Sibling Rivalry? Behavioral Differences When Browns and Rainbows Share a Stream

Updated: 3 days ago

Previously, we highlighted the history and characteristics of rainbow trout, the good, the bad, and the ugly. We explored the history of their rise to prominence in North America; you can explore those articles here: Article 1, Article 2.

We have long wanted to expand the discussion to incorporate brown trout, but realized that, for anglers, a more interesting article might be to compare the behavioral differences among these two common angling sport fish. After all, discussing trout behavior is a favorite topic on this blog. So, let’s take a look at the subtle but important differences between angling for brown and rainbow trout. Specifically, let's examine how the two species behave differently when cohabiting a stream. Even more importantly, let's look at how you, as an angler, can take advantage of these traits to better tailor your angling experience!

But before we consider these differences, there are two important exceptions to clarify: fish density within a system and water temperature. In rivers with low trout density, regardless of the variety, fish will primarily occupy the best holding spots that are available for their size. Whether the factors limiting fish density are habitat, food availability, or something else, fish may be forced into certain spots simply to survive. In this situation, it’s less likely to find drastic differences based on habitat. I know that some anglers don’t enjoy fishing rivers with a low density of trout, but there are some advantages for savvy anglers willing to put in the work on these types of streams. First, reading the water can be very simple. Find the best looking water and work it well! In some systems, like tailwaters, where food availability or habitat are somewhat regulated, trout can still grow to enormous proportions thanks to low rates of competition with other fish. So, low density isn't always such a bad thing. You’ll likely find less pressured or more aggressive fish. It’s unlikely that angling pressure is overwhelming on these types of rivers and more likely that fish will aggressively defend their prime spots in the river, which makes this type of angling more rewarding and exciting. Moving on...

The other caveat is water temperature. Simply put, warmer water will encourage fish to move further for food or move into higher velocity habitat patches with greater dissolved oxygen, while colder temperatures force fish deeper into slower water where they are required to expend less energy with their slower metabolisms. So for cold blooded animals like trout, behavior is contingent on the environment. For a more detailed examination of temperature preferences for trout, check out our Angler’s Guide to Stream Temperatures.

In systems with higher fish densities, water flows and food are more favorable. This more evenly disperses trout throughout the river system where they occupy all kinds of different spots to reduce competition and maximize comfort. Remember, trout aren’t lazy, they are optimizers.