Europe has experienced a substantial increase in non-indigenous crayfish species (NICS) since the mid-20th century due to their extensive use in fisheries, aquaculture and, more recently, pet trade. Despite relatively long invasion histories of some NICS and negative impacts on biodiversity and ecosystem functioning, large spatio-temporal analyses of their occurrences are lacking. Here, we used a large freshwater macroinvertebrate database to evaluate what information on NICS can be obtained from widely applied biomonitoring approaches and how usable such data is for descriptions of trends in identified NICS species. We found 160 time-series containing NICS between 1983 and 2019, to infer temporal patterns and environmental drivers of species and region-specific trends. Using a combination of meta-regression and generalized linear models, we found no significant temporal trend for the abundance of any species (Procambarus clarkii, Pacifastacus leniusculus or Faxonius limosus) at the European scale, but identified species-specific predictors of abundances. While analysis of the spatial range expansion of NICS was positive (i.e. increasing spread) in England and negative (significant retreat) in northern Spain, no trend was detected in Hungary and the Dutch-German-Luxembourg region. The average invasion velocity varied among countries, ranging from 30 km/year in England to 90 km/year in Hungary. The average invasion velocity gradually decreased over time in the long term, with declines being fastest in the Dutch-German-Luxembourg region, and much slower in England. Considering that NICS pose a substantial threat to aquatic biodiversity across Europe, our study highlights the utility and importance of collecting high resolution (i.e. annual) biomonitoring data using a sampling protocol that is able to estimate crayfish abundance, enabling a more profound understanding of NICS impacts on biodiversity.

Center for Applied Mathematics and Bioinformatics Department of Mathematics and Natural Sciences Gulf University for Science and Technology Hawally 32093 Kuwait

Chief Scientists Group Environment Agency Horizon House Deanery Road Bristol BS1 5AH UK

Department of Aquatic Sciences and Assessment Swedish University of Agricultural Sciences Uppsala Sweden

Department of Biology University of Florence Sesto Fiorentino Italy

Department of Plant Biology and Ecology Faculty of Science and Technology University of the Basque Country Leioa Spain

Environmental Research and Innovation Belvaux Luxembourg

GEOMAR Helmholtz Zentrum für Ozeanforschung Kiel Kiel Germany

INRAE UR RiverLy Centre de Lyon Villeurbanne 5 rue de la Doua CS70077 69626 Villeurbanne Cedex France

Leibniz Institute of Freshwater Ecology and Inland Fisheries Department of Community and Ecosystem Ecology Müggelseedamm 310 12587 Berlin Germany

Leibniz Institute of Freshwater Ecology and Inland Fisheries Department of Community and Ecosystem Ecology Müggelseedamm 310 12587 Berlin Germany; Carnegie Mellon University Institute for Green Science 4400 Forbes Ave Pittsburgh PA 15213 USA

MARE Marine and Environmental Sciences Centre Associate Laboratory ARNET Department of Life Sciences University of Coimbra Coimbra Portugal

RPTU Kaiserslautern Landau Institute for Environmental Sciences Landau Germany

School of Biological and Behavioural Sciences Queen Mary University of London London UK

Swedish University of Agricultural Sciences Department of Aquatic Sciences and Assessment Uppsala Sweden; Institute for Mental and Physical Health and Clinical Translation Deakin University Geelong Victoria Australia; University of Nebraska Lincoln School of Natural Resources Lincoln NE USA; The PRODEO Institute San Francisco CA USA

University of Murcia Department of Zoology and Physical Anthropology Murcia Spain

University of South Bohemia in České Budějovice Faculty of Fisheries and Protection of Waters South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses Zátiší 728 2 389 25 Vodňany Czech Republic

University of South Bohemia in České Budějovice Faculty of Fisheries and Protection of Waters South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses Zátiší 728 2 389 25 Vodňany Czech Republic; Center for Applied Mathematics and Bioinformatics Department of Mathematics and Natural Sciences Gulf University for Science and Technology Hawally 32093 Kuwait; Senckenberg Research Institute and Natural History Museum Frankfurt Department of River Ecology and Conservation Gelnhausen Germany

Yale University School of the Environment 195 Prospect St New Haven CT 06511 USA

References provided by Crossref.org

World of Crayfish™: a web platform towards real-time global mapping of freshwater crayfish and their pathogens