Whitefish — the Yellowstone River’s indicator species

Biologist says whitefish population serves as ‘canary in the coal mine’
By: 
Neil Patrick Healy
Yellowstone Newspapers

When people come to the Yellowstone River to fish, many of them look to reel in one of the iconic brown or rainbow trout that have become synonymous with this region of the world. So when there’s a bite and what’s on the other side of the line is a whitefish, those same people may be disappointed, but there are many misconceptions about whitefish that may be giving the species a bad name. 

For one, whitefish and the trout species do not conflict with each other over habitat or food sources. According to fisheries biologist Scott Opitz, a large amount of whitefish in the river does not indicate the trout population will decrease. 

“One misconception out there is that if we have an abundance of whitefish we’ll have a reduced volume or reduced amount of trout,” Opitz said. “It’s not really true. They do have some overlap in their interactions, but one of the big giveaways when you look at a trout’s mouth and how it feeds versus a whitefish and its downturned mouth and how it feeds. They’re targeting different areas of the prey base in general.”

In some cases, whitefish help trout in terms of food because small whitefish can become a food source for larger trout. 

During the fish kill from August of 2016, a large majority of the fish that died were whitefish, but the decrease in whitefish doesn’t mean there’s more room for trout. 

“It’s not a one-for-one replacement like a lot of people think would be the case,” Opitz said. “If we lose 10 whitefish, we don’t gain space for 10 trout. They occupy different enough niches that that kind of interaction doesn’t take place.”

With the whitefish being an abundant species in the Yellowstone, they also act as an indicator of the health of the river.

“A lot of times they’re referred to as the canary in the coal mine,” Opitz said. “They’re a pretty sensitive species when it comes to environmental conditions. They don’t do well with big swings in water quality and water quantity or temperature. They’re usually one of the first fish that gives us an idea that there may be something changing pretty significantly in the system.”  

So with a large number of whitefish indicating a healthy river, catching one could be looked at as a positive sign. 

“They save the day a lot of times, too,” Opitz said. “Sometimes it’s better to catch some fish than no fish.”

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