SFS Annual Meeting

6/06/2024  |   13:30 - 13:45   |  Salon 3/4

EFFECTS OF HABITAT ON FRESHWATER MUSSEL OCCURRENCE IN EASTERN UNITED STATES WATERSHEDS Habitat largely influences freshwater mussel presence; however, habitat-mussel relationships are often variable across space and species. An occupancy approach may help to understand habitat associated with mussel presence and absence by accounting for imperfect detection, which is a priority for focusing conservation and restoration efforts. Our study examined how habitat affects freshwater mussel occupancy and detection in the eastern United States. Data were collected by eight state partners (CT/GA/MA/MD/NC/NY/SC/VA) in the Brook Floater Working Group from 2016-2023 across 17 watersheds. Stream surveys followed a rapid assessment protocol, which includes random site selection, visual assessment of freshwater mussel presence by “lanes” (spatial replicates), and habitat collection at reach (e.g., mesohabitat, canopy, and stream temperature) and lane (e.g., depth, vegetation/algal cover, and bed texture) scales. Data were analyzed using a static occupancy model. Across all watersheds, 21 mussel species were detected. Preliminary analyses show high variability in covariates affecting mussel occupancy and detection across watersheds and species, caused in part by low occurrence of rare species. Mussel presence was positively related to increased riffle mesohabitat (A. undulata), increased distance from a road crossing (M. margaritifera), and decreased proportion of fine gravel substrate (M. margaritifera). Mussel detection was related to decreased emergent vegetation (E. complanata) and total survey effort (multiple species). The findings of this study highlight the value of regional analyses using standardized protocols to identify mussel habitat preferences.

Alexa Hershberger (Primary Presenter/Author), Organismic and Evolutionary Biology Program, Massachusetts Cooperative Fish and Wildlife Research Unit, University of Massachusetts Amherst, ahershberger@umass.edu;

Allison Roy (Co-Presenter/Co-Author), U.S. Geological Survey, Massachusetts Cooperative Fish and Wildlife Research Unit, University of Massachusetts Amherst, aroy@eco.umass.edu;

Jason Carmignani (Co-Presenter/Co-Author), The Natural Heritage & Endangered Species Program, Division of Fisheries and Wildlife, MassWildlife, jason.carmignani@state.ma.us ;

Peter Hazelton (Co-Presenter/Co-Author), Warnell School of Forestry and Natural Resources, University of Georgia, peter.hazelton@state.ma.us;

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6/06/2024  |   13:45 - 14:00   |  Salon 3/4

MORPHOLOGICAL VARIATION AND HABITAT USE PREDICT TROPHIC NICHE AREA IN FILTER-FEEDER ASSEMBLAGES Understanding the mechanisms that underly species coexistence is a fundamental goal of ecology. The physical characteristics of flowing waters and the variation within a river network provide diverse habitats and resources and therefore a big range of potential niches for aquatic organisms. Morphology can be heavily linked to habitat use as it can provide a way for organisms to adapt to different environments. Additionally, morphologically similar species are expected to occupy similar trophic niches. Freshwater mussels are a diverse and imperiled group of filter-feeders that occur in relatively stable multi-species aggregations. Mussels display great interspecific morphological variation potentially allowing them to occupy a broad range of habitats within rivers. We assessed the relationships between morphological niche space, habitat use and isotopic niche area across 22 filter-feeder assemblages in the Tennessee and Mobile River Basins in the Southeastern United States. We use a quantitative classification that grouped species into six classes based on their morphological traits. Then, we quantified morphological niche breadth for each class, as the variation in the traits used in the classification; habitat use, as the range of environmental variables where each class was found; and isotopic niche, as the standard ellipse area of ?13C and ?15N for each class across sites. We found that the breadth of morphological niche and habitat use predict the breadth of the isotopic niche for each class, suggesting that mussels that occupy a broader range of habitats, potentially facilitated by their distinct morphologies, can feed on a broader range of resources.

Irene Sanchez Gonzalez (Primary Presenter/Author), University of Alabama, irene1sanchez@gmail.com;

Garrett Hopper (Co-Presenter/Co-Author), Louisiana State University, ghopper@agcenter.lsu.edu;

Jamie Bucholz (Co-Presenter/Co-Author), University of Alabama, jbucholz@crimson.ua.edu;

Jeffrey Lozier (Co-Presenter/Co-Author), University of Alabama, jlozier@ua.edu;

Carla L. Atkinson (Co-Presenter/Co-Author), University of Alabama, clatkinson@ua.edu;

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6/06/2024  |   14:00 - 14:15   |  Salon 3/4

Drivers of Freshwater Mussel Distributions in the Northeastern United States An understanding of species distributions and their drivers is critical to successful species conservation in a changing climate. Importantly, the scale at which those distributions are assessed can influence their utility. Often, biodiversity studies are done at a small geographic scale and at the species or species richness level. However, regional assessments and more nuanced approaches to species groupings may enable more effective conservation. Regional assessments of biodiversity are valuable in that they provide a more holistic view of species distribution than localized assessments, and they can facilitate collaborative management across jurisdictions. Considering species distribution at both the species level and at the trait level may better highlight areas where at-risk species cluster. In this study, we described freshwater mussel diversity in the Northeastern U.S. and identified biological (e.g., host fish abundance), hydrological (e.g., winter flooding), water quality (e.g., nitrate concentration), and landscape (e.g., natural land cover) drivers of those distributions. We assessed species distribution individually and grouped by climate-significant traits (e.g., shell thickness, rarity). We found that some variables, such as elevation, were consistent predictors of distribution across individual species and species groups while others, such as watershed area (positively related to common but not significant for rare species) varied across trait groups. We used these groupings to identify areas (e.g., the middle reaches of the Connecticut River) that were more likely to contain species with climate vulnerable traits. Our results provide guidance on which areas in the Northeast may harbor species most vulnerable to climate change.

Rebecca O'Brien (Primary Presenter/Author), University of Massachusetts Amherst , rebeccaobrie@umass.edu;

Jason Carmignani (Co-Presenter/Co-Author), The Natural Heritage & Endangered Species Program, Division of Fisheries and Wildlife, MassWildlife, jason.carmignani@state.ma.us ;

Graziella DiRenzo (Co-Presenter/Co-Author), University of Massachusetts Amherst , gdirenzo@umass.edu;

Rebeca Quiñones (Co-Presenter/Co-Author), Massachusetts Wildlife, rebecca.quinones@mass.gov;

Todd Richards (Co-Presenter/Co-Author), Massachusetts Division of Fisheries and Wildlife , todd.richards@state.ma.us;

Jennifer Rogers (Co-Presenter/Co-Author), University of Massachusetts Amherst , jenrogers@umass.edu;

Allison Roy (Co-Presenter/Co-Author), U.S. Geological Survey, Massachusetts Cooperative Fish and Wildlife Research Unit, University of Massachusetts Amherst, aroy@eco.umass.edu;

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6/06/2024  |   14:15 - 14:30   |  Salon 3/4

Native freshwater mussel distribution in tributaries of the Colorado River downstream of Longhorn Dam near Austin, Texas, USA Native freshwater mussels provide critical ecological services and are facing significant declines in Texas with nearly 30% of the 52 recognized taxa currently listed as threatened or endangered at the state or federal level with more under consideration for listing. This decline has been attributed to a variety of anthropogenic factors including habitat loss and degradation, environmental pollution, flow management/attenuation, and invasive species. As the city of Austin expands and develops at unprecedented rates, it becomes critically important to document unionid populations within Austin’s creeks for monitoring and conservation of ecosystem services. In June through November 2018 the City of Austin’s Watershed Protection Department (WPD) conducted surveys in tributaries of the Colorado River downstream of Longhorn Dam to document unionid species presence, distribution, density, and diversity. Our study documented evidence of thirteen species of unionids with extant individuals documented at 30 of the 89 sites surveyed (34%) from 9 species. Overall, the status of native freshwater mussels in tributaries of the Colorado River downstream of Longhorn Dam do not appear to be diverse or abundant, but rather dominated by a few species with shared life history traits. Of particular interest, one live Texas Fatmucket (Lampsilis bracteata), a candidate for listing under the Endangered Species Act, was observed and documented with DNA analysis. This study may provide the foundation for future studies and policies relevant to the success of native mussels within Austin’s waterways.

Bianca Perez (Primary Presenter/Author), City of Austin, Bianca.Perez@austintexas.gov;

Ashley Seagroves Ruppel (Co-Presenter/Co-Author), USFWS, Ashley_S_Ruppel@fws.gov;

Liz Johnston (Co-Presenter/Co-Author), City of Austin, Liz.Johnston@austintexas.gov;

Andrew Clamann (Co-Presenter/Co-Author), City of Austin, Andrew.Clamann@austintexas.gov;

Aaron Richter (Co-Presenter/Co-Author), LCRA, Aaron.Richter@LCRA.org;

Mateo Scoggins (Co-Presenter/Co-Author), City of Austin, Mateo.Scoggins@austintexas.gov;

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6/06/2024  |   14:30 - 14:45   |  Salon 3/4

Can high freshwater mussel density and large mussel size restrict juvenile recruitment? Freshwater mussels are important components of stream ecosystems yet are threatened worldwide. An understanding of the factors that influence their abundance and distribution is important for their conservation. While factors such as habitat loss, water pollution, dams, and non-native species have been examined related to their survival, there has been little research on how competition among these organisms may affect successful recruitment. In this study, we examined the population structure of a high-density mussel (up to an average of 135 mussels/m2) assemblage below a small dam in Minnesota, USA. Mussels were quantitatively sampled using 0.25 m2 quadrats. We found that over 1998-2010 total density of the assemblage was stable, the dominant species, Actinonaias ligamentina, consisted of large adults (mean shell length > 107 mm), and there was little evidence of recruitment (3.5-8.2% of individuals < 70 mm). However, by 2022 the density of mussels in this assemblage declined by 60%, including large individuals of A. ligamentina (mean shell length 87 mm). There was a concurrent increase in recruitment of A. ligamentina during this period (26.8% < 70 mm). We suggest that competition for food, space, or both may have limited recruitment and with the loss of large A. ligamentina, resources and space became available for juveniles to establish. This research has implications for both dam removal and mussel relocations as conservation strategies.

Dan Hornbach (Primary Presenter/Author), Macalester College, hornbach@macalester.edu;

Bernard Sietman (Co-Presenter/Co-Author), Minnesota Department of Natural Resources, bernard.sietman@state.mn.us;

Jillian Fedarick (Co-Presenter/Co-Author), University of Maine, jillian.fedarick@maine.edu;

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6/06/2024  |   14:45 - 15:00   |  Salon 3/4

Emerging patterns from the Mussel Host Database: strengths, weaknesses, opportunities and threats for freshwater fish and mussel conservation Freshwater fishes and mussels are diverse and abundant constituents of freshwater ecosystems, and the interactions between these two omnipresent assemblages are important to many aspects of ecology. Freshwater mussels are obligate parasites of fishes, thus fishes are essential to maintaining mussel populations by facilitating reproduction and dispersal. The Freshwater Mussel Host Database, hosted and maintained by the Illinois Natural History Survey is an extensive, open-access resource aimed at standardizing and synthesizing published host-parasite observations between mussels and vertebrate hosts. Given the size, scope, and widespread use of this critical resource we sought to provide a high-level review of the database to identify data strengths, weaknesses, opportunities, and emergent patterns. Strengths include records of 386 host species for 185 mussel species from six continents. There is a strong geographic bias toward North American taxa and the identification of ‘physiological’ hosts rather than ecological hosts. Opportunities to identify mussel-host relationships in natural settings and to improve knowledge in understudied regions exist, but allocating resources and support to this work is needed. We consider applying the generalized use of the term ‘hosts’ from laboratory experiments to assess in situ interactions and conservation planning based on laboratory experiments a potential threat, as investigating mussel population-specific hosts may better inform research aimed at creating conditions for self-sustaining mussel populations. The Freshwater Mussel Host Database provides a strong foundation to launch coordinated efforts by fish and mussel conservation and management groups to better understand and manage each group and their interactions.

Garrett Hopper (Primary Presenter/Author), Louisiana State University, ghopper@agcenter.lsu.edu;

John Pfieffer (Co-Presenter/Co-Author), National Museum of Natural History, Smithsonian Institution, pfiefferj@si.edu;

Ayla Skorupa (Co-Presenter/Co-Author), Department of Environmental Conservation, University of Massachusetts, askorupa@umass.edu;

Peter Hazelton (Co-Presenter/Co-Author), Warnell School of Forestry and Natural Resources, University of Georgia, peter.hazelton@state.ma.us;

Carla L. Atkinson (Co-Presenter/Co-Author), The University of Alabama, carla.l.atkinson@ua.edu;

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