What Trout Eat

What Trout Eat

When fly fishing for trout, you of course use fishing flies designed for trout fishing. So it is helpful to know what trout eat. They eat mostly anything they can get in their mouth that is a food group. Food groups can be classified into aquatic and non-aquatic or terrestrial groups.

  1. Aquatic groups are primarily the immature or mature stage of an aquatic invertebrate insect that lives the beginning of its life underwater, hatches to become an adult and mates. Then the female lays eggs back in the stream, lake or pond to hatch the next generation.
    1. The Mayfly, Caddis fly, Stonefly, & the Midge are the four classic categories of aquatic insects a fly-tier imitates. Each has 3-5 stages in its life cycle.  The underwater stage of an aquatic insect is the nymphal form, or commonly called a nymph. (1)

      There can be more than one underwater form, or stage such as larva & pupa. An insect that passes through 3 underwater stages to becoming an adult is said to have a “complete metamorphosis”—egg, to larva, to pupa, then emerges as an adult. (1)

      Caddis flies & midges typically have a complete metamorphosis. An insect that only passes through 2 underwater stages of egg & nymph is said to have an “incomplete metamorphosis”. Mayflies & Stoneflies have an incomplete metamorphosis. (1) 

      Of these the Caddis and Midges are the most important. The caddis is important because there are between 7,000 and 9,000 different species worldwide depending on which reference you consult. In any case there a lot of caddis for trout to eat. Midges are one of the most important trout foods because they hatch year round. If not for midges, many trout and other freshwater stream fish would not survive winters. During a midge hatch the water column and stream bottom may be alive with hundreds of thousands of these small insects. (2)   
       

    2. The other main aquatic group consists of prey or forage fish such as crayfish, sculpins, scuds, minnows, other young of their own and other trout species.  Fish eggs during mating season of other trout species. Browns follow the rainbow spawn and vice versa.
    3. Aquatic Worms that live their lives in streams are also a tasty morsel.
    4. Damsel fly and dragon fly nymphs and leeches are another main aquatic food group. Damsel and dragon flies are mostly a lake or pond insect while both lakes and streams have leeches.
       
  2. Non-aquatic food groups consist of terrestrial insects such as ants, beetles, grasshoppers, earth worms. In the spring, rains can wash earth worms into streams. In the fall, winds often blow ants, grasshoppers and beetles into the water. Grasshoppers in particular are a large meaty meal for a trout or bass.

    Mice and small ducks also are eaten by larger trout. Mice tend to swim from one place to another during the darkness, early morning or dusk hours. Large brown trout in particular will take a mouse pattern in a size 2 or 4. In some ponds, the trout may grow large enough to eat small ducks off the surface.

References:

(1) High Plains Drifters FFF Club – Basic Fly Tying Manual – Reprinted with Permission
(2) Successful Fly Fishing for Trout Minicourse – Sign up for the course for more information on Trout Fly Fishing

 Flies to represent the major groups link to second article

Tight lines and Good Fishing,

Marshall Estes, Author
"Successful Fly Fishing for Trout"