Louisiana Pearlshell (Magaritifera hembeli) Species Status Assessment Version 1.0

Photo by NNFH, Service by NNFH, Photo

August 6, 2019 U.S. Fish and Wildlife Service Region 4 Atlanta, GA Louisiana Ecological Services Office Lafayette, LA

Table of Contents

ACKNOWLEDGEMENTS iii

EXECUTIVE SUMMARY iv

1 INTRODUCTION 1 1.1 Species Protection Status 2

2 SPECIES’ BIOLOGY 3 2.1 Species Description and Taxonomy 3 2.2 Life History and Demography 4 2.3 Diet 7 2.4 Habitat 8 2.5 Distribution and Abundance 9 2.6 Genetics 14

3 SPECIES NEEDS FOR VIABILITY 15 3.1 Individual Level 15 3.2 Population Level 15 3.3 Species Level 15

4 INFLUENCES ON VIABILITY 16 4.1 Factor A: Habitat Destruction and Modification 16 4.1.1 Impoundments 17 4.1.2 Beaver Activity 17 4.1.3 Water Quality Decline 18 4.2 Factor B: Overutilization 21 4.3 Factor C: Disease or Predation 21 4.4 Factor D: Inadequacy of Existing Regulation 23 4.5 Factor E: Other Natural or Man-made Factors 25 4.6 Conservation Efforts 28 4.6.1 Habitat Protection and Management 29 4.6.2 Propagation and Reintroduction 31

5 CURRENT CONDITION 32 5.1 Delineating Populations 32 5.2 Delineating Representative Units 33

5.3 Current Resilience Approach 34

i 5.3.1 Population Factors 35 5.3.1.1 Aggregation Number and Size 35 5.3.1.2 Evidence of Reproduction 38 5.3.2 Habitat Factors 38 5.3.2.1 Canopy Cover 38 5.3.2.2 Substrate 40 5.3.2.3 Stream Crossings 43 5.3.3 Resilience Scoring 45 5.4 Current Resilience, Redundancy, and Representation 47

6 FUTURE CONDITION 51 6.1 Future Resilience Assessment 52 6.1.1 Future Projection Time Frames 52 6.1.2 Aggregation Scores 52 6.1.2.1 Estimating Transition Probabilities 53 6.1.2.2 Projecting Aggregation Scores: Status Quo Scenario 56 6.1.2.2 Projecting Aggregation Scores: Conservation without Reintroductions Scenario 59 6.1.2.3 Conservation with Reintroductions Scenario 63 6.1.3 Evidence of Reproduction 65 6.1.4 Canopy Cover 66 6.1.5 Substrate 66 6.1.6 Stream Crossings 66 6.2 Future Resilience, Redundancy, and Representation 67

LITERATURE CITED 74

APPENDIX A: Maps 79

APPENDIX B: Survey Results 83

APPENDIX C: Current Resilience Factor Values 97

APPENDIX D: Future Scenario Figures 98

ii ACKNOWLEDGEMENTS

This document was prepared by Stephanie DeMay (Texas A&M Natural Resources Institute), Monica Sikes (U.S. Fish and Wildlife Service [Service]), and Brigette Firmin (Service). Assistance was provided by David Oster (Service), Michael Marshall (Service), and Drew Becker (Service). Other species expertise, guidance, and document reviews were provided by Keri Lejeune (Louisiana Department of Wildlife and Fisheries [LDWF]), Steve Shively (U.S. Forest Service [USFS]), Ted Soileau (USFS), and Jared Streeter (LDWF). Peer review was provided by Beau B. Gregory, John L. Harris, and Michael D. Kaller.

iii EXECUTIVE SUMMARY

The Louisiana pearlshell is a freshwater mussel endemic to narrow streams with low gradients in a limited area of Grant and Rapides Parishes in Louisiana. Occupied habitat in Grant Parish is mostly privately owned, while most Louisiana pearlshells in Rapides Parish occur on public land. The species was listed as a federally endangered species in 1988 (53 Federal Register (FR) 3567) and was downlisted to threatened in 1993 (58 FR 49935) after the species was found in new locations. Louisiana pearlshells depend on the presence of a host fish to complete their lifecycle. Louisiana pearlshell larvae attach to an appropriate host fish for a period ranging from 35-51 days before dropping off and settling in the streambed. The most robust and stable aggregations of Louisiana pearlshells are found on substrates with a gravel component in the overall composition. Louisiana pearlshells, which are filter feeders as adults, have a low tolerance to high silt loads. Threats to the species include land use practices that increase levels of siltation and other pollutants in the water (e.g., forestry, construction, grazing, off-road vehicle use), stream drying caused by beaver activity or drought, and mortality through predation. Positive influences on the species include management plans for habitat on public lands, beaver control, and landowner incentive programs. Captive propagation and reintroduction may be an effective recovery tool as well; Louisiana pearlshells are presently being held in captivity, and trial reintroductions are planned for the next few years.

We delineated nine extant Louisiana pearlshell populations, where multiple streams occupied by pearlshell aggregations (containing at least 100 individual mussels) were considered the same population only if the stream resulting from their confluence was also occupied by at least one pearlshell aggregation. Additionally, four populations, James Branch, Moccasin Branch, Mack Branch, and Little Bayou Clear, have been extirpated and do not presently support aggregations (though they might still support low numbers of individual Louisiana pearlshells). The nine extant populations are distributed across four HUC_10 watersheds, and genetic structuring is evident among watersheds.

We assessed current resilience using the following population and habitat factors: the number and size of aggregations (combined into a single “aggregation score”), evidence of reproduction, canopy cover, substrate, and stream crossing structures in need of replacement (Table EX1). The conditions of each of these factors were combined to classify the resilience of each population as high, moderate, or low. There are currently five Louisiana pearlshell populations with high resilience, three with moderate resilience, and one with low resilience. Two representative units (Black Creek and Bayou Rapides watersheds) contain a single population (high resilience and moderate resilience, respectively), but there is no evidence that they ever supported more populations. The remaining two representative units (Bayou Rigolette and Bayou Boeuf watersheds) each contain multiple populations. In Bayou Rigolette, one population has high resilience, and one has low resilience. In Bayou Boeuf, three have high resilience and two have moderate resilience. The four extirpated populations are also distributed across these two watersheds.

iv Table EX1. Summary of criteria for resilience factor conditions and weights used to assess current resilience for Louisiana pearlshell populations.

Population Factors Habitat Factors Aggregation Number Evidence of Canopy Substrate Stream Crossings and Size reproduction Cover Metric Sum of scores for Evidence % 100-ft Percent of # Poor stream aggregation sizes, present or not, buffer with ≥ aggregations crossings (i.e., in since 2007: since 2007 50% canopy on substrate need of upgrade or 1: 100 – 499 mussels cover within with gravel replacement) per 5 2: 500 – 999 mussels assessed component km stream length (or 3: ≥ 1,000 mussels stream length total assessed stream *Further description in length if < 5 km) Section 5.3.1 Good > 10 Evidence > 90% 75 – 100% No poor crossings Condition Moderate Up to 1 poor 6 – 10 NA 50-89% 50 – 74% Condition crossing Poor 1 – 5 No evidence < 50% 0 – 49% > 1 poor crossing Condition

To assess the future condition, we used past monitoring data to model future aggregation scores under a Status Quo scenario and a Conservation scenario (Figure EX1). We also descriptively explored a Conservation with Reintroductions scenario, but did not model population dynamics quantitatively for that scenario. Trial reintroductions are planned to occur within the next few years, but it is unknown whether they will be successful. If reintroductions are successful, it could be a valuable recovery tool to reestablish extirpated populations or prevent local extirpations, provided that reintroduction sites are suitable habitat and threats to pearlshells have been ameliorated. For the initial 10 years of quantitatively modeled future projections, population dynamics were assumed to be the same for both the Status Quo and Conservation scenarios based on the assumption that conservation actions implemented now likely will not have readily apparent results until at least 10 years have passed. The 10 year mark was chosen based on the species reproductive ecology, assuming it will take 10 years for observers to document whether recruitment is occurring in a population beginning from the time a juvenile mussel becomes reproductive to the time that it produces observable offspring. After the first 10 years, the two modeled scenarios diverge, with population dynamics improved in the Conservation scenario in response to recovery actions. Rather than making assumptions about how a variety of recovery actions might influence population dynamics, we instead assessed a range of impact magnitudes to determine how much current population growth rates need to change in order for populations to recover to current levels over 50 years. For both future scenarios, evidence of reproduction, canopy cover, and substrate were held constant at current levels, and the number of stream crossings in need of replacement were adjusted for the future based on predictions by Service personnel regarding which replacement projects are candidates for future funding.

v

Figure EX1. Summary of future scenarios for the Louisiana pearlshell.

Population resilience under the future scenarios, compared with the current condition, are summarized in Table EX2. In 10 years under either scenario, most populations were projected to remain in the same resilience classes as the current condition, with the exception of Loving Creek, which dropped from high resilience to moderate resilience. There is also a 34 percent chance that the Castor Creek population will be extirpated and a 22 percent chance that the Coleman Branch population will be extirpated in 10 years. In 50 years, the Status Quo and Conservation scenarios diverge from each other. In the Status Quo scenario, all populations except Loving Creek, which dropped from high to moderate resilience, were predicted to remain in the same resilience class as the current condition. Probabilities of extirpation for Castor Creek and Coleman Branch changed to 28 percent and 37 percent, respectively. In the Conservation Scenario, all populations except Brown Creek, which improved from moderate to high resilience, were predicted to remain in the same resilience class as the current condition. Probabilities of extirpation for Castor Creek and Coleman Branch declined to 12 percent and 10 percent, respectively.

Based on our assessment of current and future resilience, redundancy and representation are not expected to change dramatically over the next 50 years if no populations are extirpated. If Castor Creek (Bayou Boeuf management watershed) and Coleman Branch (Bayou Rigolette) become extirpated, at least one highly resilient population will remain in their respective management watersheds. In the Conservation scenario, the single population in the Bayou Rapides management watershed (Brown Creek) is expected to improve from moderate to high resilience, improving the chance that Bayou Rapides representation will persist in the future.

vi Table EX2. Current and predicted future resilience for Louisiana Pearlshell populations 10 and 50 years in the future under a Status Quo and Conservation scenario.

Representative Population Population Population Population Population Unit Resilience Resilience Resilience Resilience (Management Current Status Quo and Status Quo Conservation Watershed) Conservation 50 Years 50 Years 10 Years Bayou Boeuf Bayou Clear High High High High Bayou Boeuf Castor Creek Moderate Moderate Moderate Moderate Bayou Boeuf Long Branch High High High High Bayou Boeuf Loving Creek High Moderate Moderate High Bayou Boeuf Valentine Creek Moderate Moderate Moderate Moderate Little Bayou Bayou Boeuf Extirpated Extirpated Extirpated Extirpated Clear Bayou Boeuf Mack Branch Extirpated Extirpated Extirpated Extirpated Hailey’s Creek Not a Not a Bayou Boeuf Not a Population Not a Population Population Population Bayou Rapides Brown Creek Moderate Moderate Moderate High Bayou Rigolette Coleman Branch Low Low Low Low Bayou Rigolette Gray Creek High High High High Bayou Rigolette James Branch Extirpated Extirpated Extirpated Extirpated Moccasin Bayou Rigolette Extirpated Extirpated Extirpated Extirpated Branch Cress Creek Not a Not a Bayou Rigolette Not a Population Not a Population Population Population Black Creek Black Creek High High High High

This relative stability in resilience classes masks an overall decline in aggregation number and size that has been occurring and is expected to continue for 10 years in either scenario, and indefinitely in the Status Quo scenario. If the Status Quo scenario were projected beyond 50 years, population resilience classes would decline more dramatically. Within the 50-year projection window, most populations are expected to persist within their current resilience class.

Aggregations on public Forest Service land fared better than those on private land in the past and in the predicted future. This difference between public and private land implies that, particularly in Grant Parish where populations occur more heavily on private lands than in Rapides Parish, there is much room for improvement in habitat conditions on private lands and cooperation with private landowners can have profound positive impacts on Louisiana pearlshell conservation and recovery. Current levels of species resilience, redundancy, and representation cannot be maintained in perpetuity by focusing efforts on public lands alone.

vii 1 INTRODUCTION

The Species Status Assessment (SSA) framework (Service 2016a, entire) is intended to provide an in-depth review of a species’ biology and threats, an evaluation of its biological status, and an assessment of the resources and conditions needed to maintain long-term viability. The intent is for the SSA to be easily updated as new information becomes available and to support all functions of the Endangered Species Program from Candidate Assessment to Listing to Consultations to Recovery. This SSA for the Louisiana pearlshell (Magaritifera hembeli), a freshwater mussel, is intended to provide the biological support for an updated recovery plan that includes delisting criteria. Importantly, the SSA does not result in decisions or actions by the U.S. Fish and Wildlife Service (Service). Rather, this SSA provides a review of the available information strictly related to the biological status of the Louisiana pearlshell. Future decisions will be made by the Service after reviewing this document and all relevant laws, regulations, and policies. The results of any proposed decisions will be announced in the Federal Register, with appropriate opportunities for public input.

The Louisiana pearlshell is a unique freshwater mussel endemic to narrow streams with low gradients in four watersheds of central Louisiana. The species was listed as federally endangered in 1988 (53 Federal Register (FR) 3567) due to rarity and vulnerability to threats, and a recovery plan was completed in 1990. That plan only identified downlisting (i.e., reclassification from endangered to threatened) criteria, with no delisting criteria. Since the original recovery plan was written, the species has been found in new locations and in much higher numbers than those known previously in the 1990 plan. The Louisiana pearlshell was downlisted from federally endangered to threatened in 1993 (58 FR 49935) and research has given new insight into the species’ biology and life history.

For the purpose of this assessment, we generally define viability as the ability of the species to sustain populations in its range over time. Using the SSA framework (Figure 1), we consider what the species needs to maintain viability by characterizing the status of the species currently and in the future in terms of its resilience, redundancy, and representation (i.e., “the three Rs”; Wolf et al. 2015, entire).

• Resilience describes the ability of populations to withstand stochastic events (arising from random factors), and is positively related to population size and growth rates.

• Redundancy describes the ability of a species to withstand catastrophic impacts to any one population by having multiple populations, allowing species to spread risk across populations.

1 • Representation describes the breadth of genetic and environmental diversity within and among populations, which influences the ability of a species to adapt to changing environmental conditions over time.

Figure 1. Species Status Assessment Framework.

We assessed a range of conditions relative to the three Rs to evaluate the biological status of the Louisiana pearlshell. This SSA report provides a thorough assessment of a species’ biology and natural history and assesses risks, stressors, and limiting factors in the context of determining the viability of the species.

The format for this SSA includes: species’ biology (Chapter 2) and needs (Chapter 3), influences on viability (Chapter 4), current condition (Chapter 5), and future condition (Chapter 6). This document is a compilation of the best available scientific and commercial information and a description of past, present, and likely future risk factors to the Louisiana pearlshell.

1.1 Species Protection Status

The Service currently lists the Louisiana pearlshell as federally threatened and assigns it recovery priority number 8, which signifies a moderate degree of threat and a high recovery potential. As previously mentioned, this mussel was federally listed as an endangered species on

2 February 5, 1988 (53 FR 3567). The Service completed the first recovery plan for the Louisiana pearlshell in December 1990, at which time occurrences of Louisiana pearlshells were known only from south of the Red River. In 1993, the species was reclassified to threatened (58 FR 49935) after the U.S. Forest Service (USFS) conducted surveys and documented a larger range for the species (19 additional streams) that extended north of the Red River in the Black Creek and Bayou Rigolette management watersheds.

In addition to federal protection, the State of Louisiana has identified this mussel as an endangered species and protects it from take and harassment (Louisiana Revised Statutes 56:1901).

2 SPECIES BIOLOGY

2.1 Species Description and Taxonomy

The Louisiana pearlshell is oblong and kidney shaped. Umbos (the inflated dorsal part of the shell) are even with or slightly extended above the hinge line. The anterior end, which is typically buried in the substrate, is rounded; whereas, the exposed posterior end of the shell is pointed and may have corrugated sculpturing along the shell’s surface. The periostracum (outer shell) color is brown to black, while the nacre (inner shell) color is white to purple with a pitted surface. Large adults reach 4.6 inches long (Daniel and Brown 2012, p. 26), 2.0 inches high, and 1.2 inches wide (Figure 2).

Figure 2. Left, adult Louisiana pearlshell mussel, photo by NNFH, Service, 2018. Right, Lousiana pearlshell mussels of different ages and sizes, photo by Gary Lester, LDWF.

3 The currently accepted taxonomic ranking for the Louisiana pearlshell is described below.

Kingdom Animalia Subkingdom Bilateria Infrakingdom Protostomia Superphylum Lophozoa Phylum Mollusca Class Bivalvia Linnaeus, 1758 Subclass Palaeoheterodonta Newell, 1965 Order Unionoida Stoliczka, 1871 Superfamily Unionoidae Rafinesque, 1820 Family Margaritiferidae Haas, 1940 Genus Margaritifera Schumacher, 1816 Species Margaritifera hembeli Conrad, 1838 *Retrieved 8/31/2018 from the Integrated Taxonomic Information System on-line database, http://www.itis.gov.

The Louisiana pearlshell is one of five North American mussel species in the family Margaritiferidae, and its current taxonomic classification falls in the genus Margaritifera. None of the other species in the genus Margaritifera overlap in distribution with the Louisiana pearlshell. Margaritifera hembeli can be distinguished from Margaritifera marrianae (Alabama pearlshell) by shell morphology (Johnson 1983, p. 301) and other anatomical differences (Smith 1988, entire).

2.2 Life History and Demography

The literature has suggested several fish species as potential host for the Louisiana pearlshell, including the following species: striped shiner (Notropis chrysocephalus), redfin shiner (Lythrurus umbratilis), golden shiner (Notemigonus crysoleucas), brown madtom (Notorus phaeus), and the black spotted topminnow (Fundulus olivaceus) (Hill 1986, p. 10; Johnson and Brown 1998, p. 322). However, all reports of potential host fish were made from observing glochidia attached on the gills of wild caught fish, with none confirmed from observation of metamorphosis of glochidia (parasitic larvae) into juveniles. Similarly, the reported reproductive period for Louisiana pearlshells varies among the literature. For instance, Hill (1986, p. 10) reported observed glochidial infection from early spring through summer, with peak infection occurring from April through July. Smith (1988, p .161), however, concluded that spawning takes place between late November and late January with glochidia being released between late December and January. In addition, based on examination of specimens, Smith (1988, p. 161) determined that there was no evidence of another spawning period outside of that part of the year. Because of the time of year that Hill observed infection and because the size of the glochidia described by Hill was larger than that described by Smith; Johnson and Brown (1998, p. 326) concluded that Hill had likely observed the glochidia of Wabash pigtoe (Fusconaia flava). However, Bolden (2000, p. 42) reported observation of glochidial release in mid-

4 February. In addition, she observed less of a weight gain in Louisiana pearlshells in June as compared to February, presuming it was due to the loss of reproductive mass (glochidia).

Due to the conflicts in published information on probable time of spawning and potential host fish species, the Service’s Natchitoches National Fish Hatchery (NNFH) has initiated long-term studies of the Louisiana pearlshell to fill data gaps on the species life history and to develop species management techniques. The reproductive biology of the Louisiana pearlshell is similar to other freshwater mussel species, in that fertilization occurs after females siphon sperm that males release into the water during the spawning period. NNFH’s ongoing research (2010 - 2018) has shown that spawning and release of glochidia occur once annually between February and March. Based on that research, it is proposed that warmer water temperature may be correlated with the earlier timing of the reproductive period, which has also been observed in the closely related freshwater pearl mussel (M. Margaritifera; Hastie and Young 2003, p. 2114) and other freshwater species (Watters et al. 2001, p. 546). The sexes are monomorphic (males and females appear the same). Females brood developing embryos in the marsupia (brooding pouches) of all four gills until releasing fully developed glochidia into the water (Smith 1988, p. 161). Gravid females from large Louisiana pearlshell aggregations have been found to have a near simultaneous release of glochidia. A female releases her numerous glochidia in pigmented conglutinate (Service 2011, p. 3; Figure 3), which may mimic the shape and coloration of fish food items to attract fish and increase the chances of contact with the host fish for infestation (Haag and Warren 1997, p. 578; Haag et al. 1995, entire; Hartfield and Hartfield 1996, p. 372).

Figure 3. Left: Purple gill coloration indicates that the female is gravid. Right: Conglutinate and glochidia released in stream. Photos by Tony Brady, NNFH, Service, March 2011.

These glochidia must then attach to a species-specific host fish within a short time after being released into the water because the released glochidia will die after one to a few days if not attached to the host fish, or if they attach to the wrong species of fish (Wachtler et al. 2001, p. 100-101). Once glochidia successfully attach to the gills of the host fish, the outer tissue of the host fish encapsulates the glochidia to form a cyst, where glochidial metamorphosis takes place. The encapsulation period, the length of metamorphosis from glochidia into very young, newly metamorphosed juveniles, for the Louisiana pearlshell is 35-51 days in a captive environment,

5 with the largest number of juveniles dropping off at day 41 (Service 2018, p.4). In natural populations, after metamorphosis is complete, the juveniles release from the host fish and float downward to settle on the streambed. The reported mortality rate for species in the family Margaritiferidae from the time the glochidia are released from the female mussel until the time that juveniles reach the sediment is between 99.9982 percent and 99.999999 percent, meaning the chance for any released glochidium to transform and reach the sediment can be as low as one in 100,000,000 (Jansen et al. 2001, p. 201-203; McMahon 1991, p. 344). Gravid Louisiana pearlshells produce and release an extremely high number of small glochidia (Service 2016b, p. 2) which may be a mechanism to compensate for the probable high glochidia mortality rates in the natural environment.

Although potential host fish have been identified in published literature (Hill 1986, p. 10; Johnson and Brown 1998, p. 322), research did not lead to documentation of glochidial metamorphosis into juvenile mussels prior to the NNFH’s host fish study in 2016 (Service 2016b, p. 1-2). In NNFH’s host fish studies (Service 2016b, entire; Service 2018 entire), gravid Louisiana pearlshells were captured from the wild and brought into the hatchery before glochidia were released. Beginning in 2014, the Louisiana Department of Wildlife and Fisheries’ (LDWF) Booker Fowler Fish Hatchery in Forest Hill, Louisiana, provided additional laboratory space, equipment, and manpower to assist in the host fish trials (Service 2014, p.1). After the captured Louisiana pearlshell females released glochidia at either of the hatcheries, those glochidia were placed in controlled aquatic environments with various fish species (Service 2016b, entire) until the trials yielded a successful host fish species. In the NNFH’s 2016 host fish trials, grass pickerel (Esox americanus vermiculatus) was the only fish species successfully infested in captivity by placing the glochidia released by two wild-caught gravid Louisiana pearlshells together in a controlled aquatic environment for five minutes with eight different species of potential host fish (Service 2016b, p. 1-2). The glochidia successfully encysted on two grass pickerel. The smaller grass pickerel died shortly after it was infested because too many glochidia attached to the gills of that fish, resulting in mortality from glochidiosis and gill damage. The larger pickerel survived long enough to enable the glochidia to metamorphose into nearly 6,000 juvenile mussels before it also died from glochidiosis and gill damage (Service 2016b, p. 1-2). The glochidiosis and gill damage that caused the mortality of these two fish resulted from an artificially high inoculation and infestation (encapsulation) rate and is not representative of the infestation rate in the wild, which is currently unknown. In January 2018, seventeen grass pickerel were collected from various streams across the Kisatchie National Forest (KNF) to be used as host fish in captivity for the 2018 study year (Service 2018, p.3). All seventeen fish were inoculated with the glochidia collected from two wild-caught, gravid Louisiana pearlshells. The fish were placed in controlled aquatic environments where the glochidia to water ratio and glochidia to fish ratio were much lower than in the 2016 study (Service 2016b p. 1-2; Service 2018, p.4) to reduce the chances of mortality from glochidiosis. Sixteen of those seventeen pickerel lived to enable the metamorphosis of over 12,000 juvenile mussels (Service 2018, p.4).

6 Although these reports have not been published in peer-reviewed literature, results of this research represent the best available, most current scientific data. All of the Louisiana pearlshell females used in the study were returned to their various natal locations of capture within a few days of releasing glochidia at the hatchery; thus, only wild-caught females that were naturally impregnated at their natal location by the sperm of co-occurring males (i.e., not broodstock) have been used in propagation (Service 2016b, 2018, entire). Additionally, because it is now known that the pickerel serves as a host in captivity, research on the potential distribution of this species in Louisiana pearshell streams during the mussel’s reproductive period could provide insight into the association between the status of the host fish in relation to conservation of the Louisiana pearlshell.

Once reaching the sediment, if juvenile mussels land in sub-optimal habitat, they can move short distances horizontally across the substrate using their elongated foot (Yeager et al. 1994, p. 221). The final developmental stage into a sexually mature adult begins when a transformer settles in an environment conducive to survival. It is during this phase that the juvenile mussel will generate new shell to reach a larger adult size and complete internal development.

Because the Louisiana pearlshell is a long-lived species, the age of individual mussels is difficult to estimate, and growth rates vary among streams. Johnson and Brown (1998, entire) used growth annuli (rings on the shell laid down approximately once a year) and growth rings (layers of shell between individual annuli) to predict growth rate and longevity. An annulus is formed once several growth lines have been laid down; and the fastest growing mussels had fewer growth lines between annuli with an estimated longevity of 45 years (Johnson and Brown 1998, p. 323). The slowest growing mussels had twice as many growth lines between annuli and an estimated longevity of 71 years. Whether there is a correlation between growth rates and reproductive maturity has not been determined. Daniel and Brown (2012, p. 26) used annuli from cross cut and thin sectioned shells to estimate mussel age. The specimens ranged from (estimated) five to 38 years old, and the age at first reproduction was estimated to be five years. Other closely related species are reported to take up to 12 years to reach sexual maturity (McMahon 1991, p. 342, 345).

2.3 Diet

The diet of the Louisiana pearlshell is likely similar to that of other freshwater bivalves, including food items such as detritus (disintegrated organic debris), algae, diatoms, and bacteria (Churchill and Lewis 1924, p. 460-461; Strayer et al. 2004, p. 430-431). Adult freshwater mussels are filter feeders and generally orient themselves on or near the substrate surface to take in food and oxygen from the water column. Juveniles lack developed filter feeding structures and typically feed using their large muscular foot (pedal feeding); they burrow completely beneath the substrate surface, bringing food particles that adhere to the extended foot inside the shell for ingestion (Yeager et al. 1994, p. 219-220; Gatenby et al. 1996, p. 598).

7 2.4 Habitat

Louisiana pearlshell streams are located within upland narrow stream forests of the Lower West Gulf Coastal Plain. The riparian forest adjacent to these streams is comprised of typical upland riparian vegetation, such as southern magnolia (Magnolia grandiflora); American beech (Fagus grandifolia); laurel, water, and cherrybark oaks (Quercus laurifolia, Q. nigra, and Q. pagoda, respectively); sweetgum (Liquidambar styraciflua); bluebeech (Carpinus caroliniana); longleaf and loblolly pine (Pinus palustris and P. taeda, respectively); baldcypress (Taxodium distichum); etc. (Johnson and Brown 2000, p.274; Holcomb et al. 2015, p. 159-164). These riparian forests are generally densely vegetated and have relatively closed canopies. The LDWF’s Louisiana Natural Heritage Program (LNHP; 1998, p. 2) reports a canopy closure of 51 to 75 percent in areas occupied by Louisiana pearlshells.

Louisiana pearlshell streams are spring-fed, relatively narrow (less than 4.9 meters in width, Johnson 1995, p. 10, 19), clear, moderately swift-flowing, headwater streams having stable mineral substrate, such as a sandy bottom with rocky outcroppings, and an approximate riffle-to- pool ratio of 3:1. Within these streams, Louisiana pearlshells usually occur in shallow water (12 to 24 inches deep; Johnson 1995, p. 10, 19) often in headwater riffles where the substrate is dominated by loose, fine or very fine sand with infrequent patches of larger gravel substrate. They are rarely found in deep pools that have slower flowing water and silty bottoms (Johnson and Brown 1998, p. 327; Johnson and Brown 2000, p. 274; Bolden and Brown 2002, p. 94). Authors surmised this is likely due to the species’ intolerance to high silt loads. No substantial variation has been found in temperature, substratum type, or water quality among study streams (Johnson 1995, p. 37; Johnson and Brown 2000, p. 273-274), but variation in mussel size has been observed and may be a function of variation in channel morphometry, current velocity, or habitat stability.

Johnson and Brown (2000, entire) assessed the importance of physiochemical and microhabitat variables based on the apparent similarity of Louisiana pearlshell streams to other streams that lack Louisiana pearlshells within the same watershed. Louisiana pearlshell occurrence and abundance data indicate a preference for slightly acidic, oligotrophic systems with low sediment organics, low suspended particulates, low specific conductivity, and harder water with the species distribution skewed toward areas of the stream having a gravel-cobble substrate (Johnson and Brown 2000, p. 273). It is possible that the positive correlation between Louisiana pearlshell abundance and water hardness occurs because the streams in the geographic area have such soft water that calcium content may be a limiting factor for shell deposition (Johnson and Brown 2000, p. 274). Johnson and Brown (2000, p. 273) determined that the species’ association with the gravel-cobble substrate is unlikely due to chance alone because that type of substrate is rare in occupied streams. The authors concluded that the stability of this substrate type allows better survival of the mussel over time.

8 2.5 Distribution and Abundance

Management watersheds for the Louisiana pearlshell were delineated by aggregating HUC_12 subwatersheds with pearshells in a way that reflects relatively high connectivity and potential for genetic exchange among subwatersheds within a management watershed, and lower connectivity between management watersheds (Quantitative Ecological Services, Inc. (QES) 2014, p. 2-3). Each management watershed is made up of HUC_12 subwatersheds from a different HUC_10 watershed, but do not include all HUC_12 units within the larger HUC_10 watersheds because they do not all contain pearlshells. Later, research into the genetic structure of the species (Garrison 2018, pers. comm.) supports our delineation of these four management watersheds.

In 1988, when this mussel was listed as endangered, it was known only south of the Red River within 11 streams in the Bayou Boeuf and Bayou Rapides management watersheds of Rapides Parish. The species was reclassified to threatened in 1993 after being discovered north of the Red River in Grant Parish. The Louisiana pearlshell is currently distributed across four management watersheds: Bayou Rapides and Bayou Boeuf south of the Red River in Rapides Parish and Black Creek and Bayou Rigolette north of the Red River in Grant Parish (Figure 4). There is one historical record of the Louisiana pearlshell outside of the species’ currently known range in the early 1900’s from Dorcheat Bayou, a waterbody located in Columbia County, Arkansas (Fowler 2015, p. 1014-1015) and is archived in the American Museum of Natural History (Smith 1988, p. 159). Due to the species’ habit of occurring within large aggregations, the discovery of this single mussel shell at a location over 120 linear miles away from any known aggregation does not support extending the species’ historic range northward into Arkansas. The northernmost limits of the species’ historic range, and its current range, is considered herein as the Black Creek management watershed in Grant Parish.

9

Figure 4. Current and historical distribution of the Louisiana pearlshell, colored by management watershed. Map by QES (2014, p. 3).

Johnson (1995, p. 9-11) and Johnson and Brown (2000, p. 272-273) describe the relative connectivity of the drainages within the range of Louisiana pearlshell as follows: Bayou Rapides contains one drainage (i.e., Brown Creek drainage) and Bayou Boeuf contains three drainages (i.e., Valentine Creek, Castor Creek, and Bayou Clear drainages). Within the Bayou Rigolette watershed, there are four drainages (i.e., Black Creek, Gray Creek, James Branch, and Hudson

10 Creek). The Black Creek drainage empties into Iatt Lake and contains six streams (i.e., Black Creek, Beaver Creek, Clear Branch, Cypress Creek, Swafford Creek, and Glady Hollow). The Gray Creek drainage enters Bayou Rigolette and contains four streams (i.e., Gray Creek, Cress Creek, Chandler Creek, and Jordan Creek). The James Branch and Hudson Creek drainages also enter Bayou Rigolette, with the Hudson Creek drainage containing three streams (i.e., Hudson Creek, Coleman Branch, and Moccasin Branch). The Service’s survey (Service 1991) indicates that while the Bayou Boeuf and Red River drainages are normally separate, there is a possible connection between tributaries of Bayou Boeuf and Bayou Rapides during flood flows, which may serve to allow for periodic exchange of genetic material between the areas.

Historically, the species occurs in 11 streams in Rapides Parish. These are Patterson Branch and Brown Creek of the Bayou Rapides management watershed (Appendix A, Figure A1); and Little Loving Creek, Loving Creek, Little Brushy Creek, Long Branch, Castor Creek, Hailey’s Creek, Little Bayou Clear, Bayou Clear, and Valentine Creek in the Bayou Boeuf management watershed in Rapides (Appendix A, Figure A2). Because Valentine Creek is impounded by Lake Kincaid, the mussels in this stream are possibly biologically distinct; but for management and recovery purposes, Valentine Creek is considered to be part of the Bayou Boeuf management watershed. Research to determine the level of genetic structuring of the Louisiana pearlshells in Valentine Creek compared to the mussels found in the remainder of the Bayou Boeuf management watershed would be required to further understand the potential effects of geographic separation on the biological and genetic aspects of these mussels. In Grant Parish, there are 10 historical Louisiana pearlshell streams. These are Cypress Creek, Swafford Creek, Beaver Creek, Glady Hollow, and Black Creek in the Black Creek management watershed (Appendix A, Figure A3); and James Branch, Coleman Branch, Chandler Creek, Jordan Creek, and Gray Creek in the Bayou Rigolette management watershed (Appendix A, Figure A4).

There are multiple formerly occupied streams that no longer support Louisiana pearlshells. In Rapides Parish, Louisiana pearlshells in Burney Branch and Mack Branch have been extirpated. In Grant Parish, Louisiana pearlshells in Moccasin Branch, Cress Creek, Clear Branch, and Hudson Creek have been extirpated. Mack Branch, Clear Branch, and Hudson Creek supported very low numbers of Louisiana pearlshells during 1998-1999 range-wide surveys, but no pearlshells were found during the 2007-2009 survey. Also, data indicate noticeable declines in the number of Louisiana pearlshells in Hailey’s Creek and the KNF portions of Beaver Creek and Chandler Creek. Further, James Branch was close to drying when Moccasin Branch and Cress Creek dried in August of 2011 and exhibited extremely low water levels in the summer of 2012 (Smith 2012, pers. comm.). Fortunately, large amounts of precipitation came in September 2011, in time to allow rewatering of James Branch and prevent stranding of resident Louisiana pearlshells. James Branch exhibited extremely low water levels again in the summer of 2012 but did not dry (Smith 2012, pers. comm.).

11 The Louisiana pearlshell has one of the highest reported aggregation densities in North America among species in the genus Margaritifera (Johnson and Brown 1998, p. 325). Although it is possible to find a single Louisiana pearlshell individual or several scattered individuals, generally the species is found in aggregations of 20 to 40 mussels/m2 (Johnson and Brown 1998, p. 321). The species can be found at densities as high as 300 mussels/m2 with population density varying among streams (Johnson and Brown 1998, p. 321). In Johnson and Brown (1998, p. 321), the aggregation that had the highest density contained over 1,500 individuals. There have been no more published studies, but a U.S. Forest Service (USFS) document reports estimates of aggregations of more than 5,000 individuals within an unreported area (QES 2014, Appendix C). In the context of this report, an aggregations is considered to be 100 individuals or more that are obviously aggregated together. However, a specific density cannot be established at this time because of limitations caused by varied methodologies in previous data collection. A standardized monitoring protocol has been developed (QES 2014, entire), and the definition of aggregation will become more specific as standardized monitoring efforts continue.

Louisiana pearlshell surveys have been ongoing to some extent on the KNF and private land since 1985. In March 2014, QES was contracted by LDWF using Section 6 funds from the Service to analyze these survey data and develop methods for future monitoring of the species. The resulting Louisiana Pearlshell Mussel Trends and Monitoring Report (QES 2014, entire) analyzed survey data collected by USFS, which had monitored most known mussel aggregations in the KNF multiple times from 1985 through 2013, and data collected by the LNHP, which surveyed aggregations on private lands between 2007 and 2009. Range-wide abundance for 2007 (to align with the private land surveys) was estimated to be 74,452 mussels, with nearly three quarters of those (72.6%) occurring on private lands (Table 1).

Table 1. Estimated number of Louisiana pearlshells in 2007 by watershed and land ownership.

Management # Mussels # Mussels # Mussels Parish Watershed Private USFS Total Bayou Boeuf 4,316 15,520 19,836 Rapides Bayou Rapides 320 1,925 2,245 Subtotal 4,636 17,445 22,081 Bayou Rigolette 15,804 2,863 18,667 Grant Black Creek 33,632 72 33,704 Subtotal 49,436 2,935 52,371

Totals 54,072 20,380 74,452

The QES analysis (2014, p. 2) used monitoring data from 290 Louisiana pearlshell aggregations in 27 streams (Table 2). Of these, 105 aggregations had sufficient data (multiple surveys) to assess trends over time. Of these, abundance was stable in 80 aggregations, increasing in 9

12 aggregations, and declining in 16 aggregations (Table 3). Statistical models (generalized linear models with quasi-Poisson errors) were used to examine trends at the watershed scale and at the species scale. For Bayou Boeuf and Bayou Rapides in Rapides Parish, there was no evidence that abundance in the monitored aggregations changed over the period of 1985 through 2013, but significant declines were detected in Black Creek and Bayou Rigolette (QES 2014, p. 10). Considering all management watersheds combined, a significant overall decline for the species was detected (QES 2014, p. 10). Trends estimated were predominantly based on counts of aggregations on USFS land (93 of 105 aggregations analyzed) and are not representative of range-wide trends because only a small fraction of private lands aggregations had sufficient data to analyze trends, while over two thirds of monitored aggregations occurred on private land.

Table 2. Streams and aggregations of the Louisiana pearlshell monitored by watershed and land ownership (QES 2014, p. 2). # # # Management # Streams Aggregations Aggregations Aggregations Parish Watershed Monitored Private USFS Total Bayou Boeuf 10 29 52 81 Rapides Bayou Rapides 3 6 12 18 Subtotal 13 35 64 99 Bayou Rigolette 8 80 25 105 Grant Black Creek 6 81 5 86 Subtotal 14 161 30 191

Totals 27 196 94 290

Table 3. Temporal trends in abundance within Louisiana pearlshell aggregations. Moderate evidence refers to a statistically significant trend where p < 0.05, and weak evidence refers to trends with 0.05 ≤ p < 0.10. Trends were estimated using a generalized linear model with quasi-Poisson errors (QES 2014, p. 7 and 9).

Trend Direction and Strength of Evidence # Aggregations Moderate evidence of increase 6 Weak evidence of increase 3 No evidence of trend 80 Weak evidence of decline 4 Moderate evidence of decline 12

The report identified a lack of consistent survey methods across observers and through time as a major limitation in data analysis. Thus, the Monitoring Plan for the Louisiana Pearlshell Mussel (QES 2014, Appendix G) was developed to facilitate standardized data collection across the

13 range of the species, on both public and private land, and will improve the quality and accuracy of abundance and trend assessments in the future.

2.6 Genetics

One study provides most of what is known about Louisiana pearlshell genetics. Results from this study indicated that sampled Louisiana pearlshell populations are not completely isolated from one another, nor do they represent a single panmictic (fully mixing) population (Roe 2009, p. 10). Among the studied populations, the greatest degree of isolation and the majority of genetic difference was measured between mussels separated by the Red River, indicating that the Red River represents a significant barrier to gene flow. In addition, there are two other manmade impoundments that create significant physical barriers to host fish passage and genetic interchange: Lake Iatt in Grant Parish, constructed in 1957, and Kincaid Reservoir in Rapides Parish, constructed in 1972. There is a weak indication that Louisiana pearlshells found in the Black Creek drainage upstream from Lake Iatt are showing signs of genetic isolation from those found downstream of the impoundment. In contrast, the Louisiana pearlshells found upstream of Kincaid Reservoir in Valentine Creek are showing no evidence of genetic isolation.

Additional analyses by Roe (2009, p. 11) indicated that 3 of the 17 study populations showed genetic evidence of recent bottleneck (Little Bayou Clear, Gray Creek, and Jordan Creek), which is supported by evidence collected during field surveys (USFS 2006, p. 4-6; 2007a, p. 8-10) that showed population declines in these three creeks (Roe 2009, p. 11). However, there could be factors other than genetics contributing to these declines in abundance.

Roe (2009, p. 12-13) suggested the following ideas to guide future studies: (1) the concept that the Louisiana pearlshell may function as a “metapopulation” system, where subpopulations exchange genes through dispersal and where local extinctions of subpopulations are followed by recolonization by other subpopulations; (2) the need for specific genetic recommendations for the species pertaining to the potential for future translocation/augmentation research; and (3) recommendations for additional studies that increase sample size to better estimate the effective population size.

There is currently research in progress at the Service’s Warm Springs Conservation Genetics Lab on samples collected from one stream from each management watershed (Jordan Creek, Black Creek, Loving Creek, and Brown Creek) and a captive population with a Black Creek mother. Results further indicate genetic differentiation between populations north and south of the Red River, as well as differentiation (although to a lesser degree) between sampling locations from different management watersheds on the same side of the river (Garrison 2018, pers. comm.). Because only one creek was sampled from each management watershed, it is unknown whether genetic structuring is present across streams within management watersheds. Individuals from

14 Brown Creek (Bayou Rapides management watershed) had the lowest levels of genetic admixture, indicating that population is more isolated than the others sampled.

Based on the genetic distinctiveness of mussels in each sampled stream, augmenting natural populations using individuals with a different genetic lineage is not advised, as augmentation could result in the genetic profile of the “outside” augmentation population swamping that genetic profile of the population native to that stream (Garrison 2018, pers. comm.). Additionally, it is recommended that any reintroductions of Louisiana pearlshells occur close to the capture location of the gravid females used for propagation.

3 SPECIES NEEDS FOR VIABILITY

3.1 Individual Level

At the individual level, Louisiana pearlshells require suitable conditions to flourish during each life stage and contribute to the next generation. The species requires clear, moderately swift- flowing, perennial streams with cool water, a stable mineral substrate, and food items upon which to filter feed. Like other freshwater mussels, reproduction is dependent upon the presence of a host fish for glochidia to encyst upon and metamorphose into a transformed juvenile. Multi- year captive trials using several different fish species naturally found in Louisiana pearlshell streams (Service 2016b) have resulted in the grass pickerel being the only species known to serve as a host fish for Louisiana pearlshell glochidia; however, this has not been documented in the wild.

3.2 Population Level

For resilient populations to persist, the needs of individuals (suitable habitat structure and water conditions, food, and host fish presence) must be met at a broader scale, both spatially and temporally. Stream reaches with suitable water quality and habitat must be sufficient in size to support an adequate number of potential mates while avoiding inbreeding depression. Because Louisiana pearlshells have limited mobility as adults, they are typically unable to escape unfavorable habitat conditions; thus, populations are vulnerable to long-lasting or repeated disturbances (e.g., drought or beaver activity, further discussion in Chapter 4).

3.3 Species Level

For a species to be viable, there must be adequate redundancy (suitable number, distribution, and connectivity to allow the species to withstand catastrophic events) and representation (genetic and environmental diversity to allow the species to adapt to changing environmental conditions). Redundancy improves with increasing numbers of populations (natural or reintroduced) distributed across the species’ range, and connectivity (either natural or human-facilitated)

15 allows connected populations to “rescue” each other after catastrophes. Representation improves with the persistence of populations spread across the range of genetic and/or ecological diversity within the species. Long-term viability will require resilient populations to persist into the future; for the Louisiana pearlshell, this will mean maintaining quality stream habitat in perpetuity, to support redundant populations across the species’ range.

4 INFLUENCES ON VIABILITY

In this section, we describe the influences on the needs and viability of the Louisiana pearlshell (Figure 5) within the framework of the five factors which can contribute to the listing of a species as threatened or endangered under the Endangered Species Act, and then discuss positive influences on the viability of the species.

Figure 5. Influence diagram illustrating relationships between key habitat and population factors, influences on these factors, and species viability. This diagram does not represent a comprehensive view of all factors and influences on Louisiana pearlshell viability, but highlights key components.

4.1 Factor A: Habitat Destruction and Modification

Influences on the viability of the species that result in the destruction or modification of Louisiana pearlshell habitat include impoundments, beaver activity, water quality degradation,

16 forestry practices, gravel pits, cattle grazing, gravel and mineral mining, and construction activities.

4.1.1 Impoundments

Reservoirs, lakes, and other impoundments continue to fragment the spatial distribution of Louisiana pearlshell habitat on the landscape, as they have done from the time of initial listing. Kincaid Reservoir impounds the uppermost headwaters of Bayou Boeuf. At the time of listing, Mack Branch was the only stream above Kincaid Lake that supported the species. Since then, Louisiana pearlshells in Mack Branch have become extirpated, due to water quality and habitat changes possibly caused by impoundment (Darden 1988, p. 20, 23). The largest Louisiana pearlshell populations within the Bayou Boeuf watershed occur in the unimpounded Loving Creek, Long Branch, and Bayou Clear drainages, tributaries to Bayou Boeuf. Other impoundments of the Bayou Boeuf system that may have affected this species are Indian Creek Reservoir, Oden Lake, and Cotile Lake. Lake Iatt (an approximately 52-acre reservoir) impounds the headwater region of Bayou Rigolette. All of these impoundments pre-date listing of the Louisiana pearlshell. The presence of these permanent impoundments cannot be addressed by recovery actions; however, population level impacts resulting from limitations to host fish movement and genetic interchange could potentially be addressed by recovery actions.

4.1.2 Beaver Activity

Beaver (Castor canadensis) activity has been documented as a source of disruption throughout the species’ range since the beginning of monitoring and survey efforts. Beaver dams create small impoundments within Louisiana pearlshell watersheds, which have the potential to alter hydrology and affect the spatial distribution of the Louisiana pearlshell throughout its range. Although the exact amount of time that Louisiana pearlshells can persist in deep, stagnant water is unknown, inundation for an extended period changes the habitat characteristics that Louisiana pearlshells require to live and thrive (e.g., shallow water becomes deeper and flow becomes slower than the species can tolerate). Stagnant areas of the streams would eventually exhibit atypical low levels of dissolved oxygen, which could lead to suffocation of aquatic organisms found within the hypoxic area (Ice and Sugden 2003, p. 95). In addition, it is possible that beaver dams built directly on top of mussel aggregations can cause direct mortality of individuals. Particularly in years of low annual precipitation, beaver dams can contribute to the downstream drying of streams, causing the stranding of local Louisiana pearlshell aggregations. For example, in 2008, over 140 Louisiana pearlshells were lost in Cress Creek due to combined impacts from a beaver dam during exceedingly low water conditions (USFS 2009a, p.2), and the remaining Louisiana pearlshells in Cress Creek died from stranding after the stream dried in 2011 (USFS 2012, p. 3). Beaver dams are not thought to cause long-term impacts to the host fish because the impacts of beaver dams on the stream hydrology are seasonal and host fish are

17 more mobile than pearlshell mussels. However, Louisiana pearlshells could be impacted if host fish movement is restricted during the pearlshell reproductive period.

In Rapides Parish, Louisiana pearlshell losses and local extirpations associated with beaver activity have been documented since the beginning of the species’ monitoring effort. For instance, the Louisiana Pearlshell Recovery Plan (Service 1990, p. 5) documented approximately 1,000 individuals eliminated as a result of inundation by a beaver pond. Recently, impacts to Louisiana pearlshells or their habitat from beaver dams have been reported in Rapides Parish in Brown Creek, Long Branch, Loving Creek, Bayou Clear, Little Brushy Creek, and Patterson Branch on the KNF (USFS 2004, p. 8-9; 2007a, p. 8-9; 2010, p. 7-8); and in Bayou Clear, Little Bayou Clear, Castor Creek, Valentine Creek, and Long Branch on private land (LNHP 2009). Recent impacts from beaver dams have been reported in Grant Parish on the KNF in Cress Creek, Gray Creek, and Chandler Creek (USFS 2006, p. 4-6; 2009a); and on private land in Beaver Creek, Black Creek, Glady Hollow, Moccasin Creek, and James Branch (LNHP 2009). Overall, recent (as of 2009) impacts from beaver dams have been reported in 77 percent of streams surveyed.

Louisiana pearlshells and beavers are native to this area of Louisiana and coexisted prior to listing. However, the increases in Louisiana pearlshell habitat fragmentation and isolation as a result of human activities have exacerbated threats from beaver activity, which seem to be more extreme in years of low water (as is thought to be the case for the 2011 local extirpation of the Louisiana pearlshell in Cress Creek on the KNF in Grant Parish). Thus, beaver control has been an important conservation tool in areas where beavers pose a local threat to resident Louisiana pearlshells (further discussion in section 4.6).

4.1.3 Water Quality Decline

Multiple land use practices are impacting the Louisiana pearlshell through reductions in water quality. Water quality may be a limiting factor on the local abundance of the Louisiana pearlshell among different streams (Johnson 1995, p. 37) and declines in water quality may be a contributing factor to declines of the species.

Forestry

Forestry practices that involve the harvesting of trees up to the streambank can decrease bank stability, cause direct soil erosion into the stream, and increase runoff with resultant increases in water turbidity and scouring of the streambed, all of which can create unsuitable or unstable habitat for mussels (58 FR 49936). Streams that lose vegetated riparian buffers suffer a loss in the natural ability to filter sediment, debris, and pollutants. When trees are removed from alongside streams, the more open areas are more visible and provide easier access to the channel for humans and animals.

18

Multiple restrictions have been implemented by the USFS via issuance of the Revised Land and Resources Management Plan (RLRMP) in 1999 that protect the Louisiana pearlshell and its habitat on the KNF. For example, the USFS is now minimizing potential impacts to riparian areas through the effective use of streamside management zones, wherein riparian habitat within 100 feet (30.5 meters) along the banks of perennial and intermittent streams is maintained for benefit of water quality and wildlife habitat. Any timber harvest permitted within those zones is restricted to selective cutting of individual trees for the purpose of wildlife habitat improvement. However, streamside management zones do not necessarily extend to private lands. Many industrial timber owners in Louisiana implement streamside management zones to meet Sustainable Forestry Initiative (SFI) requirements. The Louisiana Forestry Association (LFA) published a manual on Forestry Best Management Practices (BMPs) for Louisiana (1997, p. 14- 15), which covers streamside management zones and holds educational landowner workshops; however, not all private landowners follow these guidelines because participation in the SFI and implementation of the BMPs is a voluntary decision made by the land manager. Therefore, threats to the species attributed to detrimental forestry practices remain for many of the populations found on private lands. There is also a potential for downstream impacts to Louisiana pearlshell populations on the KNF from detrimental forestry practices on private lands upstream.

Gravel Pits

At the time this mussel was listed, gravel pits were identified as a threat. There are two known gravel pit operations in the current range of the Louisiana pearlshell: one inactive in Grant Parish on Beaver Creek with seemingly no current impacts to habitat, and a large operation in Rapides Parish on Hospital Bayou, which empties into Bayou Clear (Gregory 2012, pers. comm.). In the area of the gravel mining operation, there are very few Louisiana pearlshells, which may or may not be a result of habitat impacts from the gravel pits. At this time, it is unclear if the active gravel mine on Hospital Bayou is impacting habitat on private land further downstream. If it is affecting downstream property, then gravel mining could remain a local threat to this species in that area. At this time, the construction of new gravel pits is not a threat to the Louisiana pearlshell.

Cattle Grazing

Once considered a possible threat to the Louisiana pearlshell, open range cattle grazing has been discontinued on the KNF. However, the extent to which cattle grazing affects Louisiana pearlshells on private property is uncertain. At least one Louisiana pearlshell stream, Coleman Creek, on private property in Grant Parish has been affected by cattle grazing. The Service’s Partners for Fish and Wildlife (Partners) program worked with a private landowner to provide fence exclusion to protect the stream from cattle. At this time, survey and monitoring of

19 Louisiana pearlshells by the LNHP (2017, p. 4) has not suggested that cattle grazing poses a high threat to the species. In addition to the Service’s Partners program, another avenue the Service has explored for protecting Louisiana pearlshell streams from potential damage caused by cattle grazing is through the Natural Resources Conservation Service (NRCS), which provides financial incentives for exclusion fencing for cattle through conservation programs.

Minerals Mining

The RLRMP (USFS 1999, p. 1-10, 1-11, D-4, D-9) restricts the zones of mineral development within the Louisiana pearlshell range on the KNF to protect the water quality of Louisiana pearlshell streams. There are no known restrictions on private lands; however, such details are addressed under ESA Section 7 consultation if there is a federal nexus for the proposed action when planned within the species’ range.

Construction

Construction and other soil-disturbing activities (e.g., bridge replacement, culvert installation, road maintenance, utility rights-of-way, etc.) with inadequate erosion control measures within Louisiana pearlshell watersheds can cause a direct loss of habitat; reduced capability of host fish passage; a reduction of water quality as a result of increased erosion, run-off, sediment loading and turbidity, decreased flow and dissolved oxygen; and changes in stream geomorphology (e.g., headcutting, bank sloughing, perched water tables, etc.). Potential impacts of insufficient erosion control can result from project-related soil disturbance during excavation, vegetation removal, etc., as well as from erosion occurring after construction is complete through failure to implement and maintain long-term erosion control measures, including but not limited to, restoring herbaceous groundcover on disturbed soil and armoring the stream bank to protect from scouring.

Any project or event causing chronic sedimentation degrades habitat for Louisiana pearlshells over the long-term. As filter feeders, mussels can close their shells for short periods to protect internal tissue when sediment loads in the water temporarily increase (e.g., sedimentation due to a storm event). However, chronic sedimentation, like that which would occur if erosion control measures were not properly implemented and maintained during construction, would adversely affect mussels. Chronic sedimentation, even at a relatively smaller load, can affect mussels because at some point they must open their shell and resume siphoning water across the gills. Excessive siltation degrades water quality and substrate, clogs gills, reduces feeding efficiency and growth, and can eventually smother mussels if sufficient accumulation occurs (Service 2000).

Additionally, improper stream crossing construction, placement, or bank span width can cause fragmentation of habitat by altering upstream and downstream hydrology. The Service is

20 working with landowners and managers to address potential issues with improperly installed stream crossings, generally culverts and tank cars, in Louisiana pearlshell watersheds by targeting these crossings for replacement, preferably with bottomless culverts or bridge spans.

4.2 Factor B: Overutilization

The Louisiana pearlshell is not harvested for consumption. It is not a commercially valuable species, and the small streams it inhabits are not subject to harvesting for commercial mussel species. Illegal collecting for commercial or private use could pose a threat to this species because it is often found in high densities and high numbers within a single aggregation; however, there is no evidence that this is occurring or will occur. Commercial or private harvest for reasons other than research is not a legal action, and neither the Service nor LDWF could legally issue a permit for commercial or private harvest. There is some need for collection of the species for research purposes. Obtaining a federal research permit and a state permit is required, which involves cooperation and consultation with the Service and with LDWF to develop measures to minimize potentially adverse impacts to the population.

4.3 Factor C: Disease or Predation

At this time, there is no evidence of threat from disease.

The shallow stream habitat of this species does make it vulnerable to predation by river otters (Lutra canadensis), raccoons (Procyon lotor), muskrats (Ondatra zibethicus), and possibly feral hogs (Sus scrofa). Evidence of suspected otter predation on Louisiana pearlshells at the individual level has been frequently observed (Gregory 2010, pers. comm; Shively 2010, pers. comm.; Smith 2010, pers. comm.; Kaller 2018, pers. comm.). The USFS (2009a, p. 5) reports suspected otter depredation of Louisiana pearlshells in Gray Creek, Grant Parish, to be a significant contributing factor to the decline of that local population. The suspected predation could also be from raccoons, or both raccoons and otters. It is possible that in times of low water, there is increased incidence of predation, especially by raccoons, due to easier access to the mussels.

The USFS (2012, p. 3, 8) again reported suspected predation on Louisiana pearlshells as the main factor for decline in a Louisiana pearlshell aggregation located on the KNF in Gray Creek. In 2012, biologists from the Service, the USFS, and the LNHP visited the site to collect the shell fragments and estimate the number of Louisiana pearlshells predated, source of predation, and document remaining living Louisiana pearlshells. It was estimated that 116 Louisiana pearlshells had been broken into many small pieces at this location (Figure 6), although it is unknown if the mussels were dead or alive at the time the shells were destroyed and it is

21 unknown what destroyed the shells. The evidence, as described below, indicates it was likely the large resident population of raccoons.

On October 4 and October 24, 2012, the USFS installed two wildlife cameras near a wildlife trail adjacent to the decimated aggregation and obtained pictures until November 28, 2012, after which time, one camera was broken and the other missing. On July 1, 2013, the USFS installed another camera over the location. At this point, the water level was low, and there were additional scattered mussel fragments, with only a few living Louisiana pearlshells remaining (Smith 2018, pers. comm.). The third camera remained there for 87 days, until December 16, 2013. Raccoons were consistently the most frequent users of the trail, and were pictured feeding inside the streambed where mussels were located for 90 minutes on November 14, 2013 (Smith 2018, pers. comm.). Other wildlife, mostly deer (Odocoileus virginianus) and wood duck (Aix sponsa), were also captured by the cameras using the trail. Less frequently, but at least once, coyotes (Canis latrans), fox (Vulpes vulpes), beaver, armadillos (Dasypus novemcinctus), feral hogs, herons and egrets (multiple species and genera in the family Ardeidae) were captured on film; however, none of those were pictured feeding within the stream bed. Although suspected as predators of Louisiana pearlshells in other areas of Gray Creek (USFS 2009a, p.5), no otters were captured in any of the pictures from the three cameras installed at this location on Gray Creek (Smith 2018, pers. comm.).

Other studies have shown that raccoons are more likely to consume mussels when the water is low because visibility and access is increased (Johnson et al. 2001, p. 8). Considering this research, the high numbers of resident raccoons living adjacent to the aggregation, the proximity of the wildlife crossing, and the fact that on-site wildlife cameras showed raccoons repeatedly crossing the stream and eating from the streambed at the aggregation location; it is possible that the crushed relict shells were from raccoon depredation either on living Louisiana pearlshells or on individuals that had recently died (possibly due to low water and stranding). Some evidence indicates that Louisiana pearlshells may have been dead or dying before they were consumed. In January 2013, 15 living but stressed Louisiana pearlshells were found in shallow water or on top of sand bars lying abnormally in a horizontal position rather than being positioned vertically within the substrate like typical, healthy Louisiana pearlshells (Smith 2018, pers. comm.). These individuals were properly oriented and manually situated vertically within the substrate in areas of deeper water (Smith 2018 pers. comm.). A lot of new shell fragments and about five living mussels were later found during follow-up site visits in July and August 2013, and two additional living but stressed individuals were located lying horizontally on sand bars, which were manually re-positioned within the substrate in deeper water (Smith 2018, pers. comm.). In addition, it was noted over multiple site visits that almost all the Corbicula in this particular stretch of the stream were dead, but with the valves still intact; and a few intact bodies of dead frogs and crayfish were found floating in the water on occasion, suggesting the clams, frogs, and crayfish died from some event other than predation and were not yet scavenged at the time they

22 were observed (Smith 2018, pers. comm.). To date, this is the only documented instance of depredation on an aggregation level (on recently dead or living Louisiana pearlshells).

Figure 6. Louisiana pearlshell fragments collected from Gray Creek. Photo by Emlyn Smith, USFS, 2012.

The threat to populations from the predation of one or two individuals is not likely to be a threat to the species. However, if predation events to an aggregation like the one described above were to become more common, then predation could become a serious threat.

4.4 Factor D: Inadequacy of Existing Regulation

The inadequacy of existing regulatory mechanisms was not identified as a threat to the Louisiana pearlshell in the reclassification final rule. The Louisiana pearlshell is currently protected under sections 7 and 9 of the Endangered Species Act, and it is protected at the state level by the LDWF as an endangered species (Louisiana Revised Statutes 56:1901).

Since downlisting, the USFS has implemented forest-wide restrictions on certain land use practices and modes of recreation to curtail disturbance to Louisiana pearlshells and their associated habitat. Through implementation of the USFS’s RLRMP (1999, p. 1-12, 2-13, 2-33, 2-74, D-4, D-9, F-2), restrictions have been placed on forest management activities within Louisiana pearlshell watersheds to maintain stream water quality and protect mussels. The RLRMP provides for the designation of streamside management zones that provide for the management of riparian habitat 100 feet (30.5 meters) along the banks of perennial and

23 intermittent streams to maintain water quality and wildlife habitat. Timber harvest within those zones is restricted to the selective cutting of individual trees for the purpose of wildlife habitat improvement. Although not technically a regulation, implementation of LFA’s Best Management Practices (BMPs) to meet requirements of the SFI help to maintain water quality and minimize environmental impacts associated with commercial forestry operations in Louisiana. Employing silvicultural BMPs across the species’ range reduces threats to the species associated with detrimental forestry practices on public and private lands.

Additionally, the USFS placed restrictions on the use of motorized vehicles within Louisiana pearlshell watersheds on the KNF. In the past, the KNF was open to motorized vehicle use, following the policy of “open unless posted closed.” New motorized recreation trails have been designated for trail riding, but prior to August 2008, there were no restrictions on cross-country travel except in developed recreation areas, military use areas, wilderness areas, special interest areas, and other areas posted “closed.” This decision followed development of the Kisatchie National Forest Travel Management Environmental Assessment (USFS 2007b) and amendment of USFS internal directives (USFS 2009b) regarding travel management (73 FR 74689) to make them consistent with the National Travel Management Rule (70 FR 68264) and New Motor Vehicle-Use Maps (MVUM) showing all designated routes that were developed. Operators of motor vehicles that leave the designated route will be in violation and subject to penalty.

Landowner education programs such as the LNHP’s Natural Areas Registry (Registry) and conservation areas such as the NRCS’s Wetland Reserve Program (WRP), mitigation banks, state Wildlife Management Areas (WMA) and other conservation areas could play an important role in helping curtail negative impacts to the species from activities on private lands. The LNHP’s Registry allows the state to honor and recognize owners of outstanding natural areas for their commitment to conservation. The program relies on citizen-based conservation and the willingness of landowners to safeguard natural resources on their property. Landowners with Louisiana pearlshell streams on their property would qualify for the Registry. By joining the Registry, the landowner would agree to protect the areas from damage to the best of their ability and to notify the LDWF of any threats to the area. Each year, the LDWF contacts the owner to determine whether conditions have changed or new threats have developed. Currently, over 75 acres of Louisiana pearlshell habitat on five separate properties have been enrolled in the Registry, one of which is in Rapides Parish along Bayou Clear, and four located along Jordan Creek, Black Creek, and Coleman Branch in Grant Parish (Lejeune 2018, pers. comm.).

24 4.5 Factor E: Other Natural or Man-made Factors

All-Terrain Vehicles

Recreational use of all-terrain vehicles (ATVs) in Louisiana pearlshell watersheds can decrease bank stability and lead to gully formation and heavy silt loading into streams, reducing instream water quality (LNHP 2009, Figure 7). An additional threat exists from direct mortality by crushing if vehicles cross streams where Louisiana pearlshell aggregations occur. In response to the impacts caused by the use of ATVs in Louisiana pearlshell habitat on the KNF, the USFS has enacted regulations that limit the use of ATVs to established trail systems (USFS 2007b). However, according to recommendations given by the USFS in the 2009 Louisiana Pearlshell Mussel Survey for Grant Parish, there remains a need to establish effective enforcement of the ATV regulations. This indicates that there is still some level of associated threat, as evidenced by reported impacts from the use of ATVs on several Louisiana pearlshell streams on the KNF (USFS 2007a, p. 8; 2009a; 2010, p. 8). Even so, the establishment of the ATV regulation provides substantial protection of Louisiana pearlshell habitat from recreational activity on the KNF. There are no such regulations for the use of ATVs in Louisiana pearlshell habitat on private lands, which supports the vast majority of known Louisiana pearlshells. Landowner education through written public documents and through programs, like the LNHP’s Registry and the Service’s Partners program, is possibly the best current tool for protecting Louisiana pearlshells from recreational ATV use and other threats on private lands. The LNHP and the Service are working together to find other ways to encourage the judicious use of ATVs on private lands with streams harboring Louisiana pearlshells.

Figure 7. (Left) ATV trail causing bank erosion across a Louisiana pearlshell stream on the Kisatchie National Forest. (Right) ATV tracks in the dry streambed in a Louisiana pearlshell stream on the Kisatchie National Forest. Photos by Monica Sikes, Service, August 2011.

25 Nuisance and Invasive Species

The Asian clam (Corbicula fluminea) is a freshwater bivalve that has been introduced into North America. Its prolific reproductive capability has allowed it to quickly spread its range across the continent, and the species is now almost ubiquitous throughout the range of the Louisiana pearlshell. The species is believed to compete with native mussels for resources such as food, nutrients, and space (Kraemer 1979, p. 1092, 1094). High densities of Asian clams have been found to negatively affect the survival and growth of juvenile native mussels by disturbance and displacement of young juveniles and possibly through incidental ingestion of glochidia and newly metamorphosed individuals (Strayer 1999, p. 82; Yeager et al. 2000, p. 255). Dense Asian clam populations may deplete the edible suspended particles as well as deplete the benthic food particles ingested by native subadult mussels and starve the native bivalves (Strayer 1999, p. 79, 83). Further, Asian clam populations can grow rapidly and are prone to rapid die-offs (Sousa et al. 2008, p. 90), which may affect native mussels when decomposition depletes the oxygen supply and produces high levels of ammonia (Strayer 1999, p. 82); however, typical Louisiana pearlshell streams are flowing and spring-fed in nature, which would likely lead to dispersal of the ammonia with fresh water and flushing downstream before it could concentrate to dangerous levels (Gregory 2019, pers. comm.).

The LNHP 2009 survey documented the presence of Asian clams in every Louisiana pearlshell stream surveyed on private property. The possibility of Asian clams out-competing the Louisiana pearlshell may be a concern in the future, but cannot be accurately assessed at this time due to a deficiency of available data. Streams with Asian clams should be monitored for the abundance of the invasive species and precautions should be taken to prevent the unintentional spread of the species as a result of human activity. However, this invasive species has been present in Louisiana pearlshell streams since the time of monitoring and does not seem to pose a serious threat to the Louisiana pearlshell at this time.

Another threat identified by both LNHP and USFS is the potential for feral hog rutting to cause bank instability and accelerated bank erosion and silt loading. Feral hogs have also been implicated in declines of Unionid freshwater mussels, resulting from water quality degredation from hog fecal coliforms (Kaller et al. 2007, p. 174). At the current time, there are no published estimates of the level of potential impact of feral hog activity on Louisiana pearlshell streams specifically, although feral hogs have been captured on camera using a wildlife trail adjacent to a Louisiana pearlshell aggregation in Gray Creek (Smith 2018, pers. comm.).

Drought

Extreme drought or drought-like conditions can cause the drying of Louisiana pearlshell streams. In August 2011, Moccasin Branch dried and all mussel aggregations in that stream on public and

26 private land were extirpated (over 800 mussels, Figure 8). On August 25, 2011, a search of the entire stream was conducted to assess the situation and search for any surviving mussels. Many of the Louisiana pearlshells were found buried deep in the sand, presumably using vertical movement to attempt to find moisture in the interstitial spaces of the substrate. All buried individuals were dead from desiccation. Seven Louisiana pearlshells were located still alive in stagnant, isolated pools with very little water. For temporary refugia, these mussels were moved to an area of apparently suitable habitat, but with no local population of Louisiana pearlshells. Once Moccasin Branch became re-watered, between the months of July 2011 and February 2012, six of the seven were still alive and were moved back to Moccasin Branch. Also in 2011, the Cress Creek population of approximately 53 mussels was extirpated due to stream drying. As mentioned above, it is also possible that times of low water exacerbate the risk of predation, especially by land mammals like raccoons, due to easier access to the mussels.

Figure 8. (Left) Desiccated Louisiana pearlshell aggregation in Moccasin Branch on private land. (Upper right) Desiccated Louisiana pearlshell aggregation in Moccasin Branch on the Kisatchie National Forest, dead mussels found buried inches under the streambed. (Lower right) Rescued and tagged mussels in temporary refugia in Gray Creek on the Kisatchie National Forest. Photos by Monica Sikes, Service, August 2011.

Climate Change

Climate change has the potential to increase vulnerability of the Louisiana pearlshell to random catastrophic events or alter habitat suitability within the species’ range. The climate in the southeastern United States has warmed about 1°C (about 2 °F) from a cool period in the 1960s and 1970s, and is expected to continue to rise (Carter et al. 2014, p. 398-399). Inter-annual

27 variability in precipitation has been increasing over the last several decades, with this region exhibiting either exceptionally wet or exceptionally dry summers (Kunkel et al. 2013, p. 28). Various emissions scenarios suggest that, by the end of the 21st century, average global temperatures are expected to increase 0.3 °C to 4.8 °C (0.5 °F to 8.6 °F), relative to the period 1986–2005 (Intergovernmental Panel on Climate Change (IPCC) 2014, p. 10). By the end of 2100, it is virtually certain that there will be more frequentjo hot and fewer cold temperature extremes over most land areas on daily and seasonal timescales, and it is very likely that heat waves and extreme precipitation events will occur with a higher frequency and intensity (IPCC 2014, p. 15-16). Projections for future precipitation trends in the Southeast are less certain than those for temperature, but suggest that overall annual precipitation will decrease, and that tropical storms will occur less frequently, but with more force (more category 4 and 5 hurricanes) than historical averages (Carter et al. 2014, p. 399). Warmer temperatures and decreased precipitation will increase water temperatures, change runoff regimes, and increase the frequency, duration, and intensity of droughts in the southeastern United States (Poff et al. 2002, p. ii, 7, 10,). Droughts cause decreases in water flow and dissolved oxygen levels and increases in temperature in stream systems. Although the impacts of climate change on the Louisiana pearlshell and its habitat are not certain, exceptionally hot and dry summers could lead to drying of small streams, similar to that observed in Moccasin Branch and Cress Creek in 2011.

Genetics

Genetic research indicates that some Louisiana pearlshell streams are isolated from each other (i.e., on each side of the Red River and upstream of Lake Iatt) (Roe 2009, p. 11). Evidence of genetic structuring and of recent bottlenecks was indicated for some Louisiana pearlshell stream populations (Roe 2009, p. 11). Isolation of Louisiana pearlshell streams through barriers to fish host movement results in limited or no occurrence of genetic interchange with other populations. This could result in increased risks of genetic bottlenecks and inbreeding depression, potentially resulting in reduced reproductive output, survivorship, and potential to adapt to future environmental changes. In order to retain genetic viability, movement between populations must occur, either naturally or with assistance from humans where populations have been isolated due to anthropogenic influence.

4.6 Conservation Efforts

Here, we summarize conservation efforts that have had positive influences on the viability of the Louisiana pearlshell.

28 4.6.1 Habitat Protection and Management

Of the 178,304 acres that fall within the boundaries of the four Louisiana pearlshell management watersheds, 87,846 acres have some level of federal or state protection or management (Tables 4 and 5). Across all four management watersheds, 81,284 acres fall within the KNF, owned and managed by the USFS. The remaining 6,411 acres are either an NRCS WRP easement, a state WMA, a mitigation bank, or a Farmer’s Housing Authority conservation area, but no Louisiana pearlshell stream occurs on or adjacent to any of these acres.

Table 4. Acres in Louisiana pearlshell management watershed under federal or state ownership or management.

Bayou Black Bayou Bayou Rapides Boeuf Creek Rigolette TOTAL (acres) (acres) (acres) (acres) USFS 54,842.8 3,864.6 7,830.2 14,756.2 81,293.8 WRP 277.0 0.0 0.0 3,179.1 3,456.1 Mitigation 0.0 0.0 0.0 1,550.2 1550.2 Bank WMA 1,395.3 0.0 0.0 0.0 1,395.3 Other 0.0 0.0 0.0 150.29 150.29 Conservation Area TOTAL 56,515.1 3,864.6 7,830.2 19,635.8 87,845.7

Table 5. Acres within management watersheds covered under federal or state management agreements compared to those acres without management agreements.

Bayou Black Bayou Bayou Rapides Boeuf Creek Rigolette TOTAL (acres) (acres) (acres) (acres) With 56,515.1 3,864.6 7,830.2 19,635.8 87,845.7 agreements Without 31,402.5 12,701.4 8,508.6 37,845.5 90, 458 agreements TOTAL 87,917.6 16,566.0 16,338.8 57,481.3 178,303.7

Since downlisting, the USFS has implemented forest-wide restrictions on certain land use practices and modes of recreation to curtail disturbance to Louisiana pearlshells and their associated habitat on the KNF. Through implementation of the RLRMP (USFS 1999, p. 1-12, 2-

29 13, 2-33, 2-74, D-4, D-9, F-2), restrictions have been placed on forest management activities within Louisiana pearlshell watersheds to maintain stream water quality and protect mussel aggregations. The RLRMP provides for the designation of streamside management zones for the protection of riparian habitat along the banks of perennial and intermittent streams to maintain water quality and wildlife habitat. Timber harvest within those zones is restricted to the selective cutting of individual trees for the purpose of wildlife habitat improvement. The RLRMP restricts cattle grazing within the Louisiana pearlshell watersheds and establishes protective zones that exclude mineral development. Implementation of those management guidelines has reduced threats to the species associated with detrimental forestry practices on the KNF. Additionally, the USFS placed restrictions on the use of motorized vehicles within Louisiana pearlshell habitat on the KNF. Since August 1, 2008, threats from ATV use on the KNF have diminished because of the forest-wide implementation of new travel management rules that regulated cross-country motorized travel.

The USFS has a program to control beavers on their lands within the range of the Louisiana pearlshell on the KNF. Beginning in 2000, the Lafayette Ecological Services Office (LESO) contracted with the U.S. Department of Agriculture, Wildlife Services (USDA WS) to conduct beaver damage control on impacted streams on private land in Grant and Rapides Parishes. From 2000-2010, USDA WS removed at least 140 beavers and 127 dams from streams on private lands in the Louisiana pearlshell management watersheds. Because beaver control activities/efforts have increased (i.e., extended to include private lands) since the time of reclassification, the threat to the species from beaver dams was decreased during these years. Current funding for this program is limited on private lands, and there is no assurance that future funding will be available, which puts a large portion of Louisiana pearlshell aggregations at risk to affects from beaver activity. This threat is likely to rise to higher significance especially in years with reduced precipitation because beaver dams can stop flow in streams that have reduced flow due to inadequate watering.

The RLRMP calls for annual monitoring of water quality in Louisiana pearlshell streams and surveys of mussel aggregations. The mussel aggregations occurring on the KNF are more frequently monitored and are better protected than mussel aggregations elsewhere. Thus, Louisiana pearlshells are more secure overall in the Bayou Boeuf and Bayou Rapides management watersheds because most of the aggregations occur on the KNF, whereas only a small portion of the aggregations in the Black Creek and Bayou Rigolette management watersheds occurs on the KNF.

Incentive programs are available to landowners interested in protecting water quality and conserving wetland habitat. Through the Partners for Fish and Wildlife program, the Service provides technical and up to 100 percent financial assistance for habitat protection, restoration, and enhancement on private and parish lands. To date, two Partners projects have provided on-

30 the-ground benefits to Louisiana pearlshells. One project improved water quality in Coleman Creek by funding the construction of a fence to restrict cattle access to reduce instream sedimentation and defecation. The other project funded rip-rap and vegetative restoration to increase bank stability in areas that were experiencing excessive erosion along Jordan Creek. Additionally, at least two poor culvert crossings located in Grant Parish have received technical and financial assistance for replacement through the Partners program. The construction for these two replacements has not been initiated yet. The LNHP’s Natural Areas Registry (Registry, discussed above in Section 4.4) also encourages landowners to protect habitat and their property and monitor for threats. Currently, over 75 acres of Louisiana pearlshell habitat on five separate properties have been enrolled in the Registry, one of which is in Rapides Parish along Bayou Clear, and four located along Jordan Creek, Black Creek, and Coleman Branch in Grant Parish (Lejeune 2018, pers. comm.).

The NRCS similarly offers the voluntary WRP, which provides landowner incentives to help restore and protect natural resources on private lands. To date, 3,456 acres of WRP easements have been established in Louisiana pearlshell management watersheds, 277 acres in Bayou Boeuf and 3,179 acres in Bayou Rigolette. There is also a LDWF WMA that provides for management of 1,395 acres in Bayou Boeuf management watershed and mitigation banks in Bayou Rigolette management watershed totaling 1,550 acres. There are no Louisiana pearlshell streams on or adjacent to any WRP easements, WMAs, or mitigation banks, and we are not currently able to measure directly the potential beneficial impacts to Louisiana pearlshell streams; however, these properties are managed to have beneficial impacts to water quality by reducing soil erosion through vegetative management and thereby reducing run-off into streams, which likely benefits pearlshell mussels.

4.6.2 Propagation and Reintroduction

Translocation of Louisiana pearlshells is a viable option to aid recovery, as evidenced by the successful translocation of mussels after drought impacts in 2011 (Bolden 2000, p. vii, 39; Bolden and Brown 2002, p. 89, 93). Methods for controlled propagation of the Louisiana pearlshell have been developed (Service 2016b, entire; 2018, entire). Propagation and headstarting (raising in captivity for a period of time) of Louisiana pearlshells and introduction into suitable habitat at two to three years of age will greatly reduce the mortality rates associated with the period between glochidial release and implantation into the substrate. The Louisiana pearlshell propagation, headstarting, and reintroduction program is still under development, and no mussels have yet been released into the wild. More details about potential plans to use this tool in the recovery of the Louisiana pearlshell can be found in the Louisiana Pearlshell Propagation and Reintroduction Plan, which is currently in draft.

31 The Service, the Gulf Coastal Plains and Ozarks Landscape Conservation Cooperative, the USFS, and the Nature Conservancy developed a habitat model to serve as a decision support tool to identify and prioritize areas that are currently unoccupied, but could serve as suitable areas for future introduction or reintroduction.

5 CURRENT CONDITION

As the population is the basic unit of resilience, which is then scaled up to redundancy and representation at the species level, appropriately defining and delineating populations is a crucial step to assess species viability. After delineating populations and units of representation, we then assessed the resilience of each population by synthesizing the best available information about population and habitat conditions. Population resilience was then scaled up to describe current redundancy and representation for the Louisiana pearlshell range-wide.

5.1 Delineating Populations

To delineate Louisiana pearlshell populations, we adopted a rule where multiple streams occupied by pearlshell aggregations (containing at least 100 individual mussels; additional discussion of the definition of an “aggregation” in section 5.3.1.1) were considered the same population only if the stream resulting from their confluence was also occupied by at least one pearlshell aggregation. Smaller groups of pearlshell mussels downstream of the confluence did not lead to a determination that the parent streams were the same population, as those smaller groups may have resulted from mussels that washed downstream and may not be a self- sustaining and reproducing group.

Using this rule, there are currently nine extant populations of Louisiana pearlshell: Bayou Clear, Black Creek, Brown Creek, Castor Creek, Coleman Branch, Gray Creek, Long Branch, Loving Creek, and Valentine Creek. Additionally, there are six locations where pearlshells are or were historically present, but do not presently support any aggregations of 100 or more pearlshell mussels, although some do presently support small numbers of scattered mussels. These locations were considered functionally extirpated if historical records showed they formerly contained Louisiana pearlshell aggregations (i.e., James Branch, Little Bayou Clear, Mack Branch, and Moccasin Branch). Louisiana pearlshells in Moccasin Branch were extirpated following a drought in 2011. In Mack Branch, extirpation was likely a result of beaver activity (Shively 2018, pers. comm.) or may have been a result of water and habitat quality changes caused by the impoundment of Kincaid Reservoir (which was in place prior to species listing). If there were no historical records of groups of 100 or more individuals occurring in the location, they were not considered a population (i.e., Cress Creek and Hailey’s Creek), although it is possible that aggregations could have occurred in these streams before regular monitoring began.

32 5.2 Delineating Representative Units

Representation refers to the breadth of genetic and environmental diversity within and among populations that contribute to the ability of the species to respond and adapt to changing environmental conditions over time. We used the four management watersheds within the Louisiana pearlshell range (Black Creek, Bayou Rigolette, Bayou Rapides and Bayou Boeuf) as representative units for the species (Figure 9). There is not a high degree of difference in habitat within the species’ range, but there are genetic differences among populations. Roe (2009, p. 11) identified a high degree of isolation and differentiation between pearlshell populations north and south of the Red River, which provides support for considering those two groupings different representative units. We further split the northern and southern groupings into their two constituent management watersheds based on genetic analyses performed at the Service’s Warm Springs Conservation Genetics Lab. One population was sampled from each management watershed, and all were found to be genetically distinct from each other, even those on the same side of the Red River (Garrison 2018, pers. comm.). Because only one population from each management watershed was sampled, we cannot make inferences about the degree of genetic differentiation among populations within the same management watershed, but we assumed that hydrological connectivity serves as a proxy for genetic connectivity. Each management watershed corresponds to a single HUC_10 watershed, indicating a higher degree of hydrological connectivity within a management watershed than across boundaries into adjacent HUC_10 watersheds.

33 Figure 9. Populations and representative units delineated for the Louisiana pearlshell. Thicker lines depict current populations. Thinner lines represent populations that either were extirpated, or never contained high numbers of pearlshell mussels since monitoring began.

5.3 Current Resilience Approach

Resilience of Louisiana pearlshell populations was assessed by combining the condition of two population factors (aggregation number/size and evidence of reproduction) and three habitat factors (canopy cover, substrate, and stream crossings). The conditions for all of these factors were then combined to describe the resilience of each population.

34 5.3.1 Population Factors

5.3.1.1 Aggregation Number and Size

The first population factor contributing to resilience was a combination of the number of aggregations in a population, and the number of individuals in those aggregations. Aggregations were defined as groupings of Louisiana pearlshells with 100 or more individuals. Over 90 percent of Louisiana pearlshells occur in aggregations of 100 or more individuals, and a monitoring protocol for these aggregations has been developed (QES 2014, Appendix G). Scattered individuals (those not found in groupings of 100 or more individuals) are likely individuals that have been washed downstream from a larger aggregation; they are not believed to contribute to population resilience and are not required to be monitored in the future under the QES monitoring protocol. Aggregation size (number of individuals) in addition to the number of aggregations contributed to this factor because given that a grouping of mussels contains 100 or more individuals (i.e., is defined as an aggregation), larger groups will be more resilient to stochastic stressors than smaller groups.

To assess the “current” condition of aggregations, we used survey data from 2007-2018, which encompassed the most recent range-wide surveys on both public and private lands, and included 101 aggregations across the species’ range. Data were provided by USFS and LDWF. Currently, 56 percent of current aggregations and 69 percent of mussels within aggregations occur on private lands (Table 6). Known aggregations that were not surveyed between 2007 and 2018 were not included in this assessment. The entire monitoring history of Louisiana pearlshell aggregations and smaller groups can be found in Appendix B. Most abundances from surveys were generated from complete mussel counts in aggregations, but abundance within larger aggregations was often visually estimated. Because survey methods have not been consistent in the past, a new monitoring protocol (QES 2014, Appendix G), defined methods for future surveys to count abundances in smaller aggregations, and estimate abundances in larger aggregations in a more statistically rigorous manner.

Table 6. Current (2007 – 2018) aggregations and number of mussels within aggregations on private and public lands.

Mussels in Aggregations Aggregations Private land 57 39,675 Public land 40 17,777 Total 101 57,578

The current (2007-2018) number of aggregations in each population and aggregation size were combined as follows to generate one composite aggregation score: Aggregations with 100 – 499

35 individuals received a score of 1, aggregations with 500 – 999 individuals received a score of 2, and aggregations with over 1,000 individuals received a score of 3, representing increasing contributions to resilience as aggregation sizes increased. These aggregation scores were then totaled for each population, and classified as follows:

Poor Condition: 1 – 5 total aggregation score Moderate Condition: 6 – 10 total aggregation score Good Condition: > 10 total aggregation score

Because this resilience factor incorporated two components (number of aggregations and number of aggregation size), and because of the importance of those components to resilience (a population cannot be resilient with no aggregations, regardless of how high the habitat quality is), this factor was weighted the highest of all factors for assessing overall population resilience (weighting described in more detail in section 5.3.3).

Of the nine extant populations, five were in good condition currently, one was in moderate condition, and three were in poor condition (Table 7). Population scores ranged from 1 in Castor Creek where there is one small aggregation, to 57 in Black Creek, which supports 38 aggregations, including seven aggregations with ≥ 1,000 individuals.

In order to place the current condition in historical context, we also calculated aggregation scores for the same populations in 2007. In the QES report (2014, p. 60 – 67), statistical models (generalized linear models with quasi-Poisson errors) were used to estimate aggregation abundances for aggregations that were not sampled in 2007. Based on 2007 monitoring data and the statistical estimates for 2007 for those aggregations not visited in 2007, there were six populations in good condition, one in moderate condition, and four in poor condition, for a total of 11 populations. James Branch and Moccasin Branch were both in poor condition in 2007 and have since been extirpated. Aggregation scores declined since 2007 for all but two populations; the score remained the same for Long Branch, and improved for Valentine Creek, which increased from poor condition in 2007 to moderate condition now. Four populations have experienced dramatic declines, losing at least one third of their number of pearlshells in aggregations, the number of aggregations, and/or the aggregation score, since 2007. These four populations are Brown Creek, Castor Creek, Coleman Branch, and Gray Creek, spread across three of the four management watersheds. Range-wide, the number of mussels in aggregations has declined 18.7 percent, the number of aggregations has declined 24.2 percent, and the sum of all aggregation scores has declined 24.7 percent between 2007 and the current condition.

36 Table 7. Number of Louisiana pearlshells in aggregations (groups with ≥ 100 individuals), number of aggregations, and aggregation score in 2007 and the current condition (most recent surveys of aggregations, spanning 2007 – 2018), and the percent change represented by the difference between 2007 and current conditions. Increases are highlighted in green and decreases are highlighted in red.

2007 “Current” % Change Population # Mussels # Agg # Mussels # Agg # Mussels Condition Condition # Aggs Agg Score in Aggs Aggs Score in Aggs Aggs Score in Aggs Bayou Clear 7,282 13 21 Good 6,899 14 18 Good -5.3% + 7.7% - 14.3% Black Creek 32,913 41 64 Good 29,456 38 57 Good - 10.5% - 7.3% - 10.9% Brown Creek 1,926 7 8 Moderate 1,023 4 4 Poor - 46.9% - 42.9% - 50.0% Castor Creek 777 3 3 Poor 222 1 1 Poor - 71.4% - 66.7% - 66.7% Coleman Branch 4,711 11 15 Good 670 3 3 Poor - 85.8% - 72.7% - 80.0% Gray Creek 11,052 23 34 Good 7,284 13 21 Good - 34.1% - 43.5% - 38.2% Long Branch 5,059 12 15 Good 6,272 11 15 Good + 24.0% - 8.3% 0% Loving Creek 4,499 13 15 Good 3,957 10 12 Good - 12.0% - 23.1% - 20.0% Valentine Creek 1,401 2 4 Poor 1,671 3 6 Moderate + 19.3% + 50.0% + 50.0% James Branch 709 2 2 Poor 0 0 0 ------Little Bayou Clear 0 0 0 -- 0 0 0 ------Moccasin Branch 346 1 1 Poor 0 0 0 ------Mack Branch 0 0 0 -- 0 0 0 ------Cress Creek 0 0 0 -- 0 0 0 ------Hailey’s Creek 0 0 0 -- 0 0 0 ------Range-wide 70,675 128 182 57,454 97 137 - 18.7% - 24.2% -24.7%

37 5.3.1.2 Evidence of Reproduction

The other population factor contributing to population resilience was evidence of reproduction and recruitment; a population consisting of only large old mussels with no successful reproduction and recruitment cannot persist. Because glochidia and juvenile mussels cannot easily be detected in streams, and young pearlshells (e.g., 2-3 years old) cannot be detected without damaging the substrate and aggregation, evidence of reproduction and recruitment was considered to be the presence of small individuals or aggregations that were becoming larger over survey periods. Each population was classified as either having evidence of reproduction or not having evidence of reproduction. For the current condition, we used any evidence of reproduction observed since 2007. The condition of this factor for each population was classified as follows:

Poor Condition: No evidence of reproduction Good Condition: Evidence of reproduction

It should be noted that throughout past surveys, evidence of reproduction has not been systematically recorded, so a lack of evidence of reproduction in past records does not necessarily mean that no reproduction or recruitment have occurred, only that it was not noted by surveyors. Because of this, evidence of reproduction was weighted lower than other factors for assessing overall population resilience (weighting described in more detail in section 5.3.3).

All extant populations had evidence of reproduction recorded since 2007 with the exception of Coleman Branch, where no such evidence had been recorded.

5.3.2 Habitat Factors

5.3.2.1 Canopy Cover

Canopy cover within 100 feet (30.5 meters) of Louisiana pearlshell streams was used as a measure of natural riparian and forest conditions. Forested riparian areas reduce erosion, buffer streams from pollutants, and shade surface water. Canopy cover ≥ 50 percent was considered suitable based on expert input and monitoring protocols used by the LDWF.

We calculated suitable canopy cover within 100 feet of streams for each population using the 2011 National Land Cover Database Tree Canopy dataset (NLCD; Homer et al. 2015, entire). Because the most recent NLCD was from 2011 and there have been forestry activities (e.g., clear cuts) since then, we acquired 2017 National Agriculture Imagery Program (NAIP) imagery available from the U. S. Geological Survey to compare with the 2011 canopy cover data. Where more recent forest clearing was evident from the NAIP imagery, we visually estimated the

38 canopy cover. We calculated the percent of the 100-foot buffer with suitable canopy cover along stream reaches at two spatial extents. First, we examined stream reaches between aggregations and up to 3 kilometers (km) upstream from aggregations. If the main channel containing pearlshell aggregations split into two tributaries of equal stream order, we assessed canopy cover up to 3 km upstream of aggregations along both tributaries. We included stream reaches upstream of aggregations because upstream conditions influence sediments and stream temperature downstream. It is unknown in these streams exactly how much stream length is needed for sediments to settle out of the water or for heightened temperatures caused by diminished canopy cover to decline, particularly considering the spring-fed nature of pearlshell streams. Three km was chosen as the upper extent to be consistent with distances typically considered during Section 7 consultations for the species. The second spatial extent included all tributaries upstream of pearlshell aggregations (not including those reaches included in the first extent so as not to double count them). We calculated the percent of suitable canopy cover at both spatial extents, and calculated a weighted average canopy cover where canopy cover between and within 3 km upstream of aggregations was weighted twice as high as canopy cover on other upstream tributaries, under the assumption that pearlshell mussels and their habitat are more directly impacted by canopy conditions nearby than those far away. The condition of this factor for each population was classified based on the weighted average of suitable canopy cover as follows:

Poor Condition: < 50 percent of buffer has ≥ 50 percent canopy cover Moderate Condition: 50 – 89 percent of buffer has ≥ 50 percent canopy cover Good Condition: > 90 percent of buffer has ≥ 50 percent canopy cover

All extant populations currently have good canopy cover (Table 8). Where forestry or other land use activities have reduced canopy cover, it has not been in amounts large enough to cause large declines in population-wide canopy cover.

39 Table 8. Percent (%) of suitable canopy cover within a 100-ft stream buffer at two spatial extents, and a weighted average of the two extents.

Between All Other Weighted Population Aggregations and 3 Upstream Condition Average km Upstream Tributaries Bayou Clear 100.0% 100.0% 100.0% Good Black Creek 95.4% 95.2% 95.3% Good Brown Creek 93.2% 97.2% 94.5% Good Castor Creek 100.0% 95.4% 98.5% Good Coleman Branch 100.0% 98.9% 99.6% Good Gray Creek 98.7% 93.4% 96.9% Good Little Bayou Clear 89.0% 98.1% 92.0% Good Long Branch 100.0% 100.0% 100.0% Good Loving Creek 100.0% 100.0% 100.0% Good Valentine Creek 100.0% 99.4% 99.8% Good

5.3.2.2 Substrate

Within streams, Louisiana pearlshell aggregations are associated with gravel in the substrate (Figure 10). Johnson and Brown (2000, p. 274) found a positive relationship between pearlshell density and substrate size, and during 2016-2017 surveys on private lands, the nine largest pearlshell aggregations were found on rocky or gravel substrate (LNHP 2017, p. 3). We extracted substrate data at the aggregation scale from survey reports dating back to 1998, and then calculated the percent of aggregations in each population with gravel substrate. Because substrate was not consistently recorded for all aggregations, the percent of aggregations with gravel substrate was calculated only for those aggregations with substrate data available (86 percent [70 out of 81] of current aggregations with ≥ 100 individuals had substrate data). Groups of pearlshell mussels on gravel (including groups with < 100 individuals, thus not considered “aggregations”) were significantly larger (ANOVA, p = 0.032, F = 4.7, df = 1, 113) than groups on non-gravel (i.e., sand, silt) substrates (Figure 11). It is possible that there is a feedback loop between substrate and pearlshell abundance and density; larger substrate particle sizes provide stability for pearlshell aggregations (Johnson and Brown 2000, p. 275), and as aggregations grow, the accumulation of mussels themselves might provide a stable substrate for additional recruitment.

40

Figure 10. Louisiana pearlshells in gravel substrate. Photos by Jared Streeter, LDWF (left) and NNFH, Service (right).

Figure 11. Number of mussels in groups (including groups with fewer than 100 individuals) on gravel and non-gravel substrates (n = 76 groups on gravel, 39 groups not on gravel). The figure on the left is zoomed in to highlight the difference between substrates; the figure on the right is the same data zoomed out to show all outliers.

41 The condition of this factor for each population was classified based on the percent of aggregations (for which substrate data were available) on gravel substrate as follows:

Poor Condition: 0 – 49 percent of aggregations on gravel Moderate Condition: 50 – 74 percent of aggregations on gravel Good Condition: > 75 percent of aggregations on gravel

It should be noted that throughout past surveys, substrate has not been consistently and systematically recorded. No substrate data were available for 11 aggregations, and because of differing monitoring protocols, it was sometimes unclear whether the substrate data that was available referred to substrate at the specific pearlshell locations, or anywhere in the surveyed stream reach. Additionally, substrate does not necessarily remain constant over time. It is possible for gravel to become silted over and/or uncovered. The substrate data used in this assessment represented only a snapshot in time. Because of the lack of data for all aggregations, and coarseness of the data in terms of spatial and temporal scale, substrate was weighted lower than other factors for assessing overall population resilience (weighting described in more detail in section 5.3.3).

Of the nine extant populations, five were in good condition, two were in moderate condition, and two were in poor condition (Table 9). These classifications apply only to locations where current pearlshell aggregations exist. For example, Castor Creek overall has poor substrate conditions (Shively 2018, pers. comm.), but 100 percent (of one) of current aggregations occur on gravel substrate, leading to its classification as good.

Table 9. Percent (%) of aggregations (for which substrate data are available) on gravel for each population, and the corresponding condition category.

Substrate Population Condition % of aggregations on gravel Bayou Clear 5 / 11 = 45% Poor Black Creek 14 / 14 = 100% Good Brown Creek 2 / 3 = 66.7% Moderate Castor Creek 1 / 1 = 100% Good Coleman Branch 6 / 6 = 100% Good Gray Creek 11 / 12 = 92% Good Long Branch 10 / 11 = 91% Good Loving Creek 7 / 10 = 70% Moderate Valentine Creek 1 / 3 = 33% Poor

42 5.3.2.3 Stream Crossings

Stream crossing structures (e.g., culverts, bridges, etc.) have the potential to impact Louisiana pearlshell resilience by restricting movement of the host fish, altering water quality, increasing erosion and sedimentation, which can clog the gills of pearlshell mussels and bury gravel substrates, and altering stream morphology, which can change the flow of water and sediments (Aust et al. 2011, p. 129; Roni et al. 2002, p. 5-7; Warren and Pardew 1998, p. 642). The impact of a stream crossing structure on aquatic habitat depends on the type of crossing. For example, bridges are less disruptive than fords, where vehicles ford through the stream channel, which may or may not be structurally reinforced at the crossing, with the impact of culverts typically falling between that of bridges and fords (Taylor et al. 1999, p. 17). Stream crossings classified as being in poor condition are in need of an upgrade or replacement to improve the habitat (e.g., undersized culverts, perched culverts, multiple culverts at one location).

In Grant Parish, stream crossing structures in the Louisiana pearlshell range were visited by Service and LDWF personnel during 2016 and 2018 to assess their impact on pearlshell habitat, and identify structures in need of upgrades to improve habitat (Figure 12). The same detailed stream crossing data were not available for Rapides Parish. However, on USFS lands the only areas (four identified) with crossings in poor condition are located in ephemeral streams high in their respective watersheds, and thus unlikely to be impacting pearlshell mussels (Shively 2018, pers. comm.). No data were available on stream crossings on private lands in Rapides Parish.

43 Figure 12. An example of a stream crossing structure, within the Louisiana pearlshell range, composed of 4 galvanized culverts. This structure significantly alters the flow of water and sediments, and has been targeted for replacement. Photo by Service 2016.

To assess population resilience, we counted the number of stream crossing structures identified as needing replacement/upgrade between current aggregations or up to 1 km upstream along the same channel from an aggregation. If the main channel containing pearlshell aggregations split into two tributaries of equal stream order, we included any stream crossing structures within 1 km upstream of an aggregation on either tributary. This value was then converted to a density (poor crossing structures per 5 km stream length assessed) so as to be comparable across populations of different sizes. If a population had less than 5 km assessed, we used the raw number of stream crossings as the density across 5 km, so as to prevent artificial inflation of the magnitude of poor crossings. For example, only 1.6 km of stream was assessed for the Coleman Branch population, and there was one poor stream crossing structure. In determining the condition score for stream crossings, Coleman Branch was considered to have one poor stream crossing per 5 km of stream length rather than calculating the true density per 5 km (3.15 poor crossings/5 km stream), because doing so would artificially inflate the impact of the single crossing structure.

The condition of this factor for each population was classified based on the number of poor stream crossings per 5 km of stream length, as follows:

44 Poor Condition: > 1 poor stream crossing per 5 km stream length (or entire assessed stream length if < 5 km) Moderate Condition: Up to 1 poor stream crossing per 5 km stream length (or entire assessed stream length if < 5 km) Good Condition: No poor stream crossings

Of the nine extant populations, seven were in good condition, one was in moderate condition, and one was in poor condition (Table 10).

Table 10. Poor stream crossings that can influence the habitat of Louisiana pearlshell populations.

Stream Crossings Population # Poor stream crossings per 5 km stream length Condition (or total assessed stream length if < 5 km) Bayou Clear 0 Good Black Creek 0 Good Brown Creek 0 Good Castor Creek 0 Good Coleman Branch 1 / 1.60 km (< 5 km assessed) Moderate Gray Creek 4 / 18.1 km = 1.1/5km Poor Long Branch 0 Good Loving Creek 0 Good Valentine Creek 0 Good

5.3.3 Resilience Scoring

For each resilience factor, each population was rated as currently in poor, moderate, or good condition. These categories were then converted to numerical scores 1, 2, and 3, respectively. We then calculated a weighted average of the factor scores to generate an overall resilience score. Factors had a baseline weight of 1 in the weighted average, and some weights were adjusted from 1 based on factor-specific characteristics. Aggregation score was weighted twice as important (weight of 2) because it was a combination of 2 pieces of information (number of aggregations and aggregation size), and because of its importance to resilience; a population cannot be highly resilient, even in the best habitat, if there are not large numbers of Louisiana pearlshells. Evidence of reproduction was down-weighted to 0.5 because reproduction and recruitment data were not systematically and regularly recorded during surveys for all populations. For this assessment, no evidence of reproduction could be a result of a lack of evidence in the field, or a lack of recording evidence that was present. Substrate was similarly down-weighted to 0.5 because it has not historically been systematically recorded in surveys, and because of temporal and spatial uncertainty when data were available. The final weights for all factors were:

45 Aggregation Score: 2 Evidence of Reproduction: 0.5 Canopy Cover: 1 Substrate: 0.5 Stream Crossings: 1

The total weight for all population factors was equal to the total weight for all habitat factors (both 2.5), meaning that the final resilience score for each population was equally determined by population and habitat conditions. A summary of all criteria and weights for resilience factors is shown in Table 11. The weighted average of resilience factor values was converted to population resilience as follows:

Low Resilience: < 2 weighted average of resilience factors Moderate Resilience: 2 – 2.5 weighted average of resilience factors High Resilience: > 2.5 weighted average of resilience factors

The gradient from low to high resilience represents increasing ability to persist in the face of stochastic natural and man-made conditions and events.

Table 11. Summary of criteria for resilience factor conditions and weights used to assess current resilience for Louisiana pearlshell populations.

Population Factors Habitat Factors Aggregation Number Evidence of Canopy Substrate Stream Crossings and Size reproduction Cover Metric Sum of scores for Evidence % 100-ft Percent of # Poor stream aggregation sizes, present or not, buffer with ≥ aggregations crossings per 5 km since 2007: since 2007 50% canopy on gravel stream length (or 1: 100 – 499 mussels cover within total assessed stream 2: 500 – 999 mussels assessed length if < 5 km) 3: ≥ 1,000 mussels stream length Good > 10 Evidence > 90% 75 – 100% No poor crossings Condition Moderate Up to 1 poor 6 – 10 NA 50-89% 50 – 74% Condition crossing Poor 1 – 5 No evidence < 50% 0 – 49% > 1 poor crossing Condition

Weight 2* 0.5 1 0.5 1

* If no aggregations, functionally extirpated, even if scattered mussels were present

46 5.4 Current Resilience, Redundancy, and Representation

There are currently five Louisiana pearlshell populations with high resilience, three with moderate resilience, and one with low resilience (Table 12, Figure 13; See Appendix C for more detailed table of how resilience factors were scored). Additionally, there are four known extirpated populations (i.e., historically supported aggregations and now do not, though they might still support low numbers of scattered mussels), and two locations that are not considered to be populations (i.e., historically supported low numbers of mussels, never supported aggregations in survey history, though they might still support low numbers of scattered mussels). Of the five populations with high resilience, all had aggregation scores in good condition (greater than 10), and the one population with low resilience had a poor aggregation score. However, aggregation scores alone did not determine population resilience. Of the three populations with moderate resilience, two (Castor Creek and Brown Creek) had poor aggregation scores, but showed evidence of reproduction and had favorable habitat conditions, giving them the same resilience classification as a population (Valentine Creek) that had a moderate aggregation score but poor substrate score.

47 Table 12. Summary of current resilience for Louisiana Pearlshell populations.

Population Factors Habitat Factors Aggregation Management Population Score Evidence of Canopy Stream Population Population Substrate Watershed Type (Number and reproduction Cover Crossings Resilience Size) Bayou Boeuf Bayou Clear Population Good Good Good Poor Good High Bayou Boeuf Castor Creek Population Poor Good Good Good Good Moderate Bayou Boeuf Long Branch Population Good Good Good Good Good High Bayou Boeuf Loving Creek Population Good Good Good Moderate Good High Bayou Boeuf Valentine Creek Population Moderate Good Good Poor Good Moderate Little Bayou Bayou Boeuf Extirpated 0 NA NA NA NA Extirpated Clear Bayou Boeuf Mack Branch Extirpated 0 NA NA NA NA Extirpated Not a Not a Bayou Boeuf Hailey’s Creek 0 NA NA NA NA Population Population Bayou Rapides Brown Creek Population Poor Good Good Moderate Good Moderate Coleman Bayou Rigolette Population Poor Poor Good Good Moderate Low Branch Bayou Rigolette Gray Creek Population Good Good Good Good Poor High Bayou Rigolette James Branch Extirpated 0 NA NA NA NA Extirpated Moccasin Bayou Rigolette Extirpated 0 NA NA NA NA Extirpated Branch Not a Not a Bayou Rigolette Cress Creek 0 NA NA NA NA Population Population Black Creek Black Creek Population Good Good Good Good Good High

48 Figure 13. Distribution of current Louisiana pearlshell populations by resilience class and management watershed.

Redundancy refers to having multiple populations which allows species to withstand catastrophic impacts to any one population by spreading risk across the species’ range. Random catastrophic events that could severely impact entire populations include, but are not limited to, the drying of streams during drought, and upstream and downstream impacts from beaver dams, as well as potential direct mortality at dam sites. Representation refers to the breadth of genetic and environmental diversity within and among populations that contribute to the ability of the species to respond and adapt to changing environmental conditions over time. Units of representation for the Louisiana pearlshell were considered to be the four management units, Black Creek, Bayou Boeuf, Bayou Rapides, and Bayou Rigolette. There is a moderate degree of redundancy

49 and representation across the Louisiana pearlshell range, given that the Louisiana pearlshell is an endemic species with a historically limited range.

Only one population (Black Creek, highly resilient) occurs in the Black Creek management watershed north of the Red River, but there is no evidence to suggest that any additional populations ever existed there. Though it is highly resilient, the extent of pearlshell aggregations within the population has dramatically declined, particularly in Beaver Creek and certain segments of Black Creek (sensitive location data not shown in this report).

There is also just a single population (Brown Creek, moderately resilient) in the Bayou Rapides management watershed (south of the Red River), which contains only four small Louisiana pearlshell aggregations that support a total of 1,023 individual mussels. The Brown Creek population extent, like that of the Black Creek population, has contracted, with aggregations not found as far upstream as they once were.

One management watershed north of the Red River and one to the south each contain a single Louisiana pearlshell population. The other two management watersheds, Bayou Rigolette to the north and Bayou Boeuf to the south, each contain multiple pearlshell populations. In Bayou Rigolette, the most robust population is Gray Creek (high resilience), which has lost some historical aggregations along the main stem of Gray Creek and some along one of its tributaries, Jordan Creek, but remains highly resilient. Other than this large population, Bayou Rigolette contains two extirpated populations, one stream that has historically supported low numbers of pearlshell mussels, but never enough to be considered a population, and one population with low resilience (Coleman Branch). The Coleman Branch population supports three small aggregations (185 – 245 individuals in each), no evidence of reproduction has been recorded during surveys, and one poor stream crossing is located less than 1 km upstream from aggregations. Given the status of the other pearlshell streams in Bayou Rigolette, Gray Creek is the only robust population within the representative unit.

The last management watershed, Bayou Boeuf, has the highest redundancy of resilient populations, supporting three populations with high resilience, two with moderate resilience, and three that were either extirpated or were never large enough to be considered populations.

This assessment of the current condition of the species serves as a description of the present state of the species as well as a baseline to compare against plausible future conditions, which are the subject of the next section of this report.

50 6 FUTURE CONDITION

To assess the future condition of Louisiana pearlshell populations, we projected conditions into the future under three scenarios. In the first scenario, Status Quo, we projected current population trends 10 years and 50 years into the future. We explored two conservation scenarios, Conservation with and Conservation without Reintroductions. Captive propagation for this species is ongoing, and trial reintroductions are expected to take place in coming years, but it is unknown whether they will be successful and whether reintroduction will be an effective recovery tool for Louisiana pearlshells going forward. In both Conservation scenarios, population growth received a boost from recovery actions other than reintroduction. Because it will take approximately 10 years to ascertain whether reintroductions have been successful, and for beneficial effects of many other conservation actions to become apparent, the future condition for all three scenarios in 10 years was identical, then diverged for the 50-year projections (Figure 14). Because of vast uncertainty regarding a future scenario with reintroductions, we provided description of what this scenario might look like, but did not assess it quantitatively.

Figure 14. Summary of future scenarios for the Louisiana pearlshell.

51 6.1 Future Resilience Assessment

6.1.1 Future Projection Time Frames

All scenarios were projected 50 years into the future, with an intermediate time step in 10 years where conditions were expected to follow the same trajectory regardless of scenario. After the initial 10 years, the three future scenarios diverged. These 10 and 50-year time steps were selected based on expert opinion, the lifespan and generation time of the species, and time scale at which positive and negative influences on viability operate. It is estimated that Louisiana pearlshells reach sexual maturity around five years of age (Daniel and Brown 2012, p. 26), having an estimated longevity of 70 years in streams where they exhibit slow growth and 45 years where they exhibit faster growth (Johnson and Brown 1998, p. 323). Because this is a long-lived species, population dynamics play out over a long time period. For example, even with no reproduction and recruitment of juveniles, populations of adults can remain stable for several decades. Consequently, negative impacts on reproduction from harmful land use practices or other influences might not have noticeable impacts on population dynamics for decades. Where forest clearing impacts pearlshell streams, it can take several decades for new trees to mature to stabilize and shade streams. It can also take a long time for positive impacts from conservation actions to become apparent. For example, if some recovery action increases reproductive rates and recruitment within a year or two of being implemented, the increase in juveniles will not be apparent for another two to three years after that, before which juveniles are too small and inconspicuous to be detected without destroying habitat. Those juveniles then will not be sexually mature for another few years. The 50-year time step was selected based on species and habitat characteristics that dictate how dynamics play out over a long time span. However, dramatic changes in the number and size of aggregations (primarily declines) have been apparent over the last ~10 years (since 2007), with the number of aggregations and the number of mussels in aggregations declining about 20 percent. For this reason, we also included a 10-year intermediate future time step to assess what the future condition is expected to be in the near term based on the current population trajectory, before longer-term dynamics have a chance to influence population trends.

6.1.2 Aggregation Scores

We projected aggregation scores, which reflect both the number and size of aggregations in each population, using 10-year transition probabilities estimated from a multi-state model. Below we describe first how transition probabilities were estimated, and then how they were used to project future conditions.

52 6.1.2.1 Estimating Transition Probabilities

We defined four states corresponding to the aggregation size classes used to calculate aggregation scores: less than 100 mussels, 100 – 499 mussels, 500 – 999 mussels, and greater than 1,000 mussels. We then estimated the probability of an aggregation in each state either changing to each of the other states or remaining in the same state over a period of 10 years using a multi-state model in program MARK (White and Burnham 1999, entire; Figure 15). Data used to estimate these transition probabilities were recent survey data of aggregation sizes collected by USFS and LDWF where there was approximately 10 years between repeat surveys of aggregations (range: 9 – 12 intervening years, mean: 9.5 years). All transitions were recent, in that they occurred within the last 20 years (most recent transitions used in the model were from 2007 – 2017, the oldest transitions used were from 1998 -2010). Aggregations that were only surveyed once (possibly due to inconsistent naming schemes across multiple surveys), or did not have recent repeat surveys 9 – 12 years apart were not used to calculate transition probabilities. This excluded 143 of 289 surveyed pearlshell groups because of insufficient data. In the future, adherence to the monitoring plan produced by QES (2014, Appendix G) will lead to higher quality data that can be more rigorously assessed for population trends using this or other statistical methods. For the present assessment, we assumed that the transition probabilities of the 146 aggregations with adequate data were representative of range-wide patterns. We chose to include non-aggregations (groups of fewer than 100 mussels) as a state in the model in order to capture the probability of small groups growing into aggregations, which happened for 12.5 percent (7 of 56) of non-aggregations in the transition dataset.

53 Figure 15. Conceptual diagram of a multi-state model where there are four size classes of Louisiana pearlshell aggregations, each of which has some probability of transitioning to any other size class, or remaining in the same size class, after a 10-year time period.

We estimated transition probabilities among the four size class states range-wide, as well as separate transition probabilities for aggregations on public and private lands (Table 13). Overall, aggregation sizes were more likely to decline and drop a size class than they were to grow, and these patterns of decline were stronger for aggregations on private land than public land. Small aggregations were more likely to remain small (44 percent chance) or drop below 100 individuals (51 percent chance) than to grow into medium or large aggregations (5 percent chance combined). This pattern was more alarming on private lands, where small populations had a 67 percent chance of becoming small non-aggregations, compared to a 41 percent chance on public lands. Medium aggregations range-wide were more likely to decline in size class (66 percent chance) than remain medium (25 percent chance) or grow to large (8 percent chance).

54 Table 13. Transition probabilities and (standard errors) around the estimates for Louisiana pearlshell aggregation groupings range-wide, on public lands, and private lands. Row labels indicate the initial state, and states approximately 10 years later are shown across columns. Probabilities for all transitions from the same initial state sum to 1.

Range-wide, n = 146 Non- Sample Small Medium Large Aggregations size Non- 0.86 (0.05) 0.12 (0.04) 0 (0) 0.02 (0.02) 57 Aggregations Small 0.51 (0.06) 0.44 (0.06) 0.03 (0.02) 0.02 (0.02) 63 Medium 0.08 (0.08) 0.58 (0.14) 0.25 (0.13) 0.08 (0.08) 12 Large 0.21 (0.11) 0.14 (0.09) 0.07 (0.07) 0.57 (0.13) 14 Public Lands, n = 82 Non- Sample Small Medium Large Aggregations size Non- 0.82 (0.07) 0.18 (0.07) 0 (0) 0 (0) 33 Aggregations Small 0.41 (0.08) 0.56 (0.08) 0.03 (0.03) 0 (0) 39 Medium 0 (0) 0.57 (0.19) 0.29 (0.17) 0.14 (0.13) 7 Large 0 (0) 0 (0) 0 (0) 1 (0) 3 Private Lands, n = 64 Non- Sample Small Medium Large Aggregations size Non- 0.92 (0.06) 0.04 (0.04) 0 (0) 0.04 (0.04) 24 Aggregations Small 0.67 (0.10) 0.25 (0.09) 0.04 (0.04) 0.04 (0.04) 24 Medium 0.20 (0.18) 0.60 (0.22) 0.20 (0.18) 0 (0) 5 Large 0.27 (0.13) 0.18 (0.12) 0.09 (0.09) 0.45 (0.15) 11

55 Like the pattern for small aggregations, this pattern was more dramatic on private lands (80 percent chance of dropping a size class, 20 percent chance of remaining medium, 0 percent chance of growing) compared to public lands (57 percent chance of dropping a size class, 29 percent chance of remaining medium, 14 percent chance of growing). On public lands, all large aggregations remained large after 10 years, but there was a small sample size (n = 3), whereas on private lands, large aggregations had a 45 percent chance of remaining large, and consequently a 55 percent chance of dropping one or more size classes. On private lands, non-aggregations grew into small aggregations 4 percent of the time, compared to 18 percent of the time on public lands.

6.1.2.2 Projecting Aggregation Scores: Status Quo Scenario

For the Status Quo scenario, we projected aggregation scores 50 years into the future, with an intermediate time step at 10 years in the future, using a Markov Chain simulation where the state of each aggregation (or non-aggregation) at time point t+1 depended on its state at time t and the set of transition probabilities governing the system (Table 13). Time steps for the future projection model were 10 years apart, based on the approximately 10-year difference between time points used to estimate transition probabilities from past data. Thus, our 50-year future projection was made up of five 10-year time steps. Because there were consistent and dramatic differences in the transition probabilities on private and public lands, we used those separate sets of probabilities to model future aggregation conditions rather than treating all aggregations the same. The simulation model was stochastic in that different repetitions of running the model could result in different outcomes. For example, given that a certain aggregation on private land is currently in the medium size class, the model could predict that the aggregation will be either a non-aggregation, small aggregation, or medium aggregation in 10 years (with a 20 percent, 60 percent, and 20 percent chance of each outcome, respectively). Because of this probabilistic nature of the model, we did not project aggregations into the future with the model only once, but repeated the simulation 5,000 times per scenario to determine what the median outcome was expected to be (Figure 16). All current aggregations were projected into the future, as well as current groupings that were too small to be considered aggregations, but which did have a chance of growing into an aggregation.

56 Figure 16. Hypothetical example of a 50-year simulation model of one aggregation currently in the small size class. Every 10 years, the new state of the aggregation (Non, Sm, Med, or Lg) is chosen using a set of transition probabilities. Because of the probabilistic nature of the model, each repetition (rep) can result in a different outcome. Consequently, the model is run 5,000 times to identify the median final state of the aggregation.

We also incorporated parameter uncertainty in the simulation model. Because transition probabilities (Table 13) were estimated from a sample of data, they have uncertainty associated with them, given by the standard errors of the estimates. This uncertainty in the transition probabilities was incorporated into the simulation model by drawing transition probabilities from a normal distribution defined by the estimate and standard error given by the multi-state model. That is, rather than running 5,000 simulations of a model where small aggregations on public land remain in the same size class 56 percent of the time, we randomly drew a different probability for each of the 5,000 simulations from a normal distribution (truncated so probabilities must fall between 0 and 1) with a mean of 0.56 and a standard deviation of 0.08, the standard error associated with the estimate. Because all transition probabilities from the same initial state must sum to one, randomly drawn transition probabilities were normalized so that after incorporating parameter uncertainty, they still summed to one.

After running 5,000 repetitions of the simulation model for each aggregation, the 5,000 final aggregation size classes were tallied up for each population as they were for the current condition to generate 5,000 possible future aggregation scores for each population. Large aggregations contributed three points to aggregation scores, medium aggregations contributed two points to aggregation scores, small aggregations contributed one point to aggregation scores, and non-aggregations did not contribute at all. Here we report the median aggregation score for each population, and the probability of extirpation (percent of the 5,000 repetitions where the final population aggregation score was zero) for each population (Table 14, Figures D1 – D2 in Appendix D).

57 Nearly all populations were projected to decline over the next 50 years, some considerably (e.g., Black Creek aggregation score projected to decline from 57 currently to 32 in 10 years and 20 in 50 years). The sum of all population aggregation scores was predicted to decline from 137 to 99 in 10 years, and decline further to 77 over 50 years. The Castor Creek population was projected to have a 34.4 percent chance of being extirpated (no aggregations > 100 individuals) within 10 years, and a 28.3 percent chance of being extirpated in 50 years (the probability of extirpation declined over time because of the possibility of more small groups growing into aggregations). The Coleman Branch population had a 21.8 percent chance of being extirpated in 10 years, and a 37.4 percent chance of being extirpated in 50 years. However, these extirpation probabilities were calculated using range-wide transition probabilities that included the possibility of aggregations growing as a result of reproduction and recruitment. If Coleman Branch continues to lack reproduction and recruitment in the future, extirpation will certainly occur, the only question is how long it will take. Compared to the current condition, the only populations for which the categorical value of Aggregation Score (good, moderate, or poor) changed were Loving Creek which changed from currently good to moderate at both future time steps, and Valentine Creek which changed from currently moderate to poor at both time steps.

Table 14. Summary of Status Quo scenario median aggregation scores (Agg Score), 95 percent confidence intervals (CI), and probability of extirpation (Prob of Ext) for Louisiana pearlshell populations.

Current 10 Years 50 Years Status Quo Median Median Agg 95% Prob 95% Prob Scenario Agg Condition Agg Condition Score CI of Ext CI of Ext Score Score Bayou Clear 18 14 8 - 21 0.0% Good 11 5 - 19 0.0% Good 21 - Black Creek 57 32 0.0% Good 20 8 - 33 0.0% Good 45 Brown Creek 4 4 1 - 8 0.8% Poor 5 1 - 11 0.4% Poor Castor Creek 1 1 0 - 4 34.4% Poor 1 0 - 5 28.3% Poor Coleman 3 2 0 - 6 21.8% Poor 1 0 - 6 37.4% Poor Branch** 11 - Gray Creek 21 19 0.0% Good 16 7 - 27 0.0% Good 28 Long Branch 15 12 8 - 16 0.0% Good 10 5 - 16 0.0% Good Loving Creek 12 10 6 - 14 0.0% Moderate 9 5 - 14 0.0% Moderate Valentine 6 5 3 - 8 0.0% Poor 4 3 - 8 0.0% Poor Creek Sum 137 99 77 ** Coleman Branch values calculated from transition probabilities that include aggregation growth (reproduction and recruitment). With no reproduction and recruitment (current condition for Coleman Branch), extirpation will occur more certainly as individuals die and are not replaced.

58 6.1.2.2 Projecting Aggregation Scores: Conservation without Reintroductions Scenario

For the Status Quo scenario, we projected aggregation size classes forward using the transition probabilities estimated from the multi-state model for aggregations on public and private lands. For the Conservation scenarios, the initial 10 years were identical to the Status Quo scenario, because conservation actions are expected to take at least 10 years for results to become apparent. After 10 years, transition probabilities were adjusted upwards to reflect positive effects of conservation actions. Rather than making assumptions about how certain actions will be expected to influence transition probabilities (for example, what quantitative effect will outreach and education to private landowners have on the probability of an aggregation of x size class transitioning to y size class?), we instead sought to identify what magnitude of change in transition probabilities will be needed to meet the goal of having stable or increasing populations.

We shifted transition probabilities for aggregations in increments of 0.05 (5 percent) as shown in Table 15 until transition probabilities resulted in overall stable or growing populations, with the current condition as the baseline. These shifts resulted in fewer aggregations declining in size class, and more aggregations growing. Shifts in transition probabilities were applied equally to all size classes (i.e., we assumed that conservation actions would equally benefit all size classes rather than having more impact on some size classes than others).

Table 15. Diagram of how transition probabilities were shifted to project aggregation sizes into the future under the Conservation scenario. Shifts in transition probabilities occurred in increments of 0.05 (5 percent [%]). The shaded diagonal represents the probability of an aggregation staying in the same size class. Arrows represent a shift in probability one cell to the right. Right-wards shifts continue until they reach the size class one size greater than the initial aggregation size, which absorbs the increase without passing it farther up the size classes.

Non-Aggregation Small Medium Large Non-Aggregation Shift → Absorb increase No change No change Small Shift → Shift → Absorb increase No change Medium Shift → Shift → Shift → Absorb increase Large Shift → Shift → Shift → Absorb increase

Transition probability shifts we explored include: 5 percent shift range-wide, 10 percent shift range-wide, 10 percent shift on public lands and 15 percent shift on private lands, 10 percent shift on public lands and 20 percent shift on private lands, and 5 percent shift on public lands and 15 percent shift on private lands (Table 16, Figures D3 – D7 in Appendix D). The scenario where transition probabilities shifted 10 percent on public lands and 15 percent on private lands was the smallest shift that did not result in a decline in range-wide aggregation score (the sum of

59 all population aggregation scores) compared to the current condition. In the current condition, the range-wide aggregation score was 137. In 50 years under the Status Quo scenario, the range- wide aggregation score was predicted to decline by nearly half to 77. With a 10 percent shift in transition probabilities on public lands and a 15 percent shift on private lands, the range-wide aggregation score was predicted to be 141, a small increase from the current condition. In that scenario, not every population was expected to remain stable at current population sizes or grow; notably, the Black Creek population where all current aggregations exist on private land was still expected to decline from an aggregation score of 57 to 40. However, across the species’ range, increases in other populations are expected to make up for that loss so that the range-wide aggregation score improved from the current condition.

We carried the 10 percent shift on public lands and 15 percent shift on private lands scenario forward to assess future resilience, redundancy, and representation in the Conservation scenarios because it represents stable to gradually increasing population sizes compared to the current condition across the species’ range. However, any of the other assessed transition probability shifts that we assessed, or values that we did not assess, could also be carried forward to explore their effect on species viability. The true shift in transition probabilities that will occur in the future depends heavily on the recovery actions implemented to address threats to the species and habitat and the effectiveness of those actions. Recovery actions might include: monitoring Louisiana pearlshell aggregations and threats to populations; working with USFS and other partners to improve habitat; increasing enforcement against ATV use across streams that could harm habitat or directly harm pearlshell mussels; ensuring that construction projects are conducted in such a way to minimize impacts to pearlshell habitat; developing a response plan to protect pearlshell mussels when severe droughts cause drying of streams; augmenting current populations and/or reintroducing pearlshell mussels to extirpated areas with propagated mussels; managing beavers to lessen impacts on pearlshell streams; education, outreach, and incentive programs to encourage private landowners to contribute to pearlshell conservation; and land acquisition or conservation easements. We cannot predict with certainty the amount or level of effort put into each of these recovery actions that will result in stable or growing populations, but we have shown that more effort will be needed on private lands than public lands to stabilize populations, and that populations generally will stabilize with a shift in transition probabilities of approximately 10-15 percent. Whether this benchmark of stabilizing populations is reached, exceeded, or fallen short of will depend on the levels of resources and effort committed to researching, developing, implementing, and monitoring the effects of conservation actions.

In the Status Quo scenario, nearly all populations were expected to decline over the next 50 years. In the Conservation scenario, nearly all populations were expected in 50 years to be at their current population size or to have grown (Table 17). The sum of all aggregation scores in 50 years with a 10 percent shift in transition probabilities on public lands and a 15 percent shift on private lands was 141, larger than the current range-wide sum of 137. With conservation

60 actions, the probability of extirpation for the Castor Creek population was reduced to 12.3 percent, and that for the Coleman Branch population was reduced to 9.7 percent. As in the Status Quo scenario however, these extirpation probabilities were calculated using range-wide transition probabilities that included the possibility of aggregations growing as a result of reproduction and recruitment. If Coleman Branch continues to lack reproduction and recruitment in the future, extirpation will certainly occur, the only question is how long it will take. The 10-year probabilities of extirpation were higher for these populations because the Status Quo probabilities were used for the first 10 years of the model. However, the extirpation of an aggregation in this model was not a permanent state. There was a probability (18 percent on public lands and 4 percent on private lands with Status Quo probabilities, 28 percent and 19 percent with shifted Conservation probabilities) that small groups of pearlshell mussels will grow to 100 or more individuals over 10 years. Compared to the current condition, the only population for which the categorical value of Aggregation Score (good, moderate, poor) changed after 50 years (10 year values in the Conservation scenario were identical to the 10-year Status Quo values) was Brown Creek which changed from currently poor to good.

61 Table 16. Projected aggregation scores (Agg Score) 50 years in the future for populations with transition probabilities shifted from the current condition. Probabilities of extirpation for non-zero values are shown in parentheses.

% % Current Agg Agg Score Agg Score Agg Score Agg Score Agg Score Agg Score Current Population Aggs Score Status Quo +5% +10% +5% Public +10% Public +10% Public Aggs Public Current Future Range-wide Range-wide +15% Private +15% Private +20% Private Private

Bayou Clear 57.1% 42.9% 18 11 15 18 18 20 22

Black Creek 0.0% 100.0% 57 20 26 32 37 40 48

5 Brown Creek 75.0% 25.0% 4 9 10 8 10 11 (0.4%)

1 2 2 2 2 3 Castor Creek 0.0% 100.0% 1 (28.3%) (15.7%) (9.8%) (18.1%) (12.3%) (7.6%)

Coleman 1 2 3 4 3 4 0.0% 100.0% 3 Branch** (37.4%) (22.9%) (14.9%) (5.3%) (9.7%) (5.0%)

Gray Creek 53.8% 46.2% 21 16 21 28 27 31 34

Long Branch 100.0% 0.0% 15 10 13 16 13 15 15

Loving Creek 100.0% 0.0% 12 9 11 14 10 14 14

Valentine Creek 33.3% 66.7% 6 4 4 5 6 6 7

Sum 137 77 103 128 125 141 158 ** Coleman Branch values calculated from transition probabilities that include aggregation growth (reproduction and recruitment). With no reproduction and recruitment (current condition for Coleman Branch), extirpation will occur more certainly as individuals die and are not replaced.

62 Table 17. Summary of Conservation median aggregation scores (Agg Score), 95 percent confidence intervals (95 % CI), and probability of extirpation (Prob of Ext) for Louisiana pearlshell populations. At the intermediate 10-year time point, results are the same as the Status Quo scenario because conservation actions are expected to take at least 10 years for results to become apparent.

Current 10 Years 50 Years Conservation Median Median Agg 95% Prob 95% Prob Scenario Agg Category Agg Category Score CI of Ext CI of Ext Score Score Good 20 12 - 0% Good Bayou Clear 18 14 8 - 21 0% 30 21 - Good 40 26 - 0% Good Black Creek 57 32 0% 45 56 Brown Creek 4 4 1 - 8 0.8% Poor 10 4 - 17 0% Good Castor Creek 1 1 0 - 4 34.4% Poor 2 0 - 6 12.3% Poor Coleman 3 0 - 8 9.7% 3 2 0 - 6 21.8% Poor Poor Branch** 11 - Good 31 20 - 0% Good Gray Creek 21 19 0% 28 43 Long Branch 15 12 8 - 16 0% Good 15 9 - 22 0% Good Loving Creek 12 10 6 - 14 0% Moderate 14 8 - 21 0% Good Valentine 0% 6 3 - 11 0% 6 5 3 - 8 Poor Moderate Creek Sum 137 99 141 ** Coleman Branch values calculated from transition probabilities that include aggregation growth (reproduction and recruitment). With no reproduction and recruitment (current condition for Coleman Branch), extirpation will occur more certainly as individuals die and are not replaced.

6.1.2.3 Conservation with Reintroductions Scenario

Currently, Louisiana pearlshells from the Black Creek (propagated in 2016) and Bayou Boeuf (propagated in 2018) management watersheds are being held and reared in captivity for trial reintroductions. Within the next several years, they will be reintroduced to streams within the species’ range. Because there are genetic distinctions among pearlshell mussels from different management watersheds, propagated mussels will be reintroduced into the same watershed from which their broodstock was sourced.

Because all of the pearlshell-occupied streams in the Black Creek management watershed are part of the same population (Black Creek), the Black Creek population will be the recipient of mussels propagated from Black Creek broodstock. This reintroduction is expected to take place in 2019 when the mussels are three years old, but a recipient site has not yet been determined.

63 The site selection process will be described in the Louisiana pearlshell propagation and reintroduction plan, currently in draft, before any reintroductions are made.

Reintroductions of the Bayou Boeuf pearlshell mussels are planned for 2020 or 2021 when the mussels are two or three years old, respectively. Preliminary sites identified as potential recipients for the Bayou Boeuf broodstock mussels include Mack Branch and Lamotte Creek, both relatively small isolated streams that flow into Kincaid Reservoir. Mack Branch historically supported Louisiana pearlshells, but they were extirpated. Lamotte Creek is not known to have historically supported Louisiana pearlshells. Before Louisiana pearlshells would be reintroduced into these or any locations, recipient sites will be assessed to ensure that the habitat is suitable, threats (especially for sites from which pearlshell mussels were locally extirpated) have been ameliorated, and suitable fish hosts are present. As stated above, the site selection process will be in accordance with the propagation and reintroduction plan before any reintroductions are made.

Ideal reintroduction sites would be on public lands to ensure long term access for site assessments, any habitat restoration needed, reintroductions, and follow-up monitoring, but there can be opportunities on private lands as well where there are cooperative landowners. The difference in land ownership between Grant (mostly private) and Rapides (mostly public) Parishes means that reintroductions in Grant Parish may prove to be more logistically challenging. However, most landowners with pearlshell streams on their land take pride in their stream habitat and have been cooperative with conservation and monitoring efforts (Streeter and Lejeune 2018, pers. comm.).

These preliminary reintroductions will be trials to determine whether reintroduction can be a useful tool for Louisiana pearlshell conservation. It is difficult to determine reintroduction success because monitoring does not typically continue long enough, or there simply has not been enough time since initial reintroduction, to determine whether released individuals survived, reproduced, and recruited new juveniles into the population (Jourdan et al. 2018, p. 4). Jourdan et al. (2018, p. 6-7) assessed 13 Unionid mussel reintroductions, including two Margaritifera margaritifera reintroductions in Europe, and 10 reintroductions of other mussel genera in the United States, and found that over half reported high mortality of reintroduced individuals. Only five of the mussel reintroductions did not exhibit high mortality, and only one (from Japan) reported recruitment of juveniles. The measure of success for Louisiana pearlshell reintroductions will be a self-sustaining (reproducing and recruiting) aggregation (100 or more individuals) at the reintroduction site.

From the time a propagation effort is initiated by bringing gravid females into captivity, it might take up to 10 years or more to determine whether the reintroduction was successful. Juvenile mussels will be released when two to three years old, likely reach sexual maturity around five

64 years of age, and then another few years will be necessary to detect any new juveniles produced in the wild because they are difficult to detect without destroying habitat until they reach a larger size at two to three years old. The utility and limitations of a non-invasive eDNA approach for sampling has not been determined for this species. If investigation proves eDNA to be a useful tool for detecting Louisiana pearlshell recruitment, then disturbance from hand searching through the substrate to determine juvenile presence could be reduced or eliminated.

If reintroduction is shown to be successful, this technique could be used in response to local extirpations from catastrophes. It would likely be reserved as a conservation tool to repatriate areas where mussels have become extirpated, or in other critical areas where assessments indicate that a future extirpation event is likely and that repatriation of the area would have a large benefit to the long term survival and recovery of the species. While reintroductions, if successful, might be a valuable tool in the recovery toolbox for Louisiana pearlshell, the primary focus will be on improving conditions for existing populations, and using reintroductions only when critical.

6.1.3 Evidence of Reproduction

In the Status Quo scenario, evidence of reproduction remained the same as the current condition, where all populations have exhibited recent reproduction and recruitment except for the Coleman Branch population.

In the Conservation scenario, we also made the assumption that Coleman Branch would not have reproduction and recruitment. It is possible that Coleman Branch could have reproduction and recruitment in the future. It might be that it currently is a reproducing population, and evidence was not noted by surveyors. If Coleman Branch truly is not a reproducing population, the cause of reproductive and/or recruitment failure in unknown. Aggregations on Coleman Branch occur exclusively on private lands, so access is limited. Future investigations might reveal the cause and whether it can be addressed. For this SSA however, we chose to be conservative and assume that the cause cannot be addressed and mitigated. Coleman Branch is flanked by two extirpated populations, James Branch and Moccasin Branch, suggesting that there might be large-scale impacts to pearlshell mussels that would be difficult to reverse. In the face of this uncertainty, we chose to assess the future condition assuming that reproduction in Coleman Branch cannot be restored, because the consequences of wrongly assuming that reproduction can be restored are riskier than the consequences of wrongly assuming that reproduction cannot be restored. In Section 6.2, where population resilience is summarized, we discuss how restoring reproduction and recruitment would affect projected resilience.

The aggregation score projections as described above include probabilities of Louisiana pearlshell groups growing. Under an assumption of no future reproduction and recruitment in

65 Coleman Branch, those calculated transition probabilities do not apply, and aggregation sizes will only decline. As adult pearlshells die and are not replaced, the population will become extirpated; the only question is how long it will take.

6.1.4 Canopy Cover

Canopy cover was projected to remain high (good condition) across all populations in all future scenarios. While changes in canopy cover are happening within the riparian buffer around Louisiana pearlshell streams (as evidenced by differences in 2011 NLCD canopy cover data and 2017 NAIP imagery), ongoing changes in the future are unlikely to occur at a scale wide enough to influence canopy cover values as we measured them range-wide. Where riparian forest around pearlshell streams is owned by timber companies that employ best management practices for protecting aquatic habitat, then projections are that the land is likely to remain in the timber industry rather than be sold to developers. Where forest clearing activities on private lands impact specific stream reaches or aggregations in the future, threats will need to be addressed on a case-by-case basis.

6.1.5 Substrate

Substrate was projected to remain constant in the future in all scenarios. Even where sediment flow regimes might change to either cover or uncover existing gravel beds, the gravel bed is still a constant feature of the stream (for time spans relevant to this SSA). Artificially creating gravel beds in stream segments where they do not already exist is not a simple or straightforward procedure. Stream modifications and restorations are large projects involving partners with diverse expertise (e.g., engineers, hydrologists, etc.), and are more likely to be undertaken in response to impacts from development, not to create or improve mussel habitat. Overall, we assumed for the purposes of modeling that given the difficulty in predicting specific impacts, changes in substrate conditions in pearlshell streams from natural and anthropogenic impacts would be temporary and isolated such that overall substrate composition would be similar over the time period.

6.1.6 Stream Crossings

In the Status Quo scenario, two stream crossing structures on Gray Creek were predicted to be replaced. These projects are presently funded and will be completed before the 10-year future prediction time step. While these do occur on a stream occupied by Louisiana pearlshells, they are greater than 1 km upstream of any current pearlshell aggregations, and thus were not included in the resilience assessment.

66 In the Conservation scenarios, six additional stream crossing structures in addition to the two currently funded are predicted to be replaced. These were identified as likely to be replaced within 10 years based on program funding, cost of replacement, potential willingness of landowners, and the complexity and impact of replacement. Three of these crossings are in the Black Creek population, but none fall between or 1 km upstream of aggregations, and thus do not influence resilience in this assessment. The other three crossings are in the Gray Creek population, two of which do fall between or within 1 km upstream of aggregations, and thus do influence the value of the stream crossing factor for resilience. In this future scenario, there were half as many stream crossing structures in need of replacement in the Gray Creek population compared to the current condition (decrease from 1.1 to 0.55 structures per 5 km of stream assessed), and the value of the stream crossing resilience factor improved from poor to moderate condition.

6.2 Future Resilience, Redundancy, and Representation

The conditions of each of the population and habitat factors contributing to population resilience are summarized in Table 18. Evidence of reproduction, canopy cover, and substrate were held constant at the current condition. Aggregation scores were projected using a multi-state simulation model with transition probabilities derived from past data, and adjusted in the Conservation scenario for conservation actions. The value for stream crossings changed from the current condition only in the Gray Creek population, where the condition was predicted to improve from poor to moderate in the Conservation scenario.

Values for these factors were combined as in the current condition to generate population resilience classifications, summarized in Tables 18 – 20 and Figure 17. In the current condition, there were five populations with high resilience, three with moderate resilience, and one with low resilience, for a total of nine populations. Two populations, James Branch and Moccasin Branch, were extirpated between 2007 and the present. In 10 years (2028), most populations were projected to remain in the same resilience classes as the current condition, with the exception of Loving Creek, which dropped from high resilience to moderate resilience. There is also a 34 percent chance that the Castor Creek population will be extirpated and a 22 percent chance that the Coleman Branch population will be extirpated in 10 years. In 50 years, the Status Quo and Conservation scenarios diverge from each other. In the Status Quo scenario, all populations except Loving Creek, which dropped from high to moderate resilience, were predicted to remain in the same resilience class as the current condition. Probabilities of extirpation for Castor Creek and Coleman Branch were 28 percent and 37 percent, respectively. In the Conservation Scenario, all populations except Brown Creek, which improved from moderate to high resilience, were predicted to remain in the same resilience class as the current condition. Probabilities of extirpation for Castor Creek and Coleman Branch declined to 12 percent and 10 percent, respectively.

67 Resilience of the Coleman Branch population was based on the assumption that the current state of no evidence of reproduction continues into the future under all scenarios. This assumption was made because the cause of this lack of reproduction is unknown, and consequently it is unknown whether it can be mitigated with conservation actions. If this assumption is wrong, either because the influences contributing to the lack of reproduction can be mitigated or because reproduction is currently happening but was not recorded, resilience for Coleman Branch would improve from low to moderate in all scenarios.

The Conservation scenario summarized here does not explicitly include reintroduction to return Louisiana pearlshells to streams where local extirpations have occurred or to augment extant populations. Trial reintroductions are expected to occur over the next several years, and follow- up monitoring will reveal whether reintroduction from captivity will be an effective conservation tool for this species. If reintroduction does prove successful, it still will not be the primary conservation tool; the focus will remain on improving habitat conditions for extant populations and improving connectivity within and among populations located in the same Louisiana pearlshell management watershed for the benefit of host fish movement and genetic flow. Reintroduction could be used to reestablish extirpated populations like James or Moccasin Branch, populations in danger of extirpation like Castor Creek and Coleman Branch, or create new populations in suitable habitat in previously unoccupied streams. Population augmentation from captivity could also be used to supplement populations that are experiencing drastic declines in pearlshell mussels. For any future reintroductions or augmentations, care must be taken to select suitable introduction sites, ensure that threats have been addressed such that the introduced mussels have a chance to flourish, and that broodstock are selected for reintroductions in a genetically appropriate manner (broodstock genetically similar to pearlshell mussels of the recipient stream).

68 Table 18. Summary of resilience factors for Louisiana pearlshell populations 10 and 50 years in the future. Values apply to all future scenarios unless otherwise noted. Evidence of reproduction, canopy cover, and substrate all remained in the same condition as they are presently.

Population Factors Habitat Factors Aggregation Score Aggregation Status Quo and Score Evidence of Canopy Stream Population Conservation Substrate Conservation reproduction Cover Crossings (10 Years) & (50 Years) Status Quo (50 Years) Bayou Clear Good Good Good Good Poor Good Castor Creek Poor Poor Good Good Good Good Long Branch Good Good Good Good Good Good Loving Creek Moderate Good Good Good Moderate Good Valentine Creek Poor Moderate Good Good Poor Good Little Bayou Clear 0 0 NA NA NA NA Mack Branch 0 0 NA NA NA NA Hailey’s Creek 0 0 NA NA NA NA Brown Creek Poor Good Good Good Moderate Good Coleman Branch Poor Poor Poor Good Good Moderate Poor/ Moderate Gray Creek Good Good Good Good Good (Status Quo/ Conservation) James Branch 0 0 NA NA NA NA Moccasin Branch 0 0 NA NA NA NA Cress Creek 0 0 NA NA NA NA Black Creek Good Good Good Good Good Good

69 Table 19. Current and predicted future resilience for Louisiana pearlshell populations 10 and 50 years in the future under a Status Quo and Conservation scenario.

Population Population Population Population Representative Unit Resilience Resilience Resilience Resilience (Management Population Status Quo and Current Status Quo Conservation Watershed) Conservation 50 Years 50 Years 10 Years Bayou Boeuf Bayou Clear High High High High Bayou Boeuf Castor Creek Moderate Moderate Moderate Moderate Bayou Boeuf Long Branch High High High High Bayou Boeuf Loving Creek High Moderate Moderate High Bayou Boeuf Valentine Creek Moderate Moderate Moderate Moderate Bayou Boeuf Little Bayou Clear Extirpated Extirpated Extirpated Extirpated Bayou Boeuf Mack Branch Extirpated Extirpated Extirpated Extirpated Bayou Boeuf Hailey’s Creek Not a Population Not a Population Not a Population Not a Population Bayou Rapides Brown Creek Moderate Moderate Moderate High Bayou Rigolette Coleman Branch Low Low Low Low Bayou Rigolette Gray Creek High High High High Bayou Rigolette James Branch Extirpated Extirpated Extirpated Extirpated Bayou Rigolette Moccasin Branch Extirpated Extirpated Extirpated Extirpated Bayou Rigolette Cress Creek Not a Population Not a Population Not a Population Not a Population Black Creek Black Creek High High High High

70

Figure 17. Resilience of the Louisiana pearlshell in four management watersheds under (from left to right) 1) the current condition, 2) 10 years in the future under the Status Quo and Conservation scenarios and 50 years in the future under the Status Quo scenario, and 3) 50 years in the future under the Conservation scenario.

71 Table 20. Number of Louisiana pearlshell populations in each resilience class in each scenario.

Status Quo and Current Status Quo Conservation Conservation 50 Years 50 Years 10 Years High Resilience 5 5 4 6 Moderate 3 3 4 2 Resilience Low Resilience 1 1 1 1

Based on our assessment of current and future resilience, redundancy and representation are not expected to change dramatically over the next 50 years if no populations are extirpated. If Castor Creek (Bayou Boeuf management watershed) and Coleman Branch (Bayou Rigolette) become extirpated, at least one highly resilient population will remain in their respective management watersheds. In the Conservation scenario, the single population in the Bayou Rapides management watershed (Brown Creek), is expected to improve from moderate to high resilience, improving the chance that Bayou Rapides representation will persist in the future.

This relative stability in resilience classes masks an overall decline in aggregation number and size that has been occurring and is expected to continue for 10 years in either scenario. The range-wide aggregation score was predicted to drop 28 percent (137 to 99) between the present and 2028 (either scenario), and 45 percent (137 to 77) between the present and 2068 under the Status Quo scenario (Figure 17). Although large, these declines were not apparent from the resilience classifications because they often did not cause the aggregation score to cross a threshold into a different condition (poor, moderate, or good). For example, Black Creek was predicted to decline from a current aggregation score of 57 to an aggregation score of 32 in 10 years, and 20 in 50 years in the Status Quo scenario. That represents a 65 percent decline in aggregation score over 50 years, a dramatic change, yet a population with an aggregation score of 20 is still in the good condition. Though seemingly contradictory, these results suggest that the Black Creek population, though expected to decline in aggregation number and sizes, is highly likely to persist on the landscape over the next 50 years. Beyond that time horizon, aggregations would continue to decline in a Status Quo scenario, and would presumably decline in resilience class at a later date. The same interpretation applies to Bayou Clear, Gray Creek, and Long Branch, all of which are currently highly resilient and were predicted to decline in aggregation score under the Status Quo scenario, but not enough to change resilience classes within 50 years.

72 Figure 17. Past and predicted future trajectory of Louisiana pearlshell range-wide aggregation score, which incorporates both the number and size of aggregations.

Aggregations on USFS land fared better than those on private land in the past and in the predicted future. As illustrated by the transition probabilities for each ownership type, aggregations on public lands are less likely than those on private lands to drop a size class during a 10-year time period. Small groups with less than 100 individuals on public lands are also more likely to grow into small aggregations of at least 100 individuals in 10 years (18 percent chance) than those on private lands (4 percent chance). This difference between public and private land implies that, particularly in Grant Parish where populations occur more heavily on private lands than in Rapides Parish, there is much room for improvement in habitat conditions on private lands and cooperation with private landowners can have profound positive impacts on Louisiana pearlshell conservation and recovery. Current levels of species resilience, redundancy, and representation cannot be maintained in perpetuity by focusing efforts on public lands alone.

This concludes our assessment of Louisiana pearlshell needs, current condition, and future condition. This SSA will follow the species through its ESA life cycle, through recovery planning, consultations, and all policy-related decision-making until recovery and eventual delisting. To better assess the status of the species in the future, regular monitoring of populations and habitat is needed, as well as confirmation and monitoring of the natural fish host, and this SSA should be updated as new information becomes available.

73 LITERATURE CITED

Aust, W.M., M.B. Carroll, M.C. Bolding, and C.A. Dolloff. 2011. Operational forest stream crossings effects on water quality in the Virginia Piedmont. Southern Journal of Applied Forestry 35:123-130. Bolden, S.R. 2000. Effects of translocation, microhabitat, and density on growth and movement in the threatened Louisiana pearlshell (Margaritifera hembeli). MS Thesis, Louisiana State University, Baton Rouge. 49 pages. Bolden, S.R. and K.M. Brown. 2002. Role of stream, habitat, and density in predicting translocation success in the threatened Louisiana pearlshell, Margaritifera hembeli (Conrad). Journal of the North American Benthological Society 21:89-96. Carter, L. M., J. W. Jones, L. Berry, V. Burkett, J. F. Murley, J. Obeysekera, P. J. Schramm, and D. Wear. 2014. Ch. 17: Southeast and the Caribbean. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, T.C. Richmond, and G. W. Yohe, (eds.), U.S. Global Change Research Program, 396-417. doi:10.7930/J0NP22CB. Churchill, E.P., Jr., and S.I. Lewis. 1924. Food and feeding in freshwater mussels. U.S. Bureau of Fisheries. Bulletin of the Bureau of Fisheries 39:439-471. Daniel, W.M. and K.M. Brown. 2012. Growth curves for Margaritifera hembeli from shell sectioning similar to mark and recapture estimates. Ellipsaria 14:25-27. Darden, R.L. 1988. Habitat requirements survey for the freshwater mussel Margartifiera hembeli (Bivalvia: Unionacea). Final Report to the U.S. Forest Service. Pineville, LA. 51 pages. Fowler, Allison (Ed) 2015. Arkansas Wildlife Action Plan. Arkansas Game and Fish Commission, Little Rock, Arkansas. 1678 pages. Gatenby, C. M., R. J. Neves, and B. C. Parker. 1996. Influence of sediment and algal food on cultured juvenile freshwater mussels. Journal of the North American Benthological Society 15:597–609. Haag, W.R., R.S. Butler, and P. Hartfield. 1995. An extraordinary reproductive strategy in freshwater bivalves: prey mimicry to facilitate larval dispersal. Freshwater Biology 34:471-476. Haag, W. R., and M. L. Warren Jr. 1997. Host fishes and reproductive biology of 6 freshwater mussel species from the Mobile basin, USA. Journal of North American Benthological Society 16:576-585. Hartfield, P. and E. Hartfield. 1996. Observations on the conglutinates of Ptychobranchus greeni (Conrad, 1834) (Mollusca: Bivalvia: Unionoidea). American Midland Naturalist 135:370- 375. Hastie, L.C. and M.R. Young. 2003. Timing of spawning and glochidial release in Scottish freshwater pearl mussel (Margaritifera margaritifera) populations. Freshwater Biology 48:2107-2117. Hill, A.M. 1986. The glochidia (larvae) of the freshwater mussel Margaritifera hembeli (Unionacea: Margaritiferidae) fish host species, morphology, and period of fish host infection. MS Thesis, Northwestern State University, Natchitoches, LA. 32 pages. Holcomb, S.R., A.A. Bass, C.S. Reid, M.A. Seymour, N.F. Lorenz, B.B. Gregory, S.M. Javed, and K.F. Balkum. 2015. Louisiana Wildlife Action Plan. Louisiana Department of Wildlife and Fisheries. Baton Rouge, Louisiana. 705 pages.

74 Homer, C.G., J.A. Dewitz, L. Yang, S. Jin, P. Danielson, G. Xian, J. Coulston, N.D. Herold, J.D. Wickham, and K. Megown. 2015. Completion of the 2011 National Land Cover Database for the conterminous United States-Representing a decade of land cover change information. Photogrammetric Engineering and Remote Sensing 81:345-354. Ice, G., and B. Sugden. 2003. Summer dissolved oxygen concentrations in forested streams of northern Louisiana. Southern Journal of Applied Forestry, 27(2), 92-99. Intergovernmental Panel on Climate Change (IPCC). 2014. Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. IPCC, Geneva, Switzerland, 168 pages. Available from: http://ipcc.ch/report/ar5/syr/ Jansen, W., G. Bauer, and E. Zahner-Meike. 2001. Glochidial Mortality in Freshwater Mussels. Pages 185-211 in Bauer G. and K. Wachtler, editors. Ecological Studies: Ecology and Evolution of the Freshwater Mussels Unionoida, Vol. 145. Berlin, Germany: Springer- Verlag. Johnson, P.D. 1995. A comparison of ecological factors affecting two species of lotic mollusks. PhD. Dissertation, Louisiana State University, Baton Rouge. 136 pages. Johnson, P.D., and K.M. Brown. 1998. Intraspecific life history variation in the threatened Louisiana pearlshell mussel, Margaritifera hembeli. Freshwater Biology 40:317-329. Johnson, P.D., and K.M. Brown. 2000. The importance of microhabitat factors and habitat stability to the threatened Louisiana pearlshell, Margaritifera hembeli (Conrad). Canadian Journal of Zoology 78:271-277. Johnson, P.M., A.E. Liner, S.W. Golladay, and W.K. Michener. 2001. Effects of drought on freshwater mussels and instream habitat in Coastal Plain tributaries of the Flint River, southwest, Georgia (July-October, 2000). Final Report, The Nature Conservancy. 34 pages. Johnson, R.I. 1983. Margaritifera marrianea, a new species of Unionacea (Bivalvia: Margaritiferidae) from the Mobile-Alabama-Coosa and Escambia river systems, Alabama. Occasional Papers on Mollusks, Museum of Comparative Zoology, Harvard University 4:299-304. Jourdan, J., M. Plath, J.D. Tonkin, M. Ceylan, A.C. Dumeier, G. Gellert, W. Graf, C.P. Hawkins, E. Kiel, A.W. Lorenz, C.D. Matthaei, P.F.M. Verdonschot, R.C.M. Verdenschot, and P. Haase. 2018. Reintroduction of freshwater macroinvertebrates: challenges and opportunities. Biological Reviews. doi: 10.1111/brv.12458. Kaller, M. D., J. D. Hudson III, E. C. Achberger, and W. E. Kelso. 2007. Feral hog research in western Louisiana: expanding populations and unforeseen consequences. Human- Wildlife Conflicts: 1:168-177. Kraemer, L.R. 1979. Corbicula (Bivalvia: Sphaeriacea) vs. indigenous mussels (Bivalvia: Unionacea) in U.S. Rivers: A hard case for interspecific competition? American Zoologist 19 (4):1085-1096. Kunkel, K. E., L. E. Stevens, S. E. Stevens, L. Sun, E. Janssen, D. Wuebbles, C. E. Konrad, II, C. M. Fuhrman, B. D. Keim, M. C. Kruk, A. Billet, H. Needham, M. Schafer, and J. G. Dobson. 2013. Regional Climate Trends and Scenarios for the U.S. National Climate Assessment: Part 2. Climate of the Southeast U.S. NOAA Technical Report 142-2. 103 pages, National Oceanic and Atmospheric Administration, National Environmental Satellite, Data, and Information Service, Washington D.C.

75 Louisiana Forestry Association. 1997. Forestry Best Management Practices for Louisiana. Louisiana Forestry Association, Alexandria, LA. 84 pages. Louisiana Natural Heritage Program (LNHP). 1998. 1998 Survey for the Louisiana pearlshell (Margaritifera hembeli) in Rapides Parish, LA. 18 pages. Louisiana Natural Heritage Program (LNHP). 2009. 2007-2009 Survey for the Louisiana pearlshell mussel (Margaritifera hembeli) on private lands in Louisiana, Grant and Rapides Parish. 25 pages. Louisiana Natural Heritage Program (LNHP). 2017. 2016-2017 Survey for Louisiana pearlshell mussel (Margaritifera hembeli) on private lands of Grant and Rapides Parishes, LA. 18 pages. Louisiana Revised Statutes. Title 56: Wildlife and Fisheries. Part IV: Threatened and Endangered Species Conservation. Section 1901. 1 page. McMahon, R. 1991. Mollusca: Bivalvia. Pages 315-373 in Thorp, J. and A. Covich, editors. Ecology and Classification of North American Freshwater Invertebrates. San Diego, CA: Academic Press, Inc. Quantitative Ecological Services, Inc (QES). 2014. Project Report Determining Population Trends for the Louisiana Pearlshell Mussel and Development of a Long-Term Monitoring Protocol, March 2014. Submitted to Louisiana Natural Heritage Program, Louisiana Department of Wildlife and Fisheries, Baton Rouge, LA. 72 pages. Poff, N.L., M. M. Brinson, and J. W. Day. 2002. Aquatic ecosystems and global climate change: potential impacts on inland freshwater and coastal wetland ecosystems in the United States. Pew Center on Global Climate Change. 56 pages. Roe, Kevin J. 2009. Conservation Genetics of the Freshwater Mussel Margaritifera hembeli (Bivalvia: Margaritiferidae), Final Report, November 2009. Iowa State University, Department of Natural Resource Ecology and Management, Ames, IA. 14 pages. Roni, P., T.J. Beechie, R.E. Bilby, R.E. Leonetti, M.M. Pollock, and G.R. Pess. 2002. A review of stream restoration techniques and a hierarchical strategy for prioritizing restoration in Pacific Northwest watersheds. North American Journal of Fisheries Management 22:1- 20. Smith, D.G. 1988. Notes on the biology and morphology of Margaritifera hembeli (Conrad, 1838) (Unionacea: Margaritiferidae). The Nautilus 102:159-163. Sousa, R., C. Antunes, and L. Guilhermino. 2008. Ecology of the invasive Asian clam Corbicula fluminea (Müller, 1774) in aquatic ecosystems: an overview. International Journal of Limnology 44:85-94. Strayer, D.L. 1999. Effects of alien species on freshwater mollusks in North America. Journal of the North American Benthological Society 18:74-98. Strayer, D.L, J.A. Downing, W.R. Haag, T.L. King, J.B. Layzer, T.J. Newton, and S.J. Nichols. 2004. Changing perspectives on pearly mussels, North America’s most imperiled animals. BioScience 54:429-439. Taylor, S.E., R.B. Rummer, K.H. Yoo, R.A. Welch, and J.D. Thompson. 1999. What we know – and don’t know – about water quality at stream crossings. Journal of Forestry 97:12-17. U.S. Fish and Wildlife Service (Service). 1990. Louisiana pearlshell (Margaritifera hembeli) recovery plan. U.S. Fish and Wildlife Service, Atlanta, GA. 15 pages. U.S. Fish and Wildlife Service (Service). 1991. Field survey of Margaritifera hembeli. U.S. Fish and Wildlife Service, Jackson, MS. 5 pages.

76 U.S. Fish and Wildlife Service (Service). 2000. Tennessee River Basin Freshwater Mussels. U.S. Fish and Wildlife Service, Gloucester, VA. 2 pages. U.S. Fish and Wildlife Service (Service). 2011. Life history requirements for the Louisiana pearlshell mussel Margaritifera hembeli. U.S. Fish and Wildlife Service, Natchitoches National Fish Hatchery, Natchitoches, LA. 6 pages. U.S. Fish and Wildlife Service (Service). 2014. Host study for the Louisiana Pearlshell Mussel Margaritifera hembeli 2014. U.S. Fish and Wildlife Service, Natchitoches National Fish Hatchery, Natchitoches, LA. 5 pages. U.S. Fish and Wildlife Service (Service). 2016a. USFWS species status assessment framework: an integrated analytical framework for conservation. Version 3.4, August 2016. U.S. Fish and Wildlife Service (Service). 2016b. Host study for the Louisiana Pearlshell Mussel Margaritifera hembeli 2016. U.S. Fish and Wildlife Service, Natchitoches National Fish Hatchery, Natchitoches, LA. 4 pages. U.S. Fish and Wildlife Service (Service). 2018. Methodologies used to propagate Margaritifera hembeli at Natchitoches National Fish Hatchery. U.S. Fish and Wildlife Service, Natchitoches National Fish Hatchery, Natchitoches, LA. 12 pages. U.S. Forest Service (USFS). 1999. Revised land and resource management plan Kisatchie National Forest. U.S. Forest Service, Pineville, LA. U.S. Forest Service (USFS). 2004. 2004 Survey for the Louisiana pearlshell mussel (Margaritifera hembeli) on the Evangeline Unit of the Calcasieu Ranger District, Kisatchie National Forest, Rapides Parish, LA. 15 pages. U.S. Forest Service. 2006. 2006 Survey for the Louisiana pearlshell mussel (Margaritifera hembeli) on the Catahoula Ranger District, Kisatchie National Forest, Grant Parish, LA. 8 pages. U.S. Forest Service (USFS). 2007a. 2007 Survey for the Louisiana pearlshell mussel (Margaritifera hembeli) on the Evangeline Unit of the Calcasieu Ranger District, Kisatchie National Forest, Rapides Parish, LA. 11 pages. U.S. Forest Service (USFS). 2007b. Kisatchie National Forest Travel Management Project: Claiborne, Grant, Natchitoches, Rapides, Vernon, Webster, and Winn Parishes Louisiana. Final Environmental Assessment. U.S. Forest Service, Pineville, LA. U.S. Forest Service (USFS). 2009a. 2009 Survey for the Louisiana pearlshell mussel (Margaritifera hembeli) on the Catahoula Ranger District, Kisatchie National Forest, Grant Parish, LA. 10 pages. U.S. Forest Service (USFS). 2009b. Travel Management Directives; Forest Service Manual 2350, 7700, and 7710 and Forest Service Handbook 7709.55, Final Directives. Federal Register 73:237(December 9, 2008):74689-74703. U.S. Forest Service (USFS). 2010. 2010 Survey for the Louisiana pearlshell mussel (Margaritifera hembeli) on the Evangeline Unit of the Calcasieu Ranger District, Kisatchie National Forest. 16 pages. U.S. Forest Service (USFS). 2012. 2012 Survey for the Louisiana Pearlshell Mussel (Margaritifera hembeli) on the Catahoula Ranger District, Kisatchie National Forest. 10 pages. Wachtler, K., M. Dreher-Mansur, and T. Richter. 2001. Larval Types and Early Postlarval Biology in Naiads (Unionoida). Pages 93-125 in Bauer, G. and K. Wachtler, editors. Ecological Studies: Ecology and Evolution of the Freshwater Mussels Unionoida, Vol. 145. Berlin, Germany: Springer-Verlag.

77 Warren, M.L. Jr., and M.G. Pardew. 1998. Road crossings as barriers to small-stream fish movement. Transactions of the American Fisheries Society 127:637-644. Watters, G.T., S.H. O’Dee, and S. Chordas III. 2001. Patterns of vertical migration in freshwater mussels (Bivalvia: Unionoida). Journal of Freshwater Ecology 16:541-549. White, G.C., and K.P. Burnham. 1999. Program MARK: survival estimation from populations of marked animals. Bird Study 46:sup1, S120-S139, DOI: 10.1080/00063659909477239 Wolf. S., B. Hartl, C. Carroll, M.C. Neel, and D.N. Greenwald. 2015. Beyond PVA: why recovery under the Endangered Species Act is more than population viability. BioScience 65:200-207. Yeager, M.M., D.S. Cherry, and R.J. Neves. 1994. Feeding and burrowing behaviors of juvenile rainbow mussels, Villosa iris (Bivalvia: Unionidae). Journal of the North American Benthological Society 13:217–222. Yeager, M.M., R.J. Neves, and D.S. Cherry. 2000. Competitive interactions between early life stages of Villosa iris (Bivalvia: Unionidae) and adult Asian clams (Corbicula fluminea). Pages 253–259 in P. D. Johnson and R. S. Butler (editors). Freshwater Mollusk Symposium Proceedings—Part II: Proceedings of the First Freshwater Mollusk Conservation Society Symposium, March 1999. Ohio Biological Survey, Columbus, Ohio.

78 APPENDIX A: Maps

Figure A1. Distribution of streams currently and previously occupied by Louisiana pearlshells in the Bayou Rapides management watershed

79

Figure A2. Distribution of streams currently and previously occupied by Louisiana pearlshells in the Bayou Boeuf management watershed

80

Figure A3. Distribution of streams currently and previously occupied by Louisiana pearlshells in the Black Creek management watershed .

81

Figure A4. Distribution of streams currently and previously occupied by Louisiana pearlshells in the Bayou Rigolette management watershed

82 APPENDIX B: Survey Results

Aggregation Parish Watershed Stream Ownership ‘85 ‘91 ‘98 ‘99 ‘01 ‘02 ’03 ‘04 ‘06 ‘07 ‘08 ‘09 ‘10 ‘11 ‘12 ‘13 ‘15 ‘16 ‘17 ‘18 ID BlkCr-1 Grant Black Creek Black Private 100 Creek BlkCr-10 Grant Black Creek Black Private 1 Creek BlkCr-12 Grant Black Creek Black Private Split Split Creek 2500 873, 836, 745 722.5 BlkCr-13 Grant Black Creek Black Private 282 Creek BlkCr-14 Grant Black Creek Black Private 2000 5082 4973 Creek BlkCr-15 Grant Black Creek Black Private 10 Creek BlkCr-16 Grant Black Creek Black Private 359 Creek BlkCr-2 Grant Black Creek Black Private 5000 Creek BlkCr-3 Grant Black Creek Black Private 4000 5500 Creek BlkCr-4 Grant Black Creek Black Private 325 Creek BlkCr-5 Grant Black Creek Black Private 22 Creek BlkCr-6 Grant Black Creek Black Private 489 550 390.5 Creek BlkCr-7 Grant Black Creek Black Private 0 Creek BlkCr-8 Grant Black Creek Black Private 10 Creek BlkCr-9 Grant Black Creek Black Private 0 Creek BrwnCr-10 Rapides Bayou Brown Private 291 Rapides Creek BrwnCr-8 Rapides Bayou Brown Private 26 Rapides Creek BrwnCr-9 Rapides Bayou Brown Private 2 Rapides Creek BurnyBr-1 Rapides Bayou Burney Private 1 Rapides Branch BurnyBr-2 Rapides Bayou Burney Private 0 Rapides Branch BurnyBr-3 Rapides Bayou Burney Private 0 Rapides Branch BvrCr-1 Grant Black Creek Beaver Private 0 Creek BvrCr-12 Grant Black Creek Beaver Private 326 364 173 43 44 Creek BvrCr-13 Grant Black Creek Beaver Private 730 Creek

83 Aggregation Parish Watershed Stream Ownership ‘85 ‘91 ‘98 ‘99 ‘01 ‘02 ’03 ‘04 ‘06 ‘07 ‘08 ‘09 ‘10 ‘11 ‘12 ‘13 ‘15 ‘16 ‘17 ‘18 ID BvrCr-14 Grant Black Creek Beaver Private 2 Creek BvrCr-15 Grant Black Creek Beaver Private 272 Creek BvrCr-16 Grant Black Creek Beaver Private 1673 Creek BvrCr-18 Grant Black Creek Beaver Private 79 Creek BvrCr-19 Grant Black Creek Beaver Private 173 Creek BvrCr-2 Grant Black Creek Beaver Private 0 Creek BvrCr-20 Grant Black Creek Beaver Private 218 Creek BvrCr-21 Grant Black Creek Beaver Private 111 Creek BvrCr-22 Grant Black Creek Beaver Private 1100 Creek BvrCr-23 Grant Black Creek Beaver Private 40 Creek BvrCr-24 Grant Black Creek Beaver Private 850 Creek BvrCr-3 Grant Black Creek Beaver Private 0 Creek BvrCr-4 Grant Black Creek Beaver Private 0 Creek BvrCr-5 Grant Black Creek Beaver Private 0 Creek BvrCr-6 Grant Black Creek Beaver Private 1796 Creek BvrCr-7 Grant Black Creek Beaver Private 4664 Creek BvrCr-8 Grant Black Creek Beaver Private 508 30 Creek ByuClr-1 Rapides Bayou Boeuf Bayou Private 254 Clear ByuClr-10 Rapides Bayou Boeuf Bayou Private 5 Clear ByuClr-11 Rapides Bayou Boeuf Bayou Private 60 Clear ByuClr-12 Rapides Bayou Boeuf Bayou Private 7 Clear ByuClr-13 Rapides Bayou Boeuf Bayou Private 28 Clear ByuClr-14 Rapides Bayou Boeuf Bayou Private 5 Clear ByuClr-2 Rapides Bayou Boeuf Bayou Private Split Split Clear 278, 218.5 1090 175, 182.5 482 204.5 ByuClr-3 Rapides Bayou Boeuf Bayou Private 11 Clear ByuClr-4 Rapides Bayou Boeuf Bayou Private 17 Clear

84 Aggregation Parish Watershed Stream Ownership ‘85 ‘91 ‘98 ‘99 ‘01 ‘02 ’03 ‘04 ‘06 ‘07 ‘08 ‘09 ‘10 ‘11 ‘12 ‘13 ‘15 ‘16 ‘17 ‘18 ID ByuClr-5 Rapides Bayou Boeuf Bayou Private 1686 Clear ByuClr-6 Rapides Bayou Boeuf Bayou Private 239 Clear ByuClr-7 Rapides Bayou Boeuf Bayou Private 0 Clear ByuClr-8 Rapides Bayou Boeuf Bayou Private 6 Clear ByuClr-9 Rapides Bayou Boeuf Bayou Private 57 Clear CastrCr-1 Rapides Bayou Boeuf Castor Private 0 Creek CastrCr-12.1 Rapides Bayou Boeuf Castor Private 37 ? Creek CastrCr-13 Rapides Bayou Boeuf Castor Private 200 266 273 222 Creek ChndrCr-1 Grant Bayou Chandler Private 1 Rigolette Creek ChndrCr-10 Grant Bayou Chandler Private 0 Rigolette Creek ChndrCr-2 Grant Bayou Chandler Private 3 Rigolette Creek ChndrCr-3 Grant Bayou Chandler Private 6 Rigolette Creek ChndrCr-4 Grant Bayou Chandler Private 6 Rigolette Creek ChndrCr-5 Grant Bayou Chandler Private 7 Rigolette Creek ChndrCr-6 Grant Bayou Chandler Private 10 Rigolette Creek ChndrCr-7 Grant Bayou Chandler Private 10 Rigolette Creek ChndrCr-8 Grant Bayou Chandler Private 10 Rigolette Creek ChndrCr-9 Grant Bayou Chandler Private 71 Rigolette Creek ClrBr-2 Grant Black Creek Clear Private 0 Branch ColmnBr-1 Grant Bayou Coleman Private 91 Rigolette Branch ColmnBr-10 Grant Bayou Coleman Private 229 Rigolette Branch ColmnBr-11 Grant Bayou Coleman Private Split Rigolette Branch 1192 134, 240 103 ColmnBr-12 Grant Bayou Coleman Private 878 310 245 Rigolette Branch ColmnBr-13 Grant Bayou Coleman Private 61 Rigolette Branch ColmnBr-14 Grant Bayou Coleman Private 41 Rigolette Branch ColmnBr-15 Grant Bayou Coleman Private 44 Rigolette Branch

85 Aggregation Parish Watershed Stream Ownership ‘85 ‘91 ‘98 ‘99 ‘01 ‘02 ’03 ‘04 ‘06 ‘07 ‘08 ‘09 ‘10 ‘11 ‘12 ‘13 ‘15 ‘16 ‘17 ‘18 ID ColmnBr-16 Grant Bayou Coleman Private 117 Rigolette Branch ColmnBr-2 Grant Bayou Coleman Private 153 Rigolette Branch ColmnBr-3 Grant Bayou Coleman Private 345 Rigolette Branch ColmnBr-4 Grant Bayou Coleman Private 856 121 68 Rigolette Branch ColmnBr-5 Grant Bayou Coleman Private 132 Rigolette Branch ColmnBr-6 Grant Bayou Coleman Private 330 Rigolette Branch ColmnBr-7 Grant Bayou Coleman Private 209 Rigolette Branch ColmnBr-8 Grant Bayou Coleman Private 270 152 184.5 Rigolette Branch ColmnBr-9 Grant Bayou Coleman Private 79 Rigolette Branch CL3 Grant Bayou Coleman Private 58 73.5 Rigolette Branch CypCr-2 Grant Black Creek Cypress Private 8 Creek CypCr-3 Grant Black Creek Cypress Private 0 Creek GldHol-1 Grant Black Creek Glady Private 0 Hollow GldHol-2 Grant Black Creek Glady Private 26 Hollow GldHol-3 Grant Black Creek Glady Private 121 Hollow GldHol-4 Grant Black Creek Glady Private 0 Hollow GryCr-1 Grant Bayou Gray Private 5 Rigolette Creek GryCr-2 Grant Bayou Gray Private 4 Rigolette Creek GryCr-29 Grant Bayou Gray Private 524 2000 1600 361 Rigolette Creek GryCr-3 Grant Bayou Gray Private 4 Rigolette Creek GryCr-30 Grant Bayou Gray Private 62 47 10 1 Rigolette Creek GryCr-31 Grant Bayou Gray Private 68 0 Rigolette Creek GryCr-32 Grant Bayou Gray Private 2000 2000 2000 Rigolette Creek GryCr-4 Grant Bayou Gray Private 2 Rigolette Creek GryCr-47 Grant Bayou Gray Private 187 40 41 Rigolette Creek GryCr-5 Grant Bayou Gray Private 1100 Rigolette Creek GryCr-6 Grant Bayou Gray Private 40 Rigolette Creek

86 Aggregation Parish Watershed Stream Ownership ‘85 ‘91 ‘98 ‘99 ‘01 ‘02 ’03 ‘04 ‘06 ‘07 ‘08 ‘09 ‘10 ‘11 ‘12 ‘13 ‘15 ‘16 ‘17 ‘18 ID GryCr-7 Grant Bayou Gray Private 850 Rigolette Creek HudsnCr-1 Grant Bayou Hudson Private 0 Rigolette Creek HudsnCr-2 Grant Bayou Hudson Private 0 Rigolette Creek JamsBr-2 Grant Bayou James Private 6 Rigolette Branch JamsBr-3 Grant Bayou James Private 49 Rigolette Branch JamsBr-4 Grant Bayou James Private 5 Rigolette Branch JamsBr-5 Grant Bayou James Private 20 Rigolette Branch JamsBr-6 Grant Bayou James Private 11 Rigolette Branch JamsBr-7 Grant Bayou James Private 409 Rigolette Branch JamsBr-8 Grant Bayou James Private 300 Rigolette Branch JrdnCr-1 Grant Bayou Jordan Private 460 Rigolette Creek JrdnCr-10 Grant Bayou Jordan Private 75 Rigolette Creek JrdnCr-11 Grant Bayou Jordan Private 15 Rigolette Creek JrdnCr-12 Grant Bayou Jordan Private 187 Rigolette Creek JrdnCr-13 Grant Bayou Jordan Private 189 Rigolette Creek JrdnCr-17 Grant Bayou Jordan Private 3250 Rigolette Creek JrdnCr-18 Grant Bayou Jordan Private 112 Rigolette Creek JrdnCr-19 Grant Bayou Jordan Private 2217 Rigolette Creek JrdnCr-2 Grant Bayou Jordan Private Split Rigolette Creek 125 690, 1493 310 JrdnCr-20 Grant Bayou Jordan Private 75 Rigolette Creek JrdnCr-21 Grant Bayou Jordan Private 225 Rigolette Creek JrdnCr-22 Grant Bayou Jordan Private 350 Rigolette Creek JrdnCr-23 Grant Bayou Jordan Private 55 Rigolette Creek JrdnCr-24 Grant Bayou Jordan Private 3 Rigolette Creek JrdnCr-25 Grant Bayou Jordan Private 31 Rigolette Creek JrdnCr-26 Grant Bayou Jordan Private 1 Rigolette Creek

87 Aggregation Parish Watershed Stream Ownership ‘85 ‘91 ‘98 ‘99 ‘01 ‘02 ’03 ‘04 ‘06 ‘07 ‘08 ‘09 ‘10 ‘11 ‘12 ‘13 ‘15 ‘16 ‘17 ‘18 ID JrdnCr-27 Grant Bayou Jordan Private 16 Rigolette Creek JrdnCr-28 Grant Bayou Jordan Private 0 Rigolette Creek JrdnCr-3 Grant Bayou Jordan Private 54 Rigolette Creek JrdnCr-4 Grant Bayou Jordan Private 306 282 272 Rigolette Creek JrdnCr-5 Grant Bayou Jordan Private 83 Rigolette Creek JrdnCr-6 Grant Bayou Jordan Private Split Split Rigolette Creek 879 107, 57.5, 146 154.5 JrdnCr-7 Grant Bayou Jordan Private 1300 Rigolette Creek JrdnCr-8 Grant Bayou Jordan Private 3 Rigolette Creek JrdnCr-9 Grant Bayou Jordan Private 157 Rigolette Creek LngBr-1 Rapides Bayou Boeuf Long Private 0 Branch LngBr-2 Rapides Bayou Boeuf Long Private 0 Branch LngBr-3 Rapides Bayou Boeuf Long Private 0 Branch LtlByuClr-1 Rapides Bayou Boeuf Little Private Bayou 4 Clear LtlByuClr-2 Rapides Bayou Boeuf Little Private Bayou 1 Clear LtlByuClr-3 Rapides Bayou Boeuf Little Private Bayou 0 Clear LtlByuClr-4 Rapides Bayou Boeuf Little Private Bayou 0 Clear MoccBr-1 Grant Bayou Moccasin Private 4 Rigolette Branch MoccBr-2 Grant Bayou Moccasin Private 2 Rigolette Branch MoccBr-3 Grant Bayou Moccasin Private 84 Rigolette Branch MoccBr-4 Grant Bayou Moccasin Private 78 Rigolette Branch MoccBr-42 Grant Bayou Moccasin Private 90 80 0 Rigolette Branch MoccBr-5 Grant Bayou Moccasin Private 16 Rigolette Branch MoccBr-6 Grant Bayou Moccasin Private 58 Rigolette Branch MoccBr-7 Grant Bayou Moccasin Private 346 Rigolette Branch

88 Aggregation Parish Watershed Stream Ownership ‘85 ‘91 ‘98 ‘99 ‘01 ‘02 ’03 ‘04 ‘06 ‘07 ‘08 ‘09 ‘10 ‘11 ‘12 ‘13 ‘15 ‘16 ‘17 ‘18 ID SwffCr-1 Grant Black Creek Swafford Private 0 Creek SwffCr-10 Grant Black Creek Swafford Private 340 193 130.5 Creek SwffCr-11 Grant Black Creek Swafford Private 455 426 376.5 Creek SwffCr-12 Grant Black Creek Swafford Private 1081 420 240.5 Creek SwffCr-13 Grant Black Creek Swafford Private Split Split Creek 217 158, 131.5 174 180.5 SwffCr-14 Grant Black Creek Swafford Private 1792. 2500 1937 Creek 5 SwffCr-15 Grant Black Creek Swafford Private 2000 1085 1992 Creek SwffCr-16 Grant Black Creek Swafford Private 64 Creek SwffCr-17 Grant Black Creek Swafford Private 493 Creek SwffCr-18 Grant Black Creek Swafford Private 233 Creek SwffCr-19 Grant Black Creek Swafford Private 360 Creek SwffCr-2 Grant Black Creek Swafford Private 248 Creek SwffCr-20 Grant Black Creek Swafford Private 183 Creek SwffCr-21 Grant Black Creek Swafford Private 72 Creek SwffCr-22 Grant Black Creek Swafford Private 130 Creek SwffCr-23 Grant Black Creek Swafford Private 438 Creek SwffCr-24 Grant Black Creek Swafford Private 3378 Creek SwffCr-25 Grant Black Creek Swafford Private Split Split Creek 80 526, 514.5 1030 1005 SwffCr-26 Grant Black Creek Swafford Private 69 Creek SwffCr-27 Grant Black Creek Swafford Private 32 Creek SwffCr-28 Grant Black Creek Swafford Private 252 Creek SwffCr-29 Grant Black Creek Swafford Private 85 Creek SwffCr-3 Grant Black Creek Swafford Private 110 Creek SwffCr-30 Grant Black Creek Swafford Private 11 Creek SwffCr-31 Grant Black Creek Swafford Private 141 Creek SwffCr-32 Grant Black Creek Swafford Private 61 Creek

89 Aggregation Parish Watershed Stream Ownership ‘85 ‘91 ‘98 ‘99 ‘01 ‘02 ’03 ‘04 ‘06 ‘07 ‘08 ‘09 ‘10 ‘11 ‘12 ‘13 ‘15 ‘16 ‘17 ‘18 ID SwffCr-33 Grant Black Creek Swafford Private 218 Creek SwffCr-34 Grant Black Creek Swafford Private 336 Creek SwffCr-35 Grant Black Creek Swafford Private 200 Creek SwffCr-36 Grant Black Creek Swafford Private 3 Creek SwffCr-37 Grant Black Creek Swafford Private 4 Creek SwffCr-38 Grant Black Creek Swafford Private 2 Creek SwffCr-39 Grant Black Creek Swafford Private 8 Creek SwffCr-4 Grant Black Creek Swafford Private 70 Creek SwffCr-5 Grant Black Creek Swafford Private 276 Creek SwffCr-6 Grant Black Creek Swafford Private 250 Creek SwffCr-7 Grant Black Creek Swafford Private 611 Creek SwffCr-8 Grant Black Creek Swafford Private 262 267 145 Creek SwffCr-9 Grant Black Creek Swafford Private 110 Creek ValntnCr-1 Rapides Bayou Boeuf Valentine Private 1 Creek ValntnCr-10 Rapides Bayou Boeuf Valentine Private 467 514 636 588 543 Creek ValntnCr-11 Rapides Bayou Boeuf Valentine Private 34 22 50 72 110 Creek ValntnCr-2 Rapides Bayou Boeuf Valentine Private 2 Creek ValntnCr-9 Rapides Bayou Boeuf Valentine Private 41 41 95 66 5 Creek BrwnCr-1 Rapides Bayou Brown USFS 43 60 70 29 29 2 Rapides Creek BrwnCr-2 Rapides Bayou Brown USFS 62 70 105 73 123 73 Rapides Creek BrwnCr-3 Rapides Bayou Brown USFS 67 165 309 222 94 46 136 Rapides Creek BrwnCr-4 Rapides Bayou Brown USFS 68 96 153 849 722 589 642 403 Rapides Creek BrwnCr-4.1 Rapides Bayou Brown USFS 156 145 145 127 60 Rapides Creek BrwnCr-4.2 Rapides Bayou Brown USFS 121 117 51 36 21 20 Rapides Creek BrwnCr-5 Rapides Bayou Brown USFS 40 79 395 222 273 193 Rapides Creek BrwnCr-5.1 Rapides Bayou Brown USFS 11 7 34 46 Rapides Creek BrwnCr-6 Rapides Bayou Brown USFS 120 140 95 60 32 Rapides Creek

90 Aggregation Parish Watershed Stream Ownership ‘85 ‘91 ‘98 ‘99 ‘01 ‘02 ’03 ‘04 ‘06 ‘07 ‘08 ‘09 ‘10 ‘11 ‘12 ‘13 ‘15 ‘16 ‘17 ‘18 ID BrwnCr-7 Rapides Bayou Brown USFS 128 45 45 8 27 Rapides Creek BvrCr-10 Grant Black Creek Beaver USFS 54 Creek BvrCr-11 Grant Black Creek Beaver USFS 66 Creek BvrCr-9 Grant Black Creek Beaver USFS 65 56 54 24 21 Creek ByuClr-48 Rapides Bayou Boeuf Bayou USFS 350 308 281 249 277 263 210 Clear ByuClr-49 Rapides Bayou Boeuf Bayou USFS 851 576 558 510 463 464 Clear ByuClr-50 Rapides Bayou Boeuf Bayou USFS 161 2064 1654 1611 2048 2041 2313 Clear 1 ByuClr-51 Rapides Bayou Boeuf Bayou USFS 510 624 116 95 100 95 93 72 Clear ByuClr-51.1 Rapides Bayou Boeuf Bayou USFS 111 120 99 77 70 Clear ByuClr-51.2 Rapides Bayou Boeuf Bayou USFS 178 139 277 228 181 Clear ByuClr-51.3 Rapides Bayou Boeuf Bayou USFS 46 180 205 Clear ByuClr-52 Rapides Bayou Boeuf Bayou USFS 116 705 920 737 890 525 325 304 Clear 3 ByuClr-53 Rapides Bayou Boeuf Bayou USFS 210 150 302 173 ? Clear ByuClr-54 Rapides Bayou Boeuf Bayou USFS 146 131 131 264 Clear CastrCr-14 Rapides Bayou Boeuf Castor USFS 50 250 178 125 112 42 3 2 Creek CastrCr-15 Rapides Bayou Boeuf Castor USFS 550 825 519 399 262 142 95 Creek ChndrCr-45 Grant Bayou Chandler USFS 48 20 5 Rigolette Creek ClrBr-1 Grant Black Creek Clear USFS 9 2 0 Branch CresCr-13 Grant Bayou Cress USFS 66 87 73 0 0 Rigolette Creek CresCr-44 Grant Bayou Cress USFS 52 43 23 0 Rigolette Creek CypCr-1 Grant Black Creek Cypress USFS 50 49 55 0 Creek GryCr-23 Grant Bayou Gray USFS 64 0 Rigolette Creek GryCr-24 Grant Bayou Gray USFS 179 333 129 62 27 Rigolette Creek GryCr-25 Grant Bayou Gray USFS 737 616 515 412 168 Rigolette Creek GryCr-26 Grant Bayou Gray USFS 60 0 Rigolette Creek GryCr-27 Grant Bayou Gray USFS 74 107 124 11 15 Rigolette Creek GryCr-28 Grant Bayou Gray USFS 90 99 30 22 10 Rigolette Creek

91 Aggregation Parish Watershed Stream Ownership ‘85 ‘91 ‘98 ‘99 ‘01 ‘02 ’03 ‘04 ‘06 ‘07 ‘08 ‘09 ‘10 ‘11 ‘12 ‘13 ‘15 ‘16 ‘17 ‘18 ID GryCr-33 Grant Bayou Gray USFS 102 33 12 7 0 Rigolette Creek GryCr-34 Grant Bayou Gray USFS 79 97 116 0 Rigolette Creek GryCr-35 Grant Bayou Gray USFS 79 97 116 2 4 Rigolette Creek GryCr-36 Grant Bayou Gray USFS 62 116 122 95 Rigolette Creek GryCr-37 Grant Bayou Gray USFS 115 89 61 75 116 Rigolette Creek GryCr-38 Grant Bayou Gray USFS 114 99 123 85 98 Rigolette Creek GryCr-39 Grant Bayou Gray USFS 93 121 63 80 190 Rigolette Creek GryCr-40 Grant Bayou Gray USFS 167 169 259 143 93 Rigolette Creek GryCr-41 Grant Bayou Gray USFS 82 83 103 55 85 Rigolette Creek GryCr-46 Grant Bayou Gray USFS 110 123 104 Rigolette Creek GryCr-48 Grant Bayou Gray USFS 226 65 27 Rigolette Creek HaikCr-1 Rapides Bayou Boeuf Haikey's USFS 68 21 29 15 5 Creek JamsBr-1 Grant Bayou James USFS 76 20 33 10 Rigolette Branch JrdnCr-14 Grant Bayou Jordan USFS 240 292 281 365 341 Rigolette Creek JrdnCr-15 Grant Bayou Jordan USFS 647 647 710 684 649 Rigolette Creek JrdnCr-16 Grant Bayou Jordan USFS 138 141 140 82 116 Rigolette Creek LngBr-16 Rapides Bayou Boeuf Long USFS 37 44 50 35 Branch LngBr-17 Rapides Bayou Boeuf Long USFS 176 5 0 6 Branch LngBr-18 Rapides Bayou Boeuf Long USFS 66 70 28 5 ? Branch LngBr-19 Rapides Bayou Boeuf Long USFS 156 218 308 350 235 88 Branch LngBr-20 Rapides Bayou Boeuf Long USFS 333 671 945 992 734 629 Branch LngBr-21 Rapides Bayou Boeuf Long USFS 139 88 157 246 188 145 Branch LngBr-22 Rapides Bayou Boeuf Long USFS 1000 128 165 310 464 643 596 582 Branch LngBr-23 Rapides Bayou Boeuf Long USFS 100 108 102 124 99 165 297 Branch LngBr-24 Rapides Bayou Boeuf Long USFS 2000 743 973 1096 1304 1839 1547 2374 3239 Branch LngBr-25 Rapides Bayou Boeuf Long USFS 44 29 27 10 ? Branch LngBr-26 Rapides Bayou Boeuf Long USFS 205 252 211 131 60 48 Branch

92 Aggregation Parish Watershed Stream Ownership ‘85 ‘91 ‘98 ‘99 ‘01 ‘02 ’03 ‘04 ‘06 ‘07 ‘08 ‘09 ‘10 ‘11 ‘12 ‘13 ‘15 ‘16 ‘17 ‘18 ID LngBr-27 Rapides Bayou Boeuf Long USFS 143 200 223 181 194 255 Branch LtlBrushCr-28 Rapides Bayou Boeuf Little USFS Brushy 410 303 306 258 240 260 285 Creek LtlBrushCr- Rapides Bayou Boeuf Little USFS 28.1 Brushy 62 111 115 Creek

LtlBrushCr-29 Rapides Bayou Boeuf Little USFS Brushy 227 264 257 222 268 348 Creek LtlBrushCr-30 Rapides Bayou Boeuf Little USFS Brushy 91 75 30 24 11 5 Creek LtlBrushCr- Rapides Bayou Boeuf Little USFS 30.1 Brushy 90 136 133 135 138 Creek

LtlBrushCr-31 Rapides Bayou Boeuf Little USFS Brushy 124 147 137 201 207 239 Creek LtlByuClr-47 Rapides Bayou Boeuf Little USFS Bayou 50 117 58 63 28 20 23 Clear LtlLvngCr-40 Rapides Bayou Boeuf Little USFS Loving 240 453 475 354 207 614 476 383 Creek LtlLvngCr-41 Rapides Bayou Boeuf Little USFS Loving 280 257 274 350 164 388 434 410 Creek LtlLvngCr-42 Rapides Bayou Boeuf Little USFS Loving 50 169 155 129 143 108 63 56 Creek LtlLvngCr-43 Rapides Bayou Boeuf Little USFS Loving 493 445 347 0 ? Creek LtlLvngCr-44 Rapides Bayou Boeuf Little USFS Loving 122 198 81 187 141 145 193 185 Creek LtlLvngCr-45 Rapides Bayou Boeuf Little USFS Loving 112 146 181 ? Creek LtlLvngCr-46 Rapides Bayou Boeuf Little USFS Loving 283 220 465 463 317 400 369 333 412 Creek LvngCr-32 Rapides Bayou Boeuf Loving USFS 59 84 100 137 47 117 Creek LvngCr-33 Rapides Bayou Boeuf Loving USFS 79 152 246 293 258 363 Creek LvngCr-34 Rapides Bayou Boeuf Loving USFS 783 1061 1657 2283 1553 1648 1472 Creek LvngCr-35 Rapides Bayou Boeuf Loving USFS 140 100 104 262 210 262 286 280 Creek LvngCr-35.1 Rapides Bayou Boeuf Loving USFS 45 26 6 Creek

93 Aggregation Parish Watershed Stream Ownership ‘85 ‘91 ‘98 ‘99 ‘01 ‘02 ’03 ‘04 ‘06 ‘07 ‘08 ‘09 ‘10 ‘11 ‘12 ‘13 ‘15 ‘16 ‘17 ‘18 ID LvngCr-36 Rapides Bayou Boeuf Loving USFS 50 32 105 52 131 108 234 Creek LvngCr-36.1 Rapides Bayou Boeuf Loving USFS 60 52 81 Creek LvngCr-37 Rapides Bayou Boeuf Loving USFS 250 72 88 88 114 122 32 98 Creek LvngCr-38 Rapides Bayou Boeuf Loving USFS 1000 18 17 11 15 15 Creek LvngCr-39 Rapides Bayou Boeuf Loving USFS 300 295 238 100 95 145 82 94 101 Creek LvngCr-39.1 Rapides Bayou Boeuf Loving USFS 60 107 47 64 Creek MackBr-1 Rapides Bayou Boeuf Mack USFS 380 3 0 Branch MoccBr-43 Grant Bayou Moccasin USFS 111 67 6 Rigolette Branch PattBr-8 Rapides Bayou Patterson USFS 192 88 95 88 52 28 34 56 Rapides Branch PattBr-8.1 Rapides Bayou Patterson USFS 13 5 37 7 Rapides Branch ValntnCr-12 Rapides Bayou Boeuf Valentine USFS 780 950 910 887 1050 807 1018 Creek CL1 Grant Bayou Coleman Private 121 Rigolette Branch CL2 Grant Bayou Coleman Private 152 Rigolette Branch CL3 Grant Bayou Coleman Private 57.5 Rigolette Branch CL4 Grant Bayou Coleman Private 134 Rigolette Branch CL5 Grant Bayou Coleman Private 103 Rigolette Branch CL6 Grant Bayou Coleman Private 310 Rigolette Branch J1 Grant Bayou Jordan Private 107 Rigolette Creek J2 Grant Bayou Jordan Private 146 Rigolette Creek J3 Grant Bayou Jordan Private 690 Rigolette Creek J4 Grant Bayou Jordan Private 310 Rigolette Creek J5 Grant Bayou Jordan Private 40.5 Rigolette Creek J6 Grant Bayou Jordan Private 282 Rigolette Creek B1 Grant Bayou Beaver Private 526 Rigolette Creek B2 Grant Bayou Beaver Private 1030 Rigolette Creek B3 Grant Bayou Black Private 550 Rigolette Creek B4 Grant Bayou Black Private 5082 Rigolette Creek

94 Aggregation Parish Watershed Stream Ownership ‘85 ‘91 ‘98 ‘99 ‘01 ‘02 ’03 ‘04 ‘06 ‘07 ‘08 ‘09 ‘10 ‘11 ‘12 ‘13 ‘15 ‘16 ‘17 ‘18 ID B5 Grant Bayou Black Private 873 Rigolette Creek B6 Grant Bayou Black Private 745 Rigolette Creek B7 Grant Bayou Beaver Private 420 Rigolette Creek B8 Grant Bayou Beaver Private 267 Rigolette Creek B9 Grant Bayou Beaver Private 193 Rigolette Creek B10 Grant Bayou Beaver Private 158 Rigolette Creek B11 Grant Bayou Beaver Private 174 Rigolette Creek B12 Grant Bayou Beaver Private 426 Rigolette Creek B13 Grant Bayou Beaver Private 1937 Rigolette Creek B14 Grant Bayou Beaver Private 1085 Rigolette Creek BC1 Rapides Bayou Boeuf Bayou Private 278 Clear BC2 Rapides Bayou Boeuf Bayou Private 175 Clear BC3 Rapides Bayou Boeuf Bayou Private 482 Clear

95

96 APPENDIX C: Current Resilience Factor Values Population Factors Habitat Factors Population Population Type Aggregation Score Evidence of Canopy Cover Substrate Stream Crossings Population (Number and Size) reproduction Resilience Score Metric Population, Sum of scores for Evidence Weighted average of Percent of # Poor stream crossings Extirpated, or Not a aggregation sizes: present or not, suitable canopy cover aggregations per 5 km stream length Population 1: 100 – 499 mussels since 2007 (≥50%) in a 100-ft buffer a) on gravel (or total assessed stream 2: 500 – 999 mussels between and 3 km upstream length if < 5 km) 3: ≥ 1,000 mussels of aggregations and b) all other upstream tributaries not already included. a) weighted twice as high as b) Factor Weight 2 0.5 1 0.5 1 12*1 + 0*2 + 2*3 a) 100% b) 100% Bayou Clear Population = 5/11 = 100% 18 Yes 45% 0 2.8 26*1 + 5*2 + 7*3 a) 95.4% b) 95.2% Black Creek Population = 95.3% 14/14 = 57 Yes 100% 0 3.0 4*1 + 0*2 + 0*3 a) 93.2% b) 97.2% Brown Creek Population = 94.5% 2/3 = 4 Yes 66.7% 0 2.1 1*1 + 0*2 + 0*3 a) 100% b) 95.4% Castor Creek Population = 98.5% 1/1 = 1 Yes 100% 0 2.2 3*1 + 0*2 + 0*3 a) 100% b) 98.9% 1/1.60 km assessed Coleman Population = 99.6% 6/6 = = Branch 3 No 100% 1 1.8 8*1 + 2*2 + 3*3 a) 98.7% b) 93.4% 4/18.1 km = Gray Creek Population = 96.9% 11/12 = 1.1/5km 21 Yes 92% 1.1 2.6 8*1 + 2*2 + 1*3 a) 100% b) 100% Long Branch Population = 100% 10/11 = 15 Yes 91% 0 3 9*1 + 0*2 + 1*3 a) 100% b) 100% 7/10 = Loving Creek Population = Yes 100% 70% 0 2.9

97 Population Factors Habitat Factors Population Population Type Aggregation Score Evidence of Canopy Cover Substrate Stream Crossings Population (Number and Size) reproduction Resilience Score 12 1*1 + 1*2 + 1*3 a) 100% b) 99.4% Valentine Creek Population = 99.8% 1/3 = 6 Yes 33% 0 2.4 James Branch Extirpated 0 No NA NA NA NA Little Bayou Clear Extirpated 0 No NA NA NA NA Moccasin Branch Extirpated 0 No NA NA NA NA Mack Branch Extirpated 0 No NA NA NA NA Cress Creek Not a Population 0 No NA NA NA NA Hailey’s Creek Not a Population 0 No NA NA NA NA APPENDIX D: Future Scenario Figures

98

Figure D1. Summary of 10-year future aggregation scores (frequency out of 5,000 simulation repetitions) common to all future scenarios. Vertical black lines represent the predicted median aggregation score for each population, and vertical red lines represent the current aggregation score. Where both lines are not present, they overlap.

99

Figure D2. Summary of 50-year Status Quo future scenario aggregation scores. Vertical black lines represent the predicted median aggregation score for each population, and vertical red lines represent the current aggregation score. Where both lines are not present, they overlap.

100

Figure D3. Summary of 50-year future scenario aggregation scores where transition probabilities were shifted by 5% range-wide after following the Status Quo trajectory for the first 10 years. Vertical black lines represent the predicted median aggregation score for each population, and vertical red lines represent the current aggregation score. Where both lines are not present, they overlap.

101

Figure D4. Summary of 50-year future scenario aggregation scores where transition probabilities were shifted by 10% range-wide after following the Status Quo trajectory for the first 10 years. Vertical black lines represent the predicted median aggregation score for each population, and vertical red lines represent the current aggregation score. Where both lines are not present, they overlap.

102

Figure D5. Summary of 50-year future scenario aggregation scores where transition probabilities were shifted by 10% on public lands and 15% on private lands after following the Status Quo trajectory for the first 10 years. Vertical black lines represent the predicted median aggregation score for each population, and vertical red lines represent the current aggregation score. Where both lines are not present, they overlap.

103

Figure D6. Summary of 50-year future scenario aggregation scores where transition probabilities were shifted by 10% on public lands and 20% on private lands after following the Status Quo trajectory for the first 10 years. Vertical black lines represent the predicted median aggregation score for each population, and vertical red lines represent the current aggregation score. Where both lines are not present, they overlap.

104

Figure D7. Summary of 50-year future scenario aggregation scores where transition probabilities were shifted by 5% on public lands and 15% on private lands after following the Status Quo trajectory for the first 10 years. Vertical black lines represent the predicted median aggregation score for each population, and vertical red lines represent the current aggregation score. Where both lines are not present, they overlap.

105