OARS River Log | By Sarah Kwan, OARS’ Director of Communications & Development | Published November 1 2024

On September 12th, OARS collaborated with MassWildlife to conduct a vital mussel survey in Nashoba Brook, reaching up to the base of Warner’s Pond dam. This initiative aimed to detect the presence and assess the health of native mussel populations, an often-overlooked but critical component of aquatic ecosystems.

The Role of Mussels in Aquatic Health

Mussels play an essential role in maintaining healthy waterways. Their contributions include nutrient cycling, habitat formation, and support for the broader food web. Despite these vital services, mussels are frequently underestimated in their ecological importance.

Why Survey Mussels?

Understanding mussel populations is crucial, especially in the context of dam removal projects. The potential impacts of removing a dam can vary widely depending on the site’s specific conditions. Knowing which species are present, their abundance, and the possible changes to their habitat helps inform conservation strategies. For instance, if a state-listed species like the Eastern pond mussel (Ligumia nasuta) is found, regulatory measures under the Massachusetts Endangered Species Act (MESA) may necessitate a Mussel Protection Plan to mitigate the effects of dam removal.

Challenges and Potential Benefits of Dam Removal

In the short term, dam removal can pose challenges to mussel populations, including sediment smothering, scouring flows downstream, and stranding of mussels within the former pond. Careful management is essential to prevent direct mussel mortality during this transitional phase.

However, the long-term benefits can be significant. Reconnecting waterways through dam removal can promote the movement of host fish, which is vital for mussel reproduction. This connectivity can strengthen mussel populations in the Assabet River and streams throughout the Nashoba Brook watershed.

Previous Successes in Mussel Translocation

Mussel translocation has been successfully implemented during past dam removal projects. Notable examples include:

• Mille Turner Dam, Nissitissit River (2015)
• Sucker Brook Dam, Sucker Brook (2021)
• Lyman Pond Dam, Manhan River (2022)

These cases highlight how proactive conservation measures can support mussel populations during and after dam removal.

Survey Findings and Next Steps

The survey conducted in Nashoba Brook revealed that, despite covering a considerable stretch of the stream, only a small number of mussels were found. This limited sample size means a more comprehensive assessment is needed to accurately characterize the mussel population in this area. OARS and MassWildlife plan to extend their efforts with additional surveys upstream of Warner’s Pond next year.

By continuing this work, OARS is committed to ensuring that ecological restoration projects are informed by thorough research and contribute positively to the health and resilience of our local waterways. Stay tuned for updates on these ongoing efforts and more insights into how we’re protecting and enhancing the natural beauty and biodiversity of the Sudbury, Assabet, and Concord rivers.