A fish passage of a barrier building in a flowing water, comprising: - a chamber with a first gate and with a second gate, wherein the chamber has a first by the first gate and a second by the second gate openable and lockable opening, wherein the first opening connects the chamber with an upper water side of the barrier building and the second opening connects the chamber with a lower water side of the barrier building, and wherein fish and other organisms living in the water can pass the fish passage via the chamber in several successive operating states of the fish passage; - an initial basin on the lower water side of the barrier building arranged with at least one opening in direction lower water side in flow direction downstream the chamber; - an initial basin on the upper water side of the barrier building for connecting the chamber with the upper water side and to facilitate fish finding and passing the fish passage, wherein the initial basin provided on the upper water side is designed as rise shaft; - a conduit with a first intake connecting the conduit with the upper water side and with a first discharge connecting the conduit with the lower water side; - a second intake connecting the chamber with the conduit; and - a second discharge connecting the conduit with the chamber, wherein the first discharge leads into the initial basin on the lower water side, so that the conduit is adapted to pass water by the chamber, wherein a passage outlet flowing through the first and/or second discharge (46, 50) is brought together on the lower water side of the initial basin and is flowing off to the lower water side in each of the several operating states of the fish passage by the initial basin on the lower water side and by at least one opening of the initial basin to the lower water side, and wherein the passage outlet attracts upstream migrating fish, so that these gather on the lower water side of the initial basin and wait to pass the fish passage in direction to the upper water side, and wherein the rise shaft is adapted to let the passage outlet flow through. - a chamber with a first gate and with a second gate, wherein the chamber has a first by the first gate and a second by the second gate openable and lockable opening, wherein the first opening connects the chamber with an upper water side of the barrier building and the second opening connects the chamber with a lower water side of the barrier building, and wherein fish and other organisms living in the water can pass the fish passage via the chamber in several successive operating states of the fish passage; - an initial basin on the lower water side of the barrier building arranged with at least one opening in direction lower water side in flow direction downstream the chamber; - an initial basin on the upper water side of the barrier building for connecting the chamber with the upper water side and to facilitate fish finding and passing the fish passage, wherein the initial basin provided on the upper water side is designed as rise shaft; - a conduit with a first intake connecting the conduit with the upper water side and with a first discharge connecting the conduit with the lower water side; - a second intake connecting the chamber with the conduit; and - a second discharge connecting the conduit with the chamber, wherein the first discharge leads into the initial basin on the lower water side, so that the conduit is adapted to pass water by the chamber,