Paetulunio fabalis (formerly Villosa fabalis) has experienced a significant reduction in its range and is listed as endangered in both the USA and Canada. Little life history or demographic information exists for the species, but such data are critical for effective conservation. We sampled four streams in the Lake Erie and Ohio River systems of the northeastern USA that support populations of P. fabalis. For each population, we present estimates of total and relative abundance based on catch-per-unit-effort (CPUE) and quadrat sampling, the percentage of recruits, sex-specific shell length, and sex ratios. We collected a total of 572 P. fabalis among the four streams, and the species was the fifth-most abundant overall in mussel assemblages. Recruits (< 20 mm shell length) were present in all streams and made up an average of 19.2% of individuals in CPUE samples and 38.2% in quadrat samples. Shell length varied among streams, but females were consistently smaller than males. Sex ratios did not differ from 1:1 at all streams. The presence of apparently large populations, vigorous recruitment, and balanced sex ratios suggest that all four streams support healthy, stable populations of P. fabalis that warrant protection.

We conducted a statewide survey of freshwater mussels (family Unionidae) in wadeable streams in South Dakota in 2014 and 2015. We conducted timed searches (2 person-hours/site) at 202 sites distributed among all 14 of the state's major river drainages. We collected a total of 605 live mussels and 543 recently dead shells, representing 13 unionid species. We found mussels in each of the 14 river drainages and at 91 of the 202 sites (45%), and we collected live mussels at 22% of the sites. Species richness varied among drainages from one to 10. Mussel species richness and abundance were higher in drainages east of the Missouri River (mean richness/site = 1.2 6 0.1, mean abundance/site = 5.5 6 1.5/h) compared with western drainages (mean richness/site = 0.2 6 0.1, mean abundance/site = 0.4 6 0.2/h). The Giant Floater was the most widespread and abundant species, occurring in all 14 river drainages and representing 62.1% of all live mussels. Overall, host generalists with an opportunistic life-history strategy dominated mussel assemblages in South Dakota, which may indicate stressful conditions, particularly in western drainages. A compilation of previous records from South Dakota revealed the former presence of 32 species in the state. However, because of differences in sample effort among studies, comparison of our estimates of species richness with estimates from previous surveys at specific sites and in six eastern drainages did not reveal consistent patterns of species loss. Our use of standardized timed-search methods provides a baseline that can be used to better assess future changes in species richness and distribution and mussel abundance.

Freshwater bivalves of the family Sphaeriidae (fingernail, pea, and pill clams) are difficult to survey and identify due to their small size and overlapping morphological traits. Environmental DNA (eDNA) metabarcoding offers a cost-effective method for assessing species richness and distributional patterns at large scales. We evaluated sphaeriid species richness and distribution at 15 sites in the Maumee River, Ohio, USA, based on two eDNA metabarcoding assays (broad and targeted), and we compared our results with those from a traditional benthic macroinvertebrate survey. We detected seven molecular operational taxonomic units (MOTUs) in the Maumee River, including Sphaerium transversum, five MOTUs representing Euglesa spp., and one MOTU representing Odhneripisidum sp. Sphaerium transversum was widely distributed, occurring at 10 sites, but Euglesa and Odhneripisidum were restricted to one to four sites in the upper river. Distributional patterns were broadly similar between both metabarcoding assays and benthic surveys. However, eDNA metabarcoding provided species-level identifications, resulting in higher species richness. Environmental DNA sampling augments and enhances traditional benthic surveys, but greater eDNA sample replication is needed to improve detection, and additional sphaeriid reference sequences are needed to improve species-level identification.

The Purple Wartyback (PWB; Cyclonaias tuberculata) is considered threatened in Canada due to the loss of populations in the Detroit River and Lake Erie and possible declines in remaining populations (Ausable, Sydenham, and Thames rivers). Many aspects of PWB life history and population ecology have not been investigated for Canadian populations. We used data from the Fisheries and Oceans Canada Unionid Monitoring and Biodiversity Observation network to estimate PWB population and life-history parameters in the Sydenham and Thames rivers. This mussel occurred at high density in the Sydenham River, but at low density in the Thames River; however, both populations exhibited positive population growth and strong recruitment. Population growth rate in the Sydenham River was 1.047 (credible interval [CI]: 1.037–1.058) from 1999 to 2015, and population growth rate in the Thames River was 1.157 (CI: 1.100–1.221) from 2004 to 2017. Estimated annual adult survival rate (mean 6 SE) from catch-curve analysis of empty shells, with measured ages, across both populations was 0.950 6 0.007. Estimated survival from catch-curve analysis of live individuals, with estimated ages, was 0.966 6 0.001 and 0.884 6 0.009 for the Sydenham and Thames rivers, respectively. Our results show that populations of PWB are robust in the Sydenham River and small but growing rapidly in the Thames River.