We have monitored four isolated populations of the endangered freshwater Banbury Springs limpet for eight or more years. One of these populations consistently exhibited low numbers and very limited recruitment. In an effort to increase its size and reproductive vigor, we translocated 19 limpets from a large, robust population to the smaller, declining one (focal population). This translocation effort was carried out along with a small-scale habitat management effort. Post-translocation monitoring has seen the focal population increase by up to 900%, with an increase in reproduction from 6% to 33–55% annually. Limpet densities in the focal population also have increased from 5.5 m^–2 to 43 m^–2 post-translocation, reaching densities seen in more stable populations. The augmentation of additional individuals, in addition to ongoing habitat management efforts, likely played an important role in the observed increases. The observed recruitment also suggests some level of increased genetic vigor following the translocation, but we lack the data to fully support a genetic rescue effect. Although translocation and augmentation of isolated and declining populations should be approached cautiously, our results support a growing body of literature that suggests the shortcomings associated with these techniques may have been overstated in the earlier literature. If done properly, their use can provide important conservation gains for small and isolated populations of sensitive species.

The freshwater mussel fauna of the Barren River system in Kentucky is well documented, but information on mussel occurrence in the Tennessee portion of the system was lacking. We conducted mussel surveys at 56 sites in 22 streams in the Barren River system in Tennessee. We found six species at 14 sites: Alasmidonta viridis (Slippershell), Fusconaia flava (Wabash Pigtoe), Lampsilis cardium (Plain Pocketbook), Lampsilis siliquoidea (Fatmucket), Pyganodon grandis (Giant Floater), and Villosa ortmanni (Kentucky Creekshell). Our records of V. ortmanni are the first reports of this species from Tennessee, and our records of L. siliquoidea considerably expand the known range of that species in the state. We found live or freshly dead V. ortmanni at five sites, and at least two sites supported relatively large populations with evidence of recent recruitment. These observations represent important information for the conservation of this imperiled species. Overall, mussel populations in the Barren River system of Tennessee were small and scattered, which may be due, in part, to the lower mussel abundance typical of headwater streams. However, the occurrence of widespread mussel declines in this region suggests that human factors may have further reduced mussel abundance.

Standard laboratory sediment toxicity methods have been adapted for conducting toxicity tests with juvenile freshwater mussels. However, studies looking at juvenile mussel burrowing behavior at the water-sediment interface are limited. Juvenile mussels burrow in sediment for the first 0 to 4 yr of life but also may inhabit the sediment-water interface. The objective of this study was to evaluate burrowing behavior of various species and ages of juvenile freshwater mussels in three control sediments: West Bearskin Lake, Spring River, and coarse commercial sand. Species tested included (1) Fatmucket (Lampsilis siliquoidea), (2) Notched Rainbow (Villosa constricta), (3) Washboard (Megalonaias nervosa), (4) Rainbow (Villosa iris), (5) Arkansas Fatmucket (Lampsilis powellii), and (6) Oregon Floater (Anodonta oregonensis). Greater than 95% of the mussels burrowed into test sediment within 15 min. Across species, life stage, and substrate type, most mussels were recovered from the upper layers of sediment (91% at a sediment depth of 3.4 mm or less), and only 2% of the mussels were recovered at a depth >5.1 mm. No mussels were recovered from a depth >6.8 mm. There was no difference in mussel burrowing depth at 4 h versus 24 h across species, age, and sediment type. Two ages of Fatmucket burrowed to a significantly greater depth in the West Bearskin Lake sediment compared to the Spring River sediment or Coarse Sand. However, there was no significant difference in mean depth across sediment type with the other five species of mussels tested. Based on species and age of mussels tested, juvenile mussels up to an age of at least 20 wk and a length of at least 5 mm readily burrow into sediment and likely would be exposed to contaminants in whole sediment and associated pore water throughout a laboratory sediment toxicity test.

Degraded water quality, particularly elevated concentrations of ammonia, chloride, and toxic metals, can be harmful to freshwater mussels. We investigated whether the contraction in Dwarf Wedgemussel (Alasmidonta heterodon) distribution that occurred between 2002 and 2012 within Browns Branch (BB), a stream within a predominantly agricultural watershed on the Coastal Plain of Maryland, was associated with these and other water-quality factors. We measured surface- and pore-water concentrations of different forms of nitrogen, orthophosphate, anions, and dissolved metals at two sites in BB for 7 mo in 2014. The upstream site (BBUP) represented the lower extent of the current Dwarf Wedgemussel population, and the downstream site (BBDO) represented the lower extent of the species' distribution observed in a 2002 survey. As a comparison, we also sampled one site in Nanjemoy Creek (NANJ), a largely forested Coastal Plain watershed where Dwarf Wedgemussel distribution exhibited no change over the same 10-yr period. We tested the hypothesis that concentrations of potentially toxic analytes were significantly higher at BBDO than at BBUP and NANJ. Total ammonia nitrogen (TAN) was the only analyte consistent with this hypothesis in both surface and pore water. Concentrations of pore-water un-ionized ammonia (UIA-N) at BBDO were below the U.S. Environmental Protection Agency's Ambient Water Quality Criterion, but they frequently exceeded 0.2 µg/L, a concentration previously associated with a lack of mussel recruitment. We recommend conducting a new mussel survey of BB to assess current condition. If range contraction is still evident, more frequent and extended sampling should be performed, including capturing high-flow events to determine if pulses of ammonia and other pollutants occur.

We observed evidence of predation on freshwater mussels during a field experiment. Mussels within the stream reach and experimental enclosures were dislodged from the sediment and shells were crushed whole, and the substrate and enclosures were extensively disturbed. Of the 12 mussel species detected in pre-experiment sampling, a Jacob's electivity index suggested that only two species (Fusconaia cerina and Elliptio arca) were positively selected for by the predator, with F. cerina being strongly preferred; other dominant species were avoided. We estimated that 1% of the mussel community and 6% of the F. cerina population was predated. We found that 70% of the experimental enclosures were disturbed, but those containing F. cerina were disturbed at a higher rate than other treatments. Water depth was a significant factor predicting disturbance of enclosures, and disturbance was not as severe for enclosures in deeper water. Based on characteristics of the event, we suggest that feral pigs (Sus scrofa) were responsible for the predation and disturbance. While only a small portion of the mussel community was predated, continued species and spatial selection could shift community structure and distribution. Feral pigs also may pose an indirect threat to mussel populations because substrate disturbance by rooting could decrease sediment stability.

Closely related unionid species often overlap in shell shape and can be difficult to accurately identify in the field. Ambiguity in identification can have serious impacts on conservation efforts and population surveys of threatened and endangered species. Truncilla donaciformis and Truncilla truncata are sister species that overlap in their distributions and frequently co-occur in central North America. Because T. donaciformis is endangered in Canada and imperiled in some US jurisdictions, co-occurrence with the morphologically similar T. truncata means that misidentification could seriously impact status assessments and recovery efforts. The objectives of this study were to (1) establish species identifications of specimens using DNA barcoding (COI), (2) determine how well traditional morphometrics and geometric morphometrics accurately discriminate between the two species, and (3) determine the accuracy of field identifications relative to molecular and morphometric identifications. Truncilla specimens from four rivers in southern Ontario were photographed and visceral mass swabs were taken. Positive identifications of all specimens were obtained through DNA barcoding and comparison with sequences from GenBank. Traditional and geometric morphometric approaches were used to assign specimens to species. Assignments generated were compared to identifications based on mtDNA barcodes, with traditional and geometric morphometric analyses found to be 90% and 99% accurate in species identifications, respectively. This study confirmed the presence of T. donaciformis in Ontario's Thames River, and revealed that all Truncilla collected for this study from the other three rivers were T. truncata. This study reinforces the utility of combining geometric morphometric analyses and DNA barcoding for identifying problematic unionid specimens.

Upper Mississippi River (UMR) resource managers need a quantitative means of evaluating the health of mussel assemblages to measure effects of management and regulatory actions, assess restoration techniques, and inform regulatory tasks. Our objective was to create a mussel community assessment tool (MCAT), consisting of a suite of metrics and scoring criteria, to consistently compare the relative health of UMR mussel assemblages. We developed an initial MCAT using quantitative data from 25 sites and 10 metrics. Metrics fell in five broad groups: conservation status and environmental sensitivity, taxonomic composition, population processes, abundance, and diversity. Metric scoring categories were based on quartile analysis: 25% scoring as good, 50% scoring as fair, and 25% scoring as poor. Scores were meant to facilitate establishing management priorities and mitigation options for the conservation of mussels. Scoring categories assumed that a healthy mussel assemblage consists of species with a variety of reproductive and life-history strategies, a low percentage of tolerant species, and a high percentage of sensitive species; shows evidence of adequate recruitment, a variety of age classes, and low mortality; and has high abundance, species richness, and species and tribe evenness. Metrics were validated using a modified Delphi technique. MCAT metrics generally reflected the professional opinions of UMR resource managers and provided a consistent evaluation technique with uniform definitions that managers could use to evaluate mussel assemblages. Additional data sets scored a priori by UMR resource managers were used to further validate metrics, resulting in data from 33 sites spanning over 980 km of the UMR. Initial and revised MCAT scores were similar, indicating that data represent the range of mussel assemblages in the UMR. Mussel assemblages could be evaluated using individual metrics or a composite score to suit management purposes. With additional data, metrics could be calibrated on a local scale or applied to other river systems.

Myriad anthropogenic factors have led to substantial declines in North America's freshwater mussel populations over the last century. A greater understanding of mussel dispersal abilities, genetic structure, and effective population sizes is imperative to improve conservation strategies. This study used microsatellites to investigate genetic structure among mussel beds and estimate effective population sizes of a common North American mussel species, Amblema plicata, in the Little River, Oklahoma. We used five microsatellite loci to genotype 270 individuals from nine mussel beds distributed throughout the river and one of its tributaries, the Glover River. Our results indicate that subpopulations of A. plicata in the Little River are genetically similar. Upstream subpopulations had less genetic diversity than sites located downstream of the confluence of the Glover and Little rivers. Downstream subpopulations were primarily assigned to the same genetic group as upstream subpopulations, but they were admixed with a second genetic group. Low flows during droughts likely influenced the observed genetic structuring in A. plicata populations in the Little River. Additionally, downstream subpopulations may be admixed with a genetically distinct population of A. plicata, which may account for the increased genetic diversity. Estimates of effective population sizes (N_e) of large mussel beds were low compared to the total abundance (N) of A. plicata. While our data have limitations, they provide important information on the spatial scale at which conservation plans should focus and the population sizes that should be sustained through relocation and restocking programs.