Sturgeon range throughout the Columbia River system, but the construction of Bonneville Dam and other upstream dams blocked their migration. Unlike salmon, sturgeon do not use fish ladders. Below Bonneville Dam, they travel up and down the Columbia and even into the ocean, often entering other coastal bays and rivers. Their migration depends on the availability of food and spawning cycles. For spawning success, sturgeon need fast, flowing water of moderate temperature over rocky bottoms, and an ideal spawning area lies several miles below Bonneville Dam. Above Bonneville Dam, sturgeon are isolated in pools behind the dam, and these populations are generally in poorer health.