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What's the Deal with Cutthroat Trout?

September 3 2010 | by Bruce Auchly

What’s the problem with cutthroat trout, Montana’s state fish?

When Lewis and Clark camped at the Great Falls of the Missouri 200 years ago and discovered the species, the cutthroat was numerous and unchallenged as the only trout species east of the Continental Divide. With the exception of northeast Montana, the cutthroat’s two subspecies—Yellowstone and westslope—ranged throughout the entire state’s waters.

That was then. This is now:

  • The species has been petitioned for federal listing as an endangered species. The petition has been denied but an appeal is currently working its way through the federal court system.
  • A state law requires anglers release all cutthroat trout caught in rivers and streams in Montana’s central and eastern fishing district. Lakes and reservoirs are excluded.
  • The cutthroat trout east of the Continental Divide has been reduced to about 3% of its historic range.

How did we get here?

The short answer is competition and hybridization from introduced fish species. In addition there are the usual suspects, habitat destruction and overfishing, the byproducts of civilization. As with most short answers they don’t tell the complete story.

Starting about 125 years ago, our ancestors introduced non-native but popular fish species like rainbow, brown and brook trout. Each impacted native “cutts” differently.

  • Brook trout are fall spawners, so young brookies are bigger and can outcompete young cutts for food and favorable habitat in late spring and summer.
  • Cutts are an aggressive fish and can be easily overfished. It is nearly impossible to overfish brown trout. In fact, brown trout cannot be overfished even with 10 times the fishing pressure that would decimate a cutthroat population.
  • Rainbows present the twin threat of competition for resources and hybridization. The two fish species can interbreed, leaving many an angler to scratch his head over the fish in hand that has a pink stripe down the side but red slash marks on the throat.

Current Montana law says in rivers and streams in the central and eastern fishing districts any trout with red slash marks on the throat must be released. That has led to confusion when a fish in hand appears to be an obvious hybrid. Or when an angler mistakes the faint throat slashes occasionally found on some rainbows for a cutthroat. Fish biologists are trying to help the cutthroat, establishing populations in fishless headwater streams or bolster isolated populations.

Realistically, no one is going to turn back the clock and remove the non-native trout. Besides too many people like to catch rainbows, and many a camp dinner has featured brookies sizzling in a frying pan. But in the past 10 years by removing non-native fish and building or enhancing barriers to prevent non-native fish moving upstream cutthroat populations in north central Montana have doubled from 2 percent to 4 percent in their historic habitat.

Why should we care? Well, there is history. It’s neat to catch a fish that evolved here and was first described by Lewis and Clark. And there’s the biological connection: Cutthroat trout may have adaptations we don’t know about. They evolved to local conditions over millions of years. Wouldn’t it be a shame if in just a few hundred years cutts couldn’t survive humans?