Rain or shine our scientists get out in the field to collect eDNA data that could indicate mussel presence. Immediately after a rain event the eDNA in a river may be more dilute than a sample taken after several dry sunny days.
Modeling distributions of native Western Pearlshell and Western Ridged Mussels in the Willamette River Basin, western Oregon
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By Oregon Water Science Center
September 19, 2025
Did you know Western Pearlshell mussels native to the Pacific Northwest can live up to 100 years?
Freshwater mussels can be hard to find because they nestle into riverbeds. With new tools, we can find mussels by looking for their DNA in water samples in the lab.
Freshwater mussels can be hard to find because they nestle into riverbeds. With new tools, we can find mussels by looking for their DNA in water samples in the lab.
Collecting field data
Hydrologic technicians use a ruler called a gravelometer to classify streambed particles into size classes. These data can be used to calibrate models of streambed sediment.
Hydrologic technicians use a ruler called a gravelometer to classify streambed particles into size classes. These data can be used to calibrate models of streambed sediment.
The U.S. Geological Survey is working with Tribal, federal, state, and non-profit partners to understand and predict where native Western Pearlshell and Western Ridged mussels are found in the Willamette River Basin. Freshwater mussels provide critical ecosystem services to people but are imperiled world-wide. Findings will support freshwater mussel management and conservation in the Willamette River Basin and provide a template for efforts elsewhere.
Media
Sources/Usage: Public Domain. View Media Details
Native freshwater mussels play a vital role in keeping rivers healthy by improving water quality and supporting the broader river ecosystem. Across the Pacific Northwest (PNW), there are concerns about the status of native freshwater mussels. This is particularly true in the Willamette River Basin, where rivers are heavily altered and regulated. These modifications provide critical services to local communities, such as protection from flooding, but they have also degraded the habitat and fish populations that native freshwater mussels need to complete their life cycles.
Over the past 15 years, multiple agencies across the PNW have gathered different types of mussel presence data on two culturally and ecologically important mussel species, the Western Pearlshell Mussel - Margaritifera falcata- and the Western Ridged Mussel - Gonidea angulata. Together, these data could provide powerful insights, but differences in data collection and processing techniques have made it challenging to develop a unified approach for evaluating the status of these species. To address this, the U.S. Geological Survey is working with Tribal, federal, state, and non-profit partners to develop a modeling approach that brings mussel presence data from several distinct survey methods together with river habitat data to predict where native Western Pearlshell and Western Ridged mussels may be found in the Willamette River Basin today and in the future.
This looks like:
Curating a comprehensive collection of mussel presence data for the Willamette River Basin. Data originate from surveys conducted by the US Fish and Wildlife Service, US Bureau of Land Management, US Forest Service, Oregon Department of Fish and Wildlife, Tualatin Watershed Council, the Xerces Society, and others. Data were collected using traditional visual surveys, like snorkeling, and eDNA processed with different laboratory techniques.
Building physical datasets to describe river habitats across the Willamette Basin. Datasets include streamflow, water temperature, and streambed sediment conditions – metrics capturing key river habitat conditions thought to influence where mussels are found. These river habitat conditions are shaped by river regulation and land management as well as natural differences across the Willamette Basin. Other datasets include barriers to fish passage up and down streams – such as dams, culverts, and waterfalls. Because freshwater mussels are dependent upon fish to complete their life cycles, these barriers can limit mussel distributions as well.
- Building a statistical model of freshwater mussel presence in the Willamette River Basin. The model will bring a variety of biological datasets - mussel presence - together with physical data - river habitat – in a novel way that accounts for differences in the biological datasets and places model predictions of mussel presence within the context of river management and regulation. In this way, our modeling approach facilitates decision making and the balance of human and ecosystem water needs in the Willamette River Basin.
Program information
This research is funded by the USGS Water Mission Area EcoFlows program and leverages resources and data provided by the Willamette River Basin Integrated Water Availability Assessment (IWAAs).
Integrated Water Science Basins: Willamette River
The Willamette River Basin reflects the conflicting water demands between humans and ecosystems—particularly salmon— and the challenge resource managers face throughout the Pacific Northwest.
Integrated Water Science (IWS) Basins
The U.S. Geological Survey is integrating its water science programs to better address the Nation’s greatest water resource challenges. At the heart of this effort are plans to intensively study at least 10 Integrated Water Science (IWS) basins — medium-sized watersheds (10,000-20,000 square miles) and underlying aquifers — over the next decade. The IWS basins will represent a wide range of...
Photos taken during field work.
eDNA sample collection on the South Santiam River
Rain or shine our scientists get out in the field to collect eDNA data that could indicate mussel presence. Immediately after a rain event the eDNA in a river may be more dilute than a sample taken after several dry sunny days.
Hydrologic technician uses a gravelometer
A gravelometer is a field tool used to measure and classify the size of sediment particles, like gravel, cobbles, and boulders, in streams and rivers. It’s a rectangular metal plate with different sized holes corresponding to standard grain-size classes.
A gravelometer is a field tool used to measure and classify the size of sediment particles, like gravel, cobbles, and boulders, in streams and rivers. It’s a rectangular metal plate with different sized holes corresponding to standard grain-size classes.
The U.S. Geological Survey is working with Tribal, federal, state, and non-profit partners to understand and predict where native Western Pearlshell and Western Ridged mussels are found in the Willamette River Basin. Freshwater mussels provide critical ecosystem services to people but are imperiled world-wide. Findings will support freshwater mussel management and conservation in the Willamette River Basin and provide a template for efforts elsewhere.
Media
Sources/Usage: Public Domain. View Media Details
Native freshwater mussels play a vital role in keeping rivers healthy by improving water quality and supporting the broader river ecosystem. Across the Pacific Northwest (PNW), there are concerns about the status of native freshwater mussels. This is particularly true in the Willamette River Basin, where rivers are heavily altered and regulated. These modifications provide critical services to local communities, such as protection from flooding, but they have also degraded the habitat and fish populations that native freshwater mussels need to complete their life cycles.
Over the past 15 years, multiple agencies across the PNW have gathered different types of mussel presence data on two culturally and ecologically important mussel species, the Western Pearlshell Mussel - Margaritifera falcata- and the Western Ridged Mussel - Gonidea angulata. Together, these data could provide powerful insights, but differences in data collection and processing techniques have made it challenging to develop a unified approach for evaluating the status of these species. To address this, the U.S. Geological Survey is working with Tribal, federal, state, and non-profit partners to develop a modeling approach that brings mussel presence data from several distinct survey methods together with river habitat data to predict where native Western Pearlshell and Western Ridged mussels may be found in the Willamette River Basin today and in the future.
This looks like:
Curating a comprehensive collection of mussel presence data for the Willamette River Basin. Data originate from surveys conducted by the US Fish and Wildlife Service, US Bureau of Land Management, US Forest Service, Oregon Department of Fish and Wildlife, Tualatin Watershed Council, the Xerces Society, and others. Data were collected using traditional visual surveys, like snorkeling, and eDNA processed with different laboratory techniques.
Building physical datasets to describe river habitats across the Willamette Basin. Datasets include streamflow, water temperature, and streambed sediment conditions – metrics capturing key river habitat conditions thought to influence where mussels are found. These river habitat conditions are shaped by river regulation and land management as well as natural differences across the Willamette Basin. Other datasets include barriers to fish passage up and down streams – such as dams, culverts, and waterfalls. Because freshwater mussels are dependent upon fish to complete their life cycles, these barriers can limit mussel distributions as well.
- Building a statistical model of freshwater mussel presence in the Willamette River Basin. The model will bring a variety of biological datasets - mussel presence - together with physical data - river habitat – in a novel way that accounts for differences in the biological datasets and places model predictions of mussel presence within the context of river management and regulation. In this way, our modeling approach facilitates decision making and the balance of human and ecosystem water needs in the Willamette River Basin.
Program information
This research is funded by the USGS Water Mission Area EcoFlows program and leverages resources and data provided by the Willamette River Basin Integrated Water Availability Assessment (IWAAs).
Integrated Water Science Basins: Willamette River
The Willamette River Basin reflects the conflicting water demands between humans and ecosystems—particularly salmon— and the challenge resource managers face throughout the Pacific Northwest.
Integrated Water Science (IWS) Basins
The U.S. Geological Survey is integrating its water science programs to better address the Nation’s greatest water resource challenges. At the heart of this effort are plans to intensively study at least 10 Integrated Water Science (IWS) basins — medium-sized watersheds (10,000-20,000 square miles) and underlying aquifers — over the next decade. The IWS basins will represent a wide range of...
Photos taken during field work.
eDNA sample collection on the South Santiam River
Rain or shine our scientists get out in the field to collect eDNA data that could indicate mussel presence. Immediately after a rain event the eDNA in a river may be more dilute than a sample taken after several dry sunny days.
Rain or shine our scientists get out in the field to collect eDNA data that could indicate mussel presence. Immediately after a rain event the eDNA in a river may be more dilute than a sample taken after several dry sunny days.
Hydrologic technician uses a gravelometer
A gravelometer is a field tool used to measure and classify the size of sediment particles, like gravel, cobbles, and boulders, in streams and rivers. It’s a rectangular metal plate with different sized holes corresponding to standard grain-size classes.
A gravelometer is a field tool used to measure and classify the size of sediment particles, like gravel, cobbles, and boulders, in streams and rivers. It’s a rectangular metal plate with different sized holes corresponding to standard grain-size classes.