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The Purple Wartyback (Cyclonaias tuberculata) is a long-lived species of freshwater mussel currently found in three watersheds in Canada from lower Lake Huron through Lake St. Clair. The species was assessed by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in May 2021 as Threatened, owing to a small number of extant locations and a continuing decline of habitat quality throughout its range. The species is considered extirpated from two historical locations. The Recovery Potential Assessment provides background information and scientific advice needed to fulfill various requirements of the Species at Risk Act (SARA). This research document provides the current state of knowledge on the species including its biology, distribution, population trends, habitat requirements, and threats. Purple Wartyback is a short-term brooder that is thought to use North American catfishes (Ictaluridae) as hosts for completing its life cycle. It is found in relatively deep, medium to large rivers with moderate to swift currents and occasionally lentic areas over sand, gravel, and cobble substrates. Long-term standardized sampling data suggest that at least two of the three populations in Canada may be growing; however, more years of data are required to span a full generation of this long-lived species. A threat assessment identified the greatest threats to Purple Wartyback in Canada as pollution from agricultural and urban sources, climate change (notably droughts), aquatic invasive species (including dreissenid mussels and Round Goby (Neogobius melanostomus)), and dredging. Limited information exists evaluating the impacts of these threats on Purple Wartyback specifically. Mitigation measures and alternative activities regarding habitat-related threats are presented. Important knowledge gaps remain surrounding the full extent of its distribution within known watersheds, habitat preferences by life stage, mussel-host interactions, and physiological tolerances to environmental conditions and pollutants. [ABSTRACT FROM AUTHOR]

For freshwater fishes and mussels listed under the Species at Risk Act (SARA), a federal recovery strategy or management plan identifies recovery measures for best achieving population and distribution objectives. Recovery strategies and management plans for SARAlisted freshwater fish and mussel species often identify conservation translocation, specifically supplementation or reintroduction, as a potential approach for improving survival and/or recovery. However, there has been limited progress in undertaking conservation translocations primarily due to basic information gaps on species ecology and uncertainty about how to assess the potential ecological benefits and risks to freshwater species and ecosystems. The objectives of this research document were to: 1) identify and evaluate the potential benefits and risks of conservation translocation as a tool for improving the survival, recovery, or management of SARA-listed freshwater fish and mussel species; and, 2) identify science-based considerations and methods for determining when conservation translocation would be expected to improve the survival, recovery, or management of SARA-listed freshwater fishes and mussels. Benefits and risks of conservation translocations to the focal species and broader ecosystem components are presented, including a decision support framework for evaluating the potential benefits and risks of conservation translocation for SARA-listed freshwater fishes and mussels. The decision support framework consists of five steps: 1) Identify fundamental and means objectives for conservation translocations; 2) Assess the probability of achieving the fundamental and means objectives; 3) Identify and assess the likelihood and magnitude of unintended consequences; 4) Compile and weigh the scientific evidence to inform the translocation decision; and, 5) Implement and monitor the conservation translocation. Using the decision support framework can help determine if and when the ecological benefits of conservation translocations outweigh the uncertainties and ecological risks when attempting to improve the survival and recovery of SARA-listed freshwater fishes and mussels. Future refinement of the decision support framework would benefit from several case studies in addition to those presented in the appendices. [ABSTRACT FROM AUTHOR]

We compared the genetic diversity and structure of wild versus captive-propagated at-risk species of freshwater mussels in Canada, Lampsilis fasciola (wavy-rayed lampmussel; WRL) and Ptychobranchus fasciolaris (kidneyshell; KS), using microsatellite-generated genotypes. No significant differences were detected using Kruskal–Wallis tests that compared the genetic diversity metrics of wild and captive-propagated WRL (from 12 mothers) and KS (from seven mothers). After effective population size (Ne) was estimated, considerable overlap was found in the estimated Ne between wild and captive populations of both species. Pairwise FST and Dest values among wild WRL, hatchery-raised WRL juveniles, and across different time periods (2008–2018) were generally low (FST = 0.007–0.043, Dest = 0.005–0.282). Pairwise FST and Dest for KS were not significant and low (0.012, 0.017). When comparing captive-reared offspring with the wild population, STRUCTURE analysis revealed strong support for a single genetic population. With at least seven females contributing to brood stock, genetic diversity was maintained. Further research is needed to assess the male contribution to each glochidial brood as well as the variability of genetic diversity in individual glochidial broods. [ABSTRACT FROM AUTHOR]

[Display omitted] • The LCBD approach was applied to freshwater mussels for the first time. • Sites with high LCBD value were associated with low mussel richness. • Rare (at risk) species more likely to occur at high richness and abundance sites. • Facilitation may play a major role in structuring of mussel communities. • LCBD may fail to identify conservation sites where facilitation maintains diversity. Preservation of diversity is a key issue in many conservation efforts. It has recently been suggested that beta diversity should be considered in conservation planning and that sites with high local contribution to beta diversity (LCBD) may be valuable for conservation. Yet, such an approach has not been applied to freshwater mussels, a highly imperiled group of organisms. We used a dataset on freshwater mussel from the five largest rivers of southwestern Ontario, Canada to examine whether LCBD would be an efficient approach for assessing the conservation value of sites and compared it to more traditional conservation approaches (biomonitoring, high richness, high abundance). Sites with high LCBD value were associated with low mussel richness and were often characterized by mussels that are regionally widespread and usually abundant in lentic systems or smaller streams, limiting site selection based on beta diversity. Species at risk (including IUCN categories of Critically Endangered through Near Threatened) were more likely to occur in communities with high richness and abundance at sites chosen by the more traditional approaches. Thus, protecting sites with higher alpha diversity of mussels would also support higher gamma diversity of mussels. The provision of important ecosystem services by higher abundances of mussels which was also correlated with local richness should be considered as well. Our study suggests that there likely is an important link between high richness and abundance of mussels and the presence of species at risk which we argue is driven by facilitation (i.e., positive species interaction), an important, yet understudied, process that deserves more attention in conservation. [ABSTRACT FROM AUTHOR]

Alterations to watercourses affect connectivity in aquatic systems and can influence dispersal of aquatic biota. Dams fragment populations and act as isolating barriers, but canals create connections between waterbodies that can be used as corridors for dispersal by opportunistic invaders. The Niagara Peninsula of Ontario, Canada, has a 200-y history of canal operation, resulting in major modification of the watercourses in the region. This modification allowed numerous invasive species to enter the upper Great Lakes (e.g., sea lamprey) and probably has facilitated dispersal in native species. The purpose of our study was to explore the effects of canal and dam construction on the genetic structure of Mapleleaf (Quadrula quadrula), a widespread and relatively common species in the central Great Lakes that has been found only recently in several western Lake Ontario harbors. Establishment of Q. quadrula in Lake Ontario may have been a recent event, facilitated by the Niagara Peninsula’s history of canal operation. We used analyses of microsatellite DNA genotypes to examine the effect of canals on the genetic structure of mussel populations. Structure analysis revealed a pattern of gene flow between lakes that cannot be explained by watercourse connections prior to the creation of the Welland Canal. Evidence suggestive of historical bottlenecks at some Lake Ontario sites may indicate that these populations became established after canal creation. After considering genetic structure, hydrogeography and isolation-by-distance (IBD) analysis, the first iteration of the canal (1829–1833) is most supported as the configuration that facilitated colonization. However, weak IBD signals across canal models may signify continued gene flow across configurations. Our study demonstrates the connective effect of canals on freshwater mussel populations and has the potential to improve conservation strategies for this and other unionid species at risk. [ABSTRACT FROM AUTHOR]

We examined the effect of TSS concentration on the clearance rates ( CR ) of newly transformed juvenile and adult Lampsilis fasciola , L. siliquoidea , Ligumia nasuta , and Villosa iris , as increased total suspended solids (TSS) are thought to interfere with feeding processes. Mussel CR were measured in aerated (or swirled for juveniles) chambers at TSS concentrations up to 15 mg L − 1 for laboratory-transformed juveniles, and up to 100 mg L − 1 for adult mussels. The CR of one-week old animals increased with TSS concentration, likely due to ontological differences in feeding (pedal vs. suspension feeding) and gill development, but CR decreased monotonically with TSS concentration in older animals (two-, three- and four-week old juveniles). The CR of adult mussels were significantly lower at TSS concentrations ≥ 8 mg L − 1 , which represented a threshold in CR . Although this threshold occurred at similar concentrations across the four species, the decline in CR was largest in L. fasciola (46% compared to no-TSS control), and smallest in V. iris (21%). Differences among species are likely related to differences in the TSS and substrate found in their source rivers given that greater decline occurred for species in rivers with relatively lower TSS. The decrease in CR as TSS increased is consistent across marine and freshwater bivalves, at both juvenile and adult stages. The decrease in feeding was five times greater in juvenile compared to adult bivalves, which indicates how the vulnerability to environmental stressors differ across life stages. These results demonstrate that TSS reduces suspension feeding rates in freshwater unionids, therefore TSS should be managed to ensure their survival. [ABSTRACT FROM AUTHOR]

Watershed inventories and population monitoring are essential components of efforts to conserve and recover freshwater mussel diversity in Canada. We used two datasets to assess the efficacy of a quadrat-based sampling protocol for: (1) detecting mussel species at risk; (2) characterizing species composition; (3) providing accurate estimates of abundance; and (4) detecting changes in density. The protocol is based on a systematic design (with random starts) that samples 20% of monitoring sites with visual-tactile surface searches and excavation of 1 m2 quadrats. The first dataset included 40 sampling sites in five Ontario rivers, and the second dataset consisted of complete census sampling at two 375 m2 sites that represented contrasting mussel assemblages. Our results show that the protocol can be expected to detect the majority of species present at a site and provide accurate and precise estimates of total mussel density. Excavation was essential for detection of small individuals and to accurately estimate abundance. However, the protocol was of limited usefulness for reliable detection of most species at risk. Furthermore, imprecise density estimates precluded detection of all but the most extreme changes in density of most individual species. Meeting monitoring objectives will require either substantially greater sampling effort under the current protocol, or a fundamental revision of the sampling approach. [ABSTRACT FROM AUTHOR]

Historically, the importance of dispersal ability for the distribution of organisms has often been ignored, partly because of the difficulty of measuring it. Many unionid mussels, which have larvae that are obligate parasites (usually on fish), are endangered and the conservation and management of these mussels depend on knowledge of the main drivers of their distribution., Metacommunity theory predicts that limited dispersal should weaken the association of community composition with environmental factors. We tested this prediction by comparing the strength of association with environmental factors of (i) mussels with different dispersal abilities based on mobility of known host fish and (ii) mussels with different host infection strategies targeting fish with different mobility., Mussels with more mobile host fish showed a significantly stronger association with host fish presence and catchment (as a proximate measure for large-scale differences in environmental conditions or as a spatial component) compared to mussels with less mobile host fish. Our results thus indicate that mussel distribution is more closely linked to host fish for high-dispersal mussels, which suggests the potential for species sorting. Mussel species with weak dispersal capabilities show the opposite pattern and are therefore less able to colonise all suitable sites (species sorting with limited dispersal). Thus, the absence of mussels does not necessarily indicate unsuitable environmental conditions, but can also be caused by dispersal limitation., The impact of different host infection strategies was less clear, and differences in responses could be driven by differences in host fish or even habitat specialisation in addition to potential differences in dispersal abilities., A better knowledge of the dispersal via host fish of unionid mussels and their host infection strategies will be crucial to understanding their metacommunity dynamics, a necessary precursor for effective conservation practices. [ABSTRACT FROM AUTHOR]

Aim The successful conservation of endangered mussel communities requires, in part, a thorough understanding of the processes that shape their distribution. Therefore, we tested the prediction that (1) the distribution of host fishes explains a significant amount of variation in mussel community composition. In addition, because mussel distribution also depends on spatial processes and environmental variables, we predicted that (2) the distribution and community composition of mussels in Ontario varies across eight contiguous watersheds, flowing into three different basins of the Great Lakes (Huron, St. Clair and Erie); and (3) environmental variables also explain part of the mussel distribution. Location Watersheds in south-western Ontario, North America, Great Lakes Region. Methods Existing data on the distribution of mussels and fishes, and environmental and spatial information were compiled. Variation partitioning with redundancy analysis was used to examine what proportion of the variation in mussels' community composition was explained by watershed (as a spatial component), environmental differences and host fish presence. Redundancy analysis for mussel abundances was used to illustrate the similarities in the distributions of mussels and fishes, and the association of differences in community composition of mussels among watersheds with certain mussel species and environmental variables. Results Host fish presence explained 44%, watershed identity 28% and environmental factors 23% of the variation in mussel species composition. However, much of the explained variation was shared among these components, and all three components together explained 55% of the total variation in species composition. Even after statistically eliminating the other explanatory variables, host fish distribution was the most important group of predictor variables, although we used a subset of relevant environmental variables because of the scale of the study. Main conclusions Our results highlight the important role played by host fishes in shaping current distributions of freshwater mussels and underscore the necessity of incorporating these relationships in conservation efforts and management actions. [ABSTRACT FROM AUTHOR]

Wabash Pigtoe, Fusconaia flava, and the related Round Pigtoe, Pleurobema sintoxia, are freshwater mussels (Bivalvia: Unionidae: Pleurobemini) native to the Great Lakes region of North America. Fusconaia flava is considered widespread and relatively common while P. sintoxia is considered an imperiled species. These species are similar in shell shape and coloration and have confounded many freshwater malacologists, resulting in frequent misidentifications. We sought to determine if morphometric analyses could be used to reliably distinguish between these species. Two hundred and forty-six specimens were collected from rivers in Michigan and Ontario. For each specimen, a preliminary identification was made, shell measurements and foot color (orange or white) were documented, and photos of the left shell valve were taken. A genetic sample was taken from 133 specimens for cytochrome c oxidase subunit 1 (COI) barcoding. COI sequences were used for species identification by comparing to sequences on GenBank. Twenty-one digitized landmarks along the outline of the left valve were analyzed and compared to the results of the DNA barcoding. Landmark data correctly assigned 99.2% of specimens to their DNA-confirmed species identity, compared to 82.0% accuracy of field identifications and 77.0% accuracy for foot color. The creation of a DNA-confirmed morphometric database will aid freshwater malacologists across the Great Lakes region in differentiating between these species. [ABSTRACT FROM AUTHOR]

• Modelling unionid occurrence could enhance conservation and identify refugia. • Two large rivers in the Great Lakes were surveyed for unionids over a 3-year period. • Species distribution modelling was used to determine unionid occurrence. • Models were predictive for each river individually but not between rivers. • Modelling of these rivers may require river-specific models to inform conservation. Native freshwater mussels (Bivalvia: Unionidae) were seemingly pushed to extirpation following the establishment of dreissenid mussels in the St. Clair (SCR)–Detroit River (DR) System and the current state of unionids in the main channels of the SCR remains unknown. To assess remnant unionid populations, the DR and SCR were surveyed in 2019 and 2021, respectively, using a mixture of stratified random, historical, potential refuge, and model-selected (SCR sampling only) sites (n = 56 DR sites and 51 SCR sites). Data collected from the DR (2019) were used to create unionid species distribution models in MaxEnt, which produced the model-selected sites for sampling the SCR. A total of 14 live unionids representing 9 species were found among 7 sites in the SCR; however, the DR model projected to the SCR failed to be predictive for unionid presence in the SCR (0 % success). Additional models were created for the DR and SCR using MaxEnt and classification and regression tree (CART) Analysis to elucidate the characteristic differences between the two rivers. MaxEnt modelling showed the highest contributing variable for the DR model was water velocity (m/s) while the highest contributing variable for the SCR model was river distance to the outlet which could be one explanation for why the DR model did not accurately predict unionid presence in the SCR. Additionally, when DR and SCR data were combined in the CART model, the model failed to predict any live unionid sites from the SCR. Variability in model predictions demonstrate the characteristic differences between the DR and SCR. Therefore, model verification for both rivers specific models took place in 2022 (n = 8 DR sites and 6 SCR sites). The DR unionid species distribution model identified 3 additional sites with live unionids (38 % of predicted sites), but the SCR model did not locate any additional live unionid locations (0 % of predicted sites). This research updated our knowledge on native unionid distributions and habitat use in the DR and SCR which could contribute towards unionid conservation in the future. [ABSTRACT FROM AUTHOR]

Freshwater mussels (Bivalvia: Unionidae) are the most imperilled taxon in Canada. To facilitate species recovery efforts, an understanding of species distribution and habitat that supports species persistence is needed. Detecting mussels presents unique challenges and requires considerable effort owing to their complex life histories and widespread declines. Here, observations of the imperilled Wavyrayed Lampmussel (Lampsilis fasciola Rafinesque, 1820) from the Grand and Thames rivers, Ontario, Canada, were used to quantify species detection and occupancy probabilities, and the relationship between occupancy probability and substrate size. The best model for the data included a river-specific covariate for detection and an intercept model for occupancy. Detection probability of Wavyrayed Lampmussel was higher in the Grand River than in the Thames River. Limited variation in substrate size measurements restricted occupancy modelling, but field measurements qualitatively aligned with previous habitat descriptions. Overall, knowledge of species detection and occupancy probabilities for Wavyrayed Lampmussel will not only enhance the understanding of species distribution and habitat associations, but also ensure that the response of the species to threats and recovery actions are captured. [ABSTRACT FROM AUTHOR]

1. Growth rates were examined as potential controlling agents of unionid distributions. 2. Analyses of long-term growth in unionid shells revealed two distinct patterns. Species which dominate rivers with forested riparian vegetation (e.g. Elliptio dilatata) show slow growth throughout life, whereas species which dominate grassy rivers (e.g. Pyganodon grandis) show rapid growth during early life and achieve a smaller maximum size at a younger age. 3. Pyganodon grandis, which occurs in both river types but is much more abundant in grassy habitats, demonstrates a single growth pattern in both basin types. In contrast, Lasmigona complanata (Barnes, 1823), which occurs equally in both basin types, demonstrates two growth patterns which differ depending upon which river is inhabited. In forested rivers, L. complanata grow slow and steady, whereas in grassy rivers, these unionids grow faster and achieve maximum size earlier. 4. Short-term transplant studies of P. grandis and E. dilatata confirmed this pattern of growth for specialist species. [ABSTRACT FROM AUTHOR]

Obovaria olivaria is a species of freshwater mussel native to the Mississippi River and Laurentian Great Lakes‐St. Lawrence River drainages of North America. This mussel has experienced population declines across large parts of its distribution and is imperiled in many jurisdictions. Obovaria olivaria uses the similarly imperiled Acipenser fulvescens (Lake Sturgeon) as a host for its glochidia. We employed mitochondrial DNA sequencing and restriction site‐associated DNA sequencing (RAD‐seq) to assess patterns of genetic diversity and population structure of O. olivaria from 19 collection locations including the St. Lawrence River drainage, the Great Lakes drainage, the Upper Mississippi River drainage, the Ohioan River drainage, and the Mississippi Embayment. Heterozygosity was highest in Upper Mississippi and Great Lakes populations, followed by a reduction in diversity and relative effective population size in the St. Lawrence populations. Pairwise FST ranged from 0.00 to 0.20, and analyses of genetic structure revealed two major ancestral populations, one including all St. Lawrence River/Ottawa River sites and the other including remaining sites; however, significant admixture and isolation by river distance across the range were evident. The genetic diversity and structure of O. olivaria is consistent with the existing literature on Acipenser fulvescens and suggests that, although northern and southern O. olivaria populations are genetically distinct, genetic structure in O. olivaria is largely clinal rather than discrete across its range. Conservation and restoration efforts of O. olivaria should prioritize the maintenance and restoration of locations where O. olivaria remain, especially in northern rivers, and to ensure connectivity that will facilitate dispersal of Acipenser fulvescens and movement of encysted glochidia. [ABSTRACT FROM AUTHOR]

Captive breeding programs are widely applied by conservation practitioners as a means of conserving, reintroducing, and supplementing populations of imperilled freshwater fishes and mussels. We conducted a systematic map to provide an overview of the existing literature on the effectiveness of captive breeding and release programs. A key finding is that there is limited evaluation of the effectiveness of such programs at all three stages (i.e., broodstock collection, rearing/release methods, and post-release monitoring). We identified clusters of evidence for evaluating supplementation associated with rearing/release methods for fish growth and survival metrics, and the monitoring stage for fish genetic diversity, growth, and survival metrics, primarily focused on salmonids. However, many studies had inadequate experimental designs (i.e., lacked a comparator). Overall, there was a paucity of studies on the effectiveness of captive breeding programs for imperilled freshwater mussels, highlighting the need to make such information broadly available when studies are undertaken. Outputs from this systematic map (i.e., the map database and heatmaps) suggest that the effectiveness of captive breeding and release programs requires further systematic evaluation. [ABSTRACT FROM AUTHOR]

More than 15 years have passed since Canada's Species at Risk Act was enacted. To evaluate scientific progress in support of the Act, we identified research accomplishments up to 2017 for imperilled aquatic species in the Great Lakes – St. Lawrence River basin based on recovery documents and an expert survey, spanning 1182 activities across 68 research topics for 45 fish and mussel species. Greatest progress was observed for population ecology (38% of activities with major progress) and habitat science (28%), with comparably less progress on threats (mechanisms and impacts; 19%) and recovery (threat mitigation and reintroduction; 21%). As a result of lagging progress, threat and reintroduction topics were prioritized for a Canadian Freshwater Species at Risk Research Network (SARNET; 2017–2020), which focused on addressing key knowledge gaps with novel applications. This special issue outlines the SARNET projects, which span novel field, laboratory, and analytical activities. Continued research investment into novel and existing approaches is necessary to advance scientific achievements for fishes and mussels in support of the Species at Risk Act in Canada. [ABSTRACT FROM AUTHOR]

Effective conservation requires that species recovery measures are informed by rigorous scientific research. For imperilled freshwater fishes and mussels in Canada, numerous research gaps exist, in part owing to the need for specialized research methods. The Canadian Freshwater Species at Risk Research Network (SARNET) was formed and identified or implemented approaches to address current research gaps, including (1) captive experimental research populations, (2) nonlethal methods for estimating abundance and distribution, (3) nonlethal field methods to measure life-history parameters, (4) species distribution models informed by co-occurring species, (5) conservation physiology to inform habitat and threat science, (6) evidence syntheses to evaluate threats and recovery measures, (7) disease-transmission models to understand mussel–host relationships, (8) experimental mesocosms and manipulative experiments to evaluate key habitat stressors, (9) threat and hazard models for predictive applications, and (10) rigorous evaluation of surrogate species. Over a dozen threat- and recovery-focused SARNET research applications are summarized, demonstrating the value of a coordinated research program between academics and government to advance scientific research on, and to support the recovery of, imperilled freshwater species. [ABSTRACT FROM AUTHOR]

The reintroduction of endangered species is a potentially useful conservation strategy, which in the case of freshwater unionid mussels, must be preceded by the successful laboratory rearing of juvenile mussels on their host fishes. However, an understanding of the genetic and environmental implications of reintroductions of artificially propagated mussels is required. Unfortunately, there is a dearth of information on these issues with respect to freshwater mussels. In general, regarding the genetic effects of reintroductions, small founder populations may lead to low heterozygosity (reduced genetic variability) in the reintroduced populations, which can make them more susceptible to extinction. Captive breeding programs may also alter the genetic composition of species through artificial selection, whether intentional or unintentional. Captive breeding may also affect an individual’s interactions with conspecifics or predators by altering behaviour. Genetic problems in reintroduced populations also have the potential to affect wild populations, particularly by reducing variability among populations of the same species and eliminating local adaptation. There is also the possibility that diseases, parasites, or exotic species may be spread when populations are relocated or augmented. Recommendations related to the minimization of these impacts are presented for freshwater mussels, with the recognition that many of the issues will require additional study. [ABSTRACT FROM AUTHOR]

Bayluscide, a chemical lampricide, is used by government agencies in the Great Lakes basin to assess Sea Lamprey (Petromyzon marinus) as part of bi-national efforts to control the species. The use of granular Bayluscide has been highly successful in identifying and suppressing Sea Lamprey populations. However, the ecological risk of Bayluscide for fishes and mussels listed under Canada's Species at Risk Act and other species of conservation concern is not well understood. This document: 1) identifies potential pathways (direct, indirect) and mechanisms (physiological, non-physiological) by which the application of granular Bayluscide may influence fishes and mussels of conservation concern; 2) evaluates the relative ecological risk of applications based on four metrics (spatial distribution, application intensity, habitat associations that predispose species to exposure, toxicity); 3) identifies mitigation measures that may reduce potential impacts to non-target species; and, 4) identifies uncertainties needed to refine risk estimates. Spatial analyses indicated that between 2011 and 2017, Bayluscide applications occurred within the distribution of 21 fish and 15 mussel species of conservation concern including areas identified as critical habitat for 16 species (6 fishes, 10 mussels). For fishes, relative risk was greatest for native lampreys (Silver Lamprey [Ichthyomyzon unicuspis] and Northern Brook Lamprey [Ichthyomyzon fossor]) followed by Lake Sturgeon (Acipenser fulvescens) and Northern Madtom (Noturus stigmosus). Native lampreys exhibited high relative risk given habitat preferences and the toxicity of Bayluscide to those species. Northern Madtom ranked highly due to exposure (spatial and temporal patterns of application) and toxicity. Lake Sturgeon ranked highly due to exposure, though results were not directly comparable with other species due to assessment methods. For mussels, relative risk was greatest for Salamander Mussel (Simpsonaias ambigua), Threehorn Wartyback (Obliquaria reflexa), and Hickorynut (Obovaria olivaria). Salamander Mussel and Threehorn Wartyback ranked highly due to exposure and toxicity. A high risk ranking for Hickorynut occurred due to exposure and habitat preference. Mitigation measures to reduce the ecological consequences of Bayluscide applications are numerous and include modifying the frequency and timing of treatments, decreasing the size of application sites, and avoiding areas near critical habitat. However, the effect of potential mitigation measures should be rigorously tested to ensure that desired outcomes for species of conservation concern are realized while avoiding unintended consequences. Lastly, as reduced control effectiveness of Sea Lamprey would have undesirable effects on species of conservation concern susceptible to parasitism by Sea Lamprey (e.g., Lake Sturgeon), optimization measures may be warranted to account for such trade-offs. [ABSTRACT FROM AUTHOR]

Ligumia nasuta (Say, 1817; Eastern Pondmussel) is an imperiled freshwater mussel (Unionidae) in eastern North America. Population declines in the Laurentian Great Lakes resulting from the introduction of dreissenid mussels and habitat destruction in the 20th Century have greatly reduced and limited its distribution. To properly inform restoration and management efforts for L. nasuta , fine-scale genetic analyses must be performed on the remnant populations. This study used Illumina paired-end shotgun sequencing to identify potential microsatellite loci for L. nasuta , utilizing two samples to develop the Illumina paired-end shotgun library. Forty-eight primer pairs were tested on the remaining 24 samples. Twenty-nine of the 48 microsatellite primer sets screened were successfully amplified using 24 L. nasuta samples collected from the Great Lakes watershed. The estimated fragment size ranged from 167 to 445 base-pairs (bp) and the number of alleles per locus varied between 5 and 16 (mean = 9.7). Only five of the loci deviated significantly from Hardy–Weinberg expectations after Bonferroni corrections. The development of these new microsatellite loci will greatly facilitate future genetic studies on L. nasuta . [ABSTRACT FROM AUTHOR]