Fish pass, Cardiff barrage, Cardiff, Wales, UK. This fish pass, also called fishway and fish ladder, allows migratory salmon and sea trout to return to the River Taff and the River Ely in Wales. Fresh water flows into the fish pass from the bay and down a system of pools and waters. These allow the fish to swim, whatever the state of the tide, from the estuary into the bay. The fish outside the bay sense the fresh water from their particular home river and enter the fish pass. Photographed in 2005.