NatureScot Research Report 1141 - Freshwater pearl mussel survey of a river in the Trossachs

Freshwater pearl mussels were noted in the past few years in areas where they were not previously recorded and activities in the river could be damaging them. Scotland has an important population of these rare mussels, but they are very sensitive creatures to water quality, wildlife crime and physical crushing. We commissioned several surveys and produced a series of management recommendations because we found large numbers of freshwater pearl mussels all along the river and in places we would not have expected to find them. We hope to conduct further surveys in local rivers and use this information to change the way we manage the land around them in order to protect the freshwater pearl mussels.
Year of publication: 2020
Authors: McDermott, T. & Barry, S.
Cite as: McDermott, T. & Barry, S. 2020. Freshwater pearl mussel survey of a river in the Trossachs. Scottish Natural Heritage Research Report No. 1141.
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Keywords
freshwater pearl mussel; habitat; Trossachs; snorkel
Background
Surveys were conducted along a river in the Trossachs to assess the distribution and abundance of freshwater pearl mussel. The survey was in response to recent records, indicating freshwater pearl mussels may be more widespread than previously thought. Using a combination of habitat walkovers and standard and novel, snorkel-based, methods, suitable habitat was recorded and validated with surveys during the summer of 2018.
Main findings
- The distribution of the freshwater pearl mussel extends along most of the river, and across all observed river types.
- Not all suitable habitat areas are occupied; however, mussels were commonly recorded in suboptimal habitats.
- Juvenile mussels (≤ 65mm) were rare.
- Pressure from livestock causing excessive erosion and poaching, development and declines in the salmonid host are the main risks to the mussels.
- The results suggest that unrecorded mussels may be found in other channels within the catchment.
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