Fishing 101

Fish Behavior 101.

Why fish eat and why they don’t.

“Any man who claims to understand fish is a fool.” T G

“When you are guiding; some days you will be the dog, other days you’ll be the tree.” TG

Fish are weird; there is just no getting around it. One day they are jumping in the boat, the next, they are nowhere to be found. Some people say that this is what keeps bringing us back to the stream, that this uncertainty we call “fishing” makes us more competitive. After all these years I do understand a little about fish and I would like to share some ideas on why fish are happy one day and not the next.

First and foremost, the fish have to be present in the area of water that you are fishing.

Fish are not always going to be in the same spot. This is especially true at Lees Ferry where you have water that fluctuates on a daily and monthly basis. A spot that is stacked with fish at one flow may be a “fish desert” at another level.

FOOD and SHELTER: the two things that determine the location of fish.

If there is no food present there is no reason for a fish to be in a specific location. However, if you find the highest concentration of food, you will always find the highest concentration of fish, assuming that this concentration of food has been present long enough for the fish to locate it.

At Lees Ferry we have two different feeding plots (each with hundreds of sub-plots). The first is PROLIFIC MIDGE HATCHES. Midges hatch throughout the year; however, by far the largest hatches occur in the spring. The life cycle of a midge is very similar to a butterfly; the adult midge’s sole purpose is to make babies. In a nut shell, this is how it works: the adult midge mates with other midges in a swarm, then the female lands on the water to lay the fertilized eggs, she stays on the water for a second or so then flies off the water and then lands again to lay more eggs (this is a survival mechanism which helps protect her from being eaten by a fish). The eggs slowly sink and eventually hatch into a larvae (think of a tiny caterpillar); the midge lives as a larvae for a long time, living in the algae and mud. Then, though some miracle of nature, the midge larvae get a call to pupate in mass, (think of a butterfly chrysalis). As they pupate, the midge slowly floats to the surface. The size and color of the midge pupae varies with the specie and with 50 different species of midges inhabiting Lees Ferry we have a large variety of sizes and colors of pupae. When the pupae reaches the surface, the midge hatches through the husk and the adult midge crawls out, dries his wings and flies off to repeat the entire process.

Fish do feed on adult midges but mostly on the carcasses of dead midges that accumulate in back-eddies. The importance of a midge as a food source occurs in the emerging stage. When midges hatch, they often do so in mass numbers and for long durations. The fish know this is happening and move into the riffles to feed on the emerging midges.


Midge pupae are small, anywhere from a size #18 to #30. It takes a lot of midges to sustain a Lees Ferry trout; however, if you were to measure the midges as a percentage of total biomass, they far exceed all other food sources combined. Riffles are areas of river where the water transitions from very shallow to slowly deeper water. Do not confuse “points” with riffles, they look similar, however, the water on “points” transitions from shallow to deep in a short area.  Fish move into the shallowest part of the riffles to feed on the CONCENTRATED MIDGES. Imagine if you had a thousand midges in a column of water that was 3-feet deep or 6-inches deep, the midges are going to be much more concentrated in the 6-inch deep water. This is why we often tell people that they are wading in areas that they should be fishing.

The other kicker to midge hatches is water volume: as the water flow increase the midge hatches decrease. This is something that I do not understand, but I know it to be true. So the best midge fishing is always in lower water flows. If I were to put a number to it I would say the best midge fishing is in water less than 14,000-cfs. This is why in the spring, (March, April, and May) some of our best fishing is on the weekends when the water is at the lowest level of the week. We often see good midge hatches in September and October, but not the swarms that happen in the spring.

The other situation that makes fish eat at Lees Ferry is HIGH WATER FLOWS. Anytime the water flows are high (above 16,000-cfs) food is dislodged, moved around, and transported by the current. Here we are talking about WORMS and SCUDS. High water flows normally occur four months each year, the two hottest months, July and August, and the two coldest months, December and January.  This is all about electrical demand and high demand equals high flows. There are exceptions and high flows can occur at other times if there is a high lake level in Lake Powell and high runoff into the lake. This happened 1983-86 and a couple of other times in the ’90’s. The best fishing periods at Lees Ferry has always been preceded by periods of higher than normal water flows. In high water, the fish will concentrate in the riffles and the tail out of the riffles to feed on the drifting food. In addition to the riffles, feeding fish can be found though longs runs between riffles. This is the time of year that the most productive fishing is usually from a drifting boat as opposed to wading.

WEATHER. Any change in the weather can shut off fish feeding. I cannot explain why this happens, however I guarantee you that it is true. I was in Placentia, Belize fishing with noted guide Eworth Gartbutt. A cold front was pushing through (it dropped to a frigid 78 degrees) and Eworth said “Terry, you realize that permit fishing and a north wind do not go together.” I thought to myself how fishing is fishing no matter where you are in the world.

Impending weather change makes fish at Lees Ferry not want to eat. It might look like a normal day, the sun may be shining and not a breeze is blowing, but a storm is on the way and the fish know it and for whatever reason they decide to take the day off from eating. I saw it a week when I was fishing with a customer I have fished with for two decades and the weather that day was a classic cold front: it was windy, cold, and spitting rain. My client is a good stick and at the end of the day he had landed two fish and his companion had landed three.  They were all smaller fish. The next day started cold, but warmed quickly due to the cloudless day and bright sunshine. They landed more than 30-fish including a 19-inch football and several that were in the 18-inch range. If they had only fished the one day they might have concluded that the fishing at Lees Ferry sucks or that we are “blowing smoke” or overrating how good the fishing is … that actually happened with one trip when a couple of guys had a similar experience fishing with me one day with a cold front pushing through.

So, poor weather makes for poor fishing most of the time, however, there are exceptions and I have seen some great fishing on days the wind is howling and the snow is flying. I can’t explain this, but I can tell you that more often than not, a change in the weather will affect fishing in a negative way.