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There is a hero amongst us in every river and stream system across North America, though discreet and unassuming, as it supports underwater ecosystems. In the journey we are about to explore, our hero is the mighty freshwater mussel. Mussels are essential to aquatic environments and are considered “ecosystem engineers” due to their ability to modify aquatic habitat, making environmental conditions more suitable for themselves and other organisms. Mussels also act as indicator organisms, and their abundance, or decline, and condition, can inform us of the health of an aquatic system.

There are many mussel species in peril right now, and federal, state, and provincial agencies are tasked with maintaining these overlooked natural resources. Conservation of protected and listed mussel species is often necessary during dewatering of aquatic habitats, and therefore some dam owners may find themselves in a unique situation when it comes to endangered or at-risk mussel species in their jurisdictions as they approach needed dewatering for infrastructure maintenance and/or dam removal.

What is a Mussel Rescue?

As the water level recedes at a project site, mussels can become exposed to the air and lose connection to the main waterbody, which could result in harm to important species. A mussel rescue includes an organized team of environmental scientists and dedicated stakeholders who plan and execute the removal of vulnerable mussel species when the mussel habitats must be dewatered. In some instances, mussels are manually removed from the area before dewatering and relocated to other areas with suitable habitat where they can thrive.

Other methods may include temporarily holding mussels until their habitat is under water again, and then returning the mussels to their original habitat, or permanent relocation to suitable habitat within the same or nearby waterbody.

Why Consider a Mussel Rescue?

Projects that require dewatering may or may not need a mussel rescue. If dewatering  needs to happen, there are ways to mitigate how that will affect species at risk. For example, if a review of potentially affected habitat should reveal that the proposed dewatered zone may not provide suitable substrates for mussels, then a survey may not be necessary, or there may be adequate historic data to confirm whether mussels are known to be present in the affected area. The need for mussel relocation is typically dictated by the agency responsible for approving any required state, provincial, or federal permits.

Factors to be Considered

The species and abundance of mussels located in the project area.

• Project specific risk(s) to the mussels (e.g., dewatering, burial, crushing).
• Bathymetric and substrate information is helpful to understand how much habitat may be exposed by the drawdown and how quickly, as well as inform on areas likely to have mussels present based on suitable substrate.
• Access to the area of work and mussel survey/relocation area.
• The rate of draw down and exposure of substrates.
• Duration of the exposure or how long the area will remain dewatered.
• Suitable areas for potential temporary or permanent relocation of rescued mussels.
• Time of year and water temperature

The level of effort should be evaluated to determine the appropriate resources needed to canvas the area and collect stranded mussels in a timely matter. The level of effort for a mussel rescue will be related to the amount of habitat that will be dewatered, and the potential number of individual mussels that will be targeted. There is a limited amount of time for scientists to respond to the action of saving the mussels. Many mussels, especially sensitive species, cannot survive for extended periods of time when exposed.

Meeting the Mentor

The mentors of our story are scientists with technical expertise who have the superhero ability to identify mussel species, using both visual and tactile inspections. A team of biologists, planners, and subject matter experts is responsible for the overall mussel rescue. Volunteers may also be organized and trained as mentors to help with the rescue as part of the plan. Mentors come in many shapes and sizes including divers, snorkelers, waders, paddlers, walkers, observers, and floaters.

The mentors will methodically search the area to find mussels in need of rescuing. Large areas can be divided into smaller sections so that mentors can better focus on locating individuals, as it is easy to overlook mussels that blend in with their surroundings. Effort can be focused in areas of suitable habitat where mussels are likely to occur. The search often focuses on newly dewatered areas around the perimeter as the water recedes. This approach helps to minimize the duration in which mussels are subject to dewatered conditions.

The mentors ensure that our heroes, mussels, are not left out of the water for too long. The rescued mussels are kept safe, with continuous water exposure as they move through a series of tests and paths. The mussels are identified by species, which requires an examination ofthe exterior shell. Rescuers must consider air temperatures, as the threat to exposed mussels increases during hot weather. Collection containers can be filled with water, or wet burlap and ice packs. When collection buckets, baskets, coolers, or bags get close to mussel holding capacity, the mussels are transferred to a holding facility.

If a containment is not available, or if the waterbody will not be completely dewatered, then mussels can be moved to an area that will remain watered for temporary holding or permanent relocation. This may include relocating mussels to adjacent waterbodies with suitable habitat.

The Reward

As our hero returns to the habitat in which it came, and the journey concludes, our mentors can be comforted by the fact that the mussel rescue was a success. Throughout all the trials and tribulations, our hero has remained safe thanks to its mentors, and it can now bury back into its mussel bed to continue its place in the ecosystem.

Despite the challenges faced, our hero had to go through the journey in order to survive and, hopefully, now thrive. The experience has also aided in an evolution through education on the power to implement such a rescue.

Throughout the hero’s journey, the lessons taught are vast – taking the plunge when the call to action occurs, staying resilient through challenges, and ending in the same place that the adventure began.

Kleinschmidt has performed many mussel studies and rescues across North America for both owners as well as public and private organizations. Kleinschmidt performs and manages studies and analyses, and work with and/or for agencies, conservationists, and developers to mitigate adverse impacts on freshwater, estuarine, and marine aquatic resources. Their team of experts has the passion and experience to work with you to make your project a success.

To Learn More

To download the complete mussel rescue paper, please click here.

For more information, or to learn more about mussel rescue, including scheduling time to consulate with the mussel mentors, please email solutions@kleinschmidtgroup.com