Water Temperature

What is the most essential tool you should never be without when stillwater fishing, the one item that directs your choice of line, where and when you fish, your presentation approach, retrieve styles, and fly selection? Hint: one tool answers all of these questions.

Photo by V. Loftus, all rights reserved

Photo by V. Loftus

Did you guess thermometer? If so, you got it! Using a thermometer and understanding how water temperature effects feeding behavior is critical to success. Water temperature is the supreme ruler in determining where trout seek shelter, find food, and whether they have adequate oxygen. If their basic needs are not met, trout will not feed. External conditions such as low barometric pressures, northerly winds, and a full moon can stop the bite or at a minimum drastically slow it down. Water temperature, however, is key to determining what, where, and when fish eat.

A quick trip over to one of the Oregon Fishing Club lakes offered a delightful respite from the long, dark and rainy Northwest weather. Lakes in the Portland Valley lose their ice in January as they are low in elevation. Frigid air temperatures have cooled the surface water temperature which causes the water to stratify into layers separating the cooler water above from the warmer regions below. During winter conditions, fish hold in the deeper water where it is warmer. Fish are cold-blooded and are unable to regulate their core temperature. In colder water their metabolism slows, their movements become lethargic, and their need for food reduced. Fish holding in deeper water are not feeding, so all you can do to catch them is to provoke a reactive bite. In this case it is not a matter of line selection, specific pattern or retrieve that assures success.

Photo by T. Loftus, all rights reserved

Photo by T. Loftus

Since the water temperature warms first along shallow shoreline areas, I began by probing the shoreline. Since there were no insects on the water, I used a full sink intermediate line with a sealbugger, a suggestive pattern. Yielding no results, I moved into deeper water, probing depths of 4-7 feet. As water warms, a thermocline layer develops that separates the warm and cooler levels of the lake. Fish will move into this layer which is normally 4-6 feet below the surface. The timing that this occurs is relative to external elements including elevation, size, and depth of the lake.

Slowly I moved along in 7-foot water using a slow 6-12 inch retrieve. Long slow retrieves caused the fly to sink deeper in the water column. Stopping the retrieve allowed the fly to sink even deeper. I took a break from fishing to enjoy an energy bar. While eating my snack, a trout took the fly. I started the retrieve, realized I had a fish on, and my energy bar went flying into the water as I tried to land the fish. The hook up occurred because the fly was slowly sinking and provided the necessary time for the fish to react without having to chase the fly. As a result, I added a 4-6 second pause between the strips resulting in hooking another fish. I yearned for the energy bar that had sunk to deeper depths of the lake.

I continued scouting the lake looking for underwater structure and weed beds where trout would be holding. Weed beds provide prime habitat for various food sources as well as protective cover and oxygen for the trout. During the daylight hours, plants in the top layers of the lake absorb energy from the sun and absorbing carbon dioxide while giving off oxygen through photosynthesis. I located some weed beds and cast the fly in between the weeds. This yielded a few more hook ups from the lethargic trout. With very soft takes the trout took the fly during the pause between retrieves.

In summary, during early spring conditions, start your day by taking the temperature of the water. If water temperature is below 50 degrees, fish will be reluctant to chase anything. Adjust to the cold water conditions by slowing down all aspects of the presentation, allowing more time for the trout to see the fly. Retrieve twice as slow as normal and then slow it down even more. Another form of presentation is the use of a floating line with an indicator and present a chironomid a few feet above the bottom. This can be a killer approach in attracting reluctant trout who are not willing to move in cold water conditions.

Tips when fishing in cold water:

Probe shoreline areas where water temperature warms up first.

Fish in between weedy areas that offer trout shelter, food, and oxygen.

In early spring fish mid-day when the water temperature warms.

Use suggestive patterns such as a seal bugger, leech, or minnow patterns when aquatic insects are not available.

Use slow retrieves with pronounced pauses in between.

Watch for the February Blog which discusses the question – “Which is more important fly or presentation?”


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