With this brutal hot weather in the East the last 3 weeks the pattern of emerging insects for the most part has changed and not for the good. This is especially true on streams that may be restricted by time constraints. What tends to happen is that the insects will emerge during the coolest time period as governed by the overall environmental conditions on the stream. The insects tend to have a built in thermostat. On some waters that don’t cool down until 3:00 a.m. that’s when the flies actually emerge . Furthermore, the spinners may return at the same time. You might say well then that’s when the fish will be rising…right?
Well maybe..! Because the stream temps on a freestone stream must be falling towards an optimum range for the fish in that stream. What does that mean? Well the most misunderstood thing by fisherman and even some biologists is how water temps affect trout. In each stream depending upon the fish and conditions that the trout live under they may or may not feed. In one stream when the water temps approach 69f the fish may feed while in another stream the it may be 67f or lower.
You can also get a summer blizzard where 3 or 4 species will come back in a short time period and the fish will feed like demons for around 15 minutes and that’s it for the day. I observed these patterns many years ago of Slippery Rock Creek in Western Pennsylvania where I would study and fish all night.
What about spring creeks? Well for some reason similar patterns occur even though the water temperature range is 46 to 50f. The insects tend to come off in the coolest part of the day or evening in most instances with the exceptions of midges.
I hope you enjoy this extension of Fly Hatches. We’ll be discussing all of the things that effect fly fishing hatches from stream ecology to which flies and imitations to use for better success. Your comments are invited and I wish you the best in your fly fishing pursuits.
aquatic and environmental scientist