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Critter Search


This activity is related to EEK stories included in Lakes are Great and the Water Critter Key.

After your students have been online and practiced their aquatic critter keying skills using the Water Critter Key, head out for a local river or stream, collect come critters, and give the real thing a try.

Description: Groups will collect aquatic insects and animals from streams and rivers to determine the water quality.

Objectives: By participating in this activity, your group will:
1. Identify aquatic insects and animals that live in the stream or river.
2. Learn about the water quality based on the type of macroinvertebrates collected.
3. Safely return the collected critters to the water.

Time: up to 2 hours. Best times are fall or spring.

Materials: invertebrates key, macroinvertebrate tally sheet, permission slip, hip boots or old shoes, white trays, magnifying glasses, plastic cups, tweezers, spoons, fine-meshed net with a long handle

Background: Have you ever wondered what lives in a body of water? Waterways are filled with life, from tiny insects to fish that dart between the rocks.

Many aquatic insects are sensitive to environmental changes in streams and rivers. This is because many aquatic insects life in the water for more than a year as they develop. Because of this life cycle, scientists have developed methods of determining water quality that are based on the number of "pollution sensitive" insects and animals found in a section of streams or rivers.

Critters As Water Quality Indicators
Different animals have different tolerances to pollution. The macroinvertebrate tally sheet separates insects into 4 different groups based on their sensitivity to pollution.

Group 1. These critters are very sensitive to water pollution. Insects in this group cannot live in polluted water. As the amount of pollution rises, the number of these insects goes down.

Group 2. These critters are somewhat sensitive to water pollution. Insects in this group can be found in either very clean or mildly polluted water.

Group 3. These critters are fairly tolerant to pollution. Insects in this group can be found in either clean or somewhat polluted water.

Group 4. These critters are found in poor water quality. Insects and animals in this group are very tolerant of polluted water, but they can still be found in clean water. As pollution worsens, tolerant insects and animals become more abundant.

Before Collecting
1. Inventory the area. Survey the entire stream or river that you plan to monitor. Look for possible safety concerns and take an inventory of the area.
2. Choose a site. Select an area for monitoring. You should choose a site with shallow, fast-moving water. These sites are called riffles. A riffle has fist-sized stones, with a water depth of 3-12 inches. Remember, in the spring, the water may be a little deeper.
3. Get permission. Ask for permission to monitor the site if it is located on private land.

Steps in Collecting
1. Use the net. At the riffle, place the fine-mesh net downstream from where you are standing so the water current passes you first, then flows into the net. Be sure that the bottom of the net fits tightly against the stream bed so no water can flow underneath it.
2. Kick away! Kick the rocks and gravel on the bottom of the streambed. This will dislodge critters that live on or under rocks, allowing them to float downstram into your net. Use your hands to "scrub" some of the rocks, too. Scrubbing will help you dislodge even more insects.
3. Remove the net. When you've completed Step 2, carefully remove the net from the stream or river. Use a scooping motion to bring the net towards you without losing anything that's caught in the net.
4. Empty the net into trays. Place about one inch of water in each white tray and empty the contents of your net into them. Look for anything that moves. Sift through the debris (leaves, algae, sediment) to look for small critters that may be hiding. Little animals are more abundant than big flashy things such as fish and crayfish.
5. Repeat Steps 1-4. Continue to collect insects until 100 bugs are in your basin.
6. Identify your catch. On the streambank, do your best to carefully identify your catch. Use the spoons and tweezers to pick up the insects and separate them into look-alike groups. Then, use the macroinvertebrate tally sheet to help you identify the animals.
7. Record the critters found. Use the macroinvertebrate tally to record the kind of animals that were collected from your site. Following the instructions given, use the chart to assess the stream's water quality.
8. Return the catch. Return the critters to the water after you've identified them.
9. Watch for changing water quality. Because invertebrate counts depend on the time of year, the ages of the collectors, and other factors, they are not always accurate indicators of water quality. However, these counts can be used to assess changes in water quality over time.

If your records show that water quality is getting worse, take a look at what's happening near the stream. Check for discharge pipes, erosion, runoff, and other possible sources of stream pollution. If you see drastic changes in water quality or a drastic difference between different locations on a waterway, contact your local Department of Natural Resource office.

--Reprinted with permission from the WAV program. Water Action Volunteers (WAV) is a statewide program for Wisconsin citizens of any age who want to learn about and improve the quality of Wisconsin's streams and rivers. The program is coordinated through a partnership between the Wisconsin Department of Natural Resources and the University of Wisconsin - Cooperative Extension. Materials revised winter 1998. For more information, contact the WAV Coordinator at 608-265-3887.

Note: This activity is for fun and exploration. For official monitoring data collection information, contact the WAV coordinator.

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