This Instructional Activity is a part of the Lesson 20, Unit 6, Grade 6. Yellow perch are part of the food supply of larger fish and other wildlife in the Great Lakes region. Why do you think that the scientists worried when they saw the histogram of fish lengths given previously in Exercise 2. The small percentage of short fish means that there are fewer young yellow perch than older yellow perch. Sketch a histogram representing a sample of yellow perch lengths that you think would indicate the perch are not in danger of dying out.