Targeted fish removals enhance multidimensional native fish diversity within freshwater protected areas

Freshwater ecosystems are hotspots of biodiversity and contribute significantly to food security. Yet freshwater habitats throughout the world remain plagued by overfishing, which depletes populations and diminishes provisioning of ecosystem services. There is growing interest in the use of freshwater protected areas (FPAs), which are freshwater ecosystems managed under long‐term fishing bans and conservation‐oriented regulations, to promote ecosystem recovery. Yet empirical evidence on the efficacy of FPAs indicates that ecological recovery can be complicated by non‐native species, which may also benefit from reduced harvest pressure and improved habitat conditions.

To evaluate effects of targeted fish removals (TFRs) under fully implemented FPAs, we conducted exhaustive field surveys across five Chinese lakes with and without removal efforts and assessed multiple dimensions of fish assemblage diversity.

Results showed multidimensional diversity metrics for native fishes improved significantly in FPAs with TFRs (e.g. non‐native fish removals in invasion hotspots), while these same metrics declined in control lakes. Moreover, TFRs appeared to strengthen top‐down regulation and alleviate eutrophication, as indicated by altered trophic cascade relationships and reduced phytoplankton biomass (PB) in FPAs with TFR.

Synthesis and applications. Our results indicate combining FPAs with TFRs is essential to achieve effective biodiversity recovery in these ecosystems. This integrated strategy should be prioritized in invasion‐prone or eutrophic systems, where passive protection alone is unlikely to deliver desired ecological outcomes.