Trout Diet

Trout Food

As I mentioned in my article on basic casting, the best fly caster in the world will rarely catch a fish if he isn’t presenting to the trout the right fly.  What is the right fly?  Well, that changes throughout the day and throughout the seasons.  So, a basic understanding of how trout feed and stream side entomology can help you learn to pick the right fly.  After all, the difference between the right fly and the wrong fly is the difference between catching and fishing.

So, First, let’s talk about what trout eat.  If you have come this far and are thinking about live bait or powerbait, I need to be real honest with you and say you would be better served finding another website.  Thanks for stopping by.   A fly fisherman will never use anything but artificial flies, unless he is stranded in a remote region of the world like on the shows Survivorman and Man VS Wild.  On a cautionary side note, if you are casting a fly in an environment where all the anglers around you are chucking bait, reel in and find other waters.  Just like the spoiled dog that scoffs at dog food because he has been fattened on hamburger, those trout will skip your fly for powerbait and live bait every time.

I am going to oversimplify this section to make it as easy to understand as possible.

Aquatic Insects

Basically, there are four types of aquatic insects that trout feed on.  The Mayfly, The Caddisfly, the Stonefly and The Midge.

First let’s talk about the Queen of the Waters, the Mayfly (Ephemeroptera).  There are hundreds of types of these insects.  They are typically smaller than an inch and vary in size and color from region to region.  Their life span is about a year and 99% of that is spent in the water as a nymph or larvae.  When the mayfly reaches maturity, it makes its way to the surface and emerges from its nymph case a fully formed, winged adult.  Now the mayfly is a dun because its upright wings are dun or grey in color.  When it’s wings dry and can carry the weight of the adult mayfly, it flies to the banks where it undergoes its final metamorphosis into the spinner stage.  This is the mating stage and end of the mayfly life.  On the water, fly fisherman look forward to the swarms of mayflies in this stage.  There is easily identifiable up and down flight activity at this time as the mayflies mate and the females lay their eggs on the water.  They die very soon after hitting the water with their wings laid out, or spent, flat on the surface.

The Caddis fly (Trichoptera) is different from the mayfly in that its entire metamorphosis from nymph to adult takes place under water.  From an egg, the caddis becomes a free swimming larva (also know as a free living larva) or a case larva.  The free swimmer is wormlike and slowly drifts with the current along the bottom.  The case maker caddis will construct a case around themselves from sand or organic material in the water and attach to rocks in the stream.  When the larvae begin to mature, they close off their case, or build a cocoon around itself to complete its metamorphosis to an adult.  It then reaches the Pupa Stage and is fully mature.  At this point, it will trap air in its case and rapidly make its way to the surface.  Once at the surface, the pupa sheath splits open and the adult caddis promptly takes off into the air and makes it’s way to the brush near the water’s edge.