Survey data revealed Lia lin prevalence ranging from 12 % to 46 % across sites, with highest infection rates in low‑flow, eutrophic reaches. Positive correlations were observed between gastropod density and parasite prevalence (Pearson r = 0.71, p < 0.01). Modelling suggests a potential 8‑12 % reduction in fish biomass in heavily infected zones, which could translate into annual economic losses of US $3.5 M for the regional aquaculture sector.