Freshwater mussels (family Unionidae and Margaritiferidae) are bivalves that live in lakes, streams, and wetlands across the United States. They have an interesting life cycle where adult individuals release glochidia (larval mussels) that encyst on the gills of a specific host fish until they mature and later fall off (Haag 2012). Freshwater mussels provide a myriad of valuable ecosystem services. First, mussels filter water for their food (e.g., algae and bacteria), and in the process, help cycle nutrients and improve water quality. Second, mussels provide shelter for both aquatic invertebrates and vertebrates in empty shells, and are a food source for many animals (Haag and Williams 2014). Freshwater mussels are also sensitive to anthropogenic impacts, and are therefore considered indicators of healthy aquatic environments. Unfortunately, this sensitivity contributes to a high rate of imperilment and nearly three-quarters of North America's freshwater water mussels are considered endangered, threatened, or species of greatest conservation need (Haag and Williams 2014). There are two species of native freshwater mussels in Utah, the Winged Floater and Western Pearlshell, and both are listed as species of greatest conservation need (SGCN) in the Utah Wildlife Action Plan (UWAP 2015). Both species are found in neighboring states, and range-wide, both species are considered imperiled. Winged Floater are considered vulnerable and Western Pearlshell are considered near threatened due to decreased watershed area occupancy and extent of occurrence since 1990 (Blevins et al. 2017). In Utah, some of the historical localities for these freshwater mussels were visited by UDWR biologists in recent years (2018-2021; ESMF project numbers 23, 62, 126 and 187), but these surveys were not exhaustive. New localities for these freshwater mussels are still being discovered, and more areas need to be surveyed in order to better understand the current distribution, status, and threats of these mussel species. It will be important to implement this project by FY24 so that the findings can be used to update S-Ranks for the revised UWAP in 2025. Results of this project may suggest that the two SGCN freshwater mussels are more stable than previously thought, leading to a higher S-Rank and possible removal from the SGCN list. Conversely, this study may find that they are more imperiled than previously thought. Either outcome will allow UDWR to better understand the current status of the two freshwater mussel species and move forward with appropriate conservation actions. In addition, implementing this project, along with proposed ESMF Project XX (Host-Fish Identification for Utah Freshwater Mussels), will help UDWR identify potential mussel-host fish relationships and ensure current native and sportfish management directives benefit freshwater mussels. Since freshwater mussels require specific fish hosts to complete their life cycle, fish management can directly affect the persistence of freshwater mussels. If the freshwater mussel's fish hosts are not present, they cannot reproduce, and their population will eventually die out. This project will help UDWR understand where strong and vulnerable populations are located, and with the implementation of ESMF project XX, reintroduction projects will become attainable in the future. References: Blevins, E., S. Jepsen, J. Brim Box, D. Nez, J. Howard, A. Maine, C. O'Brien. 2017. Extinction risk of western North American mussels: Anodonta nuttalliana, the Anodonta oreogonensis/kennerlyi clade, Gonidea angulata, and Margaritifera falcata. Freshwater Mollusk Biology and Conservation 20:71-88. Haag, W. R. 2012. North American freshwater mussels: natural history, ecology, and conservation. Cambridge University Press, New York, NY. Haag, W. R. and J. D. Williams. 2014. Biodiversity on the brink: an assessment of conservation strategies for North American freshwater mussels. Hydrobiologia 735: 45-60. Utah Wildlife Action Plan Joint Team (WAP). 2015. Utah Wildlife Action Plan: A plan for managing native wildlife species and their habitats to help prevent listing under the Endangered Species Act. Publication number 15-14. Utah Division of Wildlife Resources, Salt Lake City, Utah, USA. Williams, J. D., R. S. Butler.

Goal -- improve the understanding western pearlshell and winged floater distribution, general population status, and threats across UDWR's Northern, Central, and Southern regions. Objective -- conduct 205 visual-tactile surveys across 33 HUC10 basins in the Northern, Central, and Southern Regions by FY27. The breakdown of the project's total surveys and HUC10 basins per UDWR region are below: Northern Region -- 65 surveys, 13 HUC10 basins total FY24: 50 surveys, 9 HUC10 basins Central Region -- 84 surveys, 12 HUC10 basins FY24: 30 surveys - 4 HUC10 basins total Southern Region -- 56 surveys, 8 HUC10 basins total FY24: 30 surveys - 4 HUC10 basins

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1. Utah Wildlife Action plan (UWAP 2015) -- Data gaps (inadequate understanding of distribution or range) is one of the critical data gaps identified in this plan. Implementing this project will help clarify the status, distribution, and threats for Utah's native freshwater mussels, which allow UDWR to make more informed conservation decisions for these species. 2. UDWR Statewide Mollusk Conservation Strategy (Holcomb 2022). This proposed project will execute Objective 2 and Action 2.4 and 2.5. i. Objective 2 -- Conduct surveys to expand knowledge of the distribution, habitat, abundance, and threats for SGCN mollusks (with freshwater mussels being one of the highest priorities). ii. Action 2.4 -- Conduct qualitative surveys in the Raft, Bear, and Provo river drainages for Western Pearlshell. iii. Action 2.5 -- Conduct qualitative surveys for Winged Floater in areas that have not been surveyed using snorkeling gear and/or have low survey effort. Furthermore, these surveys will also provide vital information that will inform Objective 3 -- Conduct laboratory experiments to identify host-fish requirements for Western Pearlshell and Winged Floater, preferably for each major drainage or isolated water body occupied by each freshwater mussel species. References: Holcomb, K. 2022. Utah Division of Wildlife Resources Statewide Mollusk Conservation Strategy. Utah Division of Wildlife Resources, publication #22-08, Salt Lake City, Utah. Utah Wildlife Action Plan Joint Team (WAP). 2015. Utah Wildlife Action Plan: A plan for managing native wildlife species and their habitats to help prevent listing under the Endangered Species Act. Publication number 15-14. Utah Division of Wildlife Resources, Salt Lake City, Utah, USA. Williams, J. D., R. S. Butler.

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Surveys and mollusk collections will be made by UDWR biologists, so mollusk collection permits are not needed.

A total of 205 surveys will be conducted across 33 HUC10 basins. UDWR biologists prioritized survey effort in HUC10 basins across the UDWR Northern, Central, and Southern regions based on current and historical freshwater mussel observations and results of USU freshwater mussel eDNA surveys. High priority HUC10 basins will receive seven surveys and locations within each HUC10 basin will be selected non-randomly to maximize the chance of detecting freshwater mussels. Surveys efforts in FY24 will focus on high priority HUC10 basins, and in particular, priority HUC10 basins where there are anecdotal accounts of extant mussel populations that have not been thoroughly surveyed. Surveys will be conducted using visual-tactile methods (recommended in the UDWR Statewide Mollusk Strategy; Holcomb 2022). Surveyors will use snorkeling gear and hand grubbing techniques to detect mussels in the substrate of lakes, reservoirs, streams, rivers, and wetlands. Surveys will be conducted for at least one person hour (30 minutes if there are two surveyors). Surveys can be conducted longer if surveyors suspect additional time would lead to positive detection of mussels, but surveys should not exceed two person hours in most cases. This time restraint is intended to ensure survey effort is adequately spread over a larger area to better understand the mussel species distributions. Since snorkeling gear will be used, survey depth will be restricted to six feet. Surveyors will focus on examining all major habitat types in an area (e.g., range of depths, pool/riffle/run, sediment types, and vegetated areas). Surveys will be conducted during base flow conditions to maximize detection of the mussels. Surveyors will not overlap in the areas they search, and the findings of each surveyor will be recorded separately (this will allow for occupancy modeling in the future, if desired). Mussels will be held in mesh bags during the survey so that data can be recorded for each surveyor's catch at the end of the survey. At the end of the survey, each surveyor will record the mussel species present (Winged Floater, Western Pearlshell, and non-native species), number of mussels of each species, and number of live and dead individuals. Collectively, surveyors will then select 10 mussels to measure (including the smallest and largest individuals). These 10 mussels will also be checked for gravidity (are the gills puffy due to the presence of eggs or glochidia in the gills). Collecting mussel measurements and gravidity data will help determine whether the population is successfully reproducing. Empty shell vouchers (three of varying sizes) will be kept for each survey location. When larger (>50 individuals) and new populations are encountered, three live individuals (of varying sizes) will be preserved for future genetic and morphologic analyses (western Anodonta taxonomy is still in flux). Surveyors will also record date, survey time, surveyor names, location description, coordinates, survey area, water quality, habitat description, and threats for each survey site. Any non-native species that are encountered (Asian Clam, snails, crayfish, plants) and aquatic SGCN species will be recorded on the data sheet as well. Survey data will be reported to the UDWR mollusk coordinator and UDWR Natural Heritage Program at the end of each calendar year. Progress toward completing XXX surveys in XXX HUC10 basins will be evaluated annually using GIS tools. Final project outcomes will be a completion report, a freshwater mussel GIS layer that can be used for UDWR management and conservation decision making, and updated S-Ranks for Winged Floater and Western Pearlshell.

Monitoring is not an objective of this project; however, data generated from this project will be used to inform future mollusk monitoring efforts by UDWR.

This is currently a UDWR project, though there is room to bring on additional partners in the future.

This project is expected to be completed in 2-3 years. After the first year of surveys, the project will be evaluated to determine if the methods are appropriate for addressing the project objectives. For example, changes to the number of surveys per HUC10 basin, survey time, and survey method (visual-tactile vs. eDNA) needed.

Freshwater mussels are part of healthy, functional aquatic ecosystems. Any steps that UDWR takes to restore freshwater mussel populations (e.g., stream habitat improvement, dam removal) will also benefit the other aquatic invertebrates and fishes. Taking steps to prevent freshwater mussels from being listed under the Endangered Species Act will be important to reduce economic impacts to Utahns. Since freshwater mussels are associated with a variety of aquatic habitats, federally listing them could affect acquisition of water rights, groundwater pumping rates, cattle ranching practices, fishing regulations, recreation activities, and housing development.

07/01/2023

06/30/2024

2024

Goal -- improve the understanding western pearlshell and winged floater distribution, general population status, and threats across UDWR's Northern, Central, and Southern regions. Objective -- conduct visual-tactile surveys across 33 HUC10 basins in the Northern, Central, and Southern Regions by FY27. The breakdown of the project's total surveys and HUC10 basins per UDWR region are below: Northern Region Completed as of FY24: 78 surveys, 10 HUC10 basins Central Region Completed as of FY24: 23 surveys, 2 HUC10 basins Southern Region Completed as of FY24: 11 surveys, 2 HUC10 basins

There are two species of native freshwater mussels in Utah, the Winged Floater and Western Pearlshell, and both are listed as species of greatest conservation need (SGCN) in the Utah Wildlife Action Plan (UWAP 2015). Both species are found in neighboring states, and range-wide, both species are considered imperiled. Winged Floater are considered vulnerable and Western Pearlshell are considered near threatened due to decreased watershed area occupancy and extent of occurrence since 1990 (Blevins et al. 2017). In Utah, some of the historical localities for these freshwater mussels were visited by UDWR biologists in recent years (2018-2021; ESMF project numbers 23, 62, 126 and 187), but these surveys were not exhaustive. New localities for these freshwater mussels are still being discovered, and more areas need to be surveyed in order to better understand the current distribution, status, and threats of these mussel species. It will be important to implement this project by FY24 so that the findings can be used to update S-Ranks for the revised UWAP in 2025. Results of this project may suggest that the two SGCN freshwater mussels are more stable than previously thought, leading to a higher S-Rank and possible removal from the SGCN list. Conversely, this study may find that they are more imperiled than previously thought. Either outcome will allow UDWR to better understand the current status of the two freshwater mussel species and move forward with appropriate conservation actions. References: Blevins, E., S. Jepsen, J. Brim Box, D. Nez, J. Howard, A. Maine, C. O'Brien. 2017. Extinction risk of western North American mussels: Anodonta nuttalliana, the Anodonta oreogonensis/kennerlyi clade, Gonidea angulata, and Margaritifera falcata. Freshwater Mollusk Biology and Conservation 20:71-88. Haag, W. R. 2012. North American freshwater mussels: natural history, ecology, and conservation. Cambridge University Press, New York, NY. Haag, W. R. and J. D. Williams. 2014. Biodiversity on the brink: an assessment of conservation strategies for North American freshwater mussels. Hydrobiologia 735: 45-60. Utah Wildlife Action Plan Joint Team (WAP). 2015. Utah Wildlife Action Plan: A plan for managing native wildlife species and their habitats to help prevent listing under the Endangered Species Act. Publication number 15-14. Utah Division of Wildlife Resources, Salt Lake City, Utah, USA. Williams, J. D., R. S. Butler.

The results of this project will allow UDWR managers to more effectively manage and conserve Utah's two native freshwater mussel species. In addition, implementing this project will help UDWR identify potential mussel-host fish relationships and ensure current native and sportfish management directives benefit freshwater mussels. Since freshwater mussels require specific fish hosts to complete their life cycle, fish management can directly affect the persistence of freshwater mussels. If the freshwater mussel's fish hosts are not present, they cannot reproduce, and their population will eventually die out. This project will help UDWR understand where strong and vulnerable populations are located, and with the implementation host fish studies, reintroduction projects will also become attainable in the future