Name:
Estimating Population Size by Random Sampling
Scientists cannot possibly count every single lionfish in a population on a coral reef. However,
in order to predict potential ecological impacts, they need to estimate how many fish are present
in the population. In this activity, we will design a method for estimating lionfish population
size without being able to count every single fish.
The grid below represents a coral reef that is 10 meters long and 10 meters wide. Each box in
the grid is 1 meter by 1 meter. Each dot represents one lionfish.
Procedure: As a class, we will discuss and decide on a method for estimating the size of the
lionfish population. Write down the steps below.
Use the procedure we discussed to fill in the table below.
Total number of lionfish:
Average number of lionfish per cell:
Total number of lionfish on the coral reef:
Now count how many lionfish are actually in the population. Record your observations below.
Actual number of lionfish:
Estimated number of lionfish:
Questions:
1. How close was your estimated number of lionfish to the actual number of lionfish?
2. Why did we use paper slips to select grid segments?
3. A lazy ecologist collects data from the same coral reef. However, he only counts lionfish
along the sand channel where they are easy to see. He counts the fish that are located in
the ten boxes in row J. How will his estimated population size compare to yours?
4. Do you think it is ok for ecologists to estimate the size of population instead of actually
counting every individual? Why or why not?
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A B C D E F G H I J
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A B C D E F G H I J
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A B C D E F G H I J
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A B C D E F G H I J
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