When Methodological Innovation Changes the Game: A 10-Year Review of Environmental DNA (eDNA) Applied to Crayfish

The use of environmental DNA (eDNA) as a tool for monitoring represents a major innovative advance in environmental science, one that enables the detection of species without the need to observe or capture them. This article assesses the state of play of eDNA research targeting crayfish. We found a total of 41 peer-reviewed articles published between 2014 and 2023 on both native and invasive species. Most studies focused on invasive species (or a native/invasive species co-detection assessment) (65.8%). There was also a clear geographical bias across studies, with more than half conducted in Europe (51.2%) and a quarter in the United States (26.8%). In contrast, there were none conducted in Africa. The relatively large number of published studies has led to an interesting diversity of protocols designed or utilized, with most favouring the development of their own assays (69.33%). That said, filtration (as an eDNA capture method) was common (80.5%), along with the use of commercially available eDNA extraction kits (69.8%). The COI gene also appeared to be the preferred target region (89.33%). Such range of protocols is interesting, but is it optimal? Are the best protocols always being utilized? Or is the chance for novel application hampering our ability to explore larger trends across studies?