmann published a monograph describing the crayfish fauna of Pennsylvania. Since then, very few crayfish studies have been published from the state. The need to re-examine Pennsylvania‘s crayfish fauna and the opportunity to revisit previously sampled areas to assess changes in the state‘s crayfish fauna over the past century motivated much of this work. The need for basic ecological and conservation information regarding Pennsylvania‘s crayfish fauna, as well as specific strategies for managing the state‘s native species, provided further motivation. To fulfill these needs, I conducted a series of crayfish studies in Pennsylvania. The findings of these studies and others were then utilized to address a broader ecological question: what determines surface-dwelling crayfish community structure?

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I first found that a previously unstudied, widely distributed assemblage of crayfishes

(Cambarus bartonii bartonii and Orconectes obscurus) inhabiting Spruce Creek in central

Pennsylvania had strong top-down effects on other invertebrates and reduced total invertebrate density by 70%. Crayfish were in turn readily consumed by brown trout (Salmo trutta), especially large trout ( 275 mm total length). Next, I surveyed Valley Creek in southeastern

Pennsylvania for crayfishes and discovered a rare species of crayfish [Cambarus

(Puncticambarus) sp., an undescribed member of the Cambarus acuminatus complex] that had not previously been reported from the state. The basic life history characteristics, reproductive status, and habitat preferences of C. (P.) sp. are described herein. Additional surveys in southeastern Pennsylvania and comparisons of these results to historical data indicated that exotic crayfishes have invaded many parts of the region, much of which no longer supports native crayfishes. In addition, populations of C. (P.) sp. were discovered from three more streams and are now known from a total of four streams in Pennsylvania, all of which are threatened by urbanization and exotic crayfishes. This information, in combination with other historical and contemporary data from Pennsylvania and nearby states collected for this study and other studies, indicate that C. (P.) sp. is critically imperiled in Pennsylvania and possibly across its range and that the range of another native Pennsylvania crayfish, Orconectes limosus, has declined (retreated eastward) by > 200 km in Pennsylvania and northern Maryland, likely as a result of exotic crayfishes. Although C. b. bartonii was found with exotic crayfishes in a number of water bodies in Pennsylvania, it was typically a minor component of the crayfish community and may not be able to persist in those systems indefinitely. An examination of potential determinants of surface-dwelling crayfish community structure suggests that a combination of local, regional, and historical processes operating across a variety of temporal

iv and spatial scales shape these communities. More specifically, the interplay of competition with environmental conditions appears to limit the number of species that can occur in local communities, whereas regional, historical, and more recently human influences likely determine potential component species.

In light of these findings, the role of barriers (e.g., dams), environmental protection, educational programs, and regulations in preventing crayfish invasions and conserving native crayfishes is discussed and management initiatives centered on those factors are presented. The need for methods to eliminate exotics and monitor natives is highlighted. Although tailored to a specific regional fauna, the ideas presented in this dissertation have broad applicability and would likely benefit many of North America‘s crayfishes and the ecosystems in which they reside.

Table of Contents

List of Figures ...... ix List of Tables ...... xi Acknowledgments...... xii Chapter 1 Introduction ...... 1 References ...... 5 Chapter 2 The Functional Importance of Crayfish in a Mid-Atlantic Trout Stream ...... 14 Abstract ...... 14 Introduction ...... 14 Study Area ...... 16 Study Animals ...... 17 Materials and Methods ...... 17 Caging Study ...... 17 Trout Gut Contents ...... 21 Data Analysis ...... 21 Results and Discussion ...... 22 Acknowledgments ...... 25 References ...... 25 Chapter 3 The Discovery and Ecology of a Member of the Cambarus acuminatus Complex (Decapoda: Cambaridae) in Valley Creek, Southeastern Pennsylvania ...... 36 Abstract ...... 36 Introduction ...... 37 Materials and Methods ...... 40 Study Area ...... 40 Crayfish Collections ...... 40 Habitat Measurements ...... 43 Data Analysis ...... 43 Results and Discussion ...... 46 Taxonomy ...... 46 Community Composition ...... 47

Life History Characteristics ...... 48 Habitat Associations ...... 56 Conservation Status and Future Directions ...... 62 Acknowledgements ...... 63 References ...... 63 Chapter 4 Crayfish Fauna of Southeastern Pennsylvania: Distributions, Ecology, and Changes over the Last Century ...... 80 Abstract ...... 80 Introduction ...... 81 Materials and Methods ...... 83 Contemporary Data ...... 83 Historical Data ...... 87 Results and Discussion ...... 88 Taxonomy of C. (P.) sp. in Pennsylvania ...... 88 Overview of Crayfish Collections ...... 88 Contemporary Distributions and Range Changes ...... 90 Crayfish Associations ...... 100 Community Composition ...... 102 Concluding Remarks and Conservation Implications ...... 103 Acknowledgements ...... 104 References ...... 104 Chapter 5 Conservation and Management of Crayfishes: Lessons from Pennsylvania ...... 126 Abstract ...... 126 Introduction ...... 127 Materials and Methods ...... 128 Assessing Changes at Individual Sites and Across the Landscape ...... 128 Conservation Classifications ...... 130 Conservation Classifications ...... 131 Cambarus (P.) sp...... 131 Orconectes limosus ...... 134 Cambarus b. bartonii ...... 137

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Management Needs and Implications ...... 138 Crayfish Ban ...... 138 Education and Outreach ...... 141 Role of Dams, Temperature, and Nutrients ...... 142 Eliminating Exotics ...... 145 Reducing Environmental Degradation ...... 147 Additional Sampling ...... 149 Acknowledgments ...... 150 References ...... 150 Chapter 6 Determinants of Crayfish Community Structure ...... 175 Introduction ...... 175 The Combined Influence of Local, Regional, and Historical Factors ...... 177 Local Influences ...... 178 Regional and Historical Influences ...... 181 Concluding Remarks ...... 182 References ...... 183

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List of Figures

Figure 2.1. Map of the experimental pool in the lower reaches of Spruce Creek showing the approximate positions of the cages, debris shields, and uncaged control during the caging experiment...... 33

Figure 2.2. Mean (±1SE) invertebrate densities on bricks collected from cages with crayfish (enclosures, □), cages without crayfish (exclosures, ●), and an uncaged control (▲) prior to adding crayfish to enclosures (pre-sampling) and 32 days after crayfish addition (post- sampling)...... 34

Figure 2.3. Percent of wild brown trout collected from the lower reaches of Spruce Creek that had crayfish in their stomachs at the time of capture...... 35

Figure 3.1. Map of the eastern United States from Pennsylvania to South Carolina with an enlargement of the study area...... 75

Figure 3.2. Length-frequency distribution of C. (P.) sp. collected from Valley Creek in 2003. ...76

Figure 3.3. Relationship between the % of the sampling area where cobble was either the dominant or co-dominant substrate type (% cobble) and C. (P.) sp. density (no./m2) in main-channel areas of pools...... 77

Figure 3.5. Relationship between current velocity and C. (P.) sp. density (no./m2) in lateral (♦) and main-channel (O) areas of riffles...... 79

Figure 4.3. Map of the study area and nearby regions in southeastern Pennsylvania. Occurrences of C. b. bartonii, O. limosus, introduced Orconectes (O. obscurus, O. rusticus, O. virilis), and introduced Procambarus (P. acutus, P. clarkii) are shown on the map...... 124

Figure 4.4. Map of the study area and nearby regions in southeastern Pennsylvania. Occurrences of O. obscurus, O. rusticus, O. virilis, P. acutus, and P. clarkii are included on the map...... 125 ix

Figure 5.1. Map of Pennsylvania with historical and contemporary crayfish collection sites. ...169

Figure 5.2. Map of eastern Pennsylvania with historical and contemporary O. limosus collection sites...... 170

Figure 5.3. Map of eastern Pennsylvania with historical and contemporary O. obscurus collection sites...... 171

Figure 5.4. Map of eastern Pennsylvania with O. rusticus collection sites...... 172

Figure 5.5. Map of eastern Pennsylvania with O. virilis collection sites...... 173

Figure 5.6. Map of eastern Pennsylvania with historical and contemporary C. b. bartonii collection sites...... 174

List of Tables

Table 1.1. List of Pennsylvania crayfish species...... 13

Table 2.1. Comparison of invertebrate densities between treatments (enclosures vs exclosures) and sampling periods (pre-sampling vs post-sampling) using a repeated-measures, three- factor ANOVA with pair as a blocking factor...... 32

Table 3.1. Physical characteristics of electrofished areas in Valley Creek...... 72

Table 4.1. Contemporary (1968-2007) crayfish collections at individual sampling sites in southeastern Pennsylvania...... 116

Table 4.2. Comparison of contemporary (1968-2007) crayfish collections from the northern part of the study area (northern sites) to those from the southern part of the study area (southern sites)...... 121

Table 5.2. Historical and contemporary crayfish collections from resampled sites in the Susquehanna (S) and Potomac (P) River drainages of Pennsylvania...... 167

Table 5.3. Conservation classifications for several of eastern Pennsylvania's native crayfishes...... 168

Acknowledgments

The completion of this dissertation would not have been possible without the help and encouragement of many family members, co-workers, and colleagues. Throughout my graduate studies, I never doubted my wife‘s sincere belief in me and in the value of my research, which was a source of continual encouragement. Not many wives would have understood the value of my work or stuck by me to see it to completion. She also endured many long days and nights holding down the fort while I focused on my research efforts and she skillfully reviewed many of my reports and papers and helped format my dissertation. My wonderful daughters were, and continue to be, a constant source of inspiration, always asking about what I had discovered and when possible visiting me at field sites and joining me on collection trips. I couldn‘t ask for two more perfect daughters. My parents were always there for me – providing constant encouragement and support throughout this project. They also gave up huge chunks of their own time to help me in the field during the caging study portion of my research. All while working very demanding jobs themselves. Very few (if any) parents would have made the many, many sacrifices that they made for me. I would also like to thank my grandparents and great uncle and aunt who did not live to see me complete this degree but who provided me with continual encouragement and support and always emphasized the value of education. They lost everything several times due to wars and the great depression and always told me ―they can take all your possessions David but they can‘t take what‘s in your head.‖ This thesis required hard work, determination, and persistence, all of which I learned from my parents. For all these contributions, I can‘t thank my family enough.

I also greatly appreciate the many contributions of my thesis advisor, Robert F.

Carline, who I always felt believed in my abilities and gave me the freedom to pursue my own interests and develop as a researcher. He has been a great mentor for me throughout my graduate studies and I have very much enjoyed working with him over the years. Raymond W. Bouchard,

xii although not officially a member of my graduate committee, provided excellent advice and assistance throughout much of this project. I am greatly indebted to him. Eric Post very kindly agreed to serve as co-chair after Bob Carline‘s retirement and provided some important initial thoughts that eventually led to Chapter 6. James L. Rosenberger provided statistical advice, which was very much appreciated. My other committee members, Katriona Shea and Hunter J. Carrick also deserve thanks for their contributions to my graduate studies.

Co-workers at Penn State, especially Jeremy Harper, Nellie Bhattarai, Hannah M. Ingram, V.

Malissa Mengel, Paula Mooney, Adam Smith, Kristin Babcock, Jonathan Freedman, Patrick

Kocovsky, Patrick Barry, Christa Walker and her husband, Brianna Hutchison, and Dan Counahan provided extremely valuable assistance during this project and were a great group of people to work with. Many of them worked extremely hard in the field and the lab during this project. Kay Christine was always there to help in many ways – I can‘t thank her enough for all she has done for me over the years. The support of the Pennsylvania Cooperative Fish and Wildlife Research Unit, especially

Duane Diefenbach, was of critical importance and is very much appreciated. Financial support was provided by several institutions, and a number of colleagues assisted with various aspects of this project, all of which are detailed in the acknowledgments sections of the reports and peer-reviewed papers resulting from this work. Many thanks to all of you.

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Chapter 1

Introduction

Crayfish occur naturally on every continent except Africa and Antarctica; however, their diversity peaks in North America, where 400+ species and subspecies reside (Taylor 2002,

Taylor et al. 2007). Over two-thirds of these species and subspecies occur in the southeastern

United States, many of which are endemic to the region and appear to have arisen due to the isolating effects of pre- and post-Pleistocene shifts in river drainages (Crandall and Templeton

1999, Taylor et al. 2007, Crandall and Buhay 2008).

Although crayfish have long been the object of scientific inquiry (see Huxley 1879), much remains to be learned about the group. In North America, surprisingly little is known about the ecology of most species. Although existing studies indicate that crayfish often account for a major portion of macroinvertebrate biomass and production (Huryn and Wallace 1987, Momot

1995, Rabeni et al. 1995, Whitledge and Rabeni 1997, Dorn and Mittelbach 1999) and can affect energy flow along multiple pathways, interact strongly with other invertebrates and primary producers, and constitute an important food item for vertebrates including fishes, mammals, birds, reptiles, and amphibians (see Rabeni 1992, Hobbs 1993, Roell and Orth 1993, Nyström

2002, Wilson et al. 2004, Geiger et al. 2005, McCarthy et al. 2006, Nyström et al. 2006, Gherardi and Acquistapace 2007, Britton et al. 2010, Tetzlaff et al. 2011, and references within), too few data are available to assume their importance in all systems, especially given the inherent biological differences among crayfish species and the wide range of habitats (e.g., caves, swamps, lakes, streams, rivers, estuaries) that they occupy (Nyström 2002). To date, commercially-important, widely-introduced species such as the red swamp crayfish

(Procambarus clarkii), rusty crayfish (Orconectes rusticus), and signal crayfish (Pacifastacus leniusculus) have been the focus of most research efforts, whereas other North American species have been neglected.

Even the most basic ecological information (presence/absence data) is lacking for the majority of North American crayfish species. For example, Taylor et al. (2007) estimated that current distributional information is available for only 40% of the United States and Canadian fauna. Even where adequate contemporary data are available, the absence or scarcity of historical collections, particularly for large geographical areas (entire states), often makes it difficult to assess long-term changes across landscapes. Without such data it is hard to accurately classify individual species (endangered, threatened, stable) and develop conservation strategies for those in decline (Jones et al. 2005, Taylor et al. 2007).

The absence of adequate crayfish data is a major problem, because many North American species have limited distributions, are threatened by exotic (introduced) crayfish, habitat destruction, pollution, urbanization, and other human influences, and are thought to be imperiled across all or parts of their range (Master 1990, Taylor et al. 1996, Hamr 1998, Master et al. 1998,

Master et al. 2000, Wilcove et al. 2000, Lodge et al. 2000, Taylor 2002, Taylor et al. 2007). Even species that were once widely distributed are rapidly disappearing due to anthropogenic disturbances, especially crayfish introductions (Hamr 1998, Bouchard et al. 2007, Loughman et al. 2009, Kilian et al. 2010, Swecker et al. 2010, Lieb et al. 2011a, b), which typically result from intentional stocking efforts, dispersal via man-made canals, and the release or escape of fishing bait, aquarium and pond pets, and classroom, laboratory and aquaculture species (see Lodge et al. 2000, Taylor et al. 2007).

The replacement of native crayfish by introduced crayfish is believed to occur as a result of competition for shelter and food, differential susceptibility to fish predators, and/or reproductive interference and hybridization (Didonato and Lodge 1993, Hill et al. 1993, Garvey et al. 1994, Hill and Lodge 1994, Lodge et al. 2000, Perry et al. 2001). In some systems, replacements appear to occur rapidly (likely in <10 years) and interactions between exotic and resident crayfishes can result in injuries to residents (D.A. Lieb, PSU, personal observations).

Based on existing information, it appears that successful crayfish invasions do not require vacant niches (Hill et al. 1993). It also appears that, at the scale of individual streams, introduced crayfish do not always have wider niches than their native counterparts, although at larger, regional scales some invaders do have wider niches, allowing them to occupy a greater variety of stream types (Olsson et al. 2009).

The replacement of native crayfish by exotic crayfish represents a significant threat to aquatic communities because densities of introduced crayfish can approach 200 individuals/m2

(Roth and Kitchell 2005) and are often an order of magnitude higher than their native counterparts. At such high densities, introduced crayfish frequently destroy aquatic macrophyte beds and suppress benthic invertebrate communities (Lodge et al. 1994, Nyström 2002,

McCarthy et al. 2006). In addition, introduced crayfish tend to be less vulnerable to fish predation than native crayfish because many introduced crayfish quickly grow to a size that reduces their susceptibility to predation, possess large chelae, and are aggressive (Didonato and

Lodge 1993, Mather and Stein 1993, Garvey et al. 1994, Roth and Kitchell 2005). Introduced crayfish also readily consume fish eggs and can have strong negative effects on fish reproduction

(Dorn and Mittelbach 2004, Dorn and Wojdak 2004). The end result for affected fish populations

3 is often less food, decreased recruitment (Covich et al. 1999), and ultimately reduced abundance and biomass (Wilson et al. 2004, Roth et al. 2007, Bobeldyk and Lamberti 2010).

Introduced crayfish have also been implicated in global amphibian declines (Kats and

Ferrer 2003) and have strong negative effects on a variety of amphibian species. For example, introduced crayfish have been shown to readily consume the eggs and larva of California newts and have been implicated in their disappearance from streams in the Santa Monica Mountains

(Gamradt and Kats 1996). Introduced crayfish have also been associated with ranid frog disappearances in Arizona (Witte et al. 2008), declines in Pacific tree frog abundance in

California (Riley et al. 2005), and decreased salamander breeding success and amphibian species richness in southwestern Portugal (Cruz et al. 2006).

In Pennsylvania, although contemporary data are scarce and mostly unpublished, historical collections dating back more than 100 years are available for large areas of the state

(Ortmann, 1906). Ortmann‘s monograph is one of the most thorough and important crayfish studies ever conducted and one of the few large-scale surveys of its vintage from North America.

Nonetheless, given that over 100 years have passed since Ortmann‘s study, a reexamination of

Pennsylvania‘s crayfish fauna is overdue. It is important to note that the availability of historical data from Ortmann (1906) provided me the unique opportunity to revisit previously sampled areas to assess changes in Pennsylvania‘s crayfish fauna over the past century.

From this discussion, it is clear that much remains to be learned about the ecology, distribution, and conservation of North America‘s crayfish fauna. The main objective of this study is to address this need for some of eastern Pennsylvania‘s surface-dwelling crayfishes and in the process provide up-to-date information regarding the state‘s fauna. A list of the surface- dwelling crayfish species that currently occur in eastern Pennsylvania, their status in the state

(native, exotic), and the location of voucher material deposited in museums during this study is provided in Table 1.1.

To meet the objective of this study, I first assessed the functional (ecological) importance of a previously unstudied, widely distributed assemblage of crayfishes (Cambarus bartonii bartonii and Orconectes obscurus) inhabiting a mid-sized stream in central Pennsylvania by using caging studies and dietary information to determine if these crayfishes affect the density of other invertebrates and are an important food item for brown trout (Salmo trutta). I then determined the basic life history characteristics, reproductive status, and habitat preferences of a rare species of crayfish inhabiting Valley Creek in southeastern Pennsylvania. Next, I determined the distribution and ecology of southeastern Pennsylvania‘s crayfish fauna and compared those findings to those of Ortmann (1906) to estimate change over the last century. I then utilized a combination of historical and contemporary data from Pennsylvania and nearby states collected for this study and others to determine the conservation status of several native crayfishes and develop management strategies for those species. Finally, I utilized the findings of this study and others to address a broader ecological question: what determines surface-dwelling crayfish community structure?

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Table 1.1. List of surface-dwelling crayfish species that are currently found in the eastern half of Pennsylvania. The status of each species is either native to all or part of Pennsylvania (N) or not native (exotic) to the state (E). Representative voucher specimens collected by the author and colleagues were deposited in museums (Repositories). Cambarus robustus and Orconectes propinquus specimens were vouchered as a part of another study (Bouchard et al. 2007); a

Procambarus acutus specimen from southeastern Pennsylvania is in the United States

National Museum, Smithsonian Institution crayfish collection. NCSM=North Carolina State

Museum of Natural Sciences, ANSP=Academy of Natural Sciences of Philadelphia,

OSU=Ohio State University Museum, CM=Carnegie Museum of Natural History. See the

Materials and Methods sections of Chapters 3 and 4 for catalog numbers.

Species Status Repositories

Cambarus (Puncticambarus) sp.1 N NCSM, OSU, CM, ANSP

Cambarus bartonii bartonii N ANSP

Cambarus robustus N -

Orconectes limosus N ANSP

Orconectes obscurus N ANSP

Orconectes propinquus N -

Orconectes rusticus E ANSP

Orconectes virilis E ANSP

Procambarus acutus N -

Procambarus clarkii E ANSP

1An undescribed member of the Cambarus acuminatus species complex

Chapter 2

The Functional Importance of Crayfish in a Mid-Atlantic Trout Stream

Abstract

Although crayfish are often assumed to be functionally (ecologically) important, only a handful of North America‘s 400+ species and subspecies have been well studied. To address this deficiency, I used caging studies and dietary information to assess the functional importance of a previously unstudied assemblage of crayfishes (C. b. bartonii and O. obscurus) inhabiting a midsized stream (Spruce Creek) in eastern North America. I found that crayfishes had strong top- down effects on other invertebrates and reduced total invertebrate density by 70%. Crayfish were in turn readily consumed by brown trout (Salmo trutta), especially large trout ( 275 mm total length). These results indicate that crayfish are functionally important in Spruce Creek, facilitating the transfer of nutrients up the food chain to a recreationally-valuable fish species, and add to the growing body of information that suggests that crayfish are functionally important wherever they occur and are deserving of policy directed at their preservation.

Introduction

Although North America is home to a diverse crayfish fauna (400+ species and subspecies) that is highly threatened by human activities (Master et al. 1998, Wilcove et al. 1998,

Lodge et al. 2000, Taylor et al. 2007), our understanding of their functional (ecological) role in aquatic systems is limited to a handful of species, most of which are native to the Midwest and

West (e.g., O. rusticus, P. clarkii, and P. leniusculus). Few of eastern North America‘s crayfishes have been studied.

Where examined, crayfish often account for a major portion of macroinvertebrate biomass and production (sometimes > 50%) (Huryn and Wallace 1987, Momot 1995, Rabeni et al. 1995, Whitledge and Rabeni 1997, Dorn and Mittelbach 1999), exert direct and indirect effects on basal resources (detritus, algae, macrophytes) and other invertebrates (see Nyström

2002, Wilson et al. 2004, Geiger et al. 2005, McCarthy et al. 2006, Gherardi and Acquistapace

2007, and references within), and are an important food item for fishes, including recreationally and commercially important species (Rabeni 1992, Roell and Orth 1993, Nyström et al. 2006,

Britton et al. 2010, Tetzlaff et al. 2011). Crayfish are also readily consumed by a variety of other vertebrates including mammals, birds, reptiles, and amphibians (Hobbs 1993). Based on these studies, it is tempting to conclude that crayfishes are functionally important wherever they occur, affecting energy flow along multiple pathways and facilitating the transfer of nutrients up through the food chain to fishes and other vertebrates; however, too few data are available for such generalizations, especially given the inherent biological differences among crayfish species and the wide range of habitats (e.g., caves, swamps, lakes, streams, rivers, estuaries) that they occupy (Nyström 2002).

The objective of this study was to assess the functional importance of a previously unstudied assemblage of crayfishes (C. b. bartonii and O. obscurus) inhabiting a mid-sized stream in eastern North America by determining if these crayfishes affect the density of other invertebrates and are an important food item for brown trout (Salmo trutta).

Study Area

This study was conducted in Spruce Creek, which is located in the Valley and Ridge

Physiographic Province of the Appalachian Mountains in central Pennsylvania and is in the

Susquehanna River drainage. The climate of the region is temperate and yearly precipitation averages approximately 98 cm. Spruce Creek originates from limestone springs and flows for approximately 26 km through mostly forest and agricultural land before emptying into the Little

Juniata River (Carline 2001).

Spruce Creek is a mid-sized (~5-12 m wide), alkaline stream (~150 mg CaCO3/L) with temperatures that generally range from 3-20 °C, nitrate and ortho-phosphorous concentrations that average 3.2 and 0.02 mg/L, respectively, and conductivities near 280 uS/cm [Bachman 1984,

Carline 2001, and R.F. Carline, United States Geological Survey (USGS), The Pennsylvania

State University (PSU), unpublished data]. Discharge averages about 1.7-2.8 m3/s (Bachman

1984, R.F. Carline, USGS, PSU, unpublished data) and the stream bottom is primarily cobble intermixed with gravel.

Study sites were within Penn State University‘s George W. Harvey Experimental

Fisheries Research Area (PSU Research Area), which is located in the lower reaches of Spruce

Creek, approximately 1 km upstream of the Little Juniata River. Total crayfish densities in pools in lower Spruce Creek range from 22±1 individuals/m2 (mean±1SE, n=4) in rocky areas to 39±7 individuals/m2 (mean±1SE, n=6) in lateral, silty areas with shoreline root masses and/or vegetation (D.A. Lieb, PSU, unpublished data). Densities of juvenile crayfish range from 10±2 individuals/m2 in rocky areas to 26±5 individuals/m2 in lateral areas. Densities of adult crayfish range from 12±3 individuals/m2 in rocky areas to 13±4 individuals/m2 in lateral areas (D.A.

Lieb, PSU, unpublished data). Two crayfish species (C. b. bartonii and O. obscurus) occur in lower Spruce Creek; O. obscurus is the dominant species in pools (relative abundance=76-99%, n=619) (D.A. Lieb, PSU, unpublished data), whereas C. b. bartonii is the dominant species in riffles (D.A. Lieb, PSU, personal observations). Wild brown trout (Salmo trutta) are common in lower Spruce Creek (Carline 2001).

Study Animals

Orconectes obscurus is native to western Pennsylvania (Ohio River, Genesee River, and

Lake Erie drainages) and nearby states (Ortmann 1906, Hobbs 1989) but has been widely introduced in Pennsylvania and now occurs throughout the state (Bouchard et al. 2007, Lieb et al. 2011a, b). The native range of C. b. bartonii extends from Canada southward to Georgia and includes the Delaware, Potomac and Susquehanna River drainages in eastern Pennsylvania

(Hobbs 1989, Thoma and Jezerinac 1999). Orconectes obscurus and C. b. bartonii often co- occur in Pennsylvania (Lieb et al. 2011a) and elsewhere (Jezerinac et al. 1995, Hamr 1998,

Kuhlmann and Hazelton 2007) and are frequently found in streams with brown trout (D.A. Lieb,

PSU, personal observations). Cambarus b. bartonii is native to Spruce Creek, whereas O. obscurus was probably introduced to the stream.

Materials and Methods

Caging Study

Basic Design and Experimental Setup. — A 34-day caging experiment with two treatments [cages with crayfish (enclosures), cages without crayfish (exclosures)], each

17 replicated five times, and one uncaged control (Figure 2.1) was conducted to determine whether crayfish affect benthic invertebrate density in Spruce Creek. The experiment was carried out from 17 September-20 October 2002 in a large pool (~80 m long × 12 m wide, hereafter referred to as the experimental pool) at the upstream end of the PSU Research Area. I used a randomized complete block design, because there was considerable within pool variability in the benthic invertebrate assemblage. Within each of the five blocks (pairs), cages were placed side by side

(<1 m apart) in similar habitats. Differences in flow, depth, and light levels between treatments were <0.01 m/s, <0.05 m, and <56 µmole quanta m-2 s-1, respectively for all pairs. Debris shields constructed of 6-mm wire mesh were placed 2-3 m upstream of each pair to provide protection and reduce debris accumulation. Pairs of cages were spaced fairly evenly across the pool in a longitudinal (upstream-downstream) direction with 16-28 m between pairs.

The cages consisted of square wooden frames (0.84 m2) equipped with metal screens (6- mm mesh) on the bottom and each of the sides. The tops of the cages were open. Six-millimeter mesh was selected because it retains/excludes all but the smallest crayfish while allowing most other invertebrates to move in and out of the cages freely (Hart 1992). A mixture of bricks (12 per cage) and landscaping gravel (0.04 m3 per cage) was added to the cages to mimic the dominant substrates (cobble and gravel) in Spruce Creek. Bricks were conditioned for about one week in Spruce Creek before being placed in cages; bricks and gravel were evenly distributed across the bottoms of the cages. Cages were assembled and placed in the experimental pool on 9

September 2002, eight days prior to the start of the experiment (hereafter referred to as the pre- conditioning period). Cages were scrubbed 3-4 times per week throughout the experiment to prevent clogging.

An uncaged area (0.84 m2) was set up near the cages and served as an uncaged control.

Landscaping gravel and bricks were added to the uncaged control and arranged as in the cages.

The uncaged control lacked an upstream debris shield. Depth, velocity, and light levels in the uncaged control were similar to those in the cages. Free-ranging crayfish were frequently observed in the uncaged control.

Ideally, I would have included the following in my experiment: (1) additional uncaged controls, (2) an additional treatment (side-open control) with multiple replicates, (3) multiple pools, and (4) multiple years. Having additional uncaged controls would have allowed my control treatment to be included in statistical analyses; side-open controls would have allowed caging effects to be fully assessed (by comparing uncaged controls to side-open controls); and the inclusion of multiple pools and years would have allowed an assessment of spatial and temporal variability. Later experiments (conducted in 2004 and 2005) included all those elements; unfortunately, the resources necessary to process all the samples from those experiments and analyze those data were not available.

Addition of Crayfish to Cages. — One cage in each pair was randomly selected and stocked with crayfish (C. b. bartonii and O. obscurus) at densities (12 juveniles and 8 adults/m2) that were near the low end of the range found naturally in the study area. Crayfish community composition in the cages (70-100% O. obscurus, the rest C. b. bartonii) matched that in pool areas of lower Spruce Creek. The crayfish stocked in the cages were collected from the lower reaches of Spruce Creek. Carapace length (distance from tip of rostrum to the posterior median margin of the carapace; CL) for the juvenile and adult crayfish stocked in the cages averaged

18±0.2 mm (mean±1SE) and 35±0.4 mm, respectively. The uropods (tails) of all stocked crayfish

19 received a small clip prior to adding them to the cages. During the experiment, some crayfish escaped the enclosures (crayfish cages) resulting in average final densities (10 juvenile and 3 adult crayfish/m2) that were much lower than natural. More specifically, the average total crayfish density in the enclosures at the end of the experiment was 41% lower than that naturally found in rocky areas and 67% lower than that naturally found in lateral, silty areas of pools in lower Spruce Creek. All of the crayfish recovered from the enclosures at the end of the experiment had uropod clips indicating that, although the enclosures did not prevent some stocked crayfish from escaping, they did effectively exclude free-ranging crayfish. The exclosures (crayfish-free cages) were also generally effective in preventing unwanted crayfish entry resulting in low exclosure densities (0-2 individuals/m2) at the end of the experiment. The few crayfish that were found in the exclosures were unclipped and very small (10-13 mm CL).

The presence of a few small crayfish in exclosures and much lower than natural densities in enclosures did not compromise the results of this experiment, instead, this experiment represents a robust test of the effect of crayfish on benthic invertebrates in Spruce Creek.

Sample Collection and Processing. — Invertebrate samples were collected from treatment and uncaged control bricks 1 day prior to adding crayfish to cages (both treatments crayfish-free; pre-sampling) and 32 days after crayfish addition (one treatment with crayfish, the other crayfish-free; post-sampling). Samples were collected by gently lifting bricks and associated materials (e.g., detritus, inorganic particles) into a 500- m dip net positioned downstream of the sampling locations. Bricks were then scrubbed with a brush and hand-picked with forceps to remove attached invertebrates. After collection, samples were preserved in 10% buffered formalin. Invertebrates were later separated from associated materials under

20 magnification (dissecting microscope, 4-50 X power), identified (most insects to genus/species and most non-insects to class/order), and counted.

Trout Gut Contents

To determine whether brown trout in Spruce Creek consume crayfish, a total of 209 brown trout from the PSU Research Area, ranging from 165 to 406 mm total length (TL), were examined for the presence of crayfish in their stomachs. Trout were collected on June 14, 1996 using electrofishing gear and immediately transported to the stream bank where they were x- rayed using a portable x-ray machine (see Weber and Carline 2000 for further methodological details). Because crayfish were clearly visible in the stomachs of x-rayed trout (due to their hardened, calcified exoskeletons), visual inspection of x-rays was used to assess the presence of crayfish. Although these data were collected six years prior to the caging study, we assume that they provide an approximate estimate of crayfish consumption rates in Spruce Creek at the time of the caging study. Because newly molted crayfish have soft exoskeletons and are probably not discernible in x-rays, the x-ray data provided herein may underestimate the number of crayfish consumed. Data are presented separately for small (< 275 mm TL) and large ( 275 mm TL) trout because there appeared to be a natural break in the data, whereby more large than small trout had crayfish in their stomachs.

Data Analysis

A repeated-measures, three-factor (pair, treatment, sampling period) ANOVA with pair as a blocking factor was used to compare total invertebrate densities on bricks between

21 treatments (enclosures vs. exclosures) and sampling periods (pre-sampling vs. post-sampling).

All 2-way interaction terms were included in the model. The treatment×sampling period interaction was of particular interest because significance indicates that the treatment effect differed between sampling periods (e.g., enclosures and exclosures differed during post-sampling but not during pre-sampling). Analyses were completed as described in Green (1993).

Invertebrate densities were fourth-root transformed prior to analysis to correct for non-normality and unequal variances. Fourth-root transformations are often employed in benthic studies (Burd et al. 1990) and appear to be more effective than other more common transformations (e.g., log, square root) in some situations (Downing 1979, Downing 1980, Taylor 1980a, Taylor 1980b,

Downing 1981). Additional details regarding these analyses can be found at http://www.stat.psu.edu/~jlr/pub/Lieb/.

A Chi-square test was used to compare the proportion of large trout with crayfish in their stomachs to the proportion of small trout with crayfish in their stomachs. For all analyses, p- values <0.05 were considered significant and Minitab Release 15 (Minitab, Inc., State College,

Pennsylvania) was employed.

Results and Discussion

Prior to adding crayfish to cages, invertebrate densities in the treatments were almost identical; whereas, 32 days after crayfish addition, the difference between the treatments was striking (Figure 2.2; significant Treatment × Sampling Period interaction, Table 2.1). Cages with crayfish had 70% fewer invertebrates than cages without crayfish, clearly demonstrating that crayfish have strong top-down effects on other invertebrates in Spruce Creek. Invertebrate densities in enclosures resembled those in the uncaged control, suggesting that crayfish effects

22 were similar regardless of whether the crayfish were caged or free-ranging. Invertebrate densities increased in the treatments and the uncaged control during the experiment (based on the visual inspection of Figure 2.2), suggesting that the bricks were not completely colonized by invertebrates at the time of pre-sampling.

Although invertebrate densities in the uncaged control tracked those in the enclosures during the experiment, control densities were somewhat lower than enclosure densities (based on the visual inspection of Figure 2.2). This could have been due to the fact that during the pre- conditioning period, the uncaged control was accessible to free-ranging crayfish; whereas the enclosures were crayfish-free (they had not yet been stocked with crayfish). It is also possible that exposure to adult trout, white suckers, sculpin and other predatory fishes that were too big to enter the cages but had access to the uncaged control contributed to reduced control densities.

Finally, reduced control densities may not be biologically meaningful and may have resulted from the chance selection of a control site with lower density relative to the enclosures.

During post-sampling, invertebrate densities in the treatments and uncaged control were toward the upper end of the range reported for Pennsylvania streams and rivers (see Jackson et al. 1994, Lieb 1998, Lieb and Carline 1999, Thomson et al. 2005, and Carline and Walsh 2007).

Exclosure densities were particularly high and greatly exceeded most reported values, which was likely due to the exclusion of predatory crayfish and larger fish from the exclosures. Invertebrate communities in the treatments were similar to that in the uncaged control and were dominated by

Chironimidae; other taxa typically comprised < 10% of the assemblage.

In running waters, predators typically decrease local benthic invertebrate density via direct consumption, increased drift (predator avoidance), or both (Wooster et al. 1997). Declines in the density of highly mobile taxa in response to predators are usually due to a combination of

23 predator avoidance and direct consumption, whereas declines in immobile taxa are usually due to direct consumption (Wooster et al. 1997). In my study, the benthic invertebrate assemblage inhabiting pool areas of Spruce Creek was dominated by immobile Chironomidae, which accounted for 77±3% (mean±1SE) of the invertebrates collected from the cages and the control during this study. For this reason, the declines in invertebrate density that I observed in Spruce

Creek were probably caused by the direct consumption of invertebrates by crayfish. Consumed invertebrates appear to be readily assimilated, contributing significantly to crayfish growth and production in Spruce Creek [D.A. Lieb, PSU and J.A. Freedman, Illinois Natural History Survey

(INHS), unpublished stable isotope data], as they do elsewhere (Momot 1995, Whitledge and

Rabeni 1997, Parkyn et al. 2001, Roth et al. 2006, Olsson et al. 2008, Giling et al. 2009). A substantial portion of this crayfish production is then passed up the food chain to trout, especially large individuals (Figure 2.3 and D.A. Lieb, PSU and J.A. Freedman, INHS, unpublished stable isotope data). Thus, crayfish are functionally important in Spruce Creek, facilitating the transfer of nutrients up through the food chain to fish (invertebrates→crayfish→trout), as has been demonstrated in other systems (Rabeni 1992, Roell and Orth 1993, Momot 1995, Whitledge and

Rabeni 1997, Geiger et al. 2005).

The transfer of nutrients up through the food chain to trout is likely an economically valuable service, because trout streams attract thousands of fishermen to central Pennsylvania every year. These fishermen spend money during their visits boosting local economies. For example, in 1988, the yearly economic value of a section of Spring Creek (Fisherman‘s Paradise) that is comparable to the PSU Research Area and is located about 30 km from Spruce Creek was estimated at about $44,000 per km (Shafer et al. 1993).

The results of this study clearly demonstrate the ecological importance of Spruce Creek‘s crayfish assemblage and suggest that crayfish may benefit local economies by providing a recreationally valuable fish species (brown trout) with forage. The growing realization that crayfish are functionally important but highly vulnerable suggests that future crayfish extirpations/extinctions are likely and that those losses may have far-reaching ecological consequences on aquatic resources. For this reason, it is vital that natural resource managers and policy makers recognize the value of native crayfish populations and take measures to preserve them wherever possible.

Acknowledgments

I gratefully acknowledge the help of John G. Lieb, Vivian B. Lieb, Kristin Babcock, Adam

Smith, V. Malissa Mengel, and Dan Counahan during the fall 2002 experiment.

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Parkyn, S.M., K.J. Collier, and B.J Hicks. 2001. New Zealand stream crayfish: functional

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Rabeni, C.F. 1992. Trophic linkage between stream centrarchids and their crayfish prey.

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to assess the trophic role of rusty crayfish (Orconectes rusticus) in lake littoral zones.

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Taylor, C.A., G.A. Schuster, J.E. Cooper, R.J. DiStefano, A.G. Eversole, P. Hamr, H.H. Hobbs

III, H.W. Robison, C.E. Skelton, and R.F. Thoma. 2007. Endangered species – a

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Taylor, L.R. 1980a. New light on the variance-mean view of aggregation and transformation –

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Taylor, W.D. 1980b. Aggregation, transformations, and the design of benthos sampling

programs – comment. Canadian Journal of Fisheries and Aquatic Sciences 37: 1328-

1329.

Tetzlaff, J.C., B.M. Roth, B.C. Weidel, and J.F. Kitchell. 2011. Predation by native sunfishes

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Thoma, R.F. and R.F. Jezerinac. 1999. The taxonomic status and zoogeography of Cambarus

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Thomson, J.R., D.D. Hart, D.F. Charles, T.L. Nightengale, and D.M. Winter. 2005. Effects of

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Table 2.1. Comparison of invertebrate densities between treatments (enclosures vs exclosures) and sampling periods (pre-sampling vs post-sampling) using a repeated- measures, three-factor ANOVA with pair as a blocking factor.

Source d.f. MS F P

Pair 4 1.38 0.6 0.710

Treatment 1 3.10 6.6 0.063

Pair × Treatment 4 0.47 15.6 0.010

Sampling Period 1 7.93 3.8 0.122

Pair × Sampling Period 4 2.08 68.6 0.001

Treatment × Sampling Period 1 3.02 99.6 0.001

Error 4 0.03 - -

Flow 28m

Control

Debris Shield

Cage

80m

16m

Figure 2.1. Map of the experimental pool in the lower reaches of Spruce Creek showing the approximate positions of the cages, debris shields, and uncaged control during the caging experiment.

3200

1600 Number invertebrates/brick Number

0 Pre-sampling Post-sampling

Figure 2.2. Mean (±1SE) invertebrate densities on bricks collected from cages with crayfish

(enclosures, □), cages without crayfish (exclosures, ●), and an uncaged control (▲) prior to adding crayfish to enclosures (pre-sampling) and 32 days after crayfish addition (post-sampling).

N=5 for the enclosures and exclosures and N=1 for the control.

10 % of trout stomachs crayfish stomachs of with trout %

0 <275mm ≥275mm All trout

Figure 2.3. Percent of wild brown trout collected from the lower reaches of Spruce Creek that had crayfish in their stomachs at the time of capture. Data presented for large trout, 275 mm in total length (TL) (n=52), small trout, < 275 mm TL (n=157), and all trout combined (n=209). A greater proportion of large trout had crayfish in their stomachs than did small trout (Chi-square test, p<0.001).

Chapter 3

The Discovery and Ecology of a Member of the Cambarus acuminatus Complex (Decapoda:

Cambaridae) in Valley Creek, Southeastern Pennsylvania

Modified from:

Lieb, D.A., R.F. Carline, J.L. Rosenberger, and V.M. Mengel. 2008. The discovery and ecology

of a member of the Cambarus acuminatus complex (Decapoda: Cambaridae) in Valley

Creek, Southeastern Pennsylvania. Journal of Crustacean Biology 28: 439-450.

Abstract

The Cambarus acuminatus complex is a poorly known group of crayfish species whose range has traditionally been assumed to extend from the Patapsco River drainage in Maryland southward to the Saluda River basin in South Carolina. During a recent crayfish survey of southeastern Pennsylvania, I collected a member of the C. acuminatus complex [Cambarus

(Puncticambarus) sp.] from Valley Creek. Collections were made from several habitats [pools, riffles, shallow lateral areas (SL), main-channel areas (MC)], and dominant substrate classes, current velocity, and depth were recorded in each sampling area. These collections represent a new crayfish record for Pennsylvania and the first documented occurrence of the C. acuminatus complex north of the Patapsco drainage. Life history characteristics of the population of C. (P.) sp. inhabiting Valley Creek are provided and their variation among habitats and seasons is discussed. In pools, C. (P.) sp. density was negatively related to current velocity, depth, and %

36 sand, and positively related to % silt. In riffles, C. (P.) sp. density was negatively related to current velocity. Comparisons among habitats indicated that C. (P.) sp. was abundant in SL but was scarce in MC. Although MC tended to have faster current, greater depth, more sand, and less silt than SL, other factors could have been responsible for the relative scarcity of C. (P.) sp. in

MC. More conclusively, there was a positive relationship between C. (P.) sp. density and % cobble in MC of pools, suggesting that activities such as urbanization that result in sediment deposition and burial of rocky substrates may have a negative effect on density in MC. Since MC are important for large, reproductive individuals, reduced density in these areas may affect the reproductive potential of the population. These findings indicate that Valley Creek supports an unusual and potentially threatened crayfish population that requires further study and highlight the need for additional fieldwork in the region.

Introduction

The C. acuminatus complex is a poorly known group of crayfish species whose range has traditionally been assumed to extend from the Patapsco River drainage in Maryland southward to the Saluda River basin in South Carolina (Hobbs, 1989). Published accounts of the complex are limited to collections from Maryland, Virginia, North Carolina, and South Carolina (Meredith and Schwartz, 1960; Hobbs, 1972, 1989; Taylor et al., 1996). Although the complex has not previously been reported from Pennsylvania, much of what is known about the state‘s crayfish fauna is dated and includes relatively few records from parts of southern Pennsylvania [see

Ortmann (1906) and Schwartz and Meredith (1960)], where members of the complex are most likely to be found. In particular, substantial areas of southeastern (SE) Pennsylvania have never been sampled for crayfish.

Although considerable taxonomic progress has been made in recent years with the southern members of the complex, including the description of four new species from North

Carolina (Cooper, 2001; Cooper and Cooper, 2003; Cooper, 2006a, b), northern populations remain virtually unknown [J. E. Cooper, North Carolina State Museum of Natural Sciences

(NCMNS), personal communication]. In fact, published information concerning the northern populations is currently limited to that provided by Meredith and Schwartz (1960), who reported

C. acuminatus from 18 lotic sites located along the fall line (the transitional zone between the

Piedmont and Coastal Plain) between Baltimore, Maryland and Washington D.C., but provided no additional information concerning the ecology of the species.

In early spring 2000, Jan Briede (Scientech, NES, Inc.) and Jamie Krejsa (Enviroscience,

Inc.) collected four unusual crayfish specimens from Valley Creek (Cr) within Valley Forge

National Historical Park (VFNHP) in SE Pennsylvania. Roger F. Thoma (Ohio State University

Museum) tentatively assigned those specimens to the C. acuminatus complex. If the identifications are confirmed, they represent the northern-most occurrence of the complex in the

United States. As with other northern locations where members of the C. acuminatus complex have been found, almost nothing is known about the crayfish fauna of Valley Cr.

Because land use changes (urbanization) and associated sedimentation and habitat alterations threaten all the biota of Valley Cr (Kemp and Spotila, 1997) and are problematic for crayfishes in general [see discussions in DiStefano et al. (2003a) and Westhoff et al. (2006)], it is essential that data regarding the creek‘s crayfish fauna be acquired so that informed decisions can be made about how to protect these animals. Management decisions must be based on the best possible information because not only do they have the potential to affect the future of

Valley Creek‘s crayfish fauna but also that of a possible species of concern in Pennsylvania, the

38 queen snake (Regina septemvittata). The queen snake, which is found along Valley Cr within

VFNHP, is thought to be disappearing from parts of Pennsylvania (particularly the SE part of the state) due to the adverse effects of pollution on its primary food source, crayfish (Hulse et al.,

2001). Urbanization is not the only threat to Valley Creek‘s crayfish fauna. In fact, exotic crayfish such as the rusty crayfish (O. rusticus) are potentially an even greater concern, because they have been identified as one of the biggest threats to native crayfish in North America

(Butler et al., 2003) and are abundant in several nearby streams, some of which are completely devoid of native crayfish [D. A. Lieb, The Pennsylvania State University (PSU), unpublished data].

Although this study is of obvious regional and taxonomic significance, the ecological information provided in this paper should appeal to a much broader audience because, although crayfish often have major direct and indirect effects on the structure and function of rivers and streams (Huryn and Wallace, 1987; Hart, 1992; Creed, 1994; Rabeni et al., 1995; Usio, 2000;

Schofield et al., 2001; Stenroth and Nyström, 2003; Creed and Reed, 2004), the life histories and habitat preferences of most species are unknown and are badly needed (Corey, 1988; Taylor et al., 1996; Riggert et al., 1999; Hobbs, III, 2001; DiStefano et al., 2003a;Westhoff et al., 2006).

More specifically, although approximate lower thresholds have been reported for calcium (~5 mg/L) and pH (~5.5) and data on temperature, dissolved oxygen, salinity, and pollution tolerances and refuge (e.g., cobbles, macrophytes) requirements are available for some crayfishes

(see Hobbs and Hall 1974, Lodge and Hill 1994, Nyström 2002), detailed habitat preference studies have been conducted for few species. The objectives of this study were to: 1) determine if a reproducing population of crayfish belonging to the C. acuminatus complex occurs in Valley

Cr, 2) conduct a comprehensive survey of Valley Cr within VFNHP and produce a list of all the

39 crayfish species that occur there, and 3) determine the basic life history characteristics, reproductive status, and habitat preferences of the crayfish species that occur in Valley Cr within

VFNHP.

Materials and Methods

Study Area

Valley Cr, which is located in the Piedmont of SE Pennsylvania, drains about 64 km2 of largely urbanized land in the Philadelphia suburbs. The creek consists of two main branches,

Valley Cr and Little Valley Cr, which combine and then flow for about 5 km before emptying into the Schuylkill River (Figure 3.1). Crayfish sampling stations were located in the lower reaches of Valley Cr within VFNHP. Owing mainly to the presence of the park, my sampling stations are situated in what is perhaps the least disturbed section of the creek (Steffy and

Kilham, 2004). Because much of the creek‘s flow originates from limestone springs, temperatures tend to be moderate (4-18 °C), and nutrient availability is generally high (Sloto,

1990). Additional information concerning Valley Cr and its biota are provided in Kemp and

Spotila (1997).

Crayfish Collections

I collected crayfish from four stations along Valley Cr (Figure 3.1). Each station consisted of one riffle-pool sequence and averaged 64 m in length (range = 37-87 m). Within stations, stream widths averaged 14 m (10-17 m) for pools and 12 m (6-18 m) for riffles; bottom substrates were primarily cobble, gravel, sand, and silt. Large rocks (boulders), root masses, and

40 aquatic vegetation were uncommon in most areas. At each station, crayfish samples were collected from four habitat types: shallow lateral areas of pools (SLP) and riffles (SLR) and main-channel areas of pools (MCP) and riffles (MCR). SL were within 2 m of shore. MC were

3 m from shore. Each station was sampled during daylight hours on two occasions: spring (21-22

April) and fall (18-19 October) of 2003. Sampling occurred during baseflow conditions when water clarity was high and the stream bottom was clearly visible.

Four collection techniques were employed during this survey. Seines (2.8 2.0 m bag seines with 5 mm mesh) were tried in the spring but not the fall because, as was found by Brant

(1974), they often became snagged on various obstructions and were ineffective (0 crayfish collected). Rectangular traps (~ 0.2 0.3 0.6 m) were baited with raw beef kidney and placed overnight in pools and riffles at depths ranging from 0.3-1.2 m. Similar to the findings of Eng and Daniels (1982), Rabeni et al. (1997), and DiStefano (2000), traps were not useful in Valley

Cr (a total of two crayfish captured during eight trap-nights) and were also not used in the fall.

Dipnets (hand collections) were tried in the spring (a total of two crayfish captured) but were quickly abandoned because, similar to the results of Rabeni et al. (1997), they were inefficient over large reaches relative to electrofishing gear. Single-pass electrofishing was the primary collection method used during both the spring (347 individuals captured) and fall (262 individuals captured) and, as reported by Westman et al. (1978) and Rabeni et al. (1997), was effective in collecting crayfish from all the major habitats present at my sampling stations. The relative scarcity of large rocks, which for obvious reasons can be difficult to electrofish, likely contributed to the effectiveness of electrofishing gear in this study.

Electrofishing collections were made in an upstream direction using a boat-mounted unit

(pulsed-DC current, 200-volt, Coffelt Electronics Company). Crayfish, which were often pulled

41 out from under cover (cobbles, logs) during sampling, were involuntarily drawn to the anode [as described by Westman et al. (1978)] and netted. In most cases, four separate areas at each station

(one area per habitat type) were sampled with electrofishing gear during each season. The physical characteristics of electrofished areas are listed in Table 3.1. Electrofishing data provided indices of crayfish density in each sampling area (individuals collected/m2). Care was taken to ensure consistent effort among habitat types, seasons, and stations (especially in terms of the time spent sampling per unit of stream bottom).

In the spring, human error and equipment failure prevented me from estimating density in some areas. For example, at station 1, specimens from SLR and MCR (95 total) were inadvertently placed in the same jar, thereby preventing the calculation of separate density estimates for those locations. Additionally, equipment failure prevented the collection of crayfish from SLR of station 2. Thus, in the spring, estimates of crayfish density were lacking for SLR of stations 1 and 2 and MCR of station 1.

After collection, crayfish were preserved in 95% ETOH and transported to the laboratory where they were identified and carapace length (CL; the distance from the tip of rostrum to the posterior median margin of the carapace) and male reproductive state (form I, II) determined following Hobbs (1972). Females were inspected for eggs and young. My identifications were confirmed by John E. Cooper of the NCMNS and Raymond W. Bouchard of the Academy of

Natural Sciences of Philadelphia. Voucher specimens were deposited in the crustacean collection of the NCMNS, Raleigh, North Carolina (catalogue numbers 24749-24753), the Ohio State

University Museum (catalogue numbers 6487-6491), Columbus Ohio, and the Carnegie Museum of Natural History, Pittsburgh, Pennsylvania (catalogue numbers C2005-24-27).

Habitat Measurements

Dominant substrate classes, depth, and current velocity were recorded along transects within each electrofished area. Transects were oriented perpendicular to flow and were evenly spaced within each sampling area. In the spring, there were generally 5 or 6 transects per sampling area. Exceptions were the MCR of stations 2, 3 (no habitat data available), and 4 (only two transects). One set of habitat measurements (substrate, depth, flow) was made at the center of each transect. In the fall, there were 3 or 4 transects per sampling area. Within SL areas, measurements were made at locations ≤ 0.5, 1, and 2 m from shore along each transect. Within

MC areas, 5-7 equally-spaced sets of measurements were made along each transect. Current velocity was measured at 0.6 of the distance from the water surface to the stream bottom using a portable flow meter (Marsh-McBirney Flowmate 2000). Bottom substrates were assessed visually and the two dominant substrates recorded. Approximately 0.9 m2 of stream bottom was assessed at each location. Substrates were assigned to size classes (silt, sand, gravel, cobble, boulder) based on Platts et al. (1983).

Data Analysis

Electrofishing data were used to compare C. (P.) sp. density between main habitats (pool vs. riffle) and sub-habitats (SL vs. MC) using a repeated measures, 4-factor (station, main habitat, sub-habitat, season), strip-plot ANOVA with station as a blocking factor [as described in

Steel and Torrie (1980)]. A repeated measures analysis (season terms included in the model) was used because the same areas were sampled on two occasions (spring and fall). A strip-plot (also called a split-block) design allowed me to account for the fact that, within each block, plots

(pools, riffles) and subplots (SL, MC) were adjacent [see pg. 390 of Steel and Torrie (1980)].

Station×main habitat×season and station×sub-habitat×season interaction terms could not be included in my model due to missing data (see ‗Crayfish Collections‘ section), which resulted in insufficient degrees of freedom. Thus, F-tests for sub-habitat×season and main habitat×season are approximate (but the best that can be done) because denominators consisted of the error mean square (MSE) instead of the more appropriate 3-way interaction, e.g., station×main habitat×season, mean square. Other F-tests were carried out as described in Steel and Torrie

(1980).

Electrofishing data were also used to determine if there were relationships between C.

(P.) sp. density and microhabitat characteristics (current velocity, depth, % silt, % sand, % gravel, % cobble, % boulder) using correlation analysis. Since the primary objective of these analyses was to determine whether or not there was a relationship between microhabitat and density (regardless of the form of the relationship), I used Spearman‘s rank correlations (rs) to test for associations between variables following Ott (1992) and Mendenhall and Beaver (1994).

Because microhabitat measurements were made at multiple locations within each electrofished area, but only one density estimate was available for each area (the entire area was electrofished), microhabitat data were summarized prior to correlation analysis. For depths and current velocities, mean values were calculated. For substrate characteristics, the percent of locations where a particular substrate class, e.g., cobble, was dominant or co-dominant was determined.

Pools and riffles were analyzed separately for each microhabitat characteristic. MCP were of particular interest and were also analyzed separately because it appeared that those areas were often filled with fine sediments (silt, sand) of rather recent origin and therefore may be susceptible to sedimentation from ongoing urbanization of the watershed. Spring and fall data

44 were pooled prior to analysis because relationships in the spring were similar to those in the fall and sample sizes in individual seasons were relatively low (riffle n = 3, pool n = 8, and MCP n =

4 in spring; riffle n = 8, pool n = 8, and MCP n = 4 in fall).

More complicated and potentially more definitive microhabitat analyses (multiple regression) were not conducted because relationships between several of the microhabitat characteristics (% silt, % sand, current velocity, depth), and density were confounded by the effects of sub-habitat (see ‗Habitat Associations‘ section for additional comments). An obvious solution would be to analyze each sub-habitat type separately (separate multiple regressions for

SLP, MCP, SLR, and MCR). Unfortunately, not enough data were available for separate analyses (Zar, 1999). Additionally, simple correlations were adequate because the intent of my microhabitat analyses was to identify potentially important relationships to be explored further with additional data or experiments.

All C. (P.) sp. specimens were used to compare size (CL) between seasons (spring vs. fall), habitats (pool vs. riffle and lateral vs. main channel), and sexes (male vs. female) and to compare sex ratios, and occurrence of form I males (male I) between seasons and habitats. Size comparisons were completed using a repeated measure, strip-plot ANOVA with station as a blocking factor (described previously). An additional factor (sex) was included to compare male and female size. Three-way interaction terms could not be included in the model due to missing data and the collection of only one sex from some locations, which resulted in insufficient degrees of freedom. Thus, F-tests for all 2-way interaction terms, e.g., sub-habitat×season, are approximate (but the best that can be done) because denominators for those tests consisted of the

MSE instead of the more appropriate 3-way interaction terms, e.g., station×sub-habitat× season.

Other F-tests were carried out as described in Steel and Torrie (1980). Mean sizes were used in

45 these analyses because multiple crayfish were collected (and measured) from each sampling area. I weighted mean sizes by the number of crayfish collected (n) because n varied among habitat types, stations, and seasons. Sex ratio and male I comparisons were carried out using chi- square tests.

Due to human error and equipment failure, life history data (size, sex ratio, male I) were not available for some areas (the same areas which also lacked density estimates). Further, one

C. (P.) sp. could not be measured accurately or sexed (most of its abdomen missing) and was not included in life history analyses. An additional four specimens could also not be measured accurately due to damage and were not included in size analyses.

For size and density analyses, least squares means (LSM; also sometimes referred to as adjusted marginal means) instead of simple means are reported to avoid the potential bias caused by the unequal number of observations in the cells of my multi-way classification of the data

(Milliken and Johnson, 1992). For all analyses, p-values < 0.05 were considered significant and

Minitab Release 13 (Minitab, Inc., State College, Pennsylvania) was employed. Results were confirmed using SAS version 9.1 (SAS Institute, Inc., Cary, North Carolina).

Results and Discussion

Taxonomy

My surveys yielded two species of crayfish. One of those species, C. b. bartonii, is common throughout much of the state, while the other, a member of the C. acuminatus complex

[referred to as C. (P.) sp.], has never before been reported from Pennsylvania. Although I will not be able to assign a species name to the C. (P.) sp. specimens until the complex is completely diagnosed (J. E. Cooper, NCMNS, personal communication), they are almost certainly not true

C. acuminatus, as originally described by Faxon (1884), because the native range of true C. acuminatus is likely limited to the Saluda River Basin in South Carolina (Hobbs, 1969; J. E.

Cooper, NCMNS, personal communication). Additionally, the Valley Cr specimens are clearly not one of the four recently described species in the complex, and are therefore probably a new species that has not yet been described (J. E. Cooper, NCMNS, personal communication).

Although one might argue that this paper should wait until a species name can be attached to the Valley Cr specimens, that is likely many years away (J. E. Cooper, NCMNS, personal communication), and preliminary data from ongoing surveys of SE Pennsylvania suggest that C. (P.) sp. may be native to Pennsylvania and, due to its limited range within the state (likely restricted to Valley Cr and several nearby streams) and proximity to urban centers and populations of rusty crayfish, is highly threatened (Lieb et al., 2007). Thus, the data provided in this paper are needed to ensure the continued viability of one of the few populations of C. (P.) sp. in Pennsylvania. Further, aside from a few C. b. bartonii, the specimens I have collected from

Valley Cr are all the same species, i.e., I am not lumping multiple species under the name C. (P.) sp. (J. E. Cooper, NCMNS, personal communication). Thus, because I have properly cataloged a range of specimens at several museums, it will be possible, in the future, to attach a species name to my specimens and the information provided in this paper can then easily be attributed to that species.

Community Composition

My surveys indicate that C. (P.) sp. is the dominant crayfish species in Valley Cr. Of the

613 crayfish specimens collected during the 2003 surveys, 603 were C. (P.) sp., 9 were C. b. bartonii, and 1 could not be identified to species (appeared to share characteristics of the two

47 species, may have been a hybrid). The C. (P.) sp. collections included large numbers of juveniles and adults, a wide range of sizes, and both sexes (Figure 3.2) indicating that the species is established and is reproducing in Valley Cr. In contrast, C. b. bartonii was uncommon, making the reproductive status of this species in Valley Cr uncertain. In fact, it is possible that the C. b. bartonii collected from Valley Cr were washed in from upstream tributaries during rain events, which often result in rapid discharge increases in Valley Cr (United States Geological Survey, unpublished streamflow data).

Life History Characteristics

Size Structure. — Although C. (P.) sp. collections were devoid of females with attached ova or young (reproductive females), juveniles and adults of both sexes and all sizes were well represented. In both the spring and fall, it was evident that the size structure of the population was biased toward small individuals [> 80% of the individuals collected were 9-23 mm carapace length (CL)] resulting in length-frequency distributions that are skewed to the right

(Figure 3.2). An obvious break in the fall length-frequency histogram suggests the presence of at least two distinct size classes at that time [9-18 mm CL (peak at 14) and ~ 23-38 mm CL (peak at

27)]. Size classes were less distinct in the spring, although peaks were observed at 18-20 mm CL and 34-35 mm CL. The presence of large numbers of very small (≤ 14 mm CL) individuals in the fall but not the spring collections suggests that substantial juvenile recruitment occurred sometime between the end of April and the end of October, which agrees with the general life history of many cambarid crayfishes (Hobbs III, 2001).

Males tended to be larger (LSM = 21.7 mm CL) than females (LSM = 19.7 mm CL), as is often the case for crayfish (Reynolds, 2002), but differences were not significant (NS) (Table

3.2). This result was consistent across stations, sub-habitats, and main habitats, as indicated by the lack of significant interactions between sex and those factors. In contrast, I found a significant sex×season interaction, which was driven by the fact that males tended to be larger than females in one but not both seasons (Figure 3.2). Specifically, in the spring males were, on average, 22% larger than females (male LSM = 22.1 mm CL, female LSM = 18.1 mm CL); whereas, in the fall male and female sizes were nearly identical (male LSM = 21.3 mm CL, female LSM = 21.2 mm CL). Stated another way, male size was similar across seasons, whereas females tended to be smaller in the spring than in the fall. These results are expected if large, mature females with attached ova and young, which are typically sequestered and difficult to collect (see subsequent ‗Sex Ratio‘ and ‗Gear Bias‘ sections), were present in Valley Cr at the time of the April but not the October collections. The absence of large, reproductive females from the April collections would have reduced the average size of the females collected during that time. This explanation seems plausible given that, for cambarid crayfishes, females with attached eggs and young are typically present in spring but not fall (Hobbs III, 2001). Although these results make biological sense, the p-value for the season×sex interaction was not exceptionally small (0.02) and exact F-tests for interaction terms were not possible (see ‗Data

Analysis‘ section), indicating that additional studies are needed to confirm the importance of sex×season interactions on C. (P.) sp. size.

Differences in size were readily apparent among some, but not all habitat types. For example, main-channel areas supported much larger individuals (LSM = 25.1 mm CL) than lateral areas (LSM = 16.2 mm CL), but riffles and pools supported C. (P.) sp. of similar size

(pool LSM = 20.3 mm CL, riffle LSM = 21.0 mm CL) (Table 3.2). Although interaction terms should be interpreted cautiously, the subhabitat×season interaction term was highly significant

(p-value < 0.001), indicating that the magnitude of the difference between sub-habitats (larger individuals in the main channel than in lateral areas) varied seasonally (Figure 3.2). More specifically, in the fall, individuals in the main channel were, on average, 93% larger than those in lateral areas (main channel LSM = 28.0 mm CL, lateral LSM = 14.5 mm CL), whereas, in the spring, main-channel individuals were, on average, only 23% larger than those in lateral areas

(main channel LSM = 22.2 mm CL, lateral LSM = 18.0 mm CL). Phrased differently, individuals inhabiting main-channel areas were smaller in spring than fall, whereas in lateral areas individuals were larger in spring than fall. Although this interaction is probably best explained by the substantial influx of very small individuals, which tend to prefer lateral areas, in the fall, other factors such as the scarcity of large, reproductive females, which tend to prefer main-channel areas, in the spring could also have contributed to the subhabitat×season interaction. In contrast, sub-habitat differences were consistent across stations, main habitats, and sexes, as indicated by the lack of significant interactions between sub-habitat and those factors.

Similarly, mainhabitat results (no difference between pools and riffles) were consistent across stations, sub-habitats, seasons, and sexes, as indicated by the lack of significant interactions between main habitat and those terms.

There was a subtle trend toward the collection of smaller individuals at upstream compared to downstream stations; however a significant station effect was not found (LSM for stations 1, 2, 3, and 4 = 18.6, 20.4, 20.4, and 23.3 mm CL, respectively) (Table 3.2). No significant interactions between station and the other factors were found indicating that size was similar across stations regardless of the main habitat, sub-habitat, season, or sex considered.

Seasonal comparisons showed that size in the spring (LSM = 20.1 mm CL) was not different from that in the fall (LSM = 21.2 mm CL). Seasonal effects were consistent across stations and

50 main habitats (station×season and main habitat×season not significant) but varied among sub- habitats and sexes (sub-habitat×season and sex×season significant, see above).

My finding that small individuals dominated collections of C. (P.) sp. in Valley Cr is in agreement with studies of other crayfish species (Jordan et al., 1996; Englund and Krupa, 2000;

DiStefano et al., 2003a) and is not unexpected given that crayfishes generally exhibit a type III

(concave) survivorship curve with mortality decreasing markedly with age (size) (Hobbs III,

2001). Although I was able to roughly determine the timing of recruitment for C. (P.) sp. in

Valley Cr (sometime between the end of April and the end of October) and distinguish at least two size classes in each season (especially in the fall), a more complete determination of the life cycle of C. (P.) sp. in Valley Cr would have required additional collections in other seasons

(summer, winter) and at more frequent intervals (monthly or bimonthly), which was beyond the scope of this study.

While no data, other than that in this paper, are available concerning the size-habitat relationships of any member of the C. acuminatus complex, studies of other species tend to concur with my finding that deep, main-channel areas support larger individuals than shallow, lateral areas (Taylor, 1983; Butler and Stein, 1985; Rabeni, 1985; Creed, 1994; DiStefano et al.,

2003a). Englund and Krupa (2000) explored the cause of this pattern and found that the distribution of small crayfish shifts to shallow water in the presence of fish predators. This result suggests that brown trout (Salmo trutta), which consume crayfish (Bachman, 1991; Nyström et al., 2006; Figure 2.3) and are common in Valley Cr (Kemp and Spotila, 1997), may be, at least partly, responsible for the tendency of small C. (P.) sp. to occupy shallow, lateral areas in Valley

Cr.

In contrast, much less is known about differences in crayfish size between pools and riffles and few generalities are currently possible. In one of the few available studies, DiStefano et al. (2003a), who worked with an assemblage of crayfish composed mainly of Orconectes luteus, Orconectes ozarkae, and Orconectes punctimanus, showed that the ratio of adult density to young-of-the-year (YOY) density was much greater in riffles than in pools, indicating that crayfish CL was probably greater in riffles than in pools in their study. This result confirms earlier, less direct work by Rabeni (1985), who found that O. luteus YOYs preferred low- velocity areas, whereas adults preferred high-velocity areas; again suggesting that individual size in riffles (high-velocity areas) is greater than that in pools (low-velocity areas) for O. luteus. In contrast, Gore and Bryant (1990) found that YOY Orconectes neglectus preferred high-velocity areas with cobble (generally found in riffles), whereas adults preferred low-velocity, macrophyte beds (generally found in pools). Therefore, it seems likely that individual size in pools is greater than that in riffles for O. neglectus. Thus, large individuals were concentrated in riffles for O. luteus, O. ozarkae, O. punctimanus, in pools for O. neglectus, and were spread equally among pools and riffles for C. (P.) sp. suggesting that, for crayfishes, there are species-specific differences in how juveniles and adults are distributed among certain habitat types (riffles and pools).

Although the absence of reproductive females from my collections may have contributed to the interactions observed (sex×season, sub-habitat×season), other results were probably little affected. For example, the collection of reproductive females would, undoubtedly, have increased the average size of the individuals in the main channel (because reproductive individuals tend to be large, and large individuals prefer main-channel areas), strengthening my finding that individuals in the main channel are larger than those in lateral areas. This argument

52 is based on several assumptions. First, I assume that reproductive females tend to be large, which is likely true given that many cambarid crayfishes do not reach maturity until their second or even third year of life (Hamr and Berrill, 1985; Corey, 1988; Hobbs III, 2001). Second, I assume that large reproductive females are distributed similarly to large nonreproductive females, i.e., large reproductive females prefer main-channel areas. Anecdotal support for this assertion is provided by recent surveys of nearby streams, which resulted in the collection of a few reproductive female C. (P.) sp., all of which were found in main-channel areas (D. A. Lieb, PSU, unpublished data).

Sex Ratio. — Across seasons and habitat types, the sex ratio of C. (P.) sp. was male- biased, although the bias was not extreme [1.2:1 (male:female), n = 602, Chi-square test, p =

0.01]. When individual seasons or habitat types were considered, deviations from 1:1 were sometimes larger. For example, there was a male bias in the spring (1.4:1, n = 348, p = 0.002), but not the fall (1.02:1, n = 254, p = 0.90). Similarly, when habitats were considered individually, riffles were male-biased (1.4:1, n = 201, p = 0.02), whereas pools were not (1.1:1, n

= 401, p = 0.18). Partitioning the data between main-channel and lateral areas showed a male bias in the main channel (1.6:1, n = 91, p = 0.03), but not in lateral areas (1.1:1, n = 416, p =

0.49).

Although the sex ratios of most crayfish populations are believed to be 1:1 (Reynolds,

2002), a number of authors have reported male-biased catches during at least part of the year

(Capelli and Magnuson, 1983; Taylor, 1983; Fenouil and Chaix, 1985; Van Den Brink et al.,

1988; Ackefors, 1999; Alekhnovich et al., 1999; Frutiger et al., 1999; Flinders and Magoulick,

2005) and some attributed this bias to the use of a particular collection technique, e.g., trapping

53 tends to be biased toward males. I also found that C. (P.) sp. catches were male-biased during part of my study (in the spring but not the fall) and attribute this, at least in part, to the lack of reproductive females in my collections, but not to my choice of collection techniques (see ‗Gear

Bias‘ section for further discussion).

The generality of my finding that sex ratios vary among habitats in Valley Cr (male bias in riffles and main-channel areas but not in pools and lateral areas) is unknown at this time because few data are available. However, variation in sex ratios among habitats in Valley Cr is not unexpected given that the biology of male and female crayfish often differs, especially during the breeding season. For example, females often feed less than males during the egg- bearing stage of their reproductive cycle (Hopkins, 1967; Abrahamsson, 1971; Brewis and

Bowler, 1982; Taylor, 1983; Skurdal and Qvenild, 1986; Pursiainen et al., 1987), which ultimately may result in males and females selecting habitats based on different criteria during parts of their life cycle, e.g., food availability may be a higher priority for males than females during egg-bearing. Alternatively, male-biased catches in particular habitats could have been due, at least in part, to difficulties in collecting reproductive females. For example, if reproductive females favored particular habitats, but were deeply burrowed into the substrate and were inaccessible, then male-biased catches would be expected in those areas.

Form I Males. — During this study, form I males only accounted for 7% of the total C.

(P.) sp. catch. The contribution of form I males to the catch was consistent across seasons (8% in the spring and 6% in the fall) (Chi-square test, p =0.42), but not habitats. For example, form I males accounted for a higher proportion of the catch in riffles (10%) than in pools (6%) (p =

0.04), and a higher proportion of the catch in main-channel areas (26%) than in lateral areas (3%)

(p < 0.001). Form I males were particularly well represented in main-channel riffle collections, comprising 53% of the catch in those areas. However, overall abundance in those areas was low

[only 19 of 603 C. (P.) sp. were collected there].

My finding that form I male C. (P.) sp. comprised little of the total catch in Valley Cr was expected given the results of other studies. For example, of the > 6000 specimens belonging to five different species collected by Flinders and Magoulick (2005), < 400 were form I males (<

6% of the total catch). Studies by Corey (1988) and Riggert et al. (1999) with three other species also showed that form I males were rarely collected during some seasons.

Gear Bias. — Although gear bias is a concern when studying the life history characteristics of any species, and has the potential to affect crayfish collections, the results of

Westman et al. (1978) and Rabeni et al. (1997) suggest that unlike other collection methods, which tend to be highly biased (traps favor large males; quadrant samplers favor juveniles) electrofishing is an effective method for collecting crayfish of all sizes and life stages (even reproductive females) from a variety of habitats, even where there is heavy cover. Westman et al.

(1978) cautioned that electrofishing was not effective in murky waters or depths 0.8 m; however, water clarity in Valley Cr was high throughout this study and depths 0.8 m were rarely encountered (only 3% of my depth measurements exceeded 0.8 m, Table 3.1). Based on this information, my own observations (see ‗Methods‘), and the fact that electrofishing gear has been used in similar studies of other large-bodied, freshwater crustaceans [Australian shrimps:

Richardson and Cook (2006)], it is tempting to conclude that electrofishing is completely unbiased. However, the fact remains that females with attached ova or young were not collected

55 during this study, which may have biased my collections toward males (especially in the spring when reproductive females are expected).

Studies of other members of the C. acuminatus complex suggest that this bias likely had nothing to do with gear type and was probably due to the fact that female members of the complex are extremely difficult to catch during parts of their reproductive cycle. For example, despite extensive collections of the complex (four species, > 800 individuals) from a variety of locations by a variety of collectors (presumably using a variety of sampling devices), only two females with attached young and one with attached ova have been reported from North Carolina

(Cooper, 2001; Cooper and Cooper, 2003; Cooper, 2006a, b). Similar results (few reproductive females collected) for a number of other crayfish species, collected using a variety of methods

(dipnets, kicknets, quadrant samplers, hand collections; Fenouil and Chaix, 1985; Hamr and

Berrill, 1985; Corey, 1988; Flinders and Magoulick, 2005), provide additional evidence that male-biased catches in Valley Cr were not due to the use of electrofishing gear.

Habitat Associations

Comparisons among habitats revealed that C. (P.) sp. density was much higher in lateral

(LSM = 0.26 individuals/m2) than in main-channel areas (LSM = 0.02 individuals/m2) (Table

3.3). Density of C. (P.) sp. also tended to be higher in pools (LSM = 0.17 individuals/m2) than in riffles (LSM = 0.10 individuals/m2), but differences were NS. Density of C. (P.) sp. in the spring

(0.16 individuals/m2) was similar to that in the fall (0.12 individuals/m2). C. (P.) sp. density was also similar among stations (LSM for stations 1, 2, 3, and 4 = 0.15, 0.12, 0.16, and 0.13 individuals/m2, respectively) suggesting that, at least within my study area, there is little longitudinal (upstream-downstream) variation in the abundance of this species. No significant

56 interactions were found, indicating that these results were consistent across habitats (sub and main), seasons, and stations. Although few C. (P.) sp. were found in the main channel, the individuals present were on average 55% larger than those found in lateral areas, suggesting that differences in biomass between main-channel and lateral areas may not be as large as differences in density.

Although the density values reported above likely underestimated actual density because multiple electrofishing passes are typically required to collect all the crayfish from a given area

(Westman et al., 1978; Rabeni et al., 1997; D. A. Lieb, PSU, unpublished data), comparisons among habitats, seasons, and stations were probably little affected by this bias because my sampling procedures were consistent throughout the study (particularly in terms of effort). My finding that C. (P.) sp. density in lateral areas was much greater than that in the main channel was probably particularly robust to any such bias because smaller-scale, more intensive studies elsewhere in Pennsylvania indicate that additional electrofishing passes (beyond the initial pass) substantially increase the catch of small crayfish (particularly in lateral areas; D. A. Lieb, PSU, unpublished data). Thus, actual differences in density between lateral and main channel areas were likely even greater than those I documented. More generally, my densities can be thought of as catch-per-unit-effort values (CPUE; effort standardized by the area sampled and time), which are measures of abundance that have been successfully used to determine habitat preferences in a wide range of aquatic species [see Lazzari et al. (2003), Barko and Hrabik

(2004), Jordan et al. (2004), and Wallace et al. (2006) for examples]. Additional multiple-pass removal studies in Valley Creek may allow my values to be converted to actual densities in the future (by determining the % of the total population that is captured during the first pass).

Substrate analyses revealed that there was a positive relationship between C. (P.) sp. density and the prevalence of cobble (% cobble) in main-channel areas of pools (rs = 0.76, p <

0.05; Figure 3.3). Relationships between other substrate characteristics (% sand, % silt, % gravel,

% boulder) and density were NS. When main-channel and lateral data were combined, there was a negative relationship between density and % sand (rs = -0.57, p < 0.05; Figure 3.4) and a positive relationship between density and % silt (rs = 0.62, p < 0.05) in pools. Relationships between other substrate characteristics (% gravel, % cobble, % boulder) and density were NS.

Analyses with riffle data (mainchannel and lateral data combined) did not reveal any significant relationships between density and any substrate characteristic.

Although significant, relationships between density and substrate in pools (main-channel and lateral data combined) should be viewed cautiously because sampling locations where crayfish and silt were abundant and sand was scarce were mainly found in lateral areas, whereas locations where crayfish and silt were scarce and sand was abundant were generally in the main channel (Figure 3.4). Thus, although it is tempting to conclude that sand is negatively related and silt positively related to density in pools, I cannot rule out the possibility that the relationship is driven by the fact that main-channel areas have lower density than lateral areas naturally, i.e., regardless of whether sand and silt are present or not. The fact that lateral areas appeared to have higher density than main-channel areas even when sand was abundant and silt was scare (see two data points where > 50% of the lateral areas are sand and one data point where < 15% of the lateral area is silt in Figure 3.4) suggests that, although the absence of sand and prevalence of silt may contribute to higher density in lateral areas, other factors are likely also important.

Experimental studies (sand and silt either added or removed) or additional collections in main- channel areas where sand is scarce and silt is abundant and in lateral areas where sand is

58 abundant and silt is scarce are needed to clarify the relationship between density and substrate characteristics in pool areas of Valley Cr.

There was no relationship between density and either current velocity or depth in the main-channel areas of pools. However, when main-channel and lateral data were combined, there was a negative relationship between density and both current velocity (rs = -0.72, p <

0.005; Figure 3.4) and depth (rs = -0.58, p < 0.05) in pools and between density and current velocity in riffles (rs = -0.81, p < 0.005; Figure 3.5). Although these relationships are strong, they should be viewed cautiously because sampling locations with high density, low current velocity, and shallow water were mainly found in lateral areas, whereas locations with low density, high velocity, and deep water were generally in the main channel (Figure 3.4, 3.5). Thus, the situation is analogous to that discussed previously for sand and silt. Regardless, C. (P.) sp. was completely absent from areas where average flows exceeded about 0.50 m/s, suggesting that some fast- current areas of Valley Cr are unsuitable for this species. These areas may be particularly dangerous during spates when flows increase rapidly in Valley Creek (United States Geological

Survey, unpublished streamflow data), potentially dislodging and killing crayfish (see Nyström

2002 and references within).

Within my study area, I found a strong negative relationship between crayfish density and depth in pools; however, this result may not apply to all areas of Valley Cr. This is because relationships between crayfish density and depth may be affected by the presence of predatory fish such as brown trout, and in some cases relationships may shift from strongly negative in the presence of predatory fish to strongly positive in the absence of predatory fish (Englund, 1999).

Therefore, in reaches of Valley Cr where brown trout are rare [upstream, headwater areas; see

Kemp and Spotila (1997)] I may find a different relationship than I found in downstream locations where brown trout are common (my study area).

Although C. (P.) sp. is abundant in the lateral areas of Valley Cr, where the water is shallow, current velocity is low, sand is scarce, and silt is abundant, my results can only suggest associations and cannot determine causality. This is because any number of other factors, such as the prevalence of food resources and woody debris in lateral areas, competitive interactions, or the presence of predatory fish in main-channel areas could have been responsible for the macrohabitat associations observed [see Rabeni (1985) and DiStefano et al. (2003a) for thorough discussions of many of these possibilities]. Given the flashy nature of Valley Creek‘s hydrograph, root masses, which occur in lateral areas, may also be important because tree roots afford some crayfish species protection from floods (Smith et al., 1996).

Whatever the cause, it is clear that C. (P.) sp. density was much higher in shallow, lateral areas than in the main channel during both the spring and the fall sampling periods and that this difference in density was primarily driven by the preference of small individuals (which dominated my collections) for shallow, lateral areas. This result adds to a growing list of stream- dwelling crayfishes, which, as juveniles, show a distinct preference for shallow, lateral areas

(Butler and Stein, 1985; Creed, 1994; DiStefano et al., 2003a).

One might argue that the lack of reproductive females in my collections reduced densities in the main channel relative to lateral areas (because reproductive females are expected to select main-channel areas; see ‗Size Structure‘ section); however, their absence certainly did not result in differences in density as large as I observed (> an order of magnitude). This is because crayfishes are characterized by high juvenile mortality with few individuals surviving to reproductive age (Hobbs III, 2001). Thus, the absence of reproductive females, which probably

60 account for a minor proportion of overall density in the main channel, likely had a negligible effect on my results. Further, my finding that lateral densities were greater than main-channel densities in both the spring and fall [sub-habitat×season interaction NS (p = 0.595)] would not be expected if my results were due to the absence of reproductive females. Instead, because reproductive females should be present in the spring but not the fall (see Hobbs III, 2001), differences in density between habitats should have been apparent in the April but not the

October collections resulting in a significant sub-habitat×season interaction.

Although I was unable to detect a statistical difference in crayfish density between pools and riffles, as was found by DiStefano et al. (2003b), my results are qualitatively similar to theirs

(higher densities in pools than in riffles). The much larger sampling effort (> 60 × more samples collected) of DiStefano et al. (2003b) likely provided them with far more statistical power than I was able to achieve and thus a much higher probability of detecting differences between pools and riffles.

Although I cannot say for certain why C. (P.) sp. densities were higher in lateral areas than in the main channel, I do know that there was a positive relationship between density in main-channel areas and prevalence of cobble in those areas, suggesting that activities such as road construction and development, which result in sediment deposition and burial of rocky substrates, may have a negative effect on the density of C. (P.) sp. in the main channel [see similar, although less specific, concerns echoed by DiStefano et al. (2003a) and Westhoff et al.

(2006)]. Cobble habitats may be preferred because they have the potential to reduce cannibalism and provide protection from predatory fishes such as brown trout (see Lodge and Hill 1994 and

Nyström 2002). Since main-channel areas are particularly important for large, reproductively

61 mature individuals (see ‗Life History‘ section), reduced density in the main channel may affect the reproductive potential of the population.

Conservation Status and Future Directions

The discovery of a reproducing population of C. (P.) sp. in Valley Cr is noteworthy because it is the first documented occurrence of any member of the C. acuminatus complex north of the Patapsco River basin in Maryland (Figure 3.1) and as such represents a new crayfish record for Pennsylvania. Of further interest, no member of the subgenus Puncticambarus, which includes the C. acuminatus complex, had previously been found in eastern Pennsylvania.

Although efforts to determine the range of C. (P.) sp. in Pennsylvania are not yet complete, preliminary results suggest that it is likely restricted to Valley Cr and several nearby streams and may be native to Pennsylvania (D. A. Lieb, PSU, unpublished data). Similar studies in neighboring states, where members of the C. acuminatus complex are known to occur

(Maryland, Virginia), are needed to determine the complete range of the species. The conservation status of the species depends critically on this information because, if it is a narrow endemic that is found only in SE Pennsylvania, then it may be threatened on the federal level; however, if it has a broader distribution that includes locations in other states, then it may only be threatened on the state level. Regardless, because C. (P.) sp. is only known from a few locations in Pennsylvania, all of which are threatened by urbanization and rusty crayfish (D. A.

Lieb, PSU, unpublished data), regulatory action may be necessary to prevent its extirpation from the state.

Acknowledgements

The National Park Service supported this work. Thanks go to John F. Karish, Nellie

Bhattarai, Brian Lambert (deceased), Adam Smith, and Paula Mooney for their contributions to this study. Raymond W. Bouchard, Ted R. Nuttall, Eric S. Long, John F. Karish, Matt M.

Marshall, and two anonymous reviewers provided helpful critiques of the manuscript. I also thank John E. Cooper and Raymond W. Bouchard for verifying my identifications and for many informative discussions regarding the C. acuminatus complex. Lastly, I thank Jan Briede and

Jamie Krejsa for collecting 4 unusual crayfish from Valley Cr in 2000 and Roger F. Thoma for recognizing that they belonged to the C. acuminatus complex, providing the impetus for this study.

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Table 3.1. Physical characteristics of electrofished areas in Valley Creek. Mean values (

1SE) are reported for each habitat type [shallow lateral areas of riffles (SLR) and pools

(SLP) and main-channel areas of riffles (MCR) and pools (MCP)] and were calculated by pooling data from the four sampling stations and two seasons (spring and fall). Sample sizes are provided in parentheses. Data were collected on 21-22 April and 18-19 October of 2003.

Habitat type Depth (m) Velocity (m/s) Area (m2)

SLR 0.12 ± 0.02 (67) 0.11 ± 0.03 (58) 67.2 ± 19.2 (6)

SLP 0.26 ± 0.02 (99) 0.05 ± 0.01 (94) 126.1 ± 13.8 (8)

MCR 0.23 ± 0.01 (98) 0.51 ± 0.03 (100) 156.8 ± 46.0 (7)

MCP 0.45 ± 0.02 (132) 0.17 ± 0.01 (131) 297.1 ± 40.2 (8)

Table 3.2. Comparison of mean C. (P.) sp. carapace length between main habitats (pool vs riffle), sub-habitats (lateral vs main channel), seasons (spring vs fall) and sexes (male vs female) using a repeated measures (season factor included), five factor, strip-plot (also called a split-block) ANOVA with station (1,2,3,4) as a blocking factor [as described in Steel and Torrie (1980)]. A weighting factor (number of crayfish collected) was used because the number of individuals collected varied among locations. Three-way interaction terms could not be included in the model due to missing data (see 'Crayfish Collections') and the collection of only one sex from some locations, which resulted in insufficient degrees of freedom. Thus, F-tests for all two-way interaction terms are approximate (but the best that can be done) because denominators for those tests consisted of the mean square error (MSE) instead of the more appropriate 3-way interaction terms, e.g., Station×Sub-habitat×Season. Other F-tests were carried out as described in Steel and Torrie (1980). C. (P.) sp. were collected from Valley Creek in 2003. Source d.f. MS F P Station 3 36.79 0.94 0.525 Main habitat 1 8.50 1.01 0.389 Station×Main habitat 3 8.40 0.16 0.919 Sub-habitat 1 1559.06 24.97 0.015 Station×Sub-habitat 3 62.45 1.23 0.326 Main habitat×Sub-habitat 1 184.28 3.64 0.071 Season 1 17.87 0.25 0.651 Station×Season 3 71.43 1.40 0.272 Main habitat×Season 1 0.03 0.00 0.979 Sub-habitat×Season 1 1132.91 22.27 <0.001 Sex 1 174.31 4.03 0.138 Station×Sex 3 43.29 0.85 0.483 Sub-habitat×Sex 1 11.62 0.23 0.639 Main habitat×Sex 1 206.17 4.04 0.059 Season×Sex 1 328.32 6.44 0.020 Error 19 51.09

Table 3.3. Comparison of C. (P.) sp. density between main habitats (pool vs riffle), sub-habitats (lateral vs main channel), and seasons (spring vs fall) using a repeated measures (season factor included), four factor, strip-plot (also called a split-block) ANOVA with station (1,2,3,4) as a blocking factor [as described in Steel and Torrie (1980)]. Station×Main habitat×Season and Station×Sub-habitat×Season interaction terms could not be included in the model due to missing data (see 'Crayfish Collections'), which resulted in insufficient degrees of freedom. Thus, F-tests for Sub-habitat×Season and Main habitat×Season interaction terms are approximate (but the best that can be done) because denominators for those tests consisted of the mean square error (MSE) instead of the more appropriate 3-way interaction terms, e.g., Station×Sub-habitat×Season. Other F-tests were carried out as described in Steel and Torrie (1980). C. (P.) sp. were collected from Valley Creek in 2003. Source d.f. MS F P Station 3 0.002 0.19 0.912 Main habitat 1 0.027 0.96 0.399 Station×Main habitat 3 0.028 1.39 0.388 Sub-habitat 1 0.349 486.82 <0.001 Station×Sub-habitat 3 0.001 0.03 0.990 Main habitat×Sub-habitat 1 0.022 1.05 0.380 Station×Main habitat×Sub-habitat 3 0.021 2.06 0.193 Season 1 0.007 0.65 0.479 Station×Season 3 0.011 1.09 0.415 Main habitat×Season 1 0.000 0.04 0.849 Sub-habitat×Season 1 0.003 0.31 0.595 Error 7 0.010

4 Schuylkill R 3 2 Valley Cr 1

Little Valley Cr

Crabby Cr Streams 0 1 2 3 Kilometers Sampling Stations VFNHP boundary

Figure 3.1. Map of the eastern United States from Pennsylvania to South Carolina with an enlargement of the study area. Valley Creek

sampling stations are numbered 1-4. Previous northern (tip of the down arrow) and southern (tip of the up arrow) limits of the C.

acuminatus complex are included on the map. VFNHP = Valley Forge National Historical Park, R = river, Cr = Creek.

40 50 Spring Spring 40 30 Male Lateral Female Main 30 20 20

10 10

0 0 40 50 Fall Fall

Number collected Number 40 30

30 20 20 10 10

0 0 9 14 19 24 29 34 39 9 14 19 24 29 34 39

Carapace length (mm)

Figure 3.2. Length-frequency distribution of C. (P.) sp. collected from Valley Creek in 2003. Data are broken down by sex in the spring

(male n = 200, female n = 145; top left panel) and fall (male n = 127, female n = 126; bottom left panel) and by sub-habitat in the spring

[lateral n = 196, main channel (main) n = 57; top right panel] and fall (lateral n = 219, main channel n = 34; bottom right panel). Some

76 specimens were omitted from the top right histogram because sub-habitat data were not available for 95 individuals collected in the spring.

0.12

) 2 0.08

0.04 Density(no./m

0 0 25 50 75 100 % Cobble

0.6 0.6

0.4 0.4

0.2 0.2 ) 2 0 0 0 0.2 0.4 0.6 0.8 -0.1 0 0.1 0.2 0.3 0.4 Depth (m) Current velocity (m/s)

Density(no./m 0.6 0.6

0.4 0.4

0.2 0.2

0 0 0 25 50 75 100 0 25 50 75 100 % sand % silt

Figure 3.4. Relationship between depth (upper left), current velocity (upper right), substrate characteristics and C. (P.) sp. density (no./m2) in lateral (♦) and main-channel (O) areas of pools. Substrate characteristics were calculated as the percent of the sampling area where sand (% sand, lower left) or silt (% silt, lower right) was the dominant or co-dominant substrate type. Samples were collected from Valley Creek in the spring

78 and fall of 2003.

0.4

) 2

0.2 Density(no./m

0 0 0.3 0.6 0.9 1.2 Current velocity (m/s)

Figure 3.5. Relationship between current velocity and C. (P.) sp. density (no./m2) in lateral (♦) and main-channel (O) areas of riffles. Samples were collected from Valley Creek in the spring and fall of 2003.

Chapter 4

Crayfish Fauna of Southeastern Pennsylvania: Distributions, Ecology, and Changes over

the Last Century

Modified from:

Lieb, D.A., R.W. Bouchard, and R.F. Carline. 2011. Crayfish fauna of southeastern

Pennsylvania: distributions, ecology, and changes over the last century. Journal of

Crustacean Biology 31: 166-178.

Abstract

I describe the current distributions and relative abundances of southeastern

Pennsylvania‘s crayfish; changes in the region‘s crayfish fauna over the last century; and, where pertinent, the relationship of the current fauna to site-specific characteristics, basin-wide attributes, and exotic crayfish. The crayfish fauna currently inhabiting the region bears little resemblance to the historical assemblage. Whereas historical surveys yielded Orconectes limosus and C. b. bartonii, both native species, recent collections produced eight species including five exotics. Many areas occupied by exotic Orconectes no longer support O. limosus. Cambarus b. bartonii was found in a number of invaded systems, but was typically a minor component of the crayfish community and may not be able to persist in those systems indefinitely. The distribution of C. (P.) sp., an undescribed member of the C. acuminatus complex, was extremely limited, with populations only found in four streams, all of which are threatened by urbanization and

80 exotic crayfish. Exotic species collections include the first published records for P. clarkii in

Pennsylvania and extend the ranges of Orconectes virilis and O. obscurus in the state by > 150 km. These results indicate the need for conservation and management initiatives aimed at preserving the native crayfish that remain in southeastern Pennsylvania.

Introduction

Crayfish are a conspicuous and ecologically important component of aquatic communities across the globe. In many water bodies, they account for a major portion of macroinvertebrate biomass and production (Huryn and Wallace, 1987; Momot, 1995; Rabeni et al., 1995; Haggerty et al., 2002; Haertel-Borer et al., 2005) and exert direct and indirect effects on basal resources (detritus, algae, macrophytes) and other invertebrates (Hart, 1992; Creed,

1994; Lodge et al., 1994; Parkyn et al., 1997; Schofield et al., 2001; Nyström, 2002). They are also an important food item for a number of species of fish, including some of recreational and commercial importance (Rabeni, 1992; Roell and Orth, 1993; Dorn and Mittelbach, 1999; Tay et al., 2007; Weinman and Lauer, 2007).

Crayfish diversity is highest in North America with over 400 species and subspecies

(Taylor, 2002; Taylor et al., 2007). Many of these species have limited distributions and are threatened by exotic (introduced) crayfish, habitat destruction, pollution, urbanization, and other human influences (Hamr, 1998; Wilcove et al., 2000; Lodge et al., 2000; Taylor, 2002; Taylor et al., 2007). Recent conservation status assessments indicate that about half of the North American crayfish fauna is imperiled and in need of protection (Master, 1990; Taylor et al., 1996; Master et al., 2000; Taylor et al., 2007). Even species that were once widely distributed are rapidly

81 disappearing due to man-made disturbances (Hamr, 1998; Kazyak et al., 2005; Bouchard et al.,

2007; Loughman et al., 2009).

Despite their functional importance and threatened status, efforts to preserve and protect

North America‘s crayfish are hindered by a shortage of data. Taylor et al. (2007) estimated that current distributional information is available for only 40% of the United States and Canadian fauna. Even where adequate contemporary data are available, the absence or scarcity of historical collections, particularly for large geographical areas (entire states), often makes it difficult to assess long-term changes across landscapes. Without such data it is hard to accurately classify individual species (endangered, threatened, stable) and develop conservation strategies for those in decline (Jones et al., 2005; Taylor et al., 2007).

In Pennsylvania, although contemporary data are scarce and mostly unpublished, historical collections dating back more than 100 years are available for large areas of the state

(Ortmann, 1906). Ortmann‘s monograph is one of the most thorough and important crayfish studies ever conducted and one of the few large-scale surveys of its vintage from North America.

Nonetheless, given that over 100 years has passed since Ortmann‘s study, a reexamination of

Pennsylvania‘s crayfish fauna is overdue.

Historically, the flowing waters of southeastern Pennsylvania were believed to support two native species of crayfish (O. limosus, C. b. bartonii), both of which were widely distributed in the region (Ortmann, 1906). Unfortunately, the current status of those species is uncertain.

Exotic crayfish were absent from the region at the time of Ortmann‘s survey.

Recently, a member of the C. acuminatus complex [C. (P.) sp.] was discovered in southeastern Pennsylvania (Lieb et al., 2007b; Lieb et al., 2008). Although initial surveys suggest

82 that C. (P.) sp. inhabits flowing waters, has an extremely limited range, and is native to the region, a thorough analysis of its distribution in Pennsylvania is lacking.

The main objectives of this study were to: 1) describe the current distributions and relative abundances of southeastern Pennsylvania‘s crayfish and, where pertinent, the relationship of the current fauna to site-specific characteristics, e.g., stream width, basin-wide attributes, e.g., physiography, and exotic crayfish; and 2) compare those results to historical data

(Ortmann, 1906 and miscellaneous unpublished museum records) to assess changes in the region‘s crayfish fauna over the past century. I focused my efforts on surface-dwelling crayfish; primary burrowers were not included in this survey because they are infrequent, transient inhabitants of surface waters that typically occur in wet or moist terrestrial habitats where they dig burrows to reach the underlying groundwater.

Materials and Methods

Contemporary Data

Study Area and Sampling Sites. — Contemporary (1968-2007) crayfish data from 60 lotic sites and an unknown water body (description too vague to pinpoint exact location) were included in this study (Figure 4.1, Table 4.1). Sites were located in southeastern Pennsylvania in an area roughly bordered by the Schuylkill River and tributaries to the north, the Pennsylvania state line to the south, the city of Philadelphia to the east, and the western boundary of the

Delaware River basin to the west. Sixty sites were located in the Piedmont or Coastal Plain physiographic provinces. Manatawny Creek, site 34 was positioned at the intersection of the

Ridge and Valley, New England, and Piedmont Provinces. Many sites were located in streams that flow directly or nearly directly into the Delaware River (Delaware tributaries, sites 1-8 and

10-15) or its largest tributary, the Schuylkill River (Schuylkill tributaries, sites 29-60).

Additional sites were located in the Brandywine and White Clay Creek drainages (sites 16-25), which both empty into the Delaware River via the Christina River; Big Elk Creek (site 61), which flows into the Chesapeake Bay via the Elk River; and the Schuylkill River (sites 26-28).

One site was located on Long Hook Creek (site 9), which flows out of the lower, marshy portion of a Delaware River tributary (Darby Creek) and historically entered the Delaware River. The northern part of the study area (the north) includes the headwaters of Brandywine Creek (sites

19-20) and the Schuylkill River and tributaries; the southern part of the study area (the south) includes the lower Brandywine drainage (sites 16-18 and 21-22), Delaware tributaries, Long

Hook Creek, Big Elk Creek, and the White Clay drainage (sites 23-25).

Land use change is occurring at a rapid pace throughout much of the study area. As such, many formerly rural areas are quickly becoming urbanized (Kemp and Spotila, 1997; Interlandi and Crockett, 2003; Reif, 2004; Steffy and Kilham, 2006).

Thirty-two sites on 27 streams were thoroughly surveyed for crayfish (comprehensive sites; Table 4.1). The remaining 29 sites located on 25 streams and one unknown water body were sampled for other purposes, e.g., fish surveys, not specifically for crayfish (incidental sites;

Table 4.1). Comprehensive sites were georeferenced using a handheld GPS unit (model GPS 12

XL, Garmin International). The latitudes and longitudes of the incidental sites were either provided by others or were estimated with a computer program (Terrain Navigator Pro) that uses electronic United States Geological Survey (USGS) quadrangle maps.

Crayfish Collections. — Each comprehensive site was surveyed during daylight hours when water clarity was high and the stream bottom was clearly visible. The lower reaches of

Valley Creek (lower Valley Creek, sites 50-53) were sampled twice (spring and fall 2003); other comprehensive sites were sampled once (spring 2005 or 2006). Welch Run, Fawn Run, Baptism

Creek, Spout Run, and lower Valley Creek were sampled for other projects (Lieb et al., 2007a, b;

Lieb et al., 2008); the remaining comprehensive sites were sampled specifically for this study.

At each comprehensive site, multiple riffle-pool sequences and all available habitat types were thoroughly searched. The length of stream sampled varied from approximately 40-500 m depending on the distance between habitat types and size of the stream. Each site was sampled for at least one person-hour per visit. Based on earlier surveys of 53 streams located across

Pennsylvania, this level of effort frequently results in the collection of large numbers of crayfish of all sizes and life stages and appears to be an effective method for determining community composition and compiling species lists for individual sites (Lieb et al., 2007a). Additionally, my effort was equal to or in excess of that used in a variety of settings to detect the presence of stream-dwelling crayfish species (Naura and Robinson, 1998; Light, 2003; Gil-Sánchez and

Alba-Tercedor, 2006). Species were assumed to be reproducing (established) if reproductive females (those with attached eggs or young) were found or ≥ 9 individuals, both sexes, and a range of sizes were collected.

Most comprehensive sites were sampled with dip nets and kick seines. Dip net samples were collected by sweeping the net through root masses, aquatic vegetation, and leaf deposits and by turning over rocks and chasing crayfish into the net. Kick seine samples were collected by stretching a 2.8 2.0 m bag seine with 5-mm mesh across the stream channel and disturbing the substrate (kicking, overturning rocks) upstream of the seine. Dislodged crayfish were swept into the seine by the current. Crayfish inhabiting slow-current habitats (pools and nearshore areas of riffles) were usually collected with dip nets, whereas those in fast-current habitats (main

85 channels of riffles) were mostly collected with kick seines. A few comprehensive sites (sites 50-

53) were sampled with electrofishing gear. The number of crayfish collected from sites 50-53 was greater than from the other sites because electrofishing gear tended to be more efficient than dip nets and kick seines in terms of the number of specimens collected per person-hour [see Lieb et al. (2008)] and sites 50-53 were sampled twice, whereas the other comprehensive sites were only sampled once.

At the incidental sites, most collections contained < 10 individuals (see Table 4.1) and it is unlikely that all habitat types were sampled or that species lists are complete. As a result, the

Crayfish Associations and Community Composition sections of this paper do not include data from most incidental sites. The only exception was lower Manatawny Creek (sites 35-38) which was included in the Community Composition section because collections where large (69 individuals) and the assemblage found there was not collected elsewhere during this study.

It was impossible to determine whether species were reproducing at most incidental sites because collections included few specimens and no reproductive females. The only exception was lower Manatawny Creek, where enough O. rusticus were collected (n = 60) to assume the presence of a reproducing population.

Incidental collections were gathered using a variety of methods. Specimens from Crum

Creek (site 1), Little Valley Creek, and East Branch (EB) Brandywine Creek were collected with

Lium samplers (Lium, 1974) by the USGS during benthic invertebrate sampling and those from

Manatawny Creek (site 38) were collected with seines during fisheries studies carried out by the

Academy of Natural Sciences of Philadelphia (ANSP). Specimens from Dismal Run, Webb

Creek, and the Schuylkill River (site 26) were also collected by ANSP personnel but their purpose and method of collection is unknown. Similarly, site 25 in the White Clay Creek

86 drainage was sampled for unknown reasons using unknown methods. The P. clarkii attributed to

Sandy Run was found dead on a roadway that runs parallel to the creek, but was included in this study because the species is known to exhibit overland dispersal and was likely an emigrant from

Sandy Run or another nearby water body (Bouchard et al., 2007). The remaining incidental sites were sampled with electrofishing gear during fisheries studies conducted by ANSP. Most incidental sites were sampled on one occasion (summer or fall) between 1996 and 2007 (Table

4.1).

After collection, crayfish were identified to species and reproductive females were noted.

The carapace length (CL) of specimens collected from comprehensive sites was determined.

Representative specimens of C. (P.) sp. were deposited at the North Carolina State Museum of

Natural Sciences (NCSM), Raleigh, North Carolina (NCSM 24749-24753, 26548-26553) or

ANSP, Philadelphia, Pennsylvania (not yet cataloged, A. Kirsch, personal communication).

Voucher specimens of O. virilis, O. limosus, O. obscurus, O. rusticus, C. b. bartonii, and P. clarkii were deposited at ANSP (ANSP 14573, 18349, 18398, 18413, 18419, 18421-26, 18437,

18443-45, 19345-46, 19349-50, and 19352 or not yet cataloged, A. Kirsch, personal communication). The Procambarus acutus collected from site 25 is housed at the United States

National Museum, Smithsonian Institution (USNM), Washington D.C. (USNM 129955).

Historical Data

Historical crayfish data from the study area and nearby areas were available from

Ortmann (1906), ANSP, and USNM. Ortmann (1906), which includes numerous collections from southeastern Pennsylvania and a map (Plate XLIII) that shows the original distributions of

Pennsylvania‘s crayfish (including C. b. bartonii and O. limosus), was a particularly useful

87 resource. At most of Ortmann‘s sites, it appears that efforts were made to collect all the crayfish species that were present. Collections were generally made by hand or with a dip net. Additional collection information is provided in Ortmann (1906). For the remaining historical sites (USNM and ANSP records), sampling methods were not recorded.

Results and Discussion

Taxonomy of C. (P.) sp. in Pennsylvania

Although it will not be possible to attach a species name to my C. (P.) sp. collections until a thorough taxonomic analysis of the northern members of the C. acuminatus complex is completed (Lieb et al., 2008), I doubt that they include multiple species because of the proximity of my collection sites (Figure 4.2) and morphological similarity of my specimens. If later taxonomic studies were to show that multiple species of Puncticambarus occur within the study area, it will be possible to attach the correct species name to my collections because I have deposited representative specimens of C. (P.) sp. from all the streams where it was collected in museums.

Overview of Crayfish Collections

A total of 1416 crayfish belonging to eight species was collected during contemporary surveys (Table 4.1, 4.2). Of these, 1165 were collected from 37 sites (25 streams) in the north; the remaining 251 were collected from 24 sites (20 streams) in the south (Figure 4.1, Table 4.1,

4.2). More crayfish were collected from lower Valley Creek (613 individuals) than from the other northern sites (552 individuals) because sampling efforts were greater in lower Valley

Creek than elsewhere. Due to this potential bias, the abundance summaries (number collected, relative abundance) provided in the remainder of this section do not include data from lower

Valley Creek (see Table 4.2 for further explanation).

Contemporary surveys yielded five exotic crayfish including P. acutus, which is native to extreme southeastern Pennsylvania (Coastal Plain and nearby areas of the Piedmont) but not to most of the study area (Bouchard et al., 2007); O. obscurus, which is native to western but not eastern Pennsylvania (Ortmann, 1906; Bouchard et al., 2007); and O. virilis, O. rusticus, and P. clarkii, which are not naturally found anywhere in the state (Taylor et al., 1996, 2007) (Table

4.1, 4.2). The P. clarkii data provided herein are of particular significance because they are the first published records for Pennsylvania (Ortmann, 1906; Hobbs, 1972, 1989; and Taylor et al.,

2007) and increase the number of known crayfish species in the state. Records of O. rusticus, O. virilis, and O. obscurus are the first that have been published for southeastern Pennsylvania.

Contemporary collections also included C. b. bartonii and O. limosus, which historically occurred throughout the study area (Ortmann, 1906), and the recently discovered C. (P.) sp.

(Table 4.1, 4.2). Collectively, recent efforts have added five species (four exotics and one native) to the known crayfish fauna of southeastern Pennsylvania. The region‘s crayfish fauna is now vastly different than that encountered by Ortmann (1906). Such differences tended to be much more pronounced to the north, where exotic crayfish (mostly Orconectes) were common, than to the south (Figure 4.2, 4.3, Table 4.1, 4.2).

Across the study area, C. b. bartonii was the most frequently collected crayfish (269 individuals, 33% of the catch), followed by O. rusticus (204 individuals, 25% of the catch) and

O. limosus (144 individuals, 18% of the catch); other crayfish accounted for < 10% of the catch

(Table 4.1, 4.2). In the north, O. rusticus was the most commonly collected crayfish, followed by

C. b. bartonii and O. obscurus; other crayfish were uncommon (Table 4.2). The scarcity of O. limosus in the north, an area that it once fully occupied, was especially noticeable. In contrast, in the south, O. limosus was the most frequently collected crayfish, followed by C. b. bartonii and

C. (P.) sp.; other crayfish were rarely collected (Table 4.2). The rarity of O. rusticus, O. obscurus, and O. virilis in the south was particularly evident given their comparative abundance to the north.

Contemporary Distributions and Range Changes

Cambarus b. bartonii. — During this study, C. b. bartonii was collected from 31 sites

(29 streams) (Figure 4.3, Table 4.1, 4.2). These sites were in the Coastal Plain (n = 1), Piedmont

(n = 29), and at the intersection of the Ridge and Valley, New England, and Piedmont (n = 1).

Cambarus b. bartonii was found in 21 of the 24 small to midsized streams that were comprehensively surveyed and was common throughout all parts of the study area except the

Coastal Plain. These results agree with Ortmann (1906) who concluded that, although C. b. bartonii was generally absent from large rivers in Pennsylvania, ‗‗conditions seem to be favorable for this species everywhere, possibly with the exception of the Coastal Plain‘‘ and suggests that the range of C. b. bartonii in southeastern Pennsylvania has remained relatively stable over the past century.

Cambarus b. bartonii has been able to persist over the long-term in a number of streams in the study area. More specifically, C. b. bartonii was collected from Cobbs and Darby creeks in the early 1900s (ANSP 4783-84 and 5023), from Ridley and White Clay creeks in the 1950s

(ANSP 6149, 6215-18, and 6224-25), and from all four of those creeks in 2006 (Figure 4.3,

Table 4.1). However, exotic crayfish are currently not found in any of those waterways and it

90 remains to be seen whether C. b. bartonii can coexist with exotic crayfish over the long-term in southeastern Pennsylvania.

Cambarus (P.) sp. — During this study, C. (P.) sp. was collected from 13 sites (eight streams) (Figure 4.2, Table 4.1, 4.2). These sites were in the Coastal Plain (n = 1) and Piedmont

(n = 12) and were located within a relatively small area (~ 220 km2) extending from Pickering

Creek southeast to the lower reaches of Darby Creek within ~ 30 km of Philadelphia. Most C.

(P.) sp. sites were located to the north in the Schuylkill River and its tributaries, which is mainly due to the large number of collections from the Valley Creek basin. Cambarus (P.) sp. was also collected from tributaries of the Delaware River, but was not collected from the Brandywine and

White Clay Creek drainages. Most of the C. (P.) sp. collected during this study (n = 666) were found in the Pickering, Valley, Darby, and Crum Creek drainages. The remaining individuals were collected from Welch Run and the Schuylkill River.

A reproducing population of C. (P.) sp. occurs in Valley Creek (Lieb et al., 2008, Figure

4.2, Table 4.1). Surveys done specifically for this study uncovered additional reproducing populations of C. (P.) sp. in Pickering, Crum, and Darby creeks (Figure 4.2, Table 4.1). These findings are not particularly surprising given that the headwaters of Valley Creek are < 2 km from those of Darby, Pickering, and Crum creeks and the headwaters of Darby and Crum creeks are < 2 km from each other (Figure 4.2). Dams are located downstream of the Crum, Darby, and

Pickering Creek populations and may be preventing them from being colonized by exotic

91 crayfish, which occur in a number of nearby waterways (Lieb and Bhattarai, 2009 and Figure

4.2).

A thorough search of sites on the Schuylkill River and Welch Run resulted in the collection of only two C. (P.) sp. (Table 4.1). This suggests that reproducing populations of the species do not occur in those waterways. Instead, individuals collected at those sites were probably emigrants from nearby Valley Creek or Pickering Creek (Figure 4.2).

Orconectes limosus. — During this study, O. limosus was collected from 17 sites (16 streams) (Figure 4.3, Table 4.1, 4.2). Sites were in the Coastal Plain (n = 4), Piedmont (n = 12), and at the intersection of the Ridge and Valley, New England, and Piedmont (n = 1). Most O. limosus sites were located in the south, where exotic crayfish were rare. Northern occurrences of

O. limosus were limited to three sites, all of which were located on Schuylkill tributaries and were devoid of exotic Orconectes. Reproducing populations of O. limosus were found in eight streams, seven of which are in the south. The apparent absence of O. limosus from much of the north (Figure 4.3, Table 4.1, 4.2), a region it once fully occupied [see Ortmann (1906)], suggests a substantial range reduction over the past century, although it is possible that some undiscovered populations remain to the north or that population sizes have declined substantially making existing populations extremely difficult to detect.

In the early 1900s, O. limosus was collected from a ~ 90 km stretch of the Schuylkill

River (Philadelphia upstream to Reading) where it was sometimes ‗‗exceedingly abundant‘‘

(Ortmann, 1906). In the 1950s, O. limosus was again collected from multiple locations along that reach (ANSP 5674 and 6229); however, recent crayfish surveys in that section yielded large numbers of exotic O. rusticus, which was not previously collected from the Schuylkill River, but

92 no O. limosus (Table 4.1). Similarly, O. limosus was collected from an upstream reach of EB

Perkiomen Creek in the 1930s (USNM 131923), but contemporary collections produced only O. rusticus (Table 4.1). Although contemporary collections from EB Perkiomen Creek were not comprehensive, O. limosus and O. rusticus have never been found together at the same site in the study area (Table 4.1), potentially due to the elimination of resident O. limosus by exotic O. rusticus. In Pennsylvania, O. rusticus has been collected from 59 sites, but with O. limosus at only one of them, a recently invaded site in the northeastern part of the state (Bouchard et al.,

2007; Lieb et al., 2007a; D.A. Lieb, PSU and R.W. Bouchard, ANSP, unpublished data).

In other parts of the Perkiomen Creek drainage, historical collections produced only O. limosus, while those completed more recently yielded only O. rusticus (Figure 4.1, 4.3, 4.4,

Table 4.1). Direct comparisons are not possible because historical collections (1916-1943) were from headwater reaches (Perkiomen Creek at Pennsburg, ANSP 5307; Hosensack Creek, ANSP

5332; unnamed tributary of Pleasant Spring Creek, USNM 131914), whereas recent efforts have been from downstream areas (Perkiomen and Swamp Creeks). Nonetheless, since O. limosus was historically more common in the larger, downstream reaches of Pennsylvania‘s river networks than in smaller, upstream tributaries (Ortmann, 1906); it seems unlikely that O. limosus would have been found in the headwaters of Perkiomen Creek but not in downstream areas.

Thus, I suspect that O. limosus was once found throughout much of the Perkiomen drainage but no longer occurs in downstream areas. Although the headwaters of Perkiomen Creek have not been sampled in > 60 years, O. limosus may have been afforded protection from O. rusticus invasions by the dam on Green Lane Reservoir (Figure 4.3, 4.4).

In the south, O. limosus was relatively common and the species seems to have retained much of its original range (Ortmann, 1906; Figure 4.3, Table 4.1, 4.2). For example, resampling

93 efforts in Marcus Hook and Brandywine creeks found that populations of O. limosus were still present in those waterways 100 years later (Ortmann, 1906; Table 4.1). Recent collections from the headwaters of Brandywine Creek included large numbers of exotic O. virilis and O. obscurus but no O. limosus (Table 4.1), suggesting that the continued existence of downstream populations of O. limosus in Brandywine Creek is not assured.

Overall, I suspect that exotic crayfish (particularly O. obscurus, O. rusticus, and O. virilis) are a major reason for the absence of O. limosus from much of the north including a substantial section of the Schuylkill River, a number of Schuylkill tributaries, and some headwater reaches in the Brandywine basin. In contrast, the scarcity of exotic crayfish to the south probably explains the persistence of O. limosus in that region. It is also possible that environmental and/or biological conditions have changed to the north but not the south contributing to the absence of O. limosus from the north, although such changes were not apparent during field collections.

Within the study area, reproducing populations of O. limosus were found in running water systems that ranged from small streams (EB White Clay Creek: generally < 10 m wide) to large rivers (Brandywine Creek: generally > 30 m wide). This finding is in agreement with

Ortmann (1906) who found that, although O. limosus preferred larger waterways, the species occurred throughout drainage networks (headwater streams to large rivers).

Orconectes obscurus. — During this study, O. obscurus was collected from eight sites

(five streams) in the Piedmont (Figure 4.4, Table 4.1, 4.2). All were in the north, but were widely scattered, suggesting multiple introductions. One site was located in the headwaters of

Brandywine Creek, where the species is reproducing; the remaining sites were located in

Schuylkill tributaries, two of which also support reproducing populations.

The O. obscurus records herein extend the known range of the species in Pennsylvania substantially eastward. More specifically, to the best of my knowledge, the previous easternmost, published O. obscurus localities for Pennsylvania are located > 200 km to the west of

Wissahickon Creek in the north central and south central parts of the state [upper Genesee River drainage, Potter County and Willis Creek, Bedford County (Ortmann, 1906)].

In the study area, O. obscurus was collected from small to midsized streams (~ 5-30 m wide). Orconectes obscurus was not collected from any of the large river sites (Perkiomen

Creek, Brandywine Creek, Schuylkill River; Table 4.1), even though in its native range (western

Pennsylvania) it generally prefers such sites (Ortmann, 1906). The presence of O. rusticus at most of the large river sites may be responsible for the absence of O. obscurus at those locations, as has been found in parts of Ohio and New York (Thoma and Jezerinac, 2000; Kuhlmann and

Hazelton, 2007).

Orconectes rusticus. — During this study, O. rusticus was collected from 12 sites

(seven streams) in the Piedmont (Figure 4.4, Table 4.1, 4.2). All were in the north and were located either in the Schuylkill River or its tributaries. Reproducing populations of the species were found in five streams. Notably, O. rusticus was the only crayfish collected from the lower

Perkiomen Creek drainage (sites 39-42) and occurs far upstream in the headwaters of at least one tributary in that drainage (EB Perkiomen Creek). Similarly, aside from the collection of a single

C. (P.) sp., which was probably an emigrant from elsewhere, and a single P. clarkii, O. rusticus was the only crayfish collected from the Schuylkill River. Because exotic O. rusticus tend to

95 eliminate other crayfish from invaded sites through time (St. John, 1991; Taylor and Redmer,

1996; Wilson et al., 2004; Kuhlmann and Hazelton, 2007), it seems likely that, within the study area, O. rusticus introductions occurred first in the Schuylkill River or in the lower Perkiomen drainage. It also appears that environmental conditions, e.g., temperature, nutrient concentrations, at those sites are particularly favorable for O. rusticus, allowing the species to thrive there. More specifically, the Schuylkill River and lower Perkiomen Creek are relatively large (generally > 50 m wide), warm, enriched [Jaworski and Hetling, 1996; Jaworski et al.,

1997; Pennsylvania Department of Environmental Protection (PADEP), 2003], and negatively impacted by a variety of anthropogenic stressors (Weisberg and Burton, 1993; Fairchild et al.,

1998; Steyermark et al., 1999; Interlandi and Crockett, 2003; PADEP, 2003), all of which tend to favor O. rusticus relative to resident species (Momot, 1984; Jezerinac, 1986; Butler, 1988;

Momot et al., 1988; Mundahl and Benton, 1990; St. John, 1991; Jezerinac et al., 1995; Thoma and Jezerinac, 2000).

Within the study area, O. rusticus sites ranged from large, warm rivers at the base of drainage networks (Perkiomen Creek, Schuylkill River) to small, cooler streams near the headwaters (EB Perkiomen Creek) (Figure 4.4, Table 4.1) and included visibly polluted waterways in highly urbanized watersheds (Trout Creek), as well as higher quality streams draining mostly forested and agricultural lands (French and Manatawny creeks; Thomson et al.,

2005; J.K. Jackson, Stroud Water Research Center, unpublished data). Collectively, these data indicate that O. rusticus is a highly-adaptable, tolerant species that has been able to colonize a wide variety of running water systems in southeastern Pennsylvania, as has been found elsewhere (St. John, 1982, 1991; Page, 1985; Hobbs and Jass, 1988; Hobbs et al., 1989; Thoma and Jezerinac, 2000; Taylor and Schuster, 2004; Guiaşu, 2007). Because of this, the spread of O.

96 rusticus into new areas may be more limited by dispersal (both natural and human-assisted) than by the availability of suitable environmental conditions. It is possible; however, that exotic O. rusticus may be less successful in cool, nutrient-poor, headwater streams than in warmer, more productive, downstream reaches as predicted by Momot (1984) and as appears to be the case in

Ohio (Mundahl and Benton, 1990; Thoma and Jezerinac, 2000). If so, in southeastern

Pennsylvania and elsewhere, some native species may be able to persist in the headwaters of invaded systems, where O. rusticus is absent or less abundant. This is particularly likely for C. b. bartonii, which naturally occurs in headwater streams throughout the eastern United States

(Ortmann, 1906; Crocker, 1957, 1979; Francois, 1959; Meredith and Schwartz, 1960; Jezerinac et al., 1995; Seiler and Turner, 2004). Unfortunately, for those native species that prefer larger, downstream reaches, e.g., O. limosus (Ortmann, 1906), direct competition with O. rusticus may be unavoidable.

Orconectes virilis. — During this study, O. virilis was collected from three sites in the

Piedmont and one site in the Coastal Plain and was more common in the north than south (Figure

4.4, Table 4.1, 4.2). Orconectes virilis collections were widely scattered, suggesting multiple introductions and included a site in the headwaters of Brandywine Creek, where the species is reproducing, and sites on Schuylkill and Delaware tributaries.

The localities herein extend the known range of O. virilis in Pennsylvania substantially eastward. More specifically, to the best of my knowledge, the previous easternmost published O. virilis record for Pennsylvania is located > 150 km to the west of Hermesprota Creek in the south central part of the state [Marsh Creek, Adams County; USNM record listed in Hobbs (1989)].

Within the study area, O. virilis was collected from small to midsized streams (~ 5-30 m wide) that varied with regards to temperature and upstream land use. More specifically, Trout and Hermesprota creeks are warm-water fisheries, while French and West Branch (WB)

Brandywine creeks support cold-water fishes (trout) for much of the year. Similarly, Trout and

Hermesprota creeks are located in highly urbanized areas, whereas French and WB Brandywine creeks are located in more rural settings with mixed land use. Overall, O. virilis was collected from a variety of stream types in southeastern Pennsylvania, as has been found in other parts of its introduced range (Schwartz et al., 1963; Bouchard, 1976; Jezerinac et al., 1995; McGregor,

1999).

Procambarus acutus. — Procambarus acutus was collected from two sites in the

Piedmont during this study: a Schuylkill tributary in the north and a site in the White Clay drainage in the south (Figure 4.4, Table 4.1, 4.2). The distance between sites suggests separate introductions. A private aquaculture facility, which sells P. acutus and is located ~ 20 km west of the northern site, may be responsible for the presence of the species in the area.

Although P. acutus is expanding its range in Pennsylvania due to introductions, native P. acutus have not been collected from Pennsylvania since the early 1900s and few thorough surveys in its native range in southeastern Pennsylvania have been conducted (Bouchard et al.,

2007; Figure 4.1, Table 4.1). For this reason, additional surveys in its native range are needed.

Procambarus clarkii. — Procambarus clarkii was collected from three sites in the

Piedmont and one site in the Coastal Plain during this study (Figure 4.4, Table 4.1, 4.2). These collections were widely scattered suggesting multiple introductions and included sites to the

98 north in the Schuylkill River and its tributaries, one of which supports a reproducing population, and a site to the south in Long Hook Creek.

Procambarus clarkii sites varied substantially in size, gradient, and temperature. More specifically, sites on Sandy Run and Wissahickon Creek were generally < 15 m wide, whereas the Schuylkill River site was > 50 m across. Similarly, the Schuylkill River is a warm-water fishery, while Wissahickon Creek supports trout for much of the year. Long Hook Creek is a low-gradient, marshy stream, whereas Wissahickon Creek is a higher-gradient, rocky stream.

Procambarus clarkii sites tended to be similar with regards to upstream land use (all in urban areas) and nutrient status (most enriched) (Jaworski and Hetling, 1996; Jaworski et al., 1997;

Butler et al., 2001; Philadelphia Water Department, 2004; PADEP, 2006). These findings are not unexpected given that, although P. clarkii has been widely introduced to a variety of habitats

(swampy lowlands and ponds to trout streams; Hobbs et al., 1989; Dehus et al., 1999; Gherardi et al., 1999; Thoma and Jezerinac, 2000; Huner, 2002), some authors have noted their apparent preference for developed (urbanized) areas and enriched waters in parts of their introduced range

(Diéguez-Uribeondo et al., 1997; Gil-Sánchez and Alba- Tercedor, 2002; Riley et al., 2005).

The discovery of P. clarkii in southeastern Pennsylvania is not particularly surprising given the presence of exotic populations in Maryland, New York, and Ohio (Thoma and

Jezerinac, 2000; Daniels, 2004; Kazyak et al., 2005; Kilian et al., 2009) and cultured populations in western Pennsylvania. Although particular dispersal mechanisms are not known, P. clarkii probably initially reached southeastern Pennsylvania via human assistance (release or escape of laboratory specimens, aquarium pets, fishing bait, commercially cultured animals), as has occurred elsewhere (Hobbs, 1989; Campos and Rodriguez-Almaraz, 1992; Bouchard et al.,

2007; Larson and Olden, 2008; Kilian et al., 2009). Upon arrival, the presence of urbanized, enriched systems likely favored its establishment in the area.

Crayfish Associations

At most sites, either one or two species of crayfish were collected (Table 4.1). Common species pairs were C. b. bartonii and O. limosus and C. b. bartonii and C. (P.) sp. Cambarus b. bartonii was collected from all streams (and five of seven sites) where reproducing populations of C. (P.) sp. were found and six of eight streams (sites) where reproducing populations of O. limosus were found. Cambarus b. bartonii has also been collected with the C. acuminatus complex in parts of Virginia (Hobbs et al., 1967).

Cambarus b. bartonii was collected with exotic crayfish at a number of sites in the north including six of seven comprehensive sites inhabited by P. acutus, P. clarkii, O. virilis, and O. obscurus and two of six comprehensive sites inhabited by O. rusticus (Figure 4.3, 4.4, Table

4.1). The association of C. b. bartonii with O. obscurus was not surprising given they co-occur elsewhere and when sympatric appear to avoid direct competition by selecting different habitats

(Jezerinac et al., 1995; Hamr, 1998; Kuhlmann and Hazelton, 2007; D.A. Lieb, PSU and R.W.

Bouchard, ANSP, unpublished data). Cambarus b. bartonii is also found with exotic crayfish in other parts of Pennsylvania (Bouchard et al., 2007; Lieb et al., 2007a; R.W. Bouchard, ANSP and D.A. Lieb, PSU, unpublished data). These results suggest that the continued prevalence of C. b. bartonii in the north is probably due to its ability to coexist with exotic crayfish.

Cambarus b. bartonii was never found exclusively with O. rusticus, but was collected with O. rusticus and O. virilis (Table 4.1). Although it is unclear why C. b. bartonii and O. rusticus were only found together with other species, this tendency was not restricted to the study

100 area. Elsewhere in Pennsylvania, C. b. bartonii and O. rusticus were found together in eight streams but exclusively in only two of them (Lieb et al., 2007a; R.W. Bouchard, ANSP and D.A.

Lieb, PSU, unpublished data). Because exotic O. rusticus typically eliminate O. virilis (Berrill,

1978; Capelli, 1982; Taylor and Redmer, 1996; Wilson et al., 2004), they are probably not permanent associates in southeastern Pennsylvania. Instead, the O. virilis collected were probably remnants of larger populations, emigrants from elsewhere in their respective watersheds, or recent introductions. Because C. b. bartonii can sometimes persist with exotic O. rusticus (Hamr, 2002; D.A. Lieb, PSU and R.W. Bouchard, ANSP, unpublished data), their association may be more permanent.

Cambarus (P.) sp. was collected with O. rusticus in the Schuylkill River but was absent from other invaded sites (Figure 4.2, 4.4, Table 4.1). Because the single C. (P.) sp. collected from the Schuylkill River was likely an emigrant from elsewhere, C. (P.) sp. is probably only an occasional, transient associate of O. rusticus in that waterway. Crayfish surveys conducted in the summer of 2008 by the National Park Service (NPS) indicate that O. rusticus has recently invaded lower Valley Creek and currently coexists with C. (P.) sp. (Kristina Heister, NPS, personal communication), although C. (P.) sp. appears to be in decline and may eventually disappear from the system.

Orconectes limosus was only collected with exotic crayfish at one site and was never found with exotic Orconectes (Figure 4.3, Table 4.1). The apparent inability of O. limosus to coexist with exotic congeners probably contributed to its absence from much of the north.

101

Community Composition

Uninvaded sites supported one species of crayfish or if multiple species were present O. limosus or C. (P.) sp. usually accounted for a substantial portion of the collections (43-98%), with C. b. bartonii comprising most of the remaining catch (Table 4.1). The preference of O. limosus and C. (P.) sp. for slow-current areas probably favored their coexistence with C. b. bartonii, which tend to select areas with faster-current (Ortmann, 1906; Lieb et al., 2008; D.A.

Lieb, PSU, personal observations). The preference of O. limosus and C. (P.) sp. for similar habitats may have prevented their coexistence and contributed to their mostly allopatric distribution in the study area.

Collections at most invaded sites were dominated by one species of exotic Orconectes; other species were usually uncommon (Table 4.1). Where found, O. rusticus usually comprised

75% of the catch. In the absence of O. rusticus, O. obscurus and O. virilis accounted for 63-

100% of the catch, whereas those species usually constituted ≤ 25% of the catch in the presence of O. rusticus. The dominance of O. rusticus will likely increase in the future as populations of

O. obscurus and O. virilis are further reduced or eliminated.

Cambarus b. bartonii was uncommon at invaded sites (relative abundance ≤ 20%) but was frequently an important member of the crayfish community in the presence of native crayfish (relative abundance often > 20% and sometimes 50%) (Table 4.1). These data along with observations from Maryland and other parts of Pennsylvania, where C. b. bartonii is not always able to coexist with exotic crayfish (Schwartz et al., 1963; D.A. Lieb, PSU and R.W.

Bouchard, ANSP, unpublished data), suggest that, although the range of C. b. bartonii in southeastern Pennsylvania has remained relatively stable over the past century, its continued persistence in the region is not assured and will depend on its ability to coexist with exotic

102 crayfish over the long-term, potentially at reduced densities and as a minor component of the crayfish community.

Concluding Remarks and Conservation Implications

The results presented herein suggest that there have been substantial changes in the crayfish fauna of southeastern Pennsylvania over the past century. The prevalence of exotic crayfish in the region and apparent disappearance of O. limosus from invaded areas was particularly noticeable. Although C. b. bartonii was found in a number of invaded systems, it was typically a minor component of the crayfish community and may not be able to persist in those systems over the long-term.

In addition to documenting changes, this study also provides important distributional information for C. (P.) sp. More specifically, the data herein along with results from less- focused, larger-scale surveys (Lieb et al., 2007a; Bouchard et al., 2007) indicate that C. (P.) sp. has an extremely restricted distribution in Pennsylvania, with collections limited to 13 sites and reproducing populations only known from four streams, all of which are located in a rapidly expanding urban area in close proximity to several species of exotic crayfish (Figure 4.2, 4.4).

Based on these findings, the native crayfish fauna of southeastern Pennsylvania is clearly in decline and conservation measures targeting the group are urgently needed. The protection of existing populations of C. (P.) sp. and O. limosus is of particular importance and will probably require measures aimed at preventing crayfish introductions and reducing the impacts of urban development. The recent invasion of lower Valley Creek by O. rusticus and apparent decline in resident C. (P.) sp. illustrate the urgency of the situation. Although C. b. bartonii is not an immediate conservation concern in the region, existing populations (particularly those in invaded

103 systems) should be monitored periodically. Overall, I suspect that, without management intervention, native crayfish will continue to disappear from southeastern Pennsylvania and may eventually be lost from much of the region.

Acknowledgements

I thank Nellie Bhattarai, Hannah M. Ingram, and Jeremy Harper for their substantial contributions. The Wild Resources Conservation Fund, Pennsylvania Department of

Conservation and Natural Resources (Project Number AG050523); the National Park Service

(Grant Agreement H4560030064); and a Pennsylvania State Wildlife Grant (number

PFBC050305.01) provided financial support. Christopher A. Urban, Matt R. Marshall, and Sarah

Nichols administered grants and provided encouragement. Marybeth Lieb, John E. Cooper, and an anonymous reviewer provided helpful critiques of the paper and Erin Greb assisted with figure preparation. Drew Reif, Mike Bilger, Rafael Lemaitre, and especially Richard J. Horwitz and Paul F. Overbeck provided museum records or crayfish specimens. The Stroud Water

Research Center granted access to White Clay Creek.

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Table 4.1. Contemporary (1968-2007) crayfish collections at individual sampling sites in southeastern Pennsylvania. Sites denoted with single asterisks (*) were not specifically

surveyed for crayfishes (incidental sites). At the remaining sites, a thorough crayfish survey was conducted (comprehensive sites). Reproducing populations of Orconectes,

Procambarus, and C. (P.) sp. are denoted by double asterisks (**). Except for Long Hook Creek, which flows out of lower Darby Creek, tributaries are indented below the stream

they flow into. For streams sampled at multiple locations, upstream sites are listed first followed by downstream sites. Abbreviations used: WB = West Branch, EB = East

Branch, Cr = Creek, R = River, Lat = Latitude, Long = Longitude, Coll = Collection, Rel ab = Relative abundance, Phys = Physiographic province, CP = Coastal Plain, P =

Piedmont, Int = intersection of Ridge and Valley, New England, and Piedmont, P. = Procambarus (genus) or Puncticambarus (subgenus), O. = Orconectes, and C. = Cambarus.

BBerried female(s) collected. YFemale(s) with attached young collected.

Lat, Long Coll Rel ab Stream Site Phys (decimal °) date Species N (%) Delaware R ------Crum Cr 1* P 40.0078, -75.4653 31Oct82 C. b. bartonii 1 100 Crum Cr 2 P 39.98975, -75.43623 11May06 C. b. bartonii 17 53 - - - - - C. (P.) sp.**B 14 44 - - - - - O. limosus**B 1 3 Darby Cr 3 P 39.98899, -75.34277 11May06 C. b. bartonii 5 16 - - - - - C. (P.) sp.**B 26 84 Darby Cr 4* CP 39.93470, -75.27715 25Jul06 C. (P.) sp. 2 29 - - - - - O. limosus 5 71 Cobbs Cr 5 P 39.97462, -75.27971 11May06 C. b. bartonii 8 100 Cobbs Cr 6* CP 39.935, -75.237 09Dec99 O. limosus 1 100 Indian Cr 7* P 39.97776, -75.26163 02Jun98 C. b. bartonii 1 100 Hermesprota Cr 8* CP 39.89126, -75.26816 21Mar07 O. virilis 1 100 Long Hook Cr 9* CP 39.87570, -75.28708 28Jul05 P. clarkii 1 100 Marcus Hook Cr 10* CP 39.83111, -75.41056 24Jul06 C. b. bartonii 2 29 - - - - - O. limosus 5 71 Ridley Cr 11 P 39.95732, -75.44373 11May06 C. b. bartonii 11 34

116

- - - - - O. limosus**B 21 66 Ridley Cr 12* CP 39.86396, -75.34930 14Jul06 O. limosus 5 100 Dismal Run 13* P 39.94050, -75.42208 10Oct01 C. b. bartonii 7 100 WB Chester Cr 14 P 39.88972, -75.50741 11May06 O. limosus**B 7 100 Webb Cr 15* P 39.88778, -75.51085 1996 C. b. bartonii 1 100 - - - - 2001 O. limosus 3 100 Christina R ------Brandywine Cr 16 P 39.87080, -75.59408 10May06 O. limosus**B 25 100 EB Brandywine Cr 17* P 39.9264, -75.6483 16Oct84 O. limosus 1 100 Valley Cr 18 P 39.98410, -75.66499 10May06 C. b. bartonii 2 50 - - - - - O. limosus**B 2 50 Marsh Cr 19 P 40.08893, -75.72986 24May06 C. b. bartonii 6 20 - - - - - O. obscurus** 24 80 WB Brandywine Cr 20 P 40.02079, -75.84770 24May06 C. b. bartonii 1 4 - - - - - O. virilis** 25 96 Buck Run 21 P 39.93254, -75.83024 10May06 C. b. bartonii 4 36 - - - - - O. limosus**B 7 64 EB West Cr 22* P 39.89929, -75.78776 23Sep98 C. b. bartonii 1 100 White Clay Cr ------EB White Clay Cr 23 P 39.85888, -75.78330 12May06 C. b. bartonii 14 23 - - - - - O. limosus**B 47 77 Big Springs 24* P 39.87045, -75.82217 08Oct97 C. b. bartonii 1 100 Unknown Waterbody 25* P 39.82273, -75.82014 1968 P. acutus 1 100 Schuylkill R 26* P 40.15043, -75.52813 16Aug90 P. clarkii 1 100 Schuylkill R 27 P 40.11274, -75.47120 10May06 O. rusticus**Y 36 100 Schuylkill R 28 P 40.10878, -75.42163 09May06 C. (P.) sp. 1 10 - - - - - O. rusticus** 9 90 Abrams Cr 29* P 40.10171, -75.38222 19Oct99 O. limosus 1 100 Fawn Run 30 P 40.10846, -75.45197 31Mar05 C. b. bartonii 7 78

117

- - - - - Cambarus sp. 2 22 French Cr 31 P 40.13784, -75.55293 10May06 C. b. bartonii 4 9 - - - - - O. rusticus** 34 79 - - - - - O. virilis 5 12 Baptism Cr 32 P 40.20717, -75.76261 31Mar05 C. b. bartonii 52 100 Spout Run 33 P 40.20740, -75.76910 31Mar05 C. b. bartonii 80 91 - - - - - Cambarus sp. 8 9 Manatawny Cr 34 Inter 40.31870, -75.73337 25May06 C. b. bartonii 12 57 - - - - - O. limosus 9 43 Manatawny Cr 35* P 40.26862, -75.66433 25Aug06 O. rusticus** 27 100 Manatawny Cr 36* P 40.26240, -75.66155 16Aug05 O. rusticus** 1 100 - - - - 01Aug06 O. obscurus 2 9 - - - - - O. rusticus** 21 91 Manatawny Cr 37* P 40.25146, -75.65712 31Jul06 O. obscurus 5 50 - - - - - O. rusticus 5 50 Manatawny Cr 38* P 40.24663, -75.65649 29Aug05 O. rusticus 2 100 - - - - 13Oct06 O. obscurus 2 33 - - - - - O. rusticus 4 67 Perkiomen Cr 39 P 40.13085, -75.44541 10May06 O. rusticus**Y 8 100 Perkiomen Cr 40 P 40.12224, -75.44880 10May06 O. rusticus**B 39 100 EB Perkiomen Cr 41* P 40.4105, -75.2233 01Jul05 O. rusticus 5 100 Swamp Cr 42* P 40.27509, -75.53186 10Sep02 O. rusticus 2 100 Pickering Cr 43 P 40.10160, -75.53617 10May06 C. b. bartonii 1 6 - - - - - C. (P.) sp.** 17 94 Pine Cr 44* P 40.08811, -75.61318 17Oct01 C. (P.) sp. 1 100 Pigeon Cr 45 P 40.20276, -75.60206 25May06 C. b. bartonii 5 100 Stony Cr 46 P 40.12896, -75.34351 09May06 O. obscurus**B 5 100 Stony Run 47 P 40.17007, -75.57869 25May06 C. b. bartonii 1 17 - - - - - O. limosus**B 3 50

118

- - - - - P. acutus 2 33 Trout Cr 48 P 40.10587, -75.40745 09May06 C. b. bartonii 2 14 - - - - - O. rusticus**BY 11 79 - - - - - O. virilis 1 7 Valley Cr 49* P 40.0416, -75.5765 31Jul05 C. (P.) sp. 2 100 Valley Cr 50 P 40.08223, -75.45399 21Apr03 C. b. bartonii 3 2 - - - - - C. (P.) sp.** 121 98 - - - - 18Oct03 C. b. bartonii 2 2 - - - - - C. (P.) sp.** 85 97 - - - - - Cambarus sp. 1 1 Valley Cr 51 P 40.08845, -75.45674 22Apr03 C. (P.) sp.** 27 100 - - - - 18Oct03 C. (P.) sp.** 83 100 Valley Cr 52 P 40.09443, -75.45666 21Apr03 C. (P.) sp.** 145 100 - - - - 18Oct03 C. b. bartonii 4 6 - - - - - C. (P.) sp.** 60 94 Valley Cr 53 P 40.10101, -75.46265 22Apr03 C. (P.) sp.** 55 100 - - - - 19Oct03 C. (P.) sp.** 27 100 Little Valley Cr 54* P 40.0667, -75.4728 18Oct85 C. (P.) sp. 1 100 Welch Run 55 P 40.10337, -75.46904 31Mar05 C. b. bartonii 17 81 - - - - - C. (P.) sp. 1 5 - - - - - Cambarus sp. 3 14 Wissahickon Cr 56 P 40.18674, -75.25484 25May06 C. b. bartonii 1 4 - - - - - O. obscurus**Y 17 63 - - - - - P. clarkii** 9 33 Wissahickon Cr 57* P 40.07852, -75.22545 15Jul03 O. obscurus 1 100 - - - - 13Jul06 O. obscurus 1 100 Cresheim Cr 58* P 40.0604, -75.2018 04Jun98 C. b. bartonii 1 100 Rose Valley Cr 59* P 40.16030, -75.22127 02Sep03 C. b. bartonii 4 50 - - - - - O. obscurus 4 50

119

Sandy Run 60* P 40.12732, -75.16490 27Jun01 P. clarkii 1 100 Elk R ------Big Elk Cr 61 P 39.73004, -75.84828 11May06 O. limosus 1 100

120

Table 4.2. Comparison of contemporary (1968-2007) crayfish collections from the northern part of the study area (northern sites) to those from the

southern part of the study area (southern sites). Sites were assigned to the north and south as described in the text and as shown in Figure 4.1. For

individual species and groups of species (all natives, all nonnatives), the number of specimens collected (No. coll), relative abundance (Rel ab),

and number of collection sites and water bodies [No. sites (water bodies)] were reported separately for the northern and southern sites. Abundance

summaries (No. coll, Rel ab) for the northern sites were calculated without data from lower Valley Creek (LVC, sites 50-53) because LVC was

more intensively sampled than the other sites (see Materials and Methods). Thus, inclusion of data from LVC would have biased my abundance

summaries toward C. (P.) sp., which is the dominant crayfish species in LVC. Occurrence summaries [No. sites (water bodies)] for the northern

sites included data from LVC. Due to rounding errors, relative abundances may not sum to exactly 100%. Abbreviations used: P.=Procambarus

(genus) or Puncticambarus (subgenus), O.=Orconectes, and C.=Cambarus. aIncludes 13 Cambarus sp. that could not be identified to species with

absolute certainty due to their small size but were probably C. b. bartonii.

Northern sites Southern sites Species No. coll Rel ab (%) No. sites (water bodies) No. coll Rel ab (%) No. sites (water bodies) C. b. bartonii 194 35.1 17 (16) 75 29.9 14 (13) C. (P.) sp. 23 4.2 10 (6) 42 16.7 3 (2) O. limosus 13 2.4 3 (3) 131 52.2 14 (13) All natives 243a 44.0 24 (20) 248 98.8 21 (17) O. obscurus 61 11.1 8 (5) 0 0.0 0 O. rusticus 204 37.0 12 (7) 0 0.0 0 O. virilis 31 5.6 3 (3) 1 0.4 1 (1) P. acutus 2 0.4 1 (1) 1 0.4 1 (1) P. clarkii 11 2.0 3 (3) 1 0.4 1 (1) All nonnatives 309 56.0 21 (14) 3 1.2 3 (3) All species

121 552 - 37 (25) 251 - 24 (20)

Figure 4.1. Map of eastern Pennsylvania with an enlargement of the study area and nearby regions in the southeastern part of the state. Contemporary (1968-2007) crayfish collection sites are denoted by closed circles (●) and are numbered consecutively according to the scheme provided in Table 4.1. A dashed line separates the northern and southern parts of the study area. A jagged north/south line denotes the western boundary of the Delaware River basin. Fawn Run, which is extremely small and flows directly into the Schuylkill River, is completely covered by its site marker, giving the incorrect, but unavoidable appearance that site 30 is located in the Schuylkill River.

Abbreviations: EB = East Branch, Cr = Creek, R = River.

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Figure 4.2. Map of the study area and nearby regions in southeastern Pennsylvania. Occurrences of C. (P.) sp., introduced Orconectes (O. obscurus, O. rusticus, O. virilis), and introduced Procambarus (P. acutus, P. clarkii) are shown on the map. Sites supporting reproducing populations of C. (P.) sp. are denoted by asterisks (*) and are referred to as reproductive sites. Other C. (P.) sp. occurrences are denoted by open diamonds (◊) and include sites without reproducing populations and sites where the reproductive status of the species is unknown. Sites are numbered according to the scheme provided in Table 4.1. A dashed line separates the northern and southern parts of the study area. A jagged north/south line denotes the western boundary of the Delaware River basin. Selected dams located downstream of the reproductive sites are shown on the map and are denoted by symbols. A small, low- head dam located between sites 52 and 53 on Valley Creek is omitted from the figure to improve clarity. It is possible that other small dams occur downstream of the reproductive sites unbeknownst to us. Abbreviations: EB =

East Branch, Cr = Creek, R = River.

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Figure 4.3. Map of the study area and nearby regions in southeastern Pennsylvania. Occurrences of C. b. bartonii (C. bartonii in legend), O. limosus, introduced Orconectes (O. obscurus, O. rusticus, O. virilis), and introduced

Procambarus (P. acutus, P. clarkii) are shown on the map. Sites are numbered according to the scheme provided in

Table 4.1. A dashed line separates the northern and southern parts of the study area. A jagged north/south line denotes the western boundary of the Delaware River basin. The Green Lane Reservoir dam located in the upper

Perkiomen Creek drainage is shown on the map and is denoted by a symbol. Fawn Run, which is extremely small and flows directly into the Schuylkill River, is completely covered by its site marker, giving the incorrect, but unavoidable appearance that site 30 is located in the Schuylkill River. Abbreviations: EB = East Branch, Cr = Creek,

R = River.

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Figure 4.4. Map of the study area and nearby regions in southeastern Pennsylvania. Occurrences of O. obscurus, O. rusticus, O. virilis, P. acutus, and P. clarkii are included on the map. Sites are numbered according to the scheme provided in Table 4.1. A dashed line separates the northern and southern parts of the study area. A jagged north/south line denotes the western boundary of the Delaware River basin. Abbreviations: EB = East Branch, Cr =

Creek, R = River.

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Chapter 5

Conservation and Management of Crayfishes: Lessons from Pennsylvania

Modified from:

Lieb, D.A., R.W. Bouchard, R.F. Carline, T.R. Nuttall, J.R. Wallace, and C.B. Wengert. 2011.

Conservation and management of crayfishes: lessons from Pennsylvania. Fisheries 36:

489-507.

Abstract

North America‘s crayfish fauna is diverse, ecologically important, and highly threatened.

Unfortunately, up-to-date information is scarce, hindering conservation and management efforts.

In Pennsylvania and nearby states, recent efforts allowed me to determine the conservation status of several native crayfishes and develop management strategies for those species. Due to rarity and proximity to urban centers and introduced (exotic) crayfishes, C. (P.) sp., an undescribed member of the Cambarus acuminatus complex, is critically imperiled in Pennsylvania and possibly range-wide. O. limosus is more widespread; however, recent population losses have been substantial, especially in Pennsylvania and northern Maryland, where its range has declined

(retreated eastward) by > 200 km. Introduced congeners likely played a major role in those losses. Although extirpated from some areas, C. b. bartonii remains widespread and is not an immediate conservation concern. In light of these findings, the role of barriers (e.g., dams), environmental protection, educational programs, and regulations in preventing crayfish invasions 126

and conserving native crayfishes is discussed, and management initiatives centered on those factors are presented. The need for methods to eliminate exotics and monitor natives is highlighted. Although tailored to a specific regional fauna, these ideas have broad applicability and would benefit many North American crayfishes.

Introduction

North America is home to a diverse, ecologically important crayfish fauna that is threatened by human activities (Master et al. 1998; Wilcove et al. 1998; Lodge et al. 2000a;

Taylor et al. 2007). Until recently, the conservation and management of those species has been a low priority for most state, federal, and academic institutions. The recent publication of several large scale conservation assessments, which suggest that about half of North America‘s crayfishes are imperiled across all or parts of their range (Taylor et al. 1996; Master et al. 1998;

Master et al. 2000; Taylor et al. 2007), greatly increased awareness and interest in the group.

Although more focused efforts in particular regions followed, the accurate classification (e.g., vulnerable, secure) of many species remains hampered by a lack of up-to-date distributional and ecological information (Taylor et al. 2007; Simmons and Fraley 2010). This is problematic because such classifications often provide the basis for assigning conservation priorities at the local and national level (Possingham et al. 2002). Thus, incorrect classifications may be costly, resulting in biodiversity losses and wasted resources.

In Pennsylvania and nearby states, recent efforts combined with historical data (Table

5.1) allowed me to accurately classify most of eastern Pennsylvania‘s native, surface-dwelling crayfish species: (1) C. b. bartonii; (2) C. (P.) sp., an undescribed member of the Cambarus acuminatus complex; and (3) O. limosus. My ability to assess changes in the crayfish fauna at

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individual sites and across the landscape was a key element in this process. I also developed a number of management strategies that should aid in the conservation of those species.

Because P. clarkii, Cambarus robustus, O. obscurus, O. rusticus, and O. virilis have been introduced to eastern Pennsylvania and P. acutus has greatly expanded its range in the region as a result of human activities (Bouchard et al. 2007; Lieb et al. 2007a; Lieb et al. 2011), the aim of many of these management strategies is to prevent additional crayfish introductions. Successful prevention is of vital importance because introduced (exotic) crayfishes are one of the biggest threats to native crayfishes in North America and elsewhere (Lodge et al. 2000a; Taylor 2002;

Taylor et al. 2007). Although stopping the spread of exotic crayfish is difficult once they become widespread (Peters and Lodge 2009), the distributions of most introduced crayfishes in eastern

Pennsylvania are still limited (Bouchard et al. 2007; Lieb et al. 2007a; Lieb et al. 2011). Thus, in eastern Pennsylvania, as in much of North America, there is still time to stop the spread of introduced crayfishes and preserve the native stocks that remain. Although tailored to a specific fauna, the management strategies presented herein have broad applicability and would likely benefit many of North America‘s crayfishes, as well as other aquatic invertebrate species of concern.

Materials and Methods

Assessing Changes at Individual Sites and Across the Landscape

Eleven sites in the Potomac and Susquehanna drainages of Pennsylvania that historically supported O. limosus and/or C. b. bartonii were resurveyed (Table 5.2). Nine were from

Ortmann (1906); two were from the United States National Museum, Smithsonian Institution

[USNM 46320 and 48413 (Conoy Creek); USNM 310622 (Penns Creek tributary)]. USNM data

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included catch numbers for each species; Ortmann‘s data were presence/absence. In most cases, historical site descriptions were limited to stream and town names, and contemporary collections were made as close to those towns as possible. The exception was a site whose historical description was ―tributary of Penns Creek, two miles west of New Berlin.‖ Since the name of the stream was unknown, I surveyed Sweitzers Run and Tuscarora Creek, the only major Penns

Creek tributaries located < 4.8 km (3 miles) west of New Berlin.

Contemporary collections included a thorough search of multiple riffle-pool sequences and all available habitat types, which is an effective method for determining community composition and compiling species lists for individual sites (see Bouchard et al. 2007, Lieb et al.

2007a, and Lieb et al. 2011 for additional details). Historical collection methods are available from Ortmann (1906) or are unknown (USNM data). Resampling efforts at O. limosus and/or C. b. bartonii sites in the Delaware basin of Pennsylvania and nearby states are described elsewhere

(Schwartz et al. 1963; Daniels 1998; Kuhlmann and Hazelton 2007; Loughman et al. 2009;

Kilian et al. 2010; Loughman and Welsh 2010; Swecker et al. 2010; Lieb et al. 2011).

Assessments of change at larger scales were possible because of the availability of contemporary and historical crayfish data from a substantial part of the native ranges of C. b. bartonii, C. (P.) sp., and O. limosus (see Table 5.1 and range information in Hobbs 1989,

Jezerinac et al. 1995, and Lieb et al. 2011). Coverage of Pennsylvania, Maryland, and West

Virginia was especially complete allowing a particularly clear picture of change in those areas.

To illustrate change in Pennsylvania, maps showing historical and contemporary crayfish collection sites along with maps of historical and contemporary crayfish distributions were created (Figures 5.1-5.6; modified from Bouchard et al. 2007). For O. limosus, historical data were collected prior to 1957 and contemporary data were collected from 1984-2007 (no data

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available from 1957-1983). For O. obscurus, historical data were collected prior to 1912 and contemporary data were collected from 1965-2007 (no data available from 1912-1964). For C. b. bartonii, the data were split approximately in half: historical data were collected prior to 1960 and contemporary data were collected from 1964-2006 (no data available from 1960-1963). For recent invaders, only contemporary data were available (O. rusticus: 1976-2006, O. virilis: 1986-

2007). Some data could not be mapped because of incomplete site descriptions (e.g., only a county name provided). Similar maps for Maryland were published by Kilian et al. (2010).

Conservation Classifications

Conservation classifications from published sources and updated classifications developed for this study are provided in Table 5.3. Published classifications are from the

American Fisheries Society Endangered Species Committee (AFS; Taylor et al. 2007) and the

National Heritage Network (NHN; NatureServe 2010). Updated classifications relied heavily on range extent, number of populations, changes at individual sites and across landscapes, and threats to existing populations and were based on criteria and classification definitions provided by NHN. Due to the availability of historical and contemporary data, I was able to develop updated classifications for Pennsylvania (Table 5.3); those for Maryland and West Virginia are provided elsewhere (Kilian et al. 2010; Loughman and Welsh 2010). An updated range-wide classification is provided for C. b. bartonii. The range-wide status of O. limosus and C. (P.) sp. is discussed; however, updated classifications at that scale await the completion of additional taxonomic, genetic, and distributional studies.

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Conservation Classifications

Cambarus (P.) sp.

Cambarus (P.) sp. was recently discovered in Pennsylvania and has an extremely limited distribution in the state (Bouchard et al. 2007; Lieb et al. 2007b; Lieb et al. 2008; Lieb et al.

2011). More specifically, the species is only known from 13 sites in a small area (~220 km2) of southeastern (SE) Pennsylvania. Only four streams (Crum, Darby, Pickering, and Valley creeks) are known to support populations of C. (P.) sp. One of those populations (Valley Creek) was recently invaded by O. rusticus and appears to be in decline; the others are located close to dense populations of several exotic crayfishes, including O. rusticus (Lieb and Bhattarai 2009; Lieb et al. 2011). All four populations are in a rapidly urbanizing area within ~30 km of one of North

America‘s largest cities (Philadelphia; Lieb et al. 2011).

Outside of Pennsylvania, the C. acuminatus complex occurs in central Maryland,

Virginia, North Carolina, and South Carolina (Meredith and Schwartz 1960; Taylor et al. 2007;

Kilian et al. 2010). C. (P.) sp. is not one of the described species in the complex from North

Carolina and South Carolina (Lieb et al. 2008), where the complex is reasonably well known

(Cooper 2001; Cooper and Cooper 2003; Cooper 2006). Much less is known to the north of the

Carolinas, where additional taxonomic, distributional, and possibly genetic work is needed to determine whether members of the complex consist of one widely distributed species or multiple species with more restricted ranges.

Regardless, because historical collections from Pennsylvania do not include the C. acuminatus complex (Ortmann 1906), C. (P.) sp. is either an introduced species or a recently discovered native. Generally, the presence of a species where it was historically absent would

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suggest an introduction; however, historical data are not available for any of the sites where C.

(P.) sp. is found (Ortmann 1906; Lieb et al. 2011).

Some authors cite the presence of disjunct distributions as evidence for crayfish introductions (Bouchard 1976a; Crocker 1979; Jezerinac et al. 1995). Although the distribution of the C. acuminatus complex is clearly disjunct with populations in Pennsylvania separated from those in Maryland by ~125 km (Meredith and Schwartz 1960; Kilian et al. 2010; Lieb et al.

2011), introductions are probably not the cause. First, members of the C. acuminatus complex

(acuminatus species) are not typically introduced outside of their native ranges (Hobbs et al.

1989; Rodriguez and Suarez 2001; Taylor et al. 2007); probably because they are generally not sold as bait or through biological warehouses. Second, naturally adjacent but disjunct ranges have been documented for other Puncticambarus species in eastern North America (Hobbs

1969). Third, it is possible that additional populations of the C. acuminatus complex once occurred in northern Maryland and southern Pennsylvania, but that anthropogenic disturbances

(e.g., crayfish introductions, urbanization) or other physical and biological changes led to their elimination resulting in the disjunct distribution currently observed. This is especially likely along the I-95 corridor from Washington D.C. to Philadelphia, which is highly degraded and infested with exotic crayfishes (see Bouchard et al. 2007, Elmore and Kaushal 2008, and Lieb et al. 2011). Such a scenario is similar to that suspected for another Puncticambarus species,

Cambarus veteranus, which was believed to occur in two disjunct clusters of sites (one in West

Virginia and one near the border of Virginia and Kentucky) due, at least partly, to the adverse effects of coal mining in intervening areas (Jezerinac et al. 1995). Finally, it is possible that in

Pennsylvania and Maryland, the range of the C. acuminatus complex is naturally disjunct but

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that the degree of separation between clusters of sites has been exaggerated by extirpations in intervening areas.

Given these possibilities, the most likely scenario is that one or more species in the acuminatus complex once occupied a wider range in Maryland and Pennsylvania [although their distributions may have always been restricted as is common for species of Puncticambarus

(Hobbs 1969, 1989)], but that human activities reduced the range of the complex to two relic groups of populations. Therefore, C. (P.) sp. is likely native to Pennsylvania and has a very limited distribution in the state. The absence of C. (P.) sp. from the historical record is not surprising given that past surveys did not include some parts of SE Pennsylvania (Ortmann

1906). Thus, although historical surveys were sufficient to characterize the distribution of widespread species such as O. limosus and C. b. bartonii, very rare ones such as C. (P.) sp. could have been missed.

Due to rarity and proximity to urban centers and exotic crayfishes, C. (P.) sp. is clearly imperiled in Pennsylvania (Table 5.3) and in need of conservation attention. In other states, crayfishes with similarly restricted ranges (known from 9-27 sites) often garner conservation attention (Taylor and Schuster 2004; Westhoff et al. 2006; Eversole and Welch 2010) and a number of species of conservation concern in Pennsylvania have wider distributions and are less threatened than C. (P.) sp. (see Felbaum et al. 1995). Although undescribed, the lack of a specific epithet should not prevent C. (P.) sp. from being a conservation priority (see Bouchard 1976b,

Harris 1990, Jelks et al. 2008, and others, which included undescribed species in lists of imperiled crayfishes and fishes).

If the acuminatus species in Pennsylvania is different from those to the south, then range- wide conservation attention and inclusion on lists of globally imperiled species (e.g., AFS, NHN)

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may be warranted, as has already been done for two acuminatus species (Cambarus hystricosus,

Cambarus johni) known from ~25-55 locations (Cooper and Cooper 2003; Cooper 2006; Taylor et al. 2007; Simmons and Fraley 2010). Even if the Pennsylvania acuminatus species occurs elsewhere, such actions may be justified if Pennsylvania populations exhibit adaptations not present to the south making them important for maintaining the genetic variability of the species

(see Hamr 1998 for similar discussions regarding Canada‘s crayfishes and Hunter and

Hutchinson 1994 and Lesica and Allendorf 1995 for more general discussions of the value of peripheral populations). Additionally, given the restricted distribution of the C. acuminatus complex in Maryland (< 10 occurrences since 1989 and < 30 overall; see Figure 4 of Kilian et al.

2010), even if the species in Pennsylvania is the same as that in Maryland, broader scale actions may be warranted. Overall, C. (P.) sp. is probably one of the most endangered aquatic species in the state and possibly in eastern North America (if its range is limited to Pennsylvania) and, without management action, faces an uncertain future.

Orconectes limosus

Although O. limosus records exist for a large swath of the Atlantic drainage of eastern

North America (Virginia northward to Canada; Ortmann 1906; Crocker 1957; Francois 1959;

Meredith and Schwartz 1960; Crocker 1979; Hobbs 1989; McAlpine et al. 1991; Jezerinac et al.

1995; Lambert et al. 2007), recent large scale surveys indicate that the species has been extirpated from a substantial part of its former range. For example, in Pennsylvania, the range of

O. limosus has declined (retreated eastward) by ~225 km and the species has nearly been eliminated from the Susquehanna and Potomac basins (Figure 5.2; Bouchard et al. 2007).

Resampling efforts at or near historical sites in those basins yielded hundreds of introduced

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congeners but no O. limosus (Table 5.2 herein and Table 1 of Bouchard et al. 2007). Except for the presence of O. limosus in a few tributaries of the North Branch Potomac River, similar range reductions have occurred in northern Maryland (Kilian et al. 2010). The prevalence of introduced congeners in areas that lost populations of O. limosus suggests that crayfish introductions likely played a major role in those losses (Figures 5.2-5.5; Table 5.2; Bouchard et al. 2007; Kilian et al.

2010); although other factors may have also been important.

More focused efforts in the Patapsco drainage of Maryland, the upper Susquehanna drainage of New York, the Potomac drainage of West Virginia, and the lower Delaware drainage of Pennsylvania also documented the frequent replacement of O. limosus by introduced congeners (Schwartz et al. 1963; Kuhlmann and Hazelton 2007; Loughman et al. 2009;

Loughman and Welsh 2010; Swecker et al. 2010; Lieb et al. 2011). Because the lower Delaware drainage of Pennsylvania and nearby areas are an important reservoir of genetic variability for O. limosus (Filipová et al. 2011), extirpations from that area may have implications for the long- term viability and conservation status of O. limosus in the state and the region (see Ehrlich and

Daily 1993, Fetzner and Crandall 2002, and Luck et al. 2003 for discussions of the importance of genetic variability to species persistence).

These findings prompted Bouchard et al. (2007) to speculate that O. limosus may eventually be eliminated from the Piedmont of Pennsylvania and Maryland, persisting only in the

Coastal Plain where it may be better able to compete with introduced crayfishes. Unfortunately,

Pennsylvania‘s Coastal Plain is small, densely populated, and extensively modified (Bouchard et al. 2007), with additional alterations likely. Maryland‘s Coastal Plain is larger and less populated but also has a substantial human footprint (King et al. 2005; Utz et al. 2010), which will

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undoubtedly increase as the region‘s population centers, including Washington, D.C. and

Baltimore, continue to expand.

Although recent losses have been substantial, it is important to note that some of the populations that have been lost from the mid-Atlantic may not have been native to begin with

(see Ortmann 1906 and Bouchard et al. 2007 for discussions of the potential influence of man- made canals on O. limosus dispersal). Nonetheless, given the magnitude of the losses and the threats O. limosus faces, the populations that remain in Pennsylvania and Maryland have significant conservation value at the state and regional level.

This is ironic given that O. limosus has been introduced to Europe and Canada and has rapidly expanded its range, often at the expense of native crayfishes (Hamr 1998; Lambert et al.

2007; Taylor et al. 2007). As a result, O. limosus is viewed as a pest across much of its nonnative range (Hamr 2002; Filipová et al. 2011). Nonetheless, the conservation of native O. limosus is warranted because introduced populations lack the genetic diversity that is present in native stocks (Filipová et al. 2011).

Thus, although O. limosus is listed as globally secure/stable by AFS and NHN (Table

5.3), recent findings indicate that native stocks may not be as safe as previously thought. In

Pennsylvania, range reductions and the threat posed by exotic crayfishes prompted me to downgrade O. limosus from ‗Apparently Secure‘ to ‗Vulnerable‘ (Table 5.3). In West Virginia,

O. limosus is listed as ‗Critically Imperiled‘ and may have been eliminated from the state by exotic crayfish (Loughman and Welsh 2010; Swecker et al. 2010). In Maryland, O. limosus is listed as ‗Demonstrably Secure‘ but the species is threatened by exotic crayfish and significant range reductions have occurred in recent years (Kilian et al. 2010). Additional surveys along with genetic work are needed to update the status of O. limosus in other regions and across its

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range. Overall, this assessment suggests that management intervention is likely needed to ensure the continued existence of O. limosus in Pennsylvania and possibly elsewhere in its native range and illustrates the importance of periodically reevaluating the status of native crayfishes (even widespread ones).

Cambarus b. bartonii

Although the range of C. b. bartonii has remained relatively stable over the past century in Pennsylvania and Maryland (Figure 5.6; Bouchard et al. 2007; Kilian et al. 2010; Lieb et al.

2011), the species has been replaced by introduced crayfishes at some locations in those states and New York (Table 5.2; Schwartz et al. 1963; Daniels 1998; Kuhlmann and Hazelton 2007).

Additionally, C. b. bartonii may be negatively affected by nonnative O. virilis in eastern West

Virginia (Swecker et al. 2010) and is in serious decline in parts of Ontario, Canada, although introduced crayfishes are not the cause (Edwards et al. 2009).

Given this information and the continued expansion of introduced crayfishes in eastern

North America, additional losses appear likely. Fortunately, because C. b. bartonii is widely distributed in eastern North America from Canada southward to Georgia and is still common in many areas (Hobbs 1989; Bouchard et al. 2007; Kilian et al. 2010; Loughman and Welsh 2010;

Simmons and Fraley 2010), these losses do not pose an immediate threat to the species.

However, it is possible that extirpations may eventually reduce the genetic variability and long- term viability of C. b. bartonii in some areas. Although such concerns are often expressed for species with restricted ranges and small population sizes, even widespread crayfish species can suffer substantial reductions in genetic variability due to anthropogenic disturbances (Buhay and

Crandall 2005). Nonetheless, because resources are limited, it is important to emphasize that C.

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b. bartonii is not an immediate conservation concern regionally or globally (Table 5.3; Kilian et al. 2010; Loughman and Welsh 2010; Simmons and Fraley 2010).

Management Needs and Implications

Given the imperiled status of C. (P.) sp. and O. limosus in Pennsylvania and elsewhere, efforts to prevent crayfish introductions and preserve the habitat and water quality at sites that support those species should be a management priority. In subsequent sections, I describe regulatory, educational, and conservation initiatives, which should aid in this regard. I also discuss the need for methods to safely eradicate introduced crayfishes; however, the successful development of such methods will not eliminate the need for policies aimed at preventing introductions, which should remain the first line of defense. Although most specific examples are from Pennsylvania, the general concepts and management strategies that are provided have broad applicability and would likely benefit many of North America‘s crayfishes, as well as other aquatic invertebrate species of concern.

Crayfish Ban

Because introduced crayfishes occur in a number of water bodies in Pennsylvania

(Bouchard et al. 2007; Lieb et al. 2007a; Lieb et al. 2011) and are available from bait shops, biological warehouses, pet stores, live food vendors, and aquaculture facilities, which are, at best, loosely regulated, it would be difficult to prevent additional introductions in Pennsylvania without further regulations and their enforcement (see Lodge et al. 2000a, b; Burkholder and

Wallace 2001; and DiStefano et al. 2009). Although O. rusticus has been tightly regulated since

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2005 and cannot be possessed, sold, transported, or cultured within the state (58 Pa Code §

71.6.d 2008; PFBC 2009), other introduced crayfishes (P. acutus, C. robustus, O. obscurus, O. virilis) are unregulated and can be purchased from commercial dealers or collected from invaded water bodies and released legally into the state‘s waters. Additionally, although P. clarkii cannot be propagated in flow-through systems or introduced into Pennsylvania waters (PFBC 2009), the species is cultured in parts of Pennsylvania and can be possessed, sold, and transported legally within the state. This situation is not unusual because many places in North America do not strictly regulate all their introduced or potentially introduced crayfish species (DiStefano et al.

2009; Peters and Lodge 2009).

Strict regulations that only apply to a few species will not prevent crayfish introductions in most areas. Extending existing bans to other species would be hard to enforce because most natural resource managers and conservation officers have difficulty identifying crayfish (Lodge et al. 2000b; Peters and Lodge 2009). For this reason, banning the possession, sale, transportation, and culture of all native and nonnative crayfishes in Pennsylvania and elsewhere

(a complete ban) is warranted. Such a ban would make it illegal to use live crayfish as bait as recommended by Lodge et al. (2000b) and DiStefano et al. (2009) and as is already the case in

Wisconsin, Virginia and parts of Maryland and Canada (Taylor et al. 2007; DiStefano et al.

2009; MDDNR 2009). The Wisconsin ban, enacted in 1983, received nearly universal approval from the public (comments 5:1 in favor of it), ―caused no unusual controversy, and has not caused any apparent harm to Wisconsin‘s important fishing industry‖ (Lodge et al. 2000b:23).

Due to my outreach efforts, including at least 13 articles in the popular media (newspapers, magazines, internet) since 2004, and those of the Pennsylvania Sea Grant, residents of

Pennsylvania are becoming increasingly aware of the threat that introduced crayfishes pose and

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would likely support a crayfish ban. Outreach efforts are also underway elsewhere (DiStefano et al. 2009; Kilian et al. 2010), increasing the likelihood that a complete ban would be supported by the public.

Ideally, the complete ban would apply to all water bodies; however, it may be possible to permit the use of crayfish as bait in selected locations that are already infested with introduced crayfish (a partial ban). Such a measure would maintain a ban on the sale, transportation, and culture of crayfish but allow anglers to collect and fish with crayfish at some infested locations

(exempt sites). Because some noncompliance may occur (DiStefano et al. 2009), exempt sites should not be in the vicinity of imperiled crayfish. For example, substantial reaches of the

Schuylkill River in Pennsylvania are completely dominated by introduced O. rusticus (Lieb et al.

2011) and would, in theory, qualify for exempt status. However, because those reaches are in the vicinity one of Pennsylvania‘s rarest crayfish [C. (P.) sp.; Lieb et al. 2011], they should not be exempt. Locations that have never been surveyed for crayfishes or have not been surveyed recently should also not be exempt. Although not risk-free, a partial ban would provide recreational opportunities for anglers that use crayfish as bait while still reducing the chance of introductions.

Some will likely argue that anglers should be allowed to collect and fish with crayfish wherever they choose (not just at exempt sites), as long as crayfish are not moved from place to place. However, such a measure; which makes sense in theory and would allow crayfish to be possessed but not sold, transported, or cultured; would be difficult to enforce. This is because unless an individual is caught transporting, selling, or culturing crayfish it would be impossible to determine if a violation has occurred. In contrast, a complete or partial ban would be much easier to enforce because anglers would either not be allowed to use crayfish as bait anywhere

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(complete ban) or would only be permitted to use them in certain waters (partial ban). Under a complete or partial ban, the job of law enforcement would be to prevent anglers from using crayfish as bait in restricted waters, which is much easier than trying to determine if crayfish are being transported between sites.

Education and Outreach

Although education and outreach programs targeting policy makers and the general public are vitally important in preventing crayfish introductions (Lodge et al. 2000b; Hamr 2002;

Taylor 2002), until recently there was little up-to-date information to dispense in many areas, including Pennsylvania. Nonetheless, when this information became available in Pennsylvania, the state‘s regulatory agencies moved quickly, enacting a ban on O. rusticus in 2005, within approximately a year of being informed of the extent of the infestation. The general public has proven equally as responsive; providing crayfish specimens, helping to detect new invasions

(also noted by Lodge et al. 2006), and urging the passage of additional regulatory measures to prevent introductions.

To date, most outreach efforts in Pennsylvania have been restricted to articles in the popular media, invasive species workshops, and presentations at scientific and management meetings. Although productive, the effectiveness of those efforts could be increased by targeting vulnerable areas (watersheds that support imperiled species and/or are at risk of invasion) and potential sources of exotics including bait shops, biological warehouses, pet stores, live food vendors, and aquaculture facilities (see Burkholder and Wallace 2001, Puth and Allen 2004,

Keller et al. 2008, and DiStefano et al. 2009). Town-hall style gatherings in vulnerable areas and

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attempts to educate anglers and others that contact crayfish would likely extend current efforts to a different subset of the public.

The placement of warning signs along water bodies that support imperiled crayfish such as C. (P.) sp. and O. limosus (to prevent introductions) and along heavily infested waterways (to prevent the transfer of exotics elsewhere) would probably slow the spread of exotics, particularly in heavily fished areas. To decrease costs, signs could be strategically placed at boat launches and other popular access points.

Role of Dams, Temperature, and Nutrients

Although the susceptibility of individual sites to crayfish invasions is potentially influenced by a number of factors (Kershner and Lodge 1995; Light 2003; Usio et al. 2006;

Phillips et al. 2009; Capinha and Anastacio 2011); in this section, I focus on dams, temperature, and nutrients because they appear to be important for one of Pennsylvania‘s rarest crayfish [C.

(P.) sp.; Lieb and Bhattarai 2009; Lieb et al. 2011] and have the potential to influence invasions in many areas.

The ecological benefits of dam removal have been thoroughly discussed in the scientific literature and are a major reason for the recent surge in removal projects; however, the negative effects of such removals have received much less attention and are typically limited to the downstream transport of sediments, nutrients, and toxic materials and the upstream movement of introduced fish (Bednarek 2001; Bushaw-Newton et al. 2002; Hart et al. 2002; Poff and Hart

2002; Stanley and Doyle 2003). Because dams can block the dispersal of crayfish (Meyer et al.

2007), their removal may facilitate crayfish invasions in some systems, with the potential for negative effects on native communities. Despite this possibility, the potential for such effects is

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rarely discussed in the scientific literature (but see Kerby et al. 2005 and Bubb et al. 2008), or empirically tested, and is typically not considered by regulatory agencies charged with managing dam removals.

Continuing to ignore the potential influence of dams on crayfish invasions could have serious consequences, particularly for imperiled crayfishes. For example, in Pennsylvania, dams are located downstream of most of the known populations of an extremely rare crayfish [C. (P.) sp.] and may be protecting them from invasion (especially by O. rusticus; Lieb et al. 2011). At a minimum, surveys should be conducted prior to dam removal to ensure that removal will not facilitate the upstream migration of introduced crayfish. Ironically, dams that are protecting upstream areas from invasion may need to be left in place for conservation reasons. In areas prone to invasion, dams located downstream of imperiled crayfish should probably not be removed, regardless of whether exotics are present in the system or not.

Low temperatures may also play a role in protecting some uninvaded sites. For example, in Pennsylvania, water temperatures at sites with populations of C. (P.) sp. [hereafter termed C.

(P.) sp. sites] are likely lower than that preferred by O. rusticus, possibly delaying or preventing its establishment at those sites (Lieb and Bhattarai 2009). Support for this possibility is provided by Mundahl and Benton (1990), who determined that O. rusticus growth was maximized at 26-

28 °C in laboratory experiments and predicted that the species would be most successful in systems with average summer water temperatures near that range. Stream surveys in Ohio, which indicated that O. rusticus was more successful in warmer, downstream reaches that remain above

20 °C throughout the summer than in cooler headwater areas (Jezerinac 1986; Mundahl and

Benton 1990; Thoma and Jezerinac 2000), appear to support their prediction. Because temperatures at C. (P.) sp. sites are known or suspected to be <20 °C for substantial parts of the

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summer (Steffy and Kilham 2006; Lieb and Bhattarai 2009), it is possible that O. rusticus has been slow to invade those sites, at least partly, because relatively low temperatures afford resident species a bioenergetic advantage over O. rusticus (see Momot et al. 1988 for a similar example).

The recent discovery of O. rusticus at the Valley Creek C. (P.) sp. sites suggests that, although not favored by O. rusticus, low temperatures may not prevent invasions indefinitely.

The spread of O. rusticus into the northern United States and Canada (Hamr 2002; Taylor et al.

2007; Phillips et al. 2009) further indicates that low temperatures alone may not provide a permanent barrier against invasion. It is also possible that, in Valley Creek, recent temperature increases resulting from urbanization (Steffy and Kilham 2006) have tipped the bioenergetic balance in favor of O. rusticus. Mundahl and Benton (1990) and Whitledge and Rabeni (2002) voiced similar concerns regarding the potential influence of habitat and climate-driven changes in temperature on O. rusticus invasions in Ohio and Missouri. Additional temperature increases in Valley Creek and the other C. (P.) sp. sites are likely due to continued urbanization (Steffy and Kilham 2006; Kaushal et al. 2010), increasing regional ground water temperatures

(Eggleston et al. 1999), and climate change (see Mohseni et al. 1999, Chang 2003, and Kaushal et al. 2010). Such increases may eventually result in thermal conditions in many areas, including the C. (P.) sp. sites, which favor O. rusticus.

The relatively low nutrient status of the C. (P.) sp. sites (oligo-mesotrophic; Lieb and

Bhattarai 2009) is probably not optimal for O. rusticus, which —due to its high metabolic rate, high growth rate, and large size —tend to do best in productive systems where nutrients are plentiful (Momot 1984; Momot et al. 1988). However, continued urbanization of the

Philadelphia suburbs will likely increase nutrient levels at the C. (P.) sp. sites in the future (see

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Lenat and Crawford 1994 and Carpenter et al. 1998). Additionally, it has been predicted that, as atmospheric CO2 levels rise, SE Pennsylvania will become warmer and wetter, further increasing nutrient loading from urbanizing basins in the region (Chang 2004). Elevated nutrient levels may increase the likelihood of future O. rusticus invasions at the C. (P.) sp. sites and other locations that are not highly enriched, as appears to have already occurred in Ohio and West Virginia

(Jezerinac et al. 1995; Thoma and Jezerinac 2000).

These data suggest that barriers (dams, low temperatures, low nutrients) are likely preventing or slowing exotic crayfish from invading some sites in Pennsylvania that support imperiled crayfish. Unfortunately, dam removals and expected increases in water temperature and nutrient levels resulting from climate change and urbanization may compromise or weaken those barriers in the future. More generally, these findings highlight the potentially important but often overlooked role that physical and chemical barriers of natural and anthropogenic origin play in preventing crayfish invasions. Ultimately, the preservation of native crayfish in some heavily infested areas may depend on management efforts that maintain, strengthen, or expand existing barriers.

Eliminating Exotics

Although the negative effects of introduced crayfish are well documented, little is known about how to eliminate them from invaded waters. Chemical poisons are available; however, native crayfish are also killed (Gunderson 2008). Intensive harvesting may reduce population sizes, but is laborious and unlikely to result in eradication (Hamr 1999; Holdich et al. 1999;

Freeman et al. 2010). In a Wisconsin lake, O. rusticus densities were dramatically reduced

(although extirpation was not achieved) using a combination of trapping and increased fish

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predation (Hein et al. 2007). Unfortunately, the effort required was substantial and similar results in open systems (streams) are not assured. Pheromone baits could potentially reduce this effort by increasing trap efficiency (Holdich et al. 1999; Freeman et al. 2010) but are still in the early stages of development (Stebbing et al. 2003; Aquiloni and Gherardi 2010). These difficulties have led many authors (e.g., Lodge et al. 2000b; Hamr 2002; Gunderson 2008) to conclude that introduced crayfish can best be controlled by preventing future introductions.

Although I agree with this reasoning, additional introductions are likely unavoidable. As a result, the persistence of certain native crayfishes [particularly those with limited ranges such as C. (P.) sp.] may require the removal of exotics. Unfortunately, species-specific treatments that eliminate introduced crayfish with minimal effects on nontarget species are currently not available (Lodge et al. 2000b; Gunderson 2008; Freeman et al. 2010). Their development should be possible; however, because crayfish species vary in their response to a variety of substances

(Hobbs and Hall 1974; Berrill et al. 1985; Eversole and Seller 1996; Nyström 2002; Wigginton and Birge 2007). Additionally, because molting crayfish are especially sensitive to toxicants

(Wigginton and Birge 2007), it may be possible in some situations to apply treatments when exotics are at the peak of their molting cycle but natives are not to minimize effects on nontarget species. The release of sterilized males, which has long been used to control insect pests (Myers et al. 2000) but has only recently been considered for crayfish (Holdich et al. 1999; Aquiloni et al. 2009), endocrine disruptors, which interfere with molting and reproductive processes in crustaceans (Rodriguez et al. 2007; Mazurova et al. 2008), and species-specific pathogens

(Holdich et al. 1999; Davidson et al. 2010; Freeman et al. 2010) might also be effective for crayfish.

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The objective of most treatment programs would be eradication; although for some abundant, highly fecund invaders such as O. rusticus, population control may be more feasible

(Myers et al. 2000). Because introduced species are difficult to eradicate if well established

(Myers et al. 2000; Lodge et al. 2006), watersheds that support imperiled crayfish should be routinely monitored (at least once per year) to ensure that invasions are detected quickly (see similar, albeit less specific, recommendations in Lodge et al. 2006). Given that eradication/control programs require public support and can be controversial, particularly if chemicals are used in populated areas, such efforts should include outreach and public education initiatives (Myers et al. 2000; Genovesi 2005). Due to the presence of C. (P.) sp. and recent invasion by O. rusticus, Valley Creek would be an obvious candidate for treatment.

Eradication/control programs could be combined with restocking efforts to restore native crayfishes to systems where they have been extirpated.

Reducing Environmental Degradation

Anthropogenic disturbances and associated declines in habitat and water quality are a serious threat to North America‘s native crayfishes (Wilcove et al. 1998; Guiaşu 2002; Taylor et al. 2007). Many of these disturbances can be related directly or indirectly to landscape scale changes associated with agricultural and urban development. As a result, the preservation of native crayfish should include efforts to preserve natural areas, particularly in the riparian zone

(Burskey and Simon 2010), and mitigate existing impacts. Riparian forests may be of particular value because they reduce pollutant, sediment, and nutrient loading (Lowrance et al. 1984;

Peterjohn and Correll 1984; Pinho et al. 2008); lower water temperature (Burton and Likens

1973; Barton et al. 1985; Storey and Cowley 1997); and provide refugia from flooding (in the

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form of tree roots and woody debris; Smith et al. 1996; Parkyn and Collier 2004), which would benefit crayfish communities directly via improved habitat and water quality and indirectly by reducing the likelihood of crayfish invasions (see ‗Role of dams, temperature, and nutrients‘ section). In Pennsylvania, such benefits are particularly likely for C. (P.) sp. because it is typically found in streams with relatively low temperatures and nutrients and appears to be negatively affected by sedimentation and introduced crayfish (Lieb et al. 2008; Lieb and

Bhattarai 2009; Lieb et al. 2011). Nonetheless, because the benefits of riparian forests are not always apparent (particularly in highly developed areas; Roy et al. 2005, 2006, 2007), their presence alone will not necessarily assure the long-term survival of native crayfish.

In Pennsylvania, exceptional value (EV) status affords surface waters protection under state law and mandates that ―water quality be maintained and protected‖ (25 Pa Code § 93.4a

2007). Surface waters qualify for EV status if they are of ―exceptional ecological significance‖, defined as ―important, unique, or sensitive ecologically‖ (25 Pa Code § 93.1 2007). Although surface waters that support imperiled crayfish such as C. (P.) sp. and O. limosus appear to meet those criteria, most are not classified as EV and need to be reevaluated [especially those with C.

(P.) sp.]. More generally, whenever possible, imperiled crayfish should be considered when surface waters are classified and antidegradation priorities are assigned.

Because urban areas support imperiled crayfish and are crisscrossed by pipelines, railroads, and roadways that serve as conduits for wastes and toxic materials, efforts to prevent spilled materials from reaching imperiled crayfish are needed. Those efforts should include the diversion of road runoff away from populations of imperiled crayfish and the frequent inspection and maintenance of pipelines, railroads, and roadways that are in the vicinity of those populations. In Pennsylvania, such safeguards are especially pertinent to C. (P.) sp. because

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underground sewage conduits occur upstream of many C. (P.) sp. sites (Ryan and Packman

2006). Further, some of the largest and busiest highways and railroads in Pennsylvania are in the vicinity of those sites and are a major supply route for chemicals, fuels, and other toxic materials coming in and out of the Philadelphia area. Therefore, spills in this region could have serious consequences for C. (P.) sp. In recent years, at least two substantial releases of diesel fuel from tanker trucks involved in highway accidents have occurred downstream of C. (P.) sp. sites

(National Response Center 2002; Schaefer and Mastrull 2007). Given the continued expansion of urban areas in SE Pennsylvania, future spills, including those upstream of C. (P.) sp. sites, seem likely.

Additional Sampling

Because O. limosus and C. (P.) sp. are imperiled in Pennsylvania and elsewhere, efforts to better define their ranges and monitor populations are needed. Range refinement will require crayfish collections from watersheds that have not been sampled recently and more sampling of drainages that currently support C. (P.) sp. and O. limosus. Once their distributions have been refined, range-wide monitoring programs can be developed. Efforts to quickly detect crayfish invasions and relate population sizes to conditions at the reach scale (e.g., instream habitat) and basin scale (e.g., land use) should be included in those programs. Regular monitoring should allow population declines to be detected and causative factors identified, ultimately providing the information needed to protect C. (P.) sp. and O. limosus across their ranges. Initiatives of this type should have widespread applicability, assisting efforts to conserve crayfish in a variety of settings.

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Acknowledgments

I thank Nellie Bhattarai, Hannah M. Ingram, and Jeremy Harper for their substantial contributions. The Wild Resources Conservation Fund, Pennsylvania Department of

Conservation and Natural Resources (Project Number AG050523); the National Park Service

(Grant Agreement H4560030064); and a Pennsylvania State Wildlife Grant (number

PFBC050305.01) provided financial support. Christopher A. Urban, Matt R. Marshall, and Sarah

Nichols administered grants and provided encouragement. Emily and Megan Lieb assisted in the field at some sites. Patrick Martinez, an anonymous reviewer, and Marybeth Lieb provided helpful critiques of the paper.

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Table 5.1. Historical and contemporary crayfish studies that aided in the development of the conservation classifications (e.g., vulnerable, secure) and management strategies provided herein. Studies are listed by state (US) or province (Canada). Statewide refers to studies that include most of the state; NPS=National Park Service, PA=Pennsylvania. State/Province Coverage Source Historical Maryland Statewide Meredith and Schwartz 1960 Patapsco River drainage Schwartz et al. 1963 New York Statewide Crocker 1957 Pennsylvania Statewide Ortmann 1906 Statewide Bouchard et al. 2007a West Virginia Northern part of the state Ortmann 1906 Contemporary Maryland Statewide Kilian et al. 2010 New York Upper Susquehanna River drainage Kuhlmann and Hazelton 2007 Schoharie Creek drainage Daniels 1998 North Carolina Western part of the state Simmons and Fraley 2010 Pennsylvania Statewide with emphasis on eastern PA Bouchard et al. 2007 NPS properties across the state Lieb et al. 2007a Valley Creek Lieb et al. 2007b Valley Creek Lieb et al. 2008 Southeastern part of the state Lieb and Bhattarai 2009 Southeastern part of the state Lieb et al. 2011 West Virginia Statewide Jezerinac et al. 1995 Statewide Loughman et al. 2009 Statewide Loughman and Welsh 2010 Eastern Potomac River drainage Swecker et al. 2010 Ontario south-central part of the province Edwards et al. 2009 aIncludes historical museum records.

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Table 5.2. Historical and contemporary crayfish collections from resampled sites in the Susquehanna (S) and Potomac (P) River drainages of Pennsylvania. Historical data were collected in 1912 (Conoy Creek), 1956 (Penns Creek tributary), or were taken from Ortmann (1906), who did not provide collection dates for individual sites. Contemporary data were collected in 2006 and 2007. Abbreviations used: R=Raystown, Br=Branch, Cr=Creek, R=River, Trib=Tributary, NA=Not available, bartonii=C. b. bartonii, limosus=O. limosus, obscurus=O. obscurus, rusticus=O. rusticus, virilis=O. virilis.

Stream Lat, Long Historical Contemporary (drainage) County Nearby town (decimal °) Species n Species n Back Cr (P) Franklin Williamson 39.85422, -77.79622 limosus NA virilis 18 Conococheague Cr (P) Franklin Chambersburg 39.96102, -77.64832 bartonii NA bartonii 1 limosus NA obscurus 8 virilis 11 Conococheague Cr (P) Franklin Williamson 39.84675, -77.79425 limosus NA bartonii 1 obscurus 10 virilis 37 Bald Eagle Cr (S) Centre Milesburg 40.94309, -77.78700 bartonii NA obscurus 25 limosus NA Conoy Cr (S) Lancaster Bainbridge 40.08473, -76.66097 bartonii 20 rusticus 82 Conodoquinet Cr (S) Cumberland West Fairview 40.25543, -76.92745 limosus NA rusticus 22 Fishing Cr (S) Columbia Bloomsburg 40.99537, -76.47353 limosus NA obscurus 26 Montour Cr (S) Perry Green Park 40.35842, -77.31798 bartonii NA obscurus 3 limosus NA rusticus 55 R Br Juniata R (S) Bedford Bedford 40.02013, -78.50278 limosus NA obscurus 7 Trib of Penns Cr (S) Union/Snyder New Berlin 2 possibilitiesa limosus 1 bartonii 10b obscurus 17b rusticus 56b Yellow Breeches Cr (S) Cumberland/York New Cumberland 40.22395, -76.86070 limosus NA rusticus 39 a40.87208, -77.01345 (Sweitzers Run) or 40.86767, -77.00650 (Tuscarora Creek); see methods for further explanation. bTotal for Sweitzers Run and Tuscarora Creek.

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Table 5.3. Conservation classifications for several of eastern Pennsylvania's native crayfishes. Abbreviations used: CS=Currently stable; G5, S5 (species classification) and T5 (subspecies classification)=Secure; S4=Apparently secure; S3=Vulnerable; S1=Critically imperiled; NL=Not listed; AFS=American Fisheries Society; NHN=National Heritage Network; C.=Cambarus; O.=Orconectes; b.=bartonii; P.=Puncticambarus. Updated classifications were developed for this study. An asterisk (*) indicates that more information is needed to update the classification. See methods for further explanation of classification procedures and sources.

Global Pennsylvania Species AFS NHN Updated NHN Updated C. b. bartonii CS G5T5 G5T5 S5 S5 C. (P.) sp. NL NL * NL S1 O. limosus CS G5 * S4 S3

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Figure 5.1. Map of Pennsylvania with historical and contemporary crayfish collection sites. Sites from Ortmann (1906) are plotted separately from the remaining historical data. Collection dates were not available for some sites (Unknown Year). From east to west, the Delaware,

Susquehanna, Potomac, Genesee, and Ohio River drainages are delineated. The Lake Erie drainage is shown in the northwest corner of the map. For simplicity, streams that flow directly into the Chesapeake Bay are included in the Susquehanna drainage.

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Figure 5.2. Map of eastern Pennsylvania with historical and contemporary O. limosus collection sites. Sites from Ortmann (1906) are plotted separately from the remaining historical data. From east to west, the Delaware, Susquehanna, and Potomac River drainages are delineated. For simplicity, streams that flow directly into the Chesapeake Bay are included in the Susquehanna drainage. Historical O. limosus sites in the Susquehanna and Potomac drainages that were resurveyed for crayfishes are circled; O. limosus was not found at any of them. Because the Back and Conococheague Creek sites near the town of Williamson (Potomac drainage) are close together, their site markers overlap. See Table 5.2 and methods for additional details.

Figure 5.3. Map of eastern Pennsylvania with historical and contemporary O. obscurus collection sites. The Ortmann (1906) site is plotted separately from the other historical site. From east to west, the Delaware, Susquehanna, and Potomac River drainages are delineated. For simplicity, streams that flow directly into the Chesapeake Bay are included in the Susquehanna drainage. See Table 5.2 and methods for additional details.

Figure 5.4. Map of eastern Pennsylvania with O. rusticus collection sites. From east to west, the Delaware, Susquehanna, and Potomac River drainages are delineated. For simplicity, streams that flow directly into the Chesapeake Bay are included in the Susquehanna drainage. See Table 5.2 and methods for additional details.

Figure 5.5. Map of eastern Pennsylvania with O. virilis collection sites. From east to west, the Delaware, Susquehanna, and Potomac River drainages are delineated. For simplicity, streams that flow directly into the Chesapeake Bay are included in the Susquehanna drainage. Because the Back and Conococheague Creek sites near the town of Williamson (Potomac drainage) are close together, their site markers overlap. See Table 5.2 and methods for additional details.

Figure 5.6. Map of eastern Pennsylvania with historical and contemporary C. b. bartonii collection sites. Sites from Ortmann (1906) are plotted separately from the remaining historical data. From east to west, the Delaware, Susquehanna, and Potomac River drainages are delineated. For simplicity, streams that flow directly into the Chesapeake Bay are included in the Susquehanna drainage. Historical C. b. bartonii sites in the Susquehanna and Potomac drainages that were resurveyed for crayfishes are enclosed by circles; C. b. bartonii was not found at three of them. See Table 5.2 and methods for additional details.

Chapter 6

Determinants of Crayfish Community Structure

Introduction

The factors responsible for local community structure have long been debated by ecologists. Frederic E. Clements (Clements 1916, Clements et al. 1929) supposed that communities were tightly linked groups of species (complex organisms), implying that local interactions (e.g., competition, predation, mutualism) were important in determining their structure. Henry A. Gleason (Gleason 1926) opposed this view, instead arguing that communities were chance assemblages of individually distributed species that occurred together at particular points in space and time due to their need for similar environmental conditions, implying weak local interactions. Robert A. MacArthur and colleagues (e.g., MacArthur 1965, MacArthur and

Levins 1967) built on earlier work by Grinnell (1917), Lotka (1925), Volterra (1926), Elton

(1927), Gause (1934), Hutchinson (1957) and others and ushered in the era of local determinism, in which local interactions occurring in ecological time were thought to largely determine local community structure. In this view, local processes such as competition, predation, and mutualism, preceded to equilibrium rapidly, negating the importance of processes operating at larger scales (Ricklefs 2008). Local determinism predicts that local communities should be saturated with species, and that local species richness should be independent of regional species richness (Terborgh and Faaborg 1980).

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This view persisted for several decades until ecologists, most prominently Robert E.

Ricklefs (Ricklefs 1987), began to argue for the importance of regional and historical factors in determining local community structure. Plots of local verses regional species richness, which were often found to be linear (Lawton 1999, Loreau 2000, Mouquet et al. 2003), suggesting that local communities were unsaturated and that regional and historical factors rather than local factors control local community richness (Cornell and Lawton 1992, Cornell 1999, Oberdorff et al. 1998), seemed to support this view. However, this approach has been widely criticized (e.g.,

Srivastava 1999, Loreau 2000, Hillebrand and Blenckner 2002, Hillebrand 2005, Shurin and

Srivastava 2005) and it now appears that inferring the absence of strong local interactions and predominance of regional/historical factors from linear richness relationships was unfounded in most cases (Loreau 2000, Hillebrand and Blenckner 2002, Hillebrand 2005).

Today, although the debate continues, there is a growing realization that both local and regional/historical factors are important in determining local community structure (e.g., Palmer et al. 1996, Loreau 2000, Ricklefs 2000, Mouquet et al. 2003, Cottenie 2005, Harrison and

Cornell 2008, White and Hurlbert 2010), and that their relative importance varies with time, disturbance regime, the dispersal mode and ability of component species, and other factors

(Palmer et al. 1996, Valone and Hoffman 2002, Mouquet et al. 2003, Van De Meutter et al.

2007).

Hubbell‘s neutral theory (Hubbell 2001) is a more recent contribution to the debate on what structures local communities, and has stimulated much interest. However, the basic premise of the theory, mainly that species are ecologically equivalent, does not appear to fit well with what is known about crayfishes (see Nyström 2002); therefore neutral theory will not be discussed further. The objective of this chapter is to examine the potential contribution of local,

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regional, and historical factors to the local community composition of a highly competitive group of organisms, most of which are poor dispersers – the surface-dwelling crayfishes.

The Combined Influence of Local, Regional, and Historical Factors

In this chapter, I provide evidence in support of the view that a combination of local, regional, and historical factors are important in determining local (within a single water body or drainage network) surface-dwelling crayfish community structure. The idea that regional and historical factors predominate over local factors may stem from the view that local communities are artificial constructs with little ecological meaning because their boundaries are too small to encompass the complete distributions of their component species (Ricklefs 2008). For widely dispersing organisms, this is certainly a valid argument; however, for most surface-dwelling crayfishes and other aquatic organisms that disperse less readily (those that lack an aerial adult stage and are poor swimmers) and are therefore largely confined to well defined areas (drainage networks for running waters and individual water bodies for unconnected standing waters), this view may be less applicable (see Ricklefs 2004). For these organisms, communities can be viewed as islands of water among a sea of land (sensu Heino 2011) with well-defined boundaries

(e.g., stream banks, lake shorelines). In these relatively small, more or less closed systems, local factors may be at least as important as regional and historical factors in determining local community structure (see Van De Meutter et al. 2007).

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Local Influences

The interplay of competition with local environmental conditions appears to influence local community structure in surface-dwelling crayfishes. For example, in Pennsylvania, C. b. bartonii is often largely restricted to fast-current habitats (e.g., riffles) when in the presence of O. obscurus or C. (P.) sp. but is more equally distributed among fast- and slow-current habitats

(e.g., pools) when alone (D.A. Lieb, PSU and R.W. Bouchard, ANSP, unpublished data).

Similarly, researchers in West Virginia, New York, and Canada have noted that C. bartonii and

O. obscurus occupy different habitat types when sympatric (Jezerinac et al. 1995, Hamr 1998,

Kuhlmann and Hazelton 2007). In Ohio streams that have been invaded by O. rusticus, resident

O. obscurus occur in headwater areas and O. rusticus in downstream reaches; whereas in streams that have not been invaded by O. rusticus, O. obscurus occurs throughout the system (Thoma and Jezerinac 2000). Similarly, Lieb et al. (2011a) speculated that, in Pennsylvania, C. b. bartonii may be able to persist in the headwaters of streams that have been invaded by O. rusticus because those areas are not preferred by O. rusticus. More generally, in Pennsylvania, C. b. bartonii appears to prefer small to midsized streams and is uncommon in larger water ways, which are often dominated by orconectids (O. obscurus, O. propinquus, O. rusticus ) (Ortmann

1906, Lieb et al. 2011a).

Although additional surveys and experimental work are needed to elucidate the cause of these patterns, it seems plausible that, in many of these systems, competitive interactions interact with environmental conditions (habitat type) such that each species is dominant in a different habitat type and thus able to coexist at the scale of the entire stream but not at the scale of individual habitats (see similar ideas in Loreau 2000 regarding the coexistence of species in a mosaic of environmentally variable patches). This suggests that competitive interactions may

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limit the number of species in a particular habitat type (patch) but that environmental heterogeneity limits the number of species in the community.

A number of authors have noted that invasions often do not result in the loss of resident species (e.g., Moore et al. 2001, Sax et al. 2002, Stohlgren et al. 2003, Fridley et al. 2007, Davis

2009, Davis et al. 2011), which has been cited as evidence for a lack of strong local control and presumed importance of regional and historical factors in structuring local communities

(Ricklefs 1987, Ricklefs 2007, Ricklefs and Jenkins 2011). This view is based on the idea that, in species saturated communities, structured by local conditions, new species should not be able to invade without the compensatory loss of resident species (Ricklefs 1987).

Crayfish data from surface waters in Pennsylvania and elsewhere suggest that local crayfish communities are often saturated and that the addition of exotics frequently results in the loss of resident species (Schwartz et al. 1963, Berrill 1978, Capelli 1982, St. John 1991, Taylor and Redmer 1996, Lodge et al. 2000, Wilson et al. 2004, Kuhlmann and Hazelton 2007, Taylor et al. 2007, Loughman et al. 2009, Loughman and Welsh 2010, Kilian et al. 2010, Swecker et al.

2010, Lieb et al. 2011a, b). In Pennsylvania, replacements can occur rapidly (likely in <10 years) and interactions between exotic and resident crayfishes can result in injuries to residents (D.A.

Lieb, PSU, personal observations). Thus, it appears that competition, interacting with local environmental conditions, sets an upper limit to local crayfish species richness in these systems.

At larger scales, invasions have also resulted in the loss of native species (e.g., the disappearance of O. limosus from much of eastern Pennsylvania, northern Maryland, eastern

West Virginia, and south central New York and other native crayfish from parts of the Midwest,

Canada, and Europe; Holdich 1999, Kuhlmann and Hazelton 2007, Taylor et al. 2007,

Loughman et al. 2009, Loughman and Welsh 2010, Kilian et al. 2010, Swecker et al. 2010, Lieb

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et al. 2011a, b); however, some of these invaded areas currently harbor more species than they did prior to invasion (e.g., southeastern Pennsylvania; Lieb et al. 2011a). It is possible that, over longer time scales as more localities are invaded and species are excluded due to competitive interactions that the diversity of these areas will decline. It is also possible that crayfish invasions will end up increasing regional diversity (as was found by Stohlgren et al. 2003) while decreasing local diversity (via competitive exclusion). This is possible if spatial heterogeneity allows native crayfish to persist in some habitats that are not favored by exotics (e.g., C. b. bartonii in the headwaters of drainage networks invaded by O rusticus) or if dispersal rates are low enough to prevent exotics from colonizing some areas.

To date, most studies of crayfish invasions have taken place in naturally depauperate areas such as Pennsylvania and nearby states that support a relatively small number of mostly widespread species. In these areas, invasions would not be expected to immediately result in range-wide extinction. Instead at short time scales, both natives and exotics would be present across the landscape resulting in regional enrichment. At longer time scales; however, native species may be driven to extinction resulting in declines in regional diversity. The effects of crayfish invasions on more species-rich native faunas that harbor endemic species with much smaller ranges (e.g., the crayfish fauna of the southeastern United States) are not yet known and may be more pronounced, potentially resulting in relatively rapid declines in regional crayfish diversity in those areas (see related ideas in Lodge et al. 2000 and Taylor et al. 2007).

The frequent disappearance of resident species from invaded systems suggests that local crayfish communities are saturated and strongly influenced by competitive interactions. Across larger areas (e.g. entire states), crayfish invasions are ongoing and their ultimate effect on crayfish diversity at that scale is not yet known with certainty.

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Regional and Historical Influences

Although biotic interactions (mainly competition) appear to limit the number of crayfish species that can occur in individual communities, regional and historical processes likely determine potential component species (see similar ideas in Heino et al. 2003, Cottenie and De

Meester 2004, Vellend 2010). For example, because large parts of Pennsylvania were inhospitable to crayfishes during the last ice age, much of the state is occupied by relatively recent arrivals that were able to persist in southern Pennsylvania and nearby states during the last ice age (see Ortmann 1906). Ortmann (1906) even speculated that the range of one of

Pennsylvania‘s crayfish species, Cambarus dubius, may expand in the future due to the natural colonization of suitable habitats, implying that the colonization process may not be complete for some of the state‘s crayfishes. The current distributions of many of Pennsylvania‘s crayfish species can be explained by shifts in drainage patterns related to glacial advances and retreats

(Ortmann 1906), again implicating historic glacial events in determining local community composition in Pennsylvania. Glacial impacts are not limited to Pennsylvania and have had substantial effects on crayfish distributions and hence crayfish community structure in other states such as Illinois, Ohio, and New York (Crocker 1957, Page 1985, Thoma and Jezerinac

2000).

More broadly, the crayfish fauna of much of Pennsylvania and adjacent areas is relatively young, having only had ~10,000-20,000 years to develop, which has probably contributed to its depauperate state. In contrast, the crayfish fauna to the south is much older (on the order of millions to tens of millions of years or more; see Hobbs 1988, Crandall and Buhay 2008) and much richer. For example, over two-thirds of North America‘s 405 species and subspecies occur

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in the southeastern United States, many of which are endemic to the region (Taylor 2002, Taylor et al. 2007). Many of these species appear to have arisen due to the isolating effects of pre- and post-Pleistocene shifts in river drainages (Crandall and Templeton 1999, Crandall and Buhay

2008). Thus, despite strong local structuring forces (mainly competition) that appear to limit the number of species that can occur in any single water body or drainage network, unique regional and historical influences have produced an exceptionally rich crayfish fauna in some parts of

North America. In these species-rich areas, the number of potential component species in any given community may be larger than in species-poor areas.

Given the strength of competitive interactions and inability of many closely related

(within the same genus) crayfish species to coexist locally, it seems paradoxical that North

America can support such a rich crayfish fauna (400+ species and subspecies). However, this paradox is reconciled by predictions that at low to intermediate levels of dispersal there is regional coexistence of strong competitors, whereas when dispersal rates are high local competitive exclusion extends to the regional scale reducing regional diversity (see Harrison and

Cornell 2008). Applying this concept to crayfishes, it appears that, historically, in Pennsylvania and elsewhere in North America, strong competitors were able to coexist across the landscape because low natural dispersal rates prevented them from coming into contact with one another.

In modern times, human introductions have substantially altered this dynamic, resulting in much higher dispersal rates and, as predicted, competitive exclusion over large areas.

Concluding Remarks

It appears that a combination of local, regional, and historical processes operating across a variety of temporal and spatial scales have shaped the surface-dwelling crayfish fauna of

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Pennsylvania and nearby states over the long-term. In more recent times, the human-assisted spread of exotic species is rapidly changing the crayfish fauna of these areas to an extent not observed since the end of the last glacial epoch ~10,000 years ago and may eventually result in a greatly homogenized crayfish fauna. More generally, the preceding discussion provides insights into how communities of highly competitive, naturally weak dispersers might be assembled and how they might respond to anthropogenic increases in dispersal rates.

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VITA

David A. Lieb

Education

The Pennsylvania State University, PhD, Ecology 2011 The Pennsylvania State University, MS, Ecology 1998 The Pennsylvania State University, BS, Biology 1991

Selected Technical Reports and Publications

1. Lieb, D.A. and R.F. Carline. 1999. Effects of urban runoff from a detention pond on the macroinvertebrate community of a headwater stream in central Pennsylvania. Journal of the Pennsylvania Academy of Science 73: 99- 105. 2. Lieb, D.A. and R.F. Carline. 2000. Effects of urban runoff from a detention pond on water quality, temperature, and caged Gammarus minus (Say) (Amphipoda) in a headwater stream. Hydrobiologia 441: 107-116. 3. Lieb, D.A. and B. Blumberg. 2005. Crayfish Previously Unknown in Pennsylvania Found at Valley Forge. Page 71 in J. Selleck (editor), Natural Resource Year in Review – 2004. Publication D-1609. National Park Service, Washington D.C. 4. Lieb, D.A., R.F. Carline, and V.M. Mengel. 2007. Crayfish Survey and Discovery of a Member of the Cambarus acuminatus Complex (Decapoda: Cambaridae) at Valley Forge National Historical Park in Southeastern Pennsylvania. Technical Report NPS/NER/NRTR—2007/084. National Park Service, Philadelphia, Pennsylvania. 5. Lieb, D.A., R.F. Carline, and H.M. Ingram. 2007. Status of Native and Invasive Crayfish in Ten National Park Service Properties in Pennsylvania. Technical Report NPS/NER/NRTR—2007/085. National Park Service, Philadelphia, Pennsylvania. 6. Bouchard, R.W., D.A. Lieb, R.F. Carline, T.R. Nuttall, C.B. Wengert, and J.R. Wallace. 2007. 101 Years of Change (1906 to 2007). The Distribution of the Crayfishes of Pennsylvania. Part I. Eastern Pennsylvania. Academy of Natural Sciences of Philadelphia Report No. 07-11. Philadelphia, Pennsylvania. 7. Lieb, D.A., R.F. Carline, J.L. Rosenberger, and V.M. Mengel. 2008. The discovery and ecology of a member of the Cambarus acuminatus complex (Decapoda: Cambaridae) in Valley Creek, southeastern, Pennsylvania. Journal of Crustacean Biology 28:439-450. 8. Lieb, D.A. 2010. The biology and management of invasive rusty crayfish in Pennsylvania. Pages 10-11 and 18- 23 in S. Grisé (editor), Conducting an Aquatic Invasive Species Early Response Exercise in Pennsylvania: Proceedings of a Workshop for Evaluating the Effectiveness of Pennsylvania‘s Rapid Response Plan. Pennsylvania Sea Grant, Harrisburg, Pennsylvania. 9. Lieb, D.A., R.W. Bouchard, and R.F. Carline. 2011. The crayfish fauna of southeastern Pennsylvania: distributions, ecology, and changes over the last century. Journal of Crustacean Biology 31: 166-178. 10. Filipová, L., D.A. Lieb, F. Grandjean, and A. Petrusek. 2011. Haplotype variation in the spiny-cheek crayfish Orconectes limosus: colonization of Europe and genetic diversity of native stocks. Journal of the North American Benthological Society 30: 871–881. 11. Lieb, D.A., R.W. Bouchard, R.F. Carline, T.R. Nuttall, J.R. Wallace, and C.B. Wengert. 2011. Conservation and management of crayfishes: lessons from Pennsylvania. Fisheries 36: 489-507.

Professional Positions

1. Invertebrate Zoologist, Western Pennsylvania Conservancy/Pennsylvania Fish & Boat Commission, 2011-present 2. Graduate Assistant (PhD) and Researcher, The Pennsylvania State University, 2003-2011 3. Staff Scientist, Stroud Water Research Center, 1997-2003 4. Graduate Assistant (MS), The Pennsylvania State University, 1994-1997 5. Staff Scientist, Academy of Natural Sciences of Philadelphia, 1992-1994 6. Research Technician, The Pennsylvania Fish and Wildlife Cooperative Research Unit, 1991-1992 7. Research Technician, The Pennsylvania Fish and Boat Commission, summer 1990 8. Research Technician, The Pennsylvania Fish and Wildlife Cooperative Research Unit, summer 1989