Catch the Critter Game

designed for the New York Trout in the Classroom Program

    To help students learn the different pollution-tolerance levels of various species of macroinvertebrates, and to understand how scientists use macroinvertebrate sampling to judge the health of a stream.
    The streams of New York City's watersheds are home to many species of macroinvertebrates.  Scientists from the New York City Department of Environmental Protection,  New York State Department of Environmental Conservation, and other organizaions study aquatic macroinvertebrates.  By looking at the variety of animals they found in a particular stream scientists determine the health of the stream.  Although it seems contrary to have "bugs" living in our drinking water, we know that these creatures not only help clean the water but also demonstrate healthy water which is safe for drinking.  Some of the species that signify health streams include Mayflies, Stoneflies and caddisflies.

    Aquatic macroinvertebrates (such as insect larvae, mollusks, and crustaceans) are critical to stream ecosystems.   Many species are herbivores that eat the algae, aquatic plants, and fallen tree leaves in a stream.  Others are predators that prey on smaller invertebrates, or even on small fish.  Some swim in the water column, while others cling to rocks or leaves.  But no matter what their adaptations, macroinvertebrates are key species to have in streams. You can see images and find out more about aquatic macroinvertebrates at the NYSDEC Key to Aquatic Macroinvertebrates online.

    Knowing a little about what these macroinvertebrates can tolerate can help scientists and students get a picture of the health of a stream.  Critters such as leeches, midges, and many worms can live in almost any water, polluted or not.  Mayflies, stoneflies, and caddisflies, on the other hand, can only live in very pristine, clean, cool water.  A stream with these macroinvertebrates could probably support trout, and a stream without mayflies, stoneflies, and/or caddisflies would probably not be hospitable to trout (or be clean enough to drink).  When scientists see clean-stream-only insects in the stream, then they know that the stream is doing well.  Scientists also often look for biodiversity.  The more different types of animals live in a stream, the healthier it is, as well.

Catch the Critter cards, game instructions, scoresheet (2-4 copies per student), a pencil


  1. Print out sets of Catch the Critter cards on cardstock so that there are enough sets for the students to play in groups of 2-4.  (Optional pre-lesson activity: have the students decorate the backs of the cards with a repeating pattern or words and then cut out the cards.  You may want to cut the cards yourself and laminate them before playing.)
  2. Using the game instruction sheet, introduce the students to aquatic macroinvertebrates, the concept of pollution tolerance, and biodiversity.  Review how to play memory or concentration-type games.
  3. Have the students play one round of Catch the Critter, just to get the hang of it.  Then, walk them through filling out their scorecard, and have them do all the arithmetic involved.
  4. In new groups, have the students play one or two more rounds, as well as complete their scoresheets.

    In a big group, have students report out who won and why.  Which macroinvertebrates meant that the students had very clean streams?  How was pollution tolerance given value in the game?  How was biodiversity given value?  What do students expect to see when they visit their trout release site?  What kind of stream would trout like?  Why?

Donate to Trout in the Classroom

Contact Us | TU.ORG

Search This Site: