European Catfish Establishment and Long‐Term Deterioration of a Traditional Cyprinid Recreational Fishery

The effects of invasive apex predators on inland recreational fisheries remain poorly quantified. We used standardised angling competition records from Iznájar Reservoir, southern Spain (2008–2025), to test whether establishment of European catfish ( Silurus glanis ) was associated with deterioration of a traditional cyprinid fishery. Weighted annual mean catch per unit effort (CPUE) declined by ≈76% (from 4.618 to 1.121 kg·angler −1 ·h −1 ) and upper‐tail CPUE (P90) from 8.132 to 2.217 kg·angler −1 ·h −1 , whereas the annual probability of zero‐catch anglers increased from 2.72% to 39.47%. Asymptotic exponential models fitted all CPUE series better than linear trends, and segmented analyses identified 2012 as the best‐supported breakpoint. Declines were robust to rank‐based methods and to excluding the anomalous year 2018. Long‐term physicochemical and reservoir water‐level data revealed no environmental mechanism matching the timing or magnitude of the decline. Although causality cannot be demonstrated, the pattern is consistent with S. glanis as the leading identifiable explanation.