From October 2024 to September 2025, the FBA conducted an experiment as part of the LIFE R4ever Kent project. The purpose of the trial was to determine whether river water quality and food content in the Kent near the potential juvenile mussel release sites is sufficient to allow good mussel growth and survival. The trial involved three sites in the Kent, where at each, five mussel silos were placed. Mussel silos are 20kg concrete domes with a cavity inside, facilitating the containment of mussels in-situ whilst providing them with good flow. Mussels are placed inside ‘cups’ of PVC piping with mesh at the bottom and top to allow water to flow through – the cups can be opened to check on and retrieve the mussels when needed. One cup of 30 mussels is secured inside the cavity of each silo and positioned onto hard, stable substrate in the river. The silos work on the Bernoulli principle; water moves faster over the top of the silo, drawing water up from underneath which passes through the nested cups containing juveniles. This provides the mussels with a constant supply of oxygen and food. The silos were checked monthly to ensure they had not moved, and the mussels were all alive inside. Five silos were also maintained at the FBA’s Species Recovery Centre (SRC) to act as a control group, allowing a comparison of mussel growth and survival under known suitable conditions, to those in the River Kent around the potential release sites. At the end of the trial, the mussels were returned to the SRC where they were cleaned and measured before being placed into a rearing system to continue growing. Mussel growth and survival rates will now be analysed, combining this with water parameters at each silo site and observations made throughout the year about river and mussel conditions. This will ultimately serve to advise the FBA and R4ever Kent on the suitability of the chosen release sites.
The FBA also took this opportunity to work with a partner organisation in North Yorkshire, conducting a parallel trial in the River Esk. In collaboration with the North York Moors National Park Authority, three silo sites were selected and monitored in the Esk, providing a comparison of juvenile mussel growth and survival in two rivers in England. The findings of the Esk silo trial will provide guidance on whether juvenile Esk mussels being propagated at the Species Recovery Centre could be released into the Esk in the near future.