The dataset contains records of arthropods collected in the lower reaches of the Tua river, and included in the Environmental Impact Assessment of the Foz Tua Hydroelectric Dam, promoted by EDP – Energias de Portugal, S.A. Most data was collected between June 2006 and June 2008, during field visits to 7 sections of the river Tua valley. The main taxa targeted during the field visits were Lepidoptera, Coleoptera, Hemiptera, Orthoptera, and Odonata. Part of the specimens have been kept in the private collections of the collectors indicated in the dataset.