Patterns and correlates of non-native inland fishes in the circum-Mediterranean region

Abstract The circum-Mediterranean region is a global biodiversity hotspot, home to a highly distinctive freshwater fauna with a large proportion of endemic species, many of which are threatened. These ecosystems are increasingly impacted by biological invasions, particularly by non-native fishes. Here, we provide a comprehensive, updated inventory and analysis of non-native fishes recorded in inland waters across all countries bordering the Mediterranean Sea, based on an extensive review of scientific literature, databases and technical reports. A total of 151 non-native fish species were recorded in circum-Mediterranean inland waters, with Italy, Spain, Bosnia and Herzegovina, France and Croatia exhibiting the highest numbers of established species. Certain orders, such as Salmoniformes and Esociformes, were significantly overrepresented among established non-native species, whereas others, including Siluriformes and Characiformes, were underrepresented. Most introductions came from other European countries, Asia and North America, primarily through escapes or intentional releases. Non-native fish species richness showed a strong positive correlation with gross domestic product, precipitation and the number of dams, underscoring the influence of economic development and habitat availability as key drivers of species establishment. We also discuss the implications for regional biodiversity conservation and highlight the need for coordinated transnational strategies.