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Idaho State University

Trout in the Classroom

The purpose of Trout in the Classroom is to raise awareness about Idaho’s aquatic resources by providing hands-on learning opportunities for Idaho students. Trout in the Classroom encourages students to actively participate in the learning process. By observing and caring for trout, students gain an understanding and appreciation of a trout’s life cycle and habitat requirements.

Dichotomous Key to Identify Fish

Week of April 6th

A dichotomous key is a tool that allows people to identify plants, animals, rocks and anything that you might want to identify in nature. Here you will be using a dichotomous key to identify fish. Using a series of questions that divide the fish into two groups, you will be able to find the correct name for the fish.

Try out the online activity to identify the different fish.

Online Fish Identification


If you are feeling good about using a key, here is a little harder one where you will identify aquatic critters. These include some of the critters that we studied last time as trout food. They are also important indicators of water quality in a fishing stream. After the first identification, you will need to print the image below to key out each of the critters.

Aquatic Critters Identification

What Do Trout Eat?

Trout eating a mosquito larva

Week of March 23rd

The cold, clean rivers and streams in Idaho attract fly-anglers from across the country who come to fish for trout in a pristine environment. Fly-anglers use artificial flies as bait. Artificial flies look similar to the trout’s natural diet of aquatic macroinvertebrate species.

Macro means large enough to see with the naked eye and invertebrate means they have no backbone. These animals live on rocks, logs, sediment, debris and aquatic plants during some period in their life. Macroinvertebrates include crustaceans such as crayfish, mollusks such as clams and snails, aquatic worms and the immature forms of aquatic insects such as stonefly and mayfly nymphs. Aquatic macroinvertebrates, such as insect larvae, are a large part of a trout’s diet. The flying adult forms of the aquatic insects are also food for trout.

Different species of macroinvertebrates have different characteristics, including body shape, exoskeleton color, feeding preferences and in-stream behaviors.

To make their fishing flies, anglers closely study the species they are imitating. They then wrap hooks with thread, yarn, feathers, and other materials of various colors to mimic the macroinvertebrate. To be successful, fly-anglers need to have knowledge of what fish eat and need knowledge of the food being eaten. Anglers need to know what the macroinvertebrates look like and their habits to trick a fish into biting their flies.

This information comes from Trout in the Classroom Curriculum Published by the Idaho Department of Fish and Game Funding provided by Wildlife and Sport Fish Restoration.

Meet the insects Trout like to eat


Toothed Dragon