Although there are spring, summer, and fall runs of Chinook Salmon in Idaho, there is only one season for steelhead. For steelhead, it is always summer! Why are Idaho steelhead called “summer steelhead?” It has to do with when they leave the ocean and return to the Columbia River on their way to their home streams in Idaho.
Our story begins about 300 miles downstream from Idaho. When Idaho steelhead leave the ocean, they mix with other steelhead stocks as they cross Bonneville Dam. The first summer steelhead cross the dam April 1 to June 30, but don’t go very far before reaching their spawning tributaries. The bulk of the summer steelhead cross Bonneville Dam July 1 to October 31, many of which go far up the Columbia and Snake Rivers. The earlier and smaller steelhead in this group are called A-run and the later and larger steelhead are called B-run. In contrast, “winter steelhead” typically cross Bonneville Dam between November 1 - March 31, but don’t go very far. Most winter steelhead come from coastal rivers and few reach Bonneville Dam.
We begin our count of Idaho’s summer steelhead at Lower Granite Dam on the Snake River, the last dam these fish must pass before entering Idaho. The early arriving steelhead tend to migrate more slowly after passing Bonneville Dam than those arriving later, so the window of time when most steelhead pass Lower Granite Dam is shorter than downstream at Bonneville Dam. As the water temperature cools in late fall, steelhead slow their migration and seek shelter in deeper pools to spend the winter. When temperatures begin to warm in the spring, steelhead restart their migration upstream, and we see a small bump in the counts of steelhead at Lower Granite Dam as the latecomers arrive.
Finally Idaho steelhead enter their home streams to spawn from March through May. Although anglers in Idaho fish for steelhead during fall, winter, and spring, in a way they are enjoying summer!
Check out the wild salmon and steelhead page for more articles about the science behind conserving Idaho’s wild salmon and steelhead. See the steelhead fishing page for current conditions, harvest reports, dam counts, and current seasons/bag limits.