Lake Pepperidge Farm®

Teacher Instructions

Background Information:

Part of the job of game wardens and wildlife managers is to be able to make an accurate estimate of the population of certain species in an area. One of the most common ways to do this is through tag and release. The wardens catch a group of the animals, tag them, and then release them back to the wild. Later a new group of animals is caught or observed and the tagged and untagged animals are counted. This gives the wardens valuable information on game stocks, migration and predation. You may want to draw links to animals that may be observed this way in your local area such as salmon, deer etc. In this activity, tag-and-release is used to make an estimate of the population of goldfish in Lake Pepperidge Farm.

Important Information:

• Students should work alone or in pairs as the more samples you take in a class, the better your results will be.
• Rather than counting all of the goldfish before class, use the extra large boxes of chedder fis (1000+) for untagged and a small bag of pretzel for your tagged fish (~250). Then use the serving size and the number of servings to calculate the number of fish in each container.

Suggested Pre-lab activity

• This activity can be used as an introduction to proportions in math classes or as an introduction to population studies in biology. The background you provide depends on the age level of the students.

Data / Observation:

• Ask each group to record their data on the board or a transparency so that the class can share data.

Calculations:

Students should use the proportions to determine the total population of Lake Pepperidge Farm. You may also wish to determine the percent error based on the true value.

You may use a calculator, graphing calculator or spreadsheet for calculations. This depends on your resources and the skill level of the student.

To find the population of the lake students should set the ratio of tagged fish in the sample to total fish in the sample equal to the ratio of tagged fish in the lake to total fish in the lake. They could use average the results for the entire class or they could average first. Do you get the same value both ways? Which is more accurate?

Questions:

• Discuss questions raised by the students.
• Assign students to find answers to questions raised.

Notes

• If a few fish spill from the lake, remove them from the experiment. This could be called migration.
• If the students eat a few fish before the experiment, predation has occured and the students are the predators.
• If a few of the fish have holes or are missing parts, they should also be removed. They could be the victims of disease or pollution.

Student Instructions

The Big Question:

How can we determine the fish population of Lake Pepperidge Farm?

Equipment / Materials:

• Calculator or Spreadsheet
• A large bowl almost full of cheddar gold fish
• a small bag of pretzel gold fish
• cups and/or napkins

Set-Up:

• The mixing bowl should be almost full of cheddar fish. These will be the untagged fish. Count out 200 pretzel fish. These will be the tagged fish in the activity. Release these fish into the lake and allow the sample population to integrate (mix them).
• If a few fish spill from the lake, remove them from the experiment. This could be called migration.
• If the yous eat a few fish before the experiment, predation has occured and the you are the predators.
• If a few of the fish have holes or are missing parts, they should also be removed. They could be the victims of disease or pollution.

Procedures:

• Take a blind sample of fish from the lake by closing your eyes and scooping out a cup full of fish.
• Pour your fish onto a napkin and count the number of tagged (pretzel) and untagged (cheddar) fish in your sample. Record your results.
• Collect data from all the samples counted in your class and record the data in a table.

Calculations:

Using your calculator, graphing calculator or a computer spreadsheet, use proportions to determine the total number of fish (tagged and untagged) in Lake Pepperidge Farm.

Conclusions:

• Record your conclusion on your lab sheet.
• Support your conclusion with your data and your calculations.

Questions

• Why should you get your sample with your eyes closed?
• How accurate do you think your estimate is? What factors might affect the accuracy of the results?
• Do some research and find out what game wardens or wildlife managers in your area do to estimate a population.

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