Predicting fish community responses to environmental policy targets

The European Union adopted the Water Framework Directive (WFD) in year 2000 to tackle rapid degradation of freshwater systems. However, biological, hydromorphological, and physico-chemical water quality targets are currently not met, identifying successful policy implementation management actions is key importance. We built a joint species distribution model for riverine fish Flanders (Belgium) better understand response communities current environmental goals. Environmental covariates included variables hydromorphological indices, while waterway distances accounted spatial effects. detected strong effects physico-chemistry on species’ distributions. Evaluation community responses simulated scenarios revealed that targeting ‘good’ status, following WFD, increases average richness with fraction (0.13–0.69 change accumulated occurrence probabilities). Targeting ‘very good’ however, predicted an increase 0.17–1.38 richness. These simulations indicated riverbed quality, nitrogen, conductivity levels should be focal point policy. weak together complexity nutrient-associated problems, suggest challenging future river restoration Flanders.