Length–Weight Relationship and Relative Condition Factor of Invasive Micropterus nigricans and Lepomis gibbosus in Lake Banyoles 5 Years After the Electrofishing Eradication Campaigns

This study assesses the recovery and physiological condition of two invasive freshwater fish species, Micropterus nigricans and Lepomis gibbosus , in Lake Banyoles (Catalonia, Spain), 5 years after the last intensive electrofishing campaign. We analysed the length–weight relationship (LWR) and the relative condition factor ( Kr ) as indicators of population health. The LWR showed strong relationships between length and weight, with b ‐values of 3.149 for M. nigricans and 3.172 for L. gibbosus , indicating positive allometric growth. Kr values above 1 further supported good physiological condition. Our results indicate that both invasive species have successfully recovered and are currently thriving in the lake. In contrast, native species such as Barbus meridionalis and Squalius laietanus were not detected, suggesting that the recovery of invasive species may be hindering the re‐establishment of native fish populations. This absence raises concerns about the effectiveness of previous reintroduction efforts conducted under LIFE projects. Although some native species like Anguilla anguilla and Salaria fluviatilis were observed, their presence does not reflect a broader recovery of the native fish community. These findings underscore the high adaptive capacity of these non‐native species, the limited long‐term effectiveness of electrofishing and other traditional techniques as control strategies and the ongoing ecological challenges facing the conservation of native fish communities.