High morphological and ecological diversity displayed by European bullheads led Freyhof et al. (2005) to describe 15 nominal species. However, the basis for declaring these nominal species is contentious due to a lack of rigorous statistical analysis of morphological variations among populations, limitations in the inferences made from previous generations of molecular studies, a dearth of next‐generation sequencing tools for...

The invasion of the North Atlantic by pink salmon Oncorhynchus gorbuscha has raised concerns regarding their impact on coastal rivers. Although the influence of marine‐derived nutrients from returning adult O. gorbuscha on rivers in their native range has received much attention, the ecological consequences of invasive O. gorbuscha for ecosystems outside the native range are largely unknown. To investigate the impact on the de...

Freshwater fish biodiversity is undergoing a rapid decline worldwide due to habitat fragmentation, climate change, invasive species, overexploitation and pollution. Yet, for many regions, including biodiversity‐rich but underrepresented areas such as Türkiye, large‐scale assessments of species diversity and distribution remain limited. Environmental DNA (eDNA) metabarcoding offers a powerful, non‐invasive and scalable tool for...

A specimen of rosy barb Pethia conchonius of 51 mm standard length, encountered in an urban pond in London, is reported. This small cyprinid is native to lakes and streams in subtropical regions of southern Asia and is commonly sold as an ornamental fish. An invasiveness risk screening indicated that it is currently unlikely to establish in the United Kingdom due to limiting temperatures but highlights the increased risk of su...

Native to Central and Eastern Europe, the euryhaline pikeperch Sander lucioperca can acclimatize to elevated salinity levels (e.g., up to 30‰), but it remains unknown whether their invasive populations use this ability to inhabit and/or disperse through brackish waters, such as estuaries and inshore areas. To test whether invasive pikeperch show a propensity to move into areas of relatively high salinity, their spatial use and...

In mid‐May 2022, pink salmon Oncorhynchus gorbuscha smolts were caught in the rivers Botnsá, Grímsá, and Langá in Iceland. This observation provides the first evidence of successful spawning and the completion of the freshwater phase of the life cycle in Icelandic rivers. It is the most western record of O. gorbuscha smolts in Europe, further west than Russia, Norway, and the UK. Smolts originating from Iceland potentially sup...

The bleak Alburnus alburnus is a medium body-size leuciscid fish that is naturally distributed across central European and western Asian fresh waters. However, during the last two decades A. alburnus has been widely introduced elsewhere in Europe and in northern Africa, mostly as a forage species for game fishes. Given its relatively recent history of invasion in non-native Eurasian waters, where it can become highly abundant,...

This article presents a personal account of the important contribution a publication from David Noakes’ lab (Pot, Noakes, Ferguson and Coker 1984, Quantitative sampling of fishes in a simple system: failure of conventional methods. Hydrobiologia 114:249–254) made to freshwater fish science in general and to the successful public defence of a doctoral thesis in particular. Pot et al. (1984) tested the accuracy of two convention...

In spring 2022, pink salmon Oncorhynchus gorbuscha smolts were recorded in the UK. Fish were caught in the Rivers Thurso and Oykel in Scotland between 13 and 17 March. To the authors’ knowledge, this is the first observation of O. gorbuscha smolts in Europe outside the Scandinavian and Kola peninsulas, including other tributaries of the White and Barents Seas. It also provides evidence of successful spawning in 2021 and comple...

The North American channel catfish Ictalurus punctatus has been introduced to several locations in Europe but has received little or no scientific study despite its invasive attributes, including prolific reproduction, tolerance to a wide range of conditions, opportunistic feeding, at least partial ‘predator release’, and some evidence of environmental impacts (e.g. disease transmission). To assess the species’ potential invas...

Risk screening tools play a crucial role in identifying potential high‐risk non‐native (NN) fish species. In this study, potentially invasive NN fish species in the Anzali Wetland Complex (AWC), which is located on the south coast of the Caspian Sea (Iran), were identified using the Aquatic Species Invasiveness Screening Kit (AS‐ISK). Twenty‐nine freshwater fish species were screened of which 13 exist in the AWC and 16 in clos...

To inform regional managers of potentially invasive non-native (NN) freshwater fishes in the principal hydrosystem that drains the West Siberian Plain, the River Ob basin, 31 extant and potential future NN fish species were screened using the Aquatic Species Invasiveness Screening Kit (AS-ISK) with respect to current and projected future climate conditions. Calibration of the AS-ISK scores, using receiver operating characteris...

Although the European Water Framework Directive (WFD) does not refer explicitly to alien species (AS), it is clear that invasive AS (IAS) are considered a pressure on WFD water bodies. This article discusses the results of a questionnaire sent to all EU Member States, demonstrating considerable variability in the way that AS data are used in implementing the WFD. Responses were received from 18 countries. Most countries define...

Invasive non‐native species (NNS) are internationally recognized as posing a serious threat to global biodiversity, economies and human health. The identification of invasive NNS is already established, those that may arrive in the future, their vectors and pathways of introduction and spread, and hotspots of invasion are important for a targeted approach to managing introductions and impacts at local, regional and global scal...

The European Non‐native Species in Aquaculture Risk Analysis Scheme (ENSARS) was used to assess one of the most popular aquaculture species in the world, the striped catfish Pangasianodon hypophthalmus (Sauvage, 1878), in two locations of southern Anatolia (Turkey). The overall mean risk score generated for P. hypophthalmus by the ENSARS Organism module (which assesses the risks of introduction, establishment, dispersal and im...

The European Union ( EU ) has recently published its first list of invasive alien species ( IAS ) of EU concern to which current legislation must apply. The list comprises species known to pose great threats to biodiversity and needs to be maintained and updated. Horizon scanning is seen as critical to identify the most threatening potential IAS that do not yet occur in Europe to be subsequently risk assessed for future listin...