Alien animal introductions in Iberian inland waters: An update and analysis

Inland waters provide innumerable ecosystem services and for this reason are among the most negatively impacted ecosystems worldwide. This is also the case with invasive alien species, which have enormous economic and ecological impacts in freshwater ecosystems. The pace of alien introductions has not decreased in recent years and the first step to their management is to update checklists and to determine introduction pathways and origins of species. This study updates the list of alien animal species introduced and naturalised in inland waters of the Iberian Peninsula. Additionally, the most relevant characteristics and association patterns of these species (region of origin, taxonomic group, introduction pathway and main habitat) and introduction trends in the Iberian Peninsula, mainland Portugal and Galicia are analysed. We identified 125 alien animal species introduced in Iberian inland waters (increase of 30% compared to previous reviews) whereas 24 additional species have uncertain establishment or native status. We found marked associations among taxonomic groups and their region of origin, introduction pathway and main habitat used but less relationship between these three latter features. Considering the whole territory of the Iberian Peninsula, the introduction rates seem to be experiencing a decrease or to have achieved stabilization. However, this is not applicable to mainland Portugal and Galicia for which the historical delay in the first record dates for alien species is fading-out, suggesting increasing spread rates. Our results should facilitate early detections and the design of prevention protocols and taxon-specific management plans.