From the Field - Chinook Salmon

By Jim Lukens - Idaho Department of Fish and Game It's as much a hallmark of the changing seasons in central Idaho as the coloring of the leaves and the drop in temperatures. Adult Chinook salmon, also known as king salmon, return to local waters after their multi-year journey to the ocean and come back to lay eggs to complete their life cycle. During the spring, adult Chinook begin their migration back to central Idaho from the Pacific Ocean. These fish migrate up to 900 miles and climb more than a mile in elevation to return to their natal spawning streams. Spawning occurs in late August and early September. Time is short for migrating Chinook as all adult salmon die shortly after spawning. The young fish emerge from the spawning gravels the following spring and usually stay in fresh water for 18 months before traveling downstream to the ocean. Chinook typically spend one to three years at sea before returning to natal streams to spawn. For more than 50 years, Idaho Fish and Game has been conducting annual surveys of Chinook salmon spawning in the Lemhi River. For five weeks each fall, the agency's fisheries biologists walk the upper length of the river, counting salmon and mapping their redds or "nest" sites. Redds are easy to spot. The large fish scour out a depression in the gravel to create what looks like white horseshoe-shaped nurseries into which their eggs are deposited. The reason for counting redds is to track the progress of the spawning salmon and to gauge the health of the local population. This fall in the upper Lemhi River above the confluence of Hayden Creek, Fish and Game personnel counted 90 redds, which translates to about 207 spawning adult Chinook salmon. In contrast, in the late 1950s and early 1960s, when redd counts were first conducted in the Lemhi River, the average number of redds was 929 per year or roughly 2,137 spawning adult Chinook salmon per year. Although these fish still face many hurdles in rebounding to historical numbers, improvements are being made, particularly with help from private landowners. Habitat improvement projects, such as fencing along the Lemhi River corridor, have helped increase the amount of quality habitat for juvenile salmon by providing more cover from predators and increasing food availability. Fish screens have also helped protect migrating juvenile salmon from being diverted into irrigation ditches. Reconnecting tributary streams to the main Lemhi River, as done recently at Big Timber Creek, increased the amount of habitat available for fish and also the amount of the flow into the river, thereby improving spawning conditions for adults and rearing habitat for juvenile salmon. These efforts have a big impact on improving the viability of the Chinook salmon populations. As these efforts and many others successfully improve the Lemhi River watershed, the hope is that Chinook salmon can once again return in robust numbers. Jim Lukens is the regional supervisor in the Salmon Region.