Species Status Assessment Report for the Round Hickorynut Mussel (Obovaria subrotunda) Photo credit: Environment Canada October 2019 Version 1.0 U.S. Fish and Wildlife Service Region 4 Atlanta, GA 1 Primary Contributors • Andrew Henderson - Asheville Field Office, Lead Biologist (Region 4) – primary author • Heidi Crowell - Pacific Southwest Regional Office, SAT Project Manager (Region 8) • Mark Endries - Asheville Field Office (Region 4) – mapping support Contributors & Agency Reviewers (underlined) • Paul Hartfield, Leroy Koch (retired), Angela Boyer, Stephanie Chance (retired), Bob Anderson, Tyler Hern, Andy Ford, Patty Morrison (retired), Bob Butler (retired), Josh Hundley (U.S. Fish and Wildlife Service) • Dr. Todd Morris (Fisheries & Oceans Canada) • Chuck Howard (retired), Tim Keeling (Tennessee Valley Authority) • Kierstin Carlson (Western Pennsylvania Conservancy) • Steve Ahlstedt (retired) (U.S. Geological Survey) • Dr. Arthur Bogan, Jamie Smith (North Carolina Museum of Natural Sciences) • Jeremy Tiemann, Rachel Vinsel, Kevin Cummings (Illinois Natural History Survey) • Heidi Dunn, Emily Grossman (Ecological Specialists, Inc.) • Dr. Paul Johnson, Jeff Garner, Michael Buntin, Todd Fobian, Ashley Peters (Alabama Department of Conservation and Natural Resources) • Gerry Dinkins (University of Tennessee) • Matt Johnson, Greg Zimmermann (EnviroScience, Inc.) • Mike Compton, Ian Horn (Kentucky State Nature Preserves Commission) • Chad Lewis, Clarissa Lawliss (Lewis Environmental Consulting) • Nevin Welte (Pennsylvania Boat and Fish Commission) • Amy Mahar, Nick Conrad (New York Natural Heritage Program) • Darran Crabtree (New York Chapter, The Nature Conservancy) • Debbie Wolschki (Ohio Natural Heritage Program) • Janet Clayton (West Virginia Natural Resources) • Brant Fisher (Indiana Department of Natural Resources) • Dr. Monte McGregor, Adam Shepard, Keith Wethington (Kentucky Department of Fish and Wildlife Resources) • Stuart McGregor (Geological Survey of Alabama) • Don Hubbs, Jason Wisenwski (Tennessee Wildlife Resources Agency) • Dr. Robert (Bob) Jones (retired) (Mississippi Museum of Natural Sciences) • John Tetzloff (Darby Creek Watershed Association) • Peter Badra, Rebecca Rogers (Michigan Natural Features Inventory) • Scott Hanshue (Michigan Department of Natural Resources) SUGGESTED CITATION: U.S. Fish and Wildlife Service (Service). 2019. Species Status Assessment Report for the Round Hickorynut Mussel (Obovaria subrotunda), Version 1.0. Asheville Ecological Services Field Office, Asheville, North Carolina. TABLE OF CONTENTS ACRONYMS USED vii EXECUTIVE SUMMARY viii CHAPTER 1 - INTRODUCTION 12 1.1 Purpose of SSA 12 1.2 Species Basics - Taxonomy and Evolution 12 1.2.1 Taxonomy 14 1.3 Petition History 15 1.4 State Listing Status 15 CHAPTER 2 - METHODOLOGY AND DATA 17 2.1 SSA Framework 17 2.1.1 Species Needs 18 2.1.2 Current Species Condition 19 2.1.3 Future Species Condition 21 CHAPTER 3 - SPECIES BACKGROUND AND ECOLOGY 22 3.1 Physical Description 22 3.2 Genetics 23 3.3 Life History 24 3.4 Reproduction 27 CHAPTER 4 - RESOURCE NEEDS 30 4.1 Individual-level Resource Needs 31 4.1.1 Clean, Flowing Water 31 4.1.2 Appropriate Water Quality and Temperatures 32 4.1.3 In-Stream Sedimentation 32 4.1.4 Food and Nutrients 33 4.2 Population- and Species-level Needs 33 4.2.1 Connectivity of Aquatic Habitat 33 4.2.2 Dispersal-Adult Abundance and Distribution 34 4.2.3 Host Fish 35 4.3 Uncertainties 37 4.4 Summary of Resource Needs 37 CHAPTER 5 - CURRENT CONDITIONS, ABUNDANCE AND DISTRIBUTION 39 5.1 Historical Conditions For Context 40 5.2 Current Population Abundance, Trends, and Distribution 43 5.3 Estimated Viability of Round Hickorynut Mussel Based on Current Conditions 47 5.3.1 Resiliency 48 5.3.2 Representation 55 5.3.3 Redundancy 56 5.4 Uncertainties of Current Condition 57 CHAPTER 6 - FACTORS INFLUENCING VIABILITY 58 6.1 Habitat Degradation or Loss 60 6.1.1 Development/Urbanization 60 6.1.2 Transportation 63 6.1.3 Contaminants 65 6.1.4 Agricultural Activities 69 6.1.4.1 Nutrient Pollution 69 6.1.4.2 Pumping for Irrigation 70 6.1.4.3 Agriculture Exemptions from Permit Requirements 70 6.1.4.4 Agricultural Activities Summary 71 6.1.5 Dams and Barriers 73 6.1.6 Changing Climate Conditions 77 6.1.7 Resource Extraction 79 6.1.7.1 Coal Mining 79 6.1.7.2 Natural Gas Extraction 81 6.1.7.3 Gravel Mining/Dredging 81 6.1.7.4 Resource Extraction Summary 82 6.1.8 Forest Conversion 83 6.2 Invasive and Nonnative Species 85 6.3 Genetic Isolation and Displacement 89 6.4 Factors Currently Believed To Have Limited Effects on Round Hickorynut Populations 91 6.4.1 Harvest and Overutilization 91 6.4.2 Host Fishes 92 6.4.3 Enigmatic Population Declines 93 6.4.4 Parasites 94 6.4.5 Predation 94 6.5 Overall Summary of Factors Affecting the Species 95 CHAPTER 7 - FUTURE CONDITIONS 96 7.1 Future Scenario Considerations 97 7.2 Future Scenarios 97 7.3 Scenario 1 100 7.3.1 Resiliency 104 7.3.2 Representation 105 7.3.3 Redundancy 105 7.4 Scenario 2 106 7.4.1 Resiliency 110 7.4.2 Representation 111 7.4.3 Redundancy 112 7.5 Scenario 3 112 7.5.1 Resiliency 117 7.5.2 Representation 118 7.5.3 Redundancy 119 CHAPTER 8 - OVERALL SYNTHESIS 119 LITERATURE CITED 129 APPENDIX A—SUMMARY OF EXTANT POPULATIONS AND THEIR ESTIMATED SIZE 169 APPENDIX B—FORMER CONTIGUOUS POPULATIONS AND MANAGEMENT UNITS, NOW CONSIDERED EXTIRPATED, ACROSS THE ROUND HICKORYNUT RANGE 188 APPENDIX C—MAPS DEPICTING THE 62 ROUND HICKORYNUT MUSSEL POPULATIONS WITHIN MANAGEMENT UNITS ACROSS THEIR CURRENT RANGE 210 APPENDIX D—ESTIMATES OF MAGNITUDE AND IMMEDIACY OF POTENTIAL THREATS NEGATIVELY INFLUENCING THE VIABILITY OF ROUND HICKORYNUT 211 ACRONYMS USED THROUGHOUT THIS DOCUMENT AND APPENDICES ADCNR Alabama Department of KYSNPC Kentucky State Nature Preserves Conservation and Natural Commission Resources LEC Lewis Environmental Consulting AMD acid mine and saline drainage MU Management Unit ANS aquatic nuisance species NCMNS North Carolina Museum of ANSP Academy of Natural Sciences of Natural Sciences Philadelphia MCZ Museum of Comparative Zoology BMP best management practices MFM Museum of Fluviatile Mollusks CBD Center for Biological Diversity MMNS Mississippi Museum of Natural CM Carnegie Museum of Natural Sciences History MNFI Michigan Natural Features COSSARO Committee on the Status of Inventory Species at Risk in Ontario MUMC Marshall University Museum COSEWIC Committee on the Status of Collection Endangered Wildlife in NHP Natural Heritage Program Canada NPDES National Pollutant Discharge Corps U.S. Army Corps of Engineers Elimination System CWA Clean Water Act NRCS Natural Resources Conservation DNA deoxyribonucleic acid Service EKU Eastern Kentucky University OSUM Ohio State University Museum Collection PPM parts per million EPA U.S. Environmental Protection PAFBC Pennsylvania Fish and Boat Agency Commission ESA Endangered Species Act RM river mile ESI Ecological Specialists, Inc. Service U.S. Fish and Wildlife Service FMNH Florida Museum of Natural SSA Species Status Assessment History SWAP State Wildlife Action Plan FR Federal Register TDEC Tennessee Department of GIS geographic information system Environment and Conservation HUC Hydrologic unit codes TVA Tennessee Valley Authority IDEM Indiana Department of TWRA Tennessee Wildlife Resources Environmental Management Agency INDNR Indiana Department of Natural UMMZ University of Michigan Museum Resources of Zoology INHS Illinois Natural History Survey USDA U.S. Department of Agriculture IPCC Intergovernmental Panel on USNM U.S. National Museum Climate Change USGS U.S. Geological Survey IUCN International Union for UTMM University of Tennessee McClung Conservation of Nature Museum KDEP Kentucky Department for WVDEP West Virginia Department of Environmental Protection Environmental Protection KYDOW Kentucky Division of Water WVDNR West Virginia Division of KYFW Kentucky Department of Fish and Natural Resources Wildlife Resources EXECUTIVE SUMMARY The Round Hickorynut Obovaria subrotunda (Rafinesque, 1820) is a small- to medium-sized mussel up to 3 inches (75 millimeters) in size, which lives up to 15 years. It is found in small streams to large rivers, and prefers a mixture of sand, gravel, and cobble substrates. The Round Hickorynut mussel is a wide-ranging species, historically known from 12 states, though now occurs in 9, as well as the Canadaian Province of Ontario. It is currently found in five major basins: Great Lakes, Ohio (where it is most prevalent), Cumberland, Tennessee, and Lower Mississippi (where it is most rare). The number of known populations in the U.S. has declined by 78 percent, from 297 populations documented historically to 65 today. The Round Hickorynut and other aquatic species have endured negative influences commonly found in the central and eastern U.S., including: habitat fragmentation from dams and other barriers; habitat loss; degraded water quality from chemical contamination and erosion from poorly managed development, agriculture, mining, and timber operations; direct mortality from dredging and harvest; and the proliferation of invasive species, such as the Zebra Mussel. Projections 20 to 30 years into the future suggest the number of populations could remain at 65 across 5 basins or drop to as low as 19 across 3 basins, depending on the variety of considerations built into potential scenarios. It is likely that the Round Hickorynut could disappear entirely from the Cumberland and Lower Mississippi River basins given current and possible future conditions in the last remaining populations within