The endangered Catspaw, Epioblasma obliquata, is restricted to one known reproducing population in Killbuck Creek, Coshocton County, Ohio. Little is known about the genetic diversity of this small population, and such information is needed to help inform recovery planning. We nonlethally sampled 44 individuals of E. obliquata using buccal swabs, from which we developed and characterized 14 polymorphic microsatellite loci. Significant deviations from Hardy–Weinberg Equilibrium (HWE), showing deficiencies in heterozygotes, were observed at 6 of the 14 loci, and linkage disequilibrium (LD) was observed at 9 (∼10%) of 91 possible pairwise comparisons among loci. Allelic diversity ranged from 2 to 15 alleles per locus and averaged 7.6 alleles per locus. Observed heterozygosity per locus ranged from 0.091 to 1.000 and averaged 0.674. Possible explanations for deviations from HWE and LD could be from loci located close together on the same chromosome, segregation of null alleles, family structure within the small population, population bottlenecks, inbreeding, hermaphroditic reproduction, or some combination of these factors. Managers can use these microsatellite markers to assess and monitor genetic diversity in the remaining wild population in Killbuck Creek, prospective broodstock, hatchery-reared progeny, and reintroduced populations founded to promote recovery of the species.

The Clarion River, a tributary of the Allegheny River in northwestern Pennsylvania, underwent heavy industrialization during the late 19th and early 20th centuries. In the early 1900s, eight tanneries, 11 wood chemical plants, and a large paper mill operated on the Clarion River, releasing a cumulative 98 million liters of industrial effluent daily, in addition to the discharge of coal-mining wastes. By 1911, aquatic life was considered eliminated from the river, but its original mussel fauna was never recorded. In 1993, four living individuals of Strophitus undulatus, the Creeper, were discovered by chance near Clarington, Forest County, which constituted the first documented collection of mussels from the river. I conducted qualitative shell surveys from 2007 to 2019 at 157 sites to document past and present mussel distribution along a 55-km reach of the river. Recently dead shells, weathered shells, or living individuals of S. undulatus were encountered at 146 sites within the study reach. Relic shells of Actinonaias ligamentina were found at 12 sites, recently dead shells and one living individual of Lampsilis fasciola were found at five sites, and a single recently dead shell of Lampsilis ovata was collected. Ages of a subsample of 60 recently dead S. undulatus ranged from 2 to 16 yr (mean = 8.0 yr) and length ranged from 26.8 to 81.7 mm (mean = 29.8 mm), suggesting that natural recruitment may be occurring in the river. Source populations for recolonization of the river are unknown, but tributaries of the Clarion River are a possibility. My results suggest that the Clarion River now supports a substantial mussel population, but additional surveys are needed to provide a baseline for monitoring future recovery.

The upper Mississippi River (UMR) contains diverse, dense, and reproducing assemblages of native freshwater mussels. In the case of an injury to mussels and their habitats, such as a hazardous material spill, train derailment, or barge grounding, resource managers have few restoration strategies. Resource managers need a means to document, quantify, and mitigate adverse effects on mussels resulting from injury. Habitat equivalency analysis (HEA), developed for use with a wide variety of habitat types, is a restoration scaling technique that compares ecological services lost from injury to ecological services gained through restoration actions. The U.S. Fish and Wildlife Service and Iowa Department of Natural Resources modified the HEA for use with native mussels. The mussel HEA has been applied within the UMR to estimate the quantity of restoration needed to compensate the public for injuries to mussels due to contaminant spills and construction projects. Our objective was to describe the UMR HEA for a general audience and assess if the four biological input variables used in the mussel HEA were reasonable based on literature values. We also evaluated the performance of HEA under a range of input scenarios. Although the input estimates used in HEA were within ranges reported in the peer-reviewed literature or were supported by professional judgment in the absence of peer-reviewed literature, outcomes of the mussel HEA were highly variable and would benefit from additional research to reduce uncertainty in the biological inputs. The application of HEA to mussels provides resource managers with a tool to quantify mussel-related ecological services lost from injury and to guide restoration efforts in the UMR.

Freshwater unionid mussels produce a bilayered shell with the mineral proportion comprising an outer prismatic and an inner nacreous layer. The shell is the animals' primary structural means of protection from predators and environmental challenges; therefore, variations in shell strength and properties may lead to differences in survival. Few studies have systematically assessed shell properties in unionids. A major challenge in such work is separating effects of environment from those of evolutionary history, because ultimately, both can affect shell properties. We collected eight species of unionids within a small area of the Allegheny River, Pennsylvania, that was relatively homogeneous in substratum type and other environmental characteristics. For each species, we quantified shell thickness, including thickness of the prismatic and nacreous layers, and shell micromechanical properties (microhardness and crack propagation, a measure of fracture resistance) in three regions of the shell. Shell thickness varied dramatically among species and was about five times greater in the thickest-shelled species, Pleurobema sintoxia, than in the thinnest-shelled species, Villosa iris. Because all species experienced similar environmental conditions, variation in shell thickness can be attributed largely to evolutionary history. In contrast, microhardness and crack propagation showed little variation among species. Given that micromechanical properties are similar among species, shell strength may be largely a function of thickness. These results have conservation implications, as differences in shell thickness could reflect relative vulnerability to predators and physical conditions.

Four freshwater mussel species from the tribe Lampsilini found in the Laurentian Great Lakes region—Lampsilis fasciola (Wavy-rayed Lampmussel), Lampsilis cardium (Plain Pocketbook), Ortmanniana ligamentina (Mucket), and Lampsilis siliquoidea (Fatmucket)—have similar and variable shell morphologies that make some specimens difficult to identify in the field. Identification is further confounded by sexual dimorphism in three of the four species. We used landmark-based morphometric analyses of shell shape in conjunction with DNA barcoding to quantify shell-shape differences between the species. We collected specimens (N = 388) from Great Lakes tributaries in Michigan, USA, and Ontario, Canada. We photographed each specimen and made an initial identification in the field. We then took a tissue biopsy or swab from 248 of the specimens, sequenced a fragment of the mitochondrial cytochrome c oxidase subunit 1 (COI) gene, and confirmed identifications by comparing our sequences with sequences for all four species accessioned in GenBank. On the photographs, we digitized 21 two-dimensional landmarks along the shell margin and used multivariate methods to evaluate the correspondence of shell shape to our COI-confirmed species identifications and sex determinations. Principal-components analysis and linear-discriminant analysis of shell shape correctly identified only 77.8% of specimens to species and 72.2% to species and sex. Sex determination was particularly confounded by the similar shapes of female L. fasciola and female L. cardium specimens. This study demonstrates the limitations of using only two-dimensional valve shape in differentiating among some mussel species.