To provide a small water passage suitable for the ecological environment of fish and shellfish by providing a fish resting-place body having an egg collector of flow passage shape on a lower end part of a block body forming one side wall of a water passage and a communication port to be communicated with a water passage on the side of the fish resting-place.

A side wall block 1 is provided with an L-shaped concrete block body 4 to constitute one side wall of a water passage 3 arranged in contact with an excavation part 2. One side part of a fish resting-place body 5 is integrated with the block body 4, and its inside is a fish resting-place 6. The fish resting-place 6 constitutes a flow passage by connecting a plurality of side wall blocks 1 whose sides are adjacent to each other so as to be communicated with each other. A communication port 8 to communicate the fish resting-place 6 with the water passage 3 is formed on the side of the fish resting- place body 5. When water (w) is fed to the water passage 3, a fish F passes through the communication port 8 and reciprocates in the fish resting-place 6. The fish resting-place 6 presents the natural river condition through deposition of flow-down earth and sand, or natural stones 7, and the ecological environment of fish and shellfish can be maintained.