Habitat Restoration for Diadromous Fish in River Mondego, Portugal

River Mondego is one of the most important Portuguese rivers for sea lamprey Petromyzon marinus L., where several measures to restore its longitudinal continuity are being implemented. Coimbra dam (Açude-Ponte), was the upstream limit of sea lamprey’s distribution in River Mondego until 2011, when a vertical-slot fishway was installed at this dam. Since then, its efficiency and effectiveness for the target species is being evaluated by different methodologies, including visual counts, bio-telemetry (radio, physiological EMG, PIT Tags), electrofishing and inquires to local professional fishermen. Visual counts identified the upstream passage of nearly 8,000 and 22,000 lampreys, during 2013 and 2014 spawning seasons, respectively. Also, electrofishing campaigns conducted before and after fishway construction reveal a tendency to the increase in the abundancy of sea lamprey larvae upstream the dam. Following this project, another restoration action is being conducted in this river, which involves the construction of naturalized fish passages in five small weirs located in the main river, and the removal of one obstacle. These actions are integrated in order to insure the compatibility between the conservation of diadromous fish, and all the other water uses of this water basin, namely, water abstraction, hydroelectricity production, professional fisheries and different leisure activities.