Craywatch: Citizen Science in the Fight Against Invasive Crayfish
Invasive alien crayfish are causing ecological and economic problems worldwide. In Belgium, seven species have now been observed.
Despite the well-known impact of these species, Flanders previously lacked a systematic overview of their distribution. Reports remained largely sporadic and fragmented. The Craywatch project, an initiative of INBO and the Agency for Nature and Forests, utilized citizen science to fill this knowledge gap.
Between June 2024 and August 2025, a large number of volunteers went out into the field to sample waterbodies. This yielded data on the presence and absence of crayfish at no fewer than 548 locations across Flanders. This data provided a significantly improved picture of the species’ distribution and yielded several new insights. For example, the virile crayfish was observed for the first time in Belgium, and we saw a sharp increase in the observations of the red swamp and white river crayfish. Differences were also observed in species distribution between water types and in their ecological tolerances.
Craywatch underscores the importance of citizen science for the detection and monitoring of invasive species and, based on the results obtained, proposes a targeted surveillance strategy for each invasive crayfish species.
The project lays the foundation for a sustainable monitoring network for crayfish and demonstrates that citizen science has a place within it. On behalf of the INBO Craywatch team, we thank all the volunteers who contributed to the project.
Margot Vermeylen, Bieke Maex, Kevin Scheers & Frédérique Steen
Image above: virile crayfish (photo Wietse Chanet)