Idaho: A Critical Home for Chinook Salmon and Bull Trout

Idaho is known to host pristine habitat for these fish. However, there are some major barriers to accessing these natural sanctuaries for both the Chinook Salmon and Bull Trout species. Dams, mining, and other extracting projects decrease the access to habitat for Chinook Salmon and Bull Trout. Along with physical obstacles, these projects influence water temperatures and water quality, making a once perfect habitat for fish now an undesirable river for these species.

The Chinook Salmon are fascinating species. They are anadromous fish that migrate 900 miles from central Idaho all the way to the Pacific Ocean. During this time, Chinook Salmon migrating from central Idaho in the Salmon River drainage, must travel through eight dams as smolts and avoid predators to reach their destination. Once it is swim back upstream from the ocean to their inland spawning grounds, the salmon that are left make their way back through the same 900 mile journey. However, for every 100 smolts less <1 adult Chinook Salmon makes it back to its home.

Historical numbers for Chinook Salmon in the Pacific Northwest were astounding. The  Northwest Power and Conservation Council  estimated that 10-16 million Chinook Salmon annually returned up to the Columbia River and 2-6 million returned to the Snake River basin.

To the right is a map showing the current Chinook Salmon distribution in Idaho. Typically, you can find  summer and spring Chinook  spawning in the tributaries of the Clearwater and Salmon rivers. Fall Chinook Salmon can be found spawning around the main channel of the Clearwater, Salmon, and Snake rivers.

While Idaho is home to some of the best habitats for Chinook Salmon, their numbers are still dwindling. In 2022, the  estimated  return number was 15,678 for wild spring/summer Chinook Salmon. While this return number is a small increase from recent return rates, it is nowhere near the recovery goal of 127,000 wild salmon.

Climate change is contributing to the changes in habitat across the Pacific Northwest that are making it less desirable for the ESA-listed species.

Climate risks are less severe at higher elevations. The map to the right shows that most Chinook Salmon distribution lies above 4,000 ft in elevation.

However, a study from the  University of Idaho  shows that Bear Valley Creek, a tributary to the Salmon river in central Idaho, is decreasing in water volume and increasing in temperature. These conditions are expected to destroy half of the critical habitat that remains in this area for salmon by 2040.

Now more than ever it is imperative that we protect the pristine habitat for salmon in Idaho to create a sanctuary for the keystone species to thrive.

In 1999, all populations of Bull Trout in the United States were listed under the  Endangered Species Act  of 1973 as a threatened species. The alarming decline in their population was mainly due to habitat loss, climate change, and non-native species invading their home.

With Bull Trout being a native fish species to Idaho and sensitive to changes in water temperature, and sedimentation, these fish are a crucial indicator of the river system's health and functionality. In order to mitigate the many threats that Bull Trout are facing today, we must take care of the waterways they call home.

Idaho is known to be home to critical habitat for Bull Trout. Populations of the spectacular species are found distributed across the state. Bull Trout are mainly found in our pristine, cold-water rivers and streams, but they have also been found in lakes and reservoirs. During warmer seasons, Bull Trout are more often found at higher elevations.

Bull Trout are a cold water species, which is why Idaho contains an abundance of critical habitat for them. However, climate change and anthropogenic activities are warming many of the cold watersheds throughout the state.

The map to the right uses data from Climate Shield models developed by  Isaak et al. (2015)  which show the likelihood of the presence of juvenile Bull Trout. This map is modeled based on conditions where Brook Trout are absent and waterways have a baseline climate scenario from 1980.

Even though Idaho has been a great home for Bull Trout, habitat quality is dwindling. The new map on the right shows the same conditions regarding Brook Trout, but the climate scenario escalated to moderate climate conditions in 2040. Noticeably most areas now fall into the lower probability range compared to the conditions modeled from 1980.

As climate conditions worsen, so does the probability of juvenile Bull Trout being present in Idaho waters. The map to the right model's extreme climate conditions in 2080 and its impacts on Bull Trout. More waterways do not even show the presence of Bull Trout. What once was a cold-water refuge for this species will one day change into inhabitable waters.

Mining projects are popping up throughout Idaho and overtaking precious natural areas. Mines are infamous for polluting waterways in perpetuity and leaving the ecosystem worse off than how they found it (contrary to the beliefs of mining companies about their 'restoration' efforts).

Even after the mine operations have ceased, the harmful effects remain.  A study  points out that long-term pollution is typical for mines, especially with acid-generating rock, which is a very common presence and a largely unavoidable occurrence.

Bull Trout are highly sensitive to water temperature and require cold-water streams. Mining operations are notorious for altering the thermal regime of groundwater and surface water resources and degrading cold-water sanctuaries for fish. Changes to typical water temperature patterns can alter spawning occurrences, migration, growth of fish, and even survival rates.