VIDEO: Fish Creek weir provides another year of insight into Idaho's wild steelhead populations

Annual monitoring at Fish Creek has wrapped up for the season, providing another year of valuable information about one of Idaho's important wild steelhead populations.

The Lochsa River and its tributaries, including Fish Creek, are managed as a wild steelhead refuge where hatchery steelhead are absent and steelhead fishing is prohibited. Without hatchery fish competing for resources, biologists can closely monitor a naturally spawning population of wild steelhead. These fish are generally larger and older than hatchery steelhead, with most spending two or more years in the Pacific Ocean before returning to Idaho to spawn.

The Fish Creek weir provides a unique opportunity to monitor one of Idaho’s wild steelhead populations. The weir allows us to capture steelhead moving both upstream to spawn and post-spawn fish known as kelts that are beginning their journey back to the ocean. 

When an upstream-migrating steelhead is captured at the weir, we place a small mark on its gill cover (operculum) before releasing it above the weir to continue its migration. High water and small gaps in the weir can prevent us from capturing every steelhead. Because of this, later in the season we use the number of fish captured during their upstream migration, along with the number of marked and unmarked kelts we capture, to estimate how many steelhead passed the weir and spawned in Fish Creek.

"The number of steelhead returning to Fish Creek this year has been encouraging," says Regional Fisheries Biologist, Xander Lamping. "This spring we captured and marked 81 adult steelhead moving upstream. We also captured 58 kelts moving downstream."

Since monitoring by Fish and Game began in 1995, annual estimates of adult steelhead spawning in Fish Creek have ranged from fewer than 30 fish in some years to nearly 500 fish in 2011 and 2015. This year's abundance estimate is 89 adult steelhead. Although that is lower than last year's estimate of 124 fish and below the long-term average of 133 fish, it remains slightly above the recent 10-year average of about 80 fish.

More than 30 years of monitoring at Fish Creek have provided valuable insights into the status and trends of wild steelhead populations in Idaho. Each steelhead that returns completes an incredible journey of around 600 miles upriver from the Pacific Ocean back to Fish Creek to spawn. Every year of monitoring adds to biologists understanding of these fish and helps inform efforts to conserve these wild steelhead for future generations.