Let us start by saying that our favorite posts to write are fun and light hearted, but this one however, covers a timely yet serious topic that we hope everyone takes to heart. In order to enjoy fly fishing as much as we do, it is imperative to respect our surroundings and the fish we so long to catch.
It’s that time of year again where we are shedding our coats and even waders to enjoy the warm air and water. While this is refreshing and enjoyable for the angler, the trout you are targeting often feel the opposite. Although the exact water temperature threshold is grey and often debated, there’s no argument that when the water gets too warm, trout become stressed due to the decrease in dissolved oxygen in the water. Similar to fishing in the cold winter temperatures, trout go into survival mode and do whatever it takes to consume oxygen while expending as little energy as possible.
So how hot is too hot and why should we as fly fisherman care? The fact is even though trout may continue to feed at the higher temperature levels, the fight, netting and release process may be too much for the trout to handle which decreases the trout’s chance of survival. Through our research and experience, the threshold for when a fly fisherman should refrain from fishing seems to start at 67 degrees. While you will likely notice that the productivity you were experiencing in the morning is slowing dramatically, the best way to know is to carry a thermometer. Thermometers specific to fly fishing are cheap and can easily be found at your local fly shop or online. When we fish, we always keep a thermometer on hand and either check the water temperatures periodically or keep it strapped to our boot for continuous monitoring. Ultimately, knowing the temperature of the river will help you target the most productive areas of the river as well as inform you when it has become too hot to fish.
The state of Colorado is currently experiencing record-breaking temperatures and poor runoff due to the lack of snowpack. Flows at many Colorado tailwater's are unseasonably low due to the reservoirs lacking the necessary water levels to warrant a greater dam release. When bottom-release dams discharge substantial amounts of water, it cools the water temperature and creates faster currents that carry abundant levels of oxygen. Absent this, tailwater's such as the South Platte and Williams Fork are currently experiencing alarming water temperatures that are reaching the high 60’s in the afternoon. With this in mind, we want to make you aware of the current conditions but also prepare you to fish the leading hours effectively as well as how to react once you have hooked a fish.
In the early morning hours (6 am – 9 am), we recommend targeting the head of pools and the outer seams. Once you hit 9 am, the sun will be directly hitting the water and warming it at an exponential rate. At this point, we recommend shifting your attention to the riffles for the most action. Trout will recognize the warming water and will move into the riffles to consume extra oxygen and get front row seats to emerging bugs. Fishing the riffles is fast paced and often times results in aggressive takes that are a blast to experience. It is at this point, however, that we need to start being conscious of the trout’s expended energy during the fight and the amount of time we take to snap our glory shot of the fish. Reeling the trout in quickly to minimize stress, keeping the trout submerged as much as possible while releasing the hook, and taking a quick picture is critical at this time of the day. It’s at this time (11 am – 12 pm), that we need to test the water temperature to see if it’s nearing the “no fishing” threshold and as we mentioned above, if your thermometer reads 67 degrees, we highly encourage you to pack it up for the day and enjoy some celebratory beers.
The summer is an incredible time to fly fish in Colorado and we don’t intend to discourage you from enjoying a beautiful day on the water. Our only hope is that you will be conscious of the conditions and know when it’s time to call it a day and protect our trout. Let us remember why we all live by the catch and release philosophy. Catch a fish and release them in the same condition as when you hooked him.