A new non-native species detected through citizen science: the presence of a Macrobrachium species (Decapoda, Palaemonidae) in the Guadalquivir River estuary (SW Spain), with an overview of its global spread

Non-native species are of global conservation concern. Spain is also facing the same challenge, especially due to increasing marine traffic, global trade, and ocean warming. Herein, we report Macrobrachium cf. nipponense from a local fisherman through a citizen science initiative. This is the first record of any species of the genus Macrobrachium in the Iberian Peninsula and the westernmost record of this genus in the European waters. In October 2024, an individual was fished at the mouth of the Guadalquivir River. Accidental transport via ballast water is a likely vector for its introduction into the Guadalquivir River estuary, potentially facilitated by increased maritime traffic from the Danube River Basin as a result of the ongoing war between Russia and Ukraine. Our findings highlight the importance of early detection and continuous ecological monitoring, particularly approaches that incorporate citizen science, as effective tools for tracking non-native species. Engaging local stakeholders, such as fishers, can enhance detection capacity and contribute valuable data to inform for future management strategies aimed at preventing the establishment and spread of non-native and invasive species in the Guadalquivir River and other vulnerable aquatic systems.