How to Adapt to Changing River Depths

In my years of fishing, I have spent most of my time focusing on trout in smaller rivers and streams in the Wasatch range. The water in this area changes constantly and dramatically whether from snow melt or reservoir releases. This constant water depth yo-yoing can be incredibly frustrating for an angler new to fly fishing, or new to a certain river. I know I’ve experienced this a time or two in my mountain exploration. So this is a basic review on what to look for when fishing for trout in these conditions. Disclaimer: if the trout are sipping flies on top, forget the following!

Trout are very picky about their living conditions (aren’t we all)? They like cold water more than warm water, this varies by species, but generally between 50 degrees and 68 degrees Fahrenheit is a happy place. A big reason for this is because warmer water slows their metabolic rate, so they slow or stop eating. Warmer water also holds less dissolved oxygen which the fish need for survival. In addition to water temperature, fish like food. Plain and simple. And they don’t want to work for it either. If a fish can stay in the same spot and wait for the nymphs, larva and other bugs to come its way, that fish has it made. Finally, hiding spots are key. Ever noticed a fish darting up from under a log or overhang to snatch your fly? Well it isn’t because they are against the sun- it is because they like to hide from predators. Staying hidden under some logs, lily pads or an overhang keeps them safe from birds, bigger fish and other predators in the water and, naturally, us.

Understanding this basic fish behavior can be incredibly helpful when approaching a river that will require fishing beneath the surface. When the river is high and blown out (as it usually can be in spring) the fishing can be tough. This can mean cooler water temperature potentially leading to more active fish, but also means that good river structure where fish would otherwise congregate is not so prevalent or obvious from the surface. Additionally, there may be more dirt and debris floating in the water which can heavily impact water clarity- so expect to be blind casting. When the river is murky, fast, and void of clear pools, I like to use a streamer. This usually will catch the fish’s attention and frankly is easier to fish well in this type of water. While this type of fishing isn’t always pretty or flawless, it gets your fly in the water, allows for better navigation of the current. Using an indicator with a dropper can work, but choosing the right dropper in a medley of churned up bugs can prove difficult when attracting fish.

When the water is slower, the same river can provide vastly different fishing opportunities. As the seasonal snow-melt wanes, the river slows down, warms up, and opportunities change. Back eddies become more manageable, water seams become more apparent, and the fishing techniques get more technical. While streamers are always a good time in my mind, using an indicator and dropper pattern can be very successful in these situations. I generally keep my eyes on the river, because this provides excellent site fishing opportunities.
My first step, when approaching a river in this condition, is to look for bugs on the water, and in the water. I generally keep an eye on the surface to check if the fish are sipping, and try to identify the bug as well (this is easier the more you know about entomology- time of day, heat, humidity and water temperature can all play into what bugs are hatching). After I see what is on the surface, I like to pick up a rock that is in the river and check out the crawlies that are on the bottom. This can help in choosing a successful dropper if you choose to use one (something that is also fun, at least for us fly fishing nerds, is to bring a tightly woven net to sweep through the water and identify what is floating in the water column). Once you have identified your flies, it is time to fish.

Back eddies are always a good place to start- they provide slow water and an abundance of bugs for fish to collect. Hitting the seam and working your fly through the back eddy is a great way to approach that area. If there is no back eddy, I like to look for structure that causes obvious pools for the fish to sit in. Fishing on and around these pools often can be successful if fish are hiding in the structure and coming up when they see something tasty. Beware though, these provide great opportunities for snags above and below the surface. Finally, if the river is an even current from one side to another, try to take note of the depth and speed of the current. If you use a dropper in this situation, I usually do, add a little extra tippet if the current is moving swiftly, this will allow the dropper to sit lower in the water column. I typically like to fish these from the river, walking up if possible. If you must fish from the shore or close to it, try hitting different spots across the river- landing your fly at the same place on river time and again may prove for hitting a spot that a fish is not watching. Move your fly to get it in their face, an offer they can’t refuse!

Most importantly, look up, check out your surroundings, and enjoy yourself- you’re fishing afterall!