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Trouts Journal

Shades of Chocolate Milk Part I: Pre-Runoff & The Climb

Reid Baker / Apr 29, 2021

Note from the Editor: We commissioned Reid Baker to pen “Shades of Chocolate Milk” - a three-part series - dedicated to fishing techniques and strategies throughout spring runoff here in Colorado. Enjoy... - Editor, Will Rice

Spring is in the air, Colorado. New annual fishing licenses have been issued, gloves and beanies are stashed. Hopefully, we have seen the last of iced up guides. Finally, we don’t only have to fish tailwaters, midges, and baetis imitations. Yes, winter is behind us and it’s been a great early season as we start to look to some favorite freestone rivers throughout the Rockies.

Then, just when we’re getting the dust knocked off our flip flops, the first consistent high temperatures in the 60 to 70-degree range arrive. Suddenly, the hydrographs start to climb like a rocket. Seemingly just as the ice shelves break free from the banks, the river turns slightly stained, then a little more turbid. A few days or weeks go by and it looks more like the raging Wonka river than a fishable stream. Runoff has arrived.


Spring runoff is a generalized time of year in Colorado - typically May and June - when the temperatures cause snowmelt to enter the river and increase volume of water and sediment flow. It is a necessary annual flush that both sustains a healthy life cycle of the river, but tends to scare anglers off.

But I am writing today to tell you to fear not: runoff, especially on freestone(ish) rivers (*see definition at the end of this article), is a natural part of the game, and one that does not necessarily mean putting your rod away until July. Like any other time of year, it simply requires a specific understanding of how fish are behaving and the best techniques or strategies to have productive fishing days. That said, this is the most dynamic season of the fishing year, and techniques can turn on a dime.

In this first installment of this three-part series we will focus on the first stage of shoulder season fishing, ranging from pre-runoff to when the water starts to significantly climb in volume as it nears the peak.

What are the fish doing?

As spring temperatures really start to rise and days are longer, a trout’s metabolism is starting to pick up, as well as bug life starting to awaken. Some rivers throughout our region will start to have decent hatch cycles beyond midges and blue-winged olives. We’ll start to see caddisflies and even small stoneflies, depending on the river.

In this pre-runoff phase, fish may start to favor more traditional feeding lanes, if the water temps are rising enough and the flows are remaining consistent. But as snowmelt starts to enter the river in volume, flows will start to rise – obviously - but water temperatures will also start to drop again. It is snowmelt after all. When this occurs, fish will start to move out of feeding lanes and start to favor depth, slower pace, or structure and edges that provide breaks in current.

As I’ve said in other pieces here on the blog, the speed of current fish favor is directly correlated to their ability to feed without having to work overly hard for it. Positive calorie events are their top priority. So regardless of more food being in the river, if they have to spend too much energy to hold in current, or worse, the river is too turbid to see most food sources, they will start to hunker down.

Start to think bigger

So now that we know how fish are behaving, there are some key elements to change in our approach once we hit the water, or even before we’ve selected our day’s destination.

First of all, learn how to read online flow tables- or hydrographs. This will help you judge when a river is on the rise, but still fishable, or, if you should look to an alternative location. The shop can always help with this too, obviously. Secondly, this can be a good time to invest in a thermometer, as water temps fluctuate quite a bit depending on how recently snowmelt has entered the river.

If we are still in pre-runoff before the CFS (cubic feet per second) really shoots up, this can be an exceptional time to be on the water. Even if flows are starting to climb, if the water is still on the clearer side and water temps are in the mid 40Fs or higher, the fish will be active. Some species recently completed spawning and are looking to regain energy. Regardless, it's like every trout in the river knows peak flows are coming and they better stock up before the surge.

As flows and water color start to pick up, we are going to start thinking about three key elements that drive our tackle selection through all phases of runoff: 1) bigger profiles or attractor patterns 2) focusing sub-surface and getting down quickly in either nymphs or streamers and 3) fly motion is not a bad thing.

On nymph selection, size #20-24 technical flies that worked well on winter tailwaters will not cut the mustard now that food is starting to get flushed off the bottom. We are going to want more sizable profiles with darker colors or flash. Darker profiles will show up sooner in a trout’s vision as sediments start to increase. Bead heads or weighted flies are a must, and attractor patterns such as leeches, worms and eggs are very eye-catching as the flows are picking sediments off the river bed or banks.

Do not underestimate how much additional weight you may need - both when nymphing or fishing streamers. With higher velocity of flow, many of your flies are never getting down to where the fish are holding on the bottom. This is a good time of year to have sink tips or polyleaders when fishing streamers-- which is my favorite tactic personally.

And lastly, be they nymphs or streamers, fly components with movement can be another great way to attract an eat. You’ll notice many guides fishing flies with rubber legs, soft hackles, lush rabbit on streamers, or plenty of tail material that moves in the current.

Every river behaves differently this time of year, so it is worth regularly leveraging resources such as the shop to ensure you are keeping up with the changes which can occur within hours of the day, let alone between weekly report posts. Therefore, be prepared to use a variety of techniques and changes in presentation or water selection to ultimately produce results.

But at some point in runoff season, most rivers, especially true freestones, will ultimately reach their tipping point and the peak will hit. Tune in next edition for Part II of our series dedicated to fishing in peak runoff.

*Freestone(ish): by definition, a freestone river is a river unhindered by any dams. Freestone(ish) will be a term in this series to describe a river that does have dams along its journey, but the river section anglers are fishing is far enough downstream that the river starts to behave as if it were dam free. They experience annual runoff, diverse hatch cycles, and natural fluctuations in water clarity and temperature as conditions and seasons change. The Colorado River is a notable example of a freestone(ish) river.

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