Any angler can tell you that fish are always on the move. Their hotspots change from one day to the next. Each day on the lake seems like there’s a different hotspot for your Rainbow Trout, Brook Trout, and Lake Trout. But have you ever wondered what influences these fish to change locations? Several key factors determine where trout like to congregate. One of these reasons that fishermen may not be as familiar with that influences the trout water temperature are layers of water.
In this article, we’re going to take a look at the three layers of water for trout fishing. They are the epilimnion, the thermocline, and the hypolimnion. We’ll also look at when you can find each trout in each layer. When we’re done, you’ll be all set up for a great day on the water.
The Three Layers of Water and Trout Water Temperature
Epilimnion
The first layer of water is the epilimnion. This layer is closest to the surface, making it the warmest and also the most oxygenated. Typically the depth of this layer is about 30–50 feet.
Thermocline (Metalimnion)
Finally, separating these two layers is the thermocline, or metalimnion. This layer of water is thermally stratified. This means that as you get deeper in the water, the temperature rapidly declines. This layer in particular is heavily affected by each season of the year. Typically its depth extends about 15 feet deeper than the epilimnion.
Hypolimnion
The lowest layer is the hypolimnion. This is the coldest and often unoxygenated layer of water. This makes it impossible for fish to go very deep into this layer. Because water begins to sink at 39 degrees, this layer frequently averages around this temperature. These temperatures well below trout’s ideal temperature, so they rarely stay this deep.
Seasonal Changes on Water Trout Temperature
Next, we’ll take a look at how these layers are impacted by the changing seasons. We’ll also look at when and where the trout are distributed amongst these layers.
Summer
In summer, the water is highly oxygenated across the board as rapid oxygenation just occurred throughout the late spring. Fish can each reside in their ideal temperatures, not constrained by a lack of oxygen.
- In general, each trout is going to reside in the thermocline. Lake Trout will be a bit deeper than their Cutthroat, Rainbow, and Brook Trout counterparts. Early in the summer, they can even be found in the upper hypolimnion.
- Brown Trout can be found right at the edge of the epilimnion and the thermocline.
Fall
During the fall, the hypolimnion cools enough to force out the Lake Trout. Both it and the Brown Trout are pushed into temperatures that are a few degrees warmer than their ideal range, making it a less ideal season for either fish. Brook, Rainbow, and Cutthroat trout remain in the Thermocline at ideal temperatures.
As fall progresses, the surface water temperature cools to its sinking temperature of 39 degrees before the oxygen-rich surface water moves to the bottom and is replaced by the warmer subsurface water. This cycle continues until the entire body of water is around 39 degrees and oxygen-rich.
At this point, the thermocline ceases to exist, and every trout species can be caught at every layer of water as the temperature and oxygen levels are uniform. During this fall turnover, the trout are especially active, making it one of the best times to catch them.
Winter
During the winter, the fish are far more lethargic due to not being able to live in their ideal water temperatures).
- In early winter, the warmest levels of water exist in the hypolimnion, away from the frozen surface, so all species of trout can be found here.
- As winter progresses, the oxygen levels in the hypolimnion deteriorate, forcing the fish upward into the even colder epilimnion.
So, fishing early in the winter means fishing deeper, towards the bottom of the lake, while later in the winter should point you towards the top.
Spring
Finally, as spring approaches and the ice begins to melt, the epilimnion layer is significantly oxygenized, although the trout remain sluggish due to the colder temperatures.
Once the oxygenated surface water warms up to 39 degrees, it begins to sink. This brings the less oxygenated, deeper waters to the surface, where they too are warmed and oxygenated and begin to sink again.
During this spring turnover, the trout are dispersed throughout the entire depth of the lake, giving you opportunities to catch every species of trout across all layers.
In Conclusion: Water phenomenon and trout water temperature
It’s important to remember that particularly with the surface water temperatures, it can fluctuate greatly depending on the time of day as well as the outside weather. Keep an eye out for active brown trout in the evening closer to the surface, or even Rainbow and cutthroat late at night! It’s all about the fish looking for their ideal temperature, and knowing where that is in the lake is key for fishing success.
Now that you’re familiar with the different layers of water in lakes and reservoirs, you’re all set up to know exactly what trout to go for, when you should fish for them, and how deep to look for these fish. So grab your rod and reel, head out to one of many beautiful colorado lakes, and watch the fish come pouring in!
