As we move into the dog days of summer, most times freshwater fisherman experience lower flows and hotter water. Fly fishing in low flows and warm water conditions can present unique challenges for anglers. As water levels drop and temperatures rise, fish behavior changes, making it crucial to adapt your tactics and approach. In this article, we will explore strategies for successfully fly fishing during lower flows and mention when water temperatures exceed 68 degrees Fahrenheit when to fish and when not to fish.

Understanding Low Flows and Warm Water Conditions

What Happens When Water Temps Reach Above 68 Degrees

Strategies for Fly Fishing Low Flows

Strategies To Stay Away From Hot Water & When To Stop Fishing

Check Out Other Species To Target

Understanding Low Flows and Warm Water Conditions

Low flows occur when rivers, streams, or creeks experience reduced water levels, often due to drought, irrigation demands, or seasonal fluctuations. Most times in the mountain west we see this happen with freestone rivers (rivers fed by snowmelt and smaller tributaries). These conditions can concentrate fish in smaller areas and make them more wary and selective when feeding. On the other hand, warm water conditions can affect fish metabolism and oxygen levels, potentially reducing their feeding activity and putting them under stress. Typically, in mid to late summer, some water temps on freestone rivers will breach 68 degrees, where if these fish are caught they might have a tough time swimming away.

What Happens To Trout When Water Temps Reach Above 68 Degrees

Before your outing, make sure to pick up a stream-side thermometer or pick one up at your local fly shop. The best practice in low flows is to take a water temp with a stream-side thermometer to double check where you’re at. If the water temperature is below 65 degrees you know you’re in the clear to embark on your journey. It is ok to fish in water just over 65 degrees, but typically once it reaches above 66-67 degrees fahrenheit you should call it quits.

The biggest reason behind calling it quits when water temps reach over 68 degrees is because oxygen levels decrease. Trout at this point will still eat your flies; however, when these fish get to this point, they may not revive and might die off after you catch them within these conditions. Check out the few reasons why this happens below:

  1. Increased Stress: Warm water conditions put additional stress on trout. The combination of elevated water temperature and the physical stress of being caught can lead to exhaustion and reduced energy reserves. Trout may struggle to recover from the stress of being hooked and fought, making them more susceptible to injury or disease.
  2. Reduced Oxygen Levels: Warmer water holds less dissolved oxygen than colder water. As a result, trout may struggle to obtain sufficient oxygen to meet their metabolic needs. This can weaken them and make them more vulnerable to predation, infections, and other stressors.
  3. Decreased Feeding Activity: Trout’s metabolism slows down in warmer water, leading to a decrease in their appetite. They become less inclined to actively feed, making it more challenging to entice them with flies or other bait.
  4. Limited Habitat Options: Trout seek out areas with cooler water when faced with warm conditions. In rivers and streams, they may concentrate in deeper pools, undercuts, areas with colder inflows, or near channels that hold more whitewater or oxygen. This can result in increased competition for these limited habitats, which may further stress the fish and affect their behavior.
  5. Increased Susceptibility to Disease: Warm water can promote the growth of harmful bacteria, parasites, and fungi, which can negatively impact trout health. When caught and handled in warm water, trout may suffer from open wounds or damaged fins, providing entry points for infections and diseases.

If you’re in a location that is below 68 degrees, approach the water cautiously, keeping a low profile and avoiding sudden movements. Stay back from the bank and use longer casts to minimize the chances of disturbing the fish.

Insect activity becomes even more critical when fishing in lower flows. Spend time observing the water and the insects present. Match your fly selection to the prevalent hatches and focus on imitating the natural food sources available to the fish. if you’re unsure, always be sure to stop by your local fly shop for fishing tips, techniques, and advice from local guides. Never fish for trout in water above 68 degrees!

Strategies for Fly Fishing Low Flows

A key strategy for fishing lower flows is to first check on your location with online knowledge from the United States Geological Survey site, known as “USGS.” Most rivers and streams have USGS flow meters that track information like water temperature, cubic feet per second, turbidity, pH levels, and precipitation that flow in. If you haven’t checked your favorite spot on flows or water temperature, simply search in Google “water temperatures at…” or “cubic feet per second (CFS) at…” to get the knowledge you need before your outing.

  1. Rope Up: Rope up with heavier tippet to land the fish quicker. Keep them wet and skip the pictures to minimize their time out of the water.
  2. Check USGS: Check USGS to get real-time data on flows, temperatures, cubic feet per second, turbidity, pH levels, and more.
  3. Keep ’em wet: If you’ve gotten to this point and the water is breaching 65 degrees, keep the fish wet and practice catch-and-release.

When it comes to photography, be sure to keep the fish in the water even when the water temperatures are below 68 degrees. Most times in the summer months, fish can be stressed due to lower oxygen levels during the hottest months of the year. If you’re looking for a grip and grin, get your hands wet and think twice before taking that fish out of the water. If you’re the one that loves taking photos, look into the AxisGo housings made for iPhones by clicking HERE.

Also be sure to get a stream-side thermometer by clicking HERE!

Strategies To Stay Away From Hot Water & When To Stop Fishing:

Photo from Dan Towsley

One thing to examine before fishing is to determine the right area to fish, and check the flows, turbidity, and temperatures before embarking on an angling journey. Fish early or late in the day (before water temps exceed 68 degrees, and when temps drop below 68 degrees). When water temperatures rise, fish are more active during cooler parts of the day. Plan your fishing trips for early mornings or late evenings. This way, you can take advantage of the fish’s increased activity levels and make sure they can be released safely.

Be sure to choose the right locations. Look for areas where the water is cooler, such as shaded sections, deep pools, or areas with natural springs or inflows. These areas often provide refuge for fish during warmer periods. Additionally, larger bodies of water, such as reservoirs or tailwaters, may have cooler water releases from deeper depths, attracting fish, and would be a better option than fishing sections that have hot water.

Practice Catch-and-Release: Warm water conditions put additional stress on fish, and their survival rate after being caught decreases. Consider practicing catch-and-release to minimize the impact on fish populations and their overall health during these challenging conditions and be sure to Keep Fish Wet.

Check Out Other Species To Target

Even if you’re an experienced trout angler, chances are there are other species in proximity to where you live and are just as fun to catch on the fly. Fly fishing for most is about the exploration, fishing new water, and learning about fish behavior, so why not try and target a new species? If trout fishing is not an option, consider fishing for carp or bass. These species are very fun to catch on the fly and can be “another ball game” to most anglers. Be sure to check in with your local fly shop or check out the articles below to learn more about other freshwater species to target on the fly.

Article from Nelson Oxley. Graphic from Trout Unlimited. Get your stream-side thermometer by clicking HERE.

Check out the articles below:

Summertime Fly Fishing: What You Need to Know

How To Catch Carp On The Fly

Enter the Stonefly Summer Giveaway!!



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