The Effects of Wild Brown Trout on Native Brook Trout

By Connor Olsson

If you’re an avid freshwater fisherman, you’ve almost certainly been intrigued by the elusive yet attainable wild brown trout. These beautifully colored fish are capable of reaching impressive sizes in the wild and have become a staple for trout anglers across the United States. Brown trout are highly sought after due to their size, the waters they inhabit, and their aggressive nature when conditions align for an unforgettable fishing experience.

Despite their popularity, brown trout present a complicated challenge within many freshwater ecosystems—particularly when it comes to their impact on native species.

Native vs. Wild Trout

There is an important distinction between wild and native fish species. A wild fish species originates from a different part of the world (or another region within the same country) and, through human introduction, establishes a self-sustaining population in new waters. A native fish species, by contrast, occurs naturally in a waterway without human introduction and has often existed in that environment for generations.

One of the most iconic native trout species on the East Coast of the United States is the brook trout. This stunning fish is a favorite among anglers—including myself—and holds the honor of being the state fish in multiple states. I’ve been fortunate enough to locate and fish many native brook trout streams throughout New Jersey and Pennsylvania. Unfortunately, many of these same waters now support established populations of wild brown trout.

Competition in Shared Waters

So what happens when brown trout and brook trout occupy the same streams? Unfortunately for brook trout, brown trout tend to be larger, more aggressive, and more efficient feeders. They also prey on brook trout, especially juveniles. These advantages often give brown trout the upper hand in shared habitats.

That said, brook trout are not without defenses. They tend to find refuge in smaller, colder streams with dense cover—environments that are less favorable to brown trout. These colder headwater systems often act as critical sanctuaries for native brook trout populations.

From my experience as a trout angler, I’ve encountered many rivers and streams where brook trout and brown trout live side by side with healthy populations of both species. There’s little doubt that brook trout would be more abundant and reach larger average sizes if brown trout had never been introduced. Still, brook trout continue to survive and reproduce successfully, demonstrating their resilience and adaptability.

The Role of Brown Trout in River Ecosystems

Considering how long brown trout have been established in the United States, it’s fair to say they are here to stay. While their presence can negatively impact native brook trout, brown trout also provide ecological benefits that shouldn’t be ignored.

In many river systems, brown trout function as apex predators. They help strengthen natural selection among prey species and can reduce populations of invasive forage fish. Additionally, brown trout play a role in nutrient recycling. By consuming large quantities of fish and aquatic insects and excreting nutrients back into the system, they contribute to the overall productivity and balance of river ecosystems.

A Balanced Conservation Perspective

In my opinion, this issue is not black and white. Some river ecosystems are capable of supporting both brook trout and brown trout, while others are not. The most effective conservation strategy moving forward is to focus efforts on waters where coexistence is unlikely and prioritize the protection and restoration of native brook trout in those systems.

Preserving cold-water habitats, protecting headwater streams, and carefully managing trout populations are essential steps in ensuring that brook trout—one of the East Coast’s most iconic native fish—continue to thrive for generations to come.