Trout Have Keen Senses

Spawning cutthroat trout, Lamar Valley; Jay Fleming; July 2011; Catalog #19585dPhoto: flickr: Jay Fleming

Trout begin their lives as egg then hatch and live as fry with yolk sacs for about 4-5 weeks. Once the sac is finished, they must forage on their own as tiny free-swimming fish. They stay in the somewhat protected shallow water and feed on midge larvae. At 3 to 4 inches long the fry begin to eat larger macro-invertebrates. In past posts I cover nymphs and nymphing tactics. You will see how a trout’s mainstay is nymphs and other sub-surface food sources.
Trout have many predators from below, minks, otters and other fish, and from above kingfishers, osprey, heron, and raccoon. This is important to understand because many times a stealthy approach is your only chance to catch easily spooked trout. Like so many forms of wildlife, a trout’s senses are keen.

They have a 180-degree vision with each eye. Add the ability to see independently from each eye and you can understand why stealthy approaches are so important. They can focus with both eyes directly in front of their nose and consequently have a blind spot just behind them. Obviously it is best to approach a trout from behind whenever possible.

Cone of vision, in a nutshell, is the area of sight – or the angle of sight. A trout’s cone of vision is comprised of two factors: angle of vision and water refraction. At the top of the cone is the trout’s window to the out of water environment. Because of refraction a trout’s cone of vision is reduced to 97 degrees. So what does this mean for us the angler? Essentially how close can you get to the fish without being seen? An additional factor is how close the trout is to the water surface. A misconception is that the closer the trout is to the surface the more it sees. Due to refraction it is actually it is the opposite but the amount you can get closer without being seen is nominal. It is fair to say that you want to maintain a stealthy approach always.

They are very sensitive to sudden movement; waving hand and stick, flash of light, and fast moving shadows as examples. Watch your movements underwater. Fish cannot hear you talking with your fishing buddy but they can sense vibration and hear your boots tumbling over the rocks underwater. The calmer the water the quieter your approach must be. When spooked trout seek safety. This is in the form of deep water, protective structure, or fleeing the area completely. If only slightly alarmed by what may be a possible predator trout may hold in their current position but remain very tense in preparation to flee to safety. This is apparent when fishing over trout that have stopped eating, such as rising, due to your presence but remain in sight.

Trout don’t have hands but they have mouths. With so much biomass floating in good water trout put things in their mouth and spit out unwanted items regularly. They do this very quickly, this is important to consider when fishing nymph imitations because the trout’s take will be quick and subtle. We’ll cover this aspect more in future posts.

I hope this article helps you find more enjoyment on the stream.

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