Complete western expansion of topmouth gudgeon Pseudorasbora parva (Temminck & Schlegel, 1846) across Europe: first record in Portugal

Pseudorasbora parva, a small cyprinid from Asia, is considered the Europe's most invasive fish.Typically introduced accidentally through fish stocking, its high habitat plasticity and early maturity enhance its invasiveness.In addition to competition, it asymptomatically transmits pathogens that harm native fish populations.First recorded on the Iberian Peninsula in 2001, it was found in a small intermittent river in the Guadiana River basin by 2010, an international river flowing from Spain to Portugal.Despite eradication efforts in Spain, the species' expansion underscores the need for coordinated management between countries to address biological invasions.The recent detection in Portugal, near the Alqueva dam, raises conservation concerns, particularly for endemic species.