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AGE, ASYMPTOTIC SIZE, AND GROWTH CONSTANTS OF EAST TEXAS FRESHWATER UNIONID MUSSELS
Anna L. Eismont,Clinton R. Robertson, Roel R. Lopez, and Charles R. Randklev

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ABSTRACT
Age and growth information helps researchers better understand how freshwater mussels (Bivalvia: Unionida)—among the most imperiled aquatic fauna worldwide—cope with environmental change. Shell thin sectioning is the primary method for estimating age and growth. Using a low-speed saw, a thin, radial cross-section of shell is taken and then mounted on an unfrosted microscope slide and read using a dissecting microscope. Thin sectioning can be time intensive, and species-specific issues, such as crowded annuli, can complicate efforts to provide accurate estimates. To date, only 69 of the approximately 300 North American species have age and growth information. Texas illustrates this issue perfectly; population-specific growth estimates are available for only 6 of the 52 species known to occur in the state. For the remaining species, information is either unavailable or inferred from closely related congeners or populations outside the state. This is problematic because incorrect inferences about age and growth can lead to erroneous assumptions about a species’ life history, which could result in management and conservation actions that, at best, waste resources, and at worst, lead to population declines. We thin-sectioned eight different mussel species, including three species of conservation concern, then estimated growth parameters using von Bertalanffy growth curves. Our work more than doubled the number of Texas species with age and growth information from populations within the state.We found that growth serves as a good proxy for species position along a continuum contrasting higher growth and shorter lifespans versus lower growth and longer lifespans. Our results should be useful for making inferences about how species respond to environmental change.


MUSSEL INVENTORY AND POPULATION DEMOGRAPHICS OF THE FEDERALLY ENDANGERED POTAMILUS CAPAX (GREEN 1832) IN THE LOWER WABASH RIVER, ILLINOIS AND INDIANA
David F. Ford, Jacob R. Miller, and John P. Spaeth

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ABSTRACT
The Wabash River is a key component of the freshwater mussel biodiversity of the Ohio River Basin. The basin historically supported approximately 75 mussel species, but currently only 30 are thought to be extant in the mainstem. Though the basin was historically well surveyed, the limited number of recent studies have primarily been small, and the last basin-wide survey effort is already over a decade old. This situation is problematic given that several rare species were historically present and populations of the federally endangered Potamilus capax may remain. We surveyed 46 sites within the lower Wabash River (river mile 0.0 to 117.0) to characterize mussel assemblages and distributional patterns. In total, we located 996 live mussels of 23 species. The assemblage was dominated by Obliquaria reflexa, P. capax, Potamilus fragilis and Potamilus ohiensis, and shell-length frequencies indicated ongoing recruitment of several species, including P. capax (multiple size classes).We did not find any evidence of major changes in species distributions or occurrences compared to other recent surveys but we did note a shift from species with equilibrium life-history strategies to species with opportunistic strategies moving downriver. Though the lower Wabash River appears to remain a sanctuary for P. capax and other smooth-shelled species, many species that were present historically remain absent.


PIT TAG APPLICATION IN NATIVE FRESHWATER MUSSELS: CASE STUDIES ACROSS SMALL, MEDIUM, AND LARGE RIVERS
Jeremy S. Tiemann, Matthew J. Ashton, Sarah A. Douglass, Alison P. Stodola, Rachel M. Vinsel, and Teresa J. Newton

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ABSTRACT
Since their first use in the mid-1980s, external passive integrated transponder (PIT) tags have facilitated innovative investigations into multiple biological traits of animals. For native freshwater mussels, PIT tags are frequently used in capture-mark-recapture applications because they allow repeated, noninvasive sampling, are easy to apply, have high retention rates, and have negligible shortterm effects on growth and survival. Because of these traits, resource managers and scientists are using PIT-tagged animals to estimate survival and movement of mussels associated with restoration efforts. However, consistency is limited in how PIT tags are affixed, monitored, and reported. Thus, our objectives were to (1) share our collective experiences in PIT tagging mussels across three case studies in small, medium, and large rivers and (2) propose guidelines for tagging and reporting data from PIT tag studies with native freshwater mussels to facilitate comparisons across future studies. The number of studies that have marked mussels with PIT tags has increased over the past 10 years. The ability to detect mussels using PIT tags has substantially advanced research in three areas of mussel ecology: (1) estimating vital rates (e.g., growth and survival), (2) tracking movements and behaviors of captively propagated, wild, and translocated individuals, and (3) improving our understanding of life history traits, such as reproductive timing. Each case study offers insights on tagging methods, tag loss, tag retention, and monitoring frequency across multiple species that range in conservation status from common to rare.We conclude with best-practice guidelines for placing PIT tags on freshwater mussels and a list of variables that could be reported in future studies to facilitate cross-system comparisons.


IMPACTS OF PROPAGATION ON POPULATION GENETICS OF THE THREERIDGE MUSSEL AMBLEMA PLICATA (SAY, 1817)
Katie A. Miller, and Kevin J. Roe

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ABSTRACT
Freshwater mussels provide many ecosystem services, but over the past century, they have become among the most imperiled taxa in the world. Often, efforts to restore mussel populations have included the propagation and release of juveniles.We utilized microsatellites to compare the genetic diversity of propagated mussels to the source population from which the broodstock was derived. Three wildfertilized female threeridge mussels (Amblema plicata) sourced from the Cedar River watershed in Minnesota were used as broodstock. We then genetically characterized a sample from the source population, a subsample of the juvenile cohort directly after transformation (Juv-0Y), and another subsample of the juvenile cohort after 1 yr of being raised in the hatchery (Juv-1Y). After correcting for sample sizes, the Juv-0Y sample set contained the greatest allelic richness, followed by the source sample set and then the Juv-1Y sample set. All three sample sets exhibited alleles that were not shared with other samples sets, henceforth referred to as “private alleles.” Private alleles in Juv-0Y and Juv-1Y indicated the dams (mothers) were likely fertilized by males living upstream of the source population, outside of the sampling effort of this study. High levels of multiple paternity were observed in the juveniles from both subsamples. In total, 89 juveniles were estimated to have been sired by 58 males, increasing the amount of genetic variability in the population. Analyses indicated the Juv-1Y samples were produced nearly entirely from a single dam, indicating that differential mortality in the hatchery reduced the amount of genetic variability in the released population. The Juv-1Y sample was significantly differentiated from the source, suggesting the juvenile population did not fully represent the source population. This study highlights the importance of genetic monitoring of mussels in hatchery environments to maximize the genetic diversity of the propagules that are released.


FINE-SCALE HABITAT AND CO-OCCURRENCE PATTERNS OF FISH, CRAYFISH, AND MUSSELS IN THE MUSKEGON RIVER, MICHIGAN, USA
Kiara C. Cushway,and Daelynn A. Woolnough

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ABSTRACT
Although the potential for species interaction at fine spatial scales is high, research on habitat and co-occurrence patterns for multifaunal groups at fine spatial scales is lacking. Video-recorded transect surveys provide the opportunity to examine abundance and distribution of multiple taxa at fine spatial scales to identify patterns in shared habitats. We examined habitat associations and patterns of species co-occurrence for fish, crayfish, and freshwater mussels by using video transect surveys at a site in the Muskegon River, Michigan, USA, in August 2020. Our results suggest that fine-scale habitat characteristics such as depth, substrate, estimated algal density, and siltation influence the distribution and abundance of fish, crayfish, and mussels at our site. Taxa co-occurrence was mostly random across transects, although there was some indication of segregated distribution of crayfish and mussels. Despite lack of strong patterns of transect-scale co-occurrence, we also found that several host fish species co-occurred with mussel species at our site, indicating that potential required life cycle interactions between mussels and host fish could still occur. Continued study of interactions and habitat requirements at fine spatial scales can inform restoration activities and elucidate the environmental and biological filters that influence the distribution of individual organisms and multifaunal communities.