Counting Fish: Watch It!
The two nets in the lake will catch a random sample of fish. This means that some fish will get caught and others will not; which ones get caught is a matter of chance. Data from a random sample often lead to more accurate results than data from a sample that is not random, so this is a good way to estimate the health of the walleye population over time.
Here's one way to think about sampling. Imagine a jar filled with gumballs: there are a lot of red, some green, and only a few yellow ones. If you reach in and grab a big handful, you will likely end up with mostly red gumballs and a couple green ones (and maybe a yellow, if you are lucky!). The gumballs in your hand will probably look very much like the rest of the jar.
It's the same with fish in the lake. When the Ojibwe pull up the nets, they will find many fish trapped inside, including bluegill, pumpkinseed, and walleye—all types of fish that live in the lake. Hopefully, this catch is representative of the larger population of fish in the lake. Scientists can use this information to estimate the abundance of each kind of fish in the lake. Watch this video and find out what the teens learned by sampling the fish in the lake. After watching, answer the question below.
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Counting Fish
How were the teens able to learn that the walleye population was healthy without catching all the fish in the lake? Explain what they did and how they decided that the walleye was healthy. Write your answer in two to three sentences.
