Shiro-maru Dam Fish Ladder Observation Facility

A fish ladder is a specialized passageway constructed alongside dams or weirs to help fish swim upstream when their paths are blocked. Fish like ayu (sweetfish), yamame (landlocked salmon), and rainbow trout migrate upstream primarily for spawning, but artificial barriers can obstruct their journey. Fish ladders feature gentle slopes and small steps filled with flowing water, enabling fish to navigate safely upstream.

One of Japan’s largest fish ladders is located at Shiro-maru Dam in Okutama, Tokyo. Stretching approximately 330 meters in length with a vertical drop of about 27 meters, this impressive structure is open to visitors on weekends, holidays, and during summer vacation periods. Visitors descend via a giant spiral staircase into an underground tunnel, where the interior of the fish ladder can be viewed up close.

Walking through the concrete tunnels with the thunderous sound of rushing water echoing around you feels like an adventurous exploration. At the end of your tour, you can enjoy a panoramic view of the fish ladder’s entrance from the top of the dam itself. It's a unique chance to witness firsthand how technology can harmoniously coexist with nature.