A systematic review of the global freshwater mussel restoration toolbox

Abstract

Abstract Halting the global decline of freshwater mussels requires an improved understanding of the restoration approaches currently in use and the identification of shortcomings to inform the development of new ones. This article reviews published evaluations of restoration efforts on the ground and those identified or proposed in the literature. This review found few reports of the effectiveness of restoration measures, and of those reported there was strong temporal and geographical bias. Reports were mostly recent and took place within mussel‐diverse regions of the Global North (i.e. North America, Europe). Efforts focused on population support encompassed relocation, translocation and population augmentation from captive breeding, and potential restoration approaches emphasized planning and prioritization. It was challenging to assess restoration success owing to differences in success metrics and varied lengths of post‐restoration monitoring. Some measures were inherently more species specific, such as population support, but some articles suggested that the use of multiple measures may allow more species to be addressed by restoration efforts. Consistent documentation and reporting of restoration measures – including failed ones – are needed to advance freshwater mussel restoration. In addition, continued work is needed to accelerate and better align the development and use of restoration approaches for freshwater mussels. Reporting of unsuccessful or partially successful attempts does not adequately reflect the long life histories of freshwater mussels. Investigation of the contexts where approaches have been effective (even partially), and concerted efforts to implement combinations of measures at a catchment scale are critical for unionids globally. As such, recommendations are posed to aid integration of research and practice to advance and further develop freshwater mussel restoration.