How are mountain whitefish populations doing in Idaho?

Fisheries biologists use the term “salmonids” to refer to members of the biological family that includes salmon and steelhead, trout, grayling, and whitefish. In Idaho, we have many different species of native and nonnative salmonids, but by far the group that gets the least attention from anglers is whitefish. You might be surprised to know Idaho actually has several native species of whitefish, but most anglers are likely to encounter the mountain whitefish. That’s because they are often caught incidentally when anglers are fishing rivers for trout. Although Idaho Fish and Game biologists regularly monitor trout to determine if populations are healthy, they rarely monitor mountain whitefish populations. Recently, that changed, with the Department conducting two different studies to look at how mountain whitefish are doing across Idaho. 

In the first study, biologists used snorkel-count data from the Salmon and Clearwater basins of central Idaho that have been collected for decades. These snorkel surveys are used to monitor wild salmon and steelhead natural production, but other game species are counted too. Biologists found that mountain whitefish populations in most rivers of the Salmon and Clearwater basins were stable or increasing going back to the mid-1980s, except in the South Fork of the Clearwater River, where declines were noticeable. The stable conditions for most populations were not surprising given that more than one-third of central Idaho is backcountry and is a stronghold for other native salmonids, including salmon and steelhead, bull trout, and cutthroat trout.

The second study focused on southern Idaho, ranging across the entire upper Snake River basin, over to the Oregon/Nevada/Wyoming borders. Dozens of streams that were surveyed in the late 1990s and early 2000s were re-surveyed over a 5-year period from 2020-2024. Biologists then looked for any changes in mountain whitefish populations compared to 20+ years ago. The survey data revealed several interesting findings. First, mountain whitefish remain very abundant in many places where they are found, with as many as 8,000 fish/mile of river at their highest abundance! Trout are rarely that abundant in Idaho or elsewhere. Unfortunately, we also observed that mountain whitefish declined in some places. For example, in streams smaller than about 60 feet wide, mountain whitefish are now often missing where they used to be present 20 years ago. Although small streams are not prime habitat for mountain whitefish – they prefer rivers – this is concerning and is something the Department will continue to monitor. We also found the declines were highest in the biggest rivers. In fact, every location we surveyed where stream width exceeded 100 feet showed a decline in whitefish numbers. The Department if now funding a graduate student at the University of Idaho to look into why some of these mountain whitefish populations might be experiencing declines in where they live and how many are present.

The Department is not concerned that mountain whitefish are generally in trouble in Idaho. On the contrary, they probably remain our most prolific salmonid in the state, and are often the unsung heros of an otherwise tough day of trout fishing. In fact, we encourage more anglers to take advantage of the bountiful abundance of mountain whitefish. In many locations, keeping a few fish to pickle or smoke won’t do a bit of harm to the population, and pickled or smoked whitefish is delicious. Nevertheless, Idaho Fish and Game plans to more closely monitor mountain whitefish populations in the future than has been done in the past, to assess whether whitefish abundance across the state changes further. More angling information on Idaho mountain whitefish populations can be found here.