Counting Piranhas in a River: teacher key

Red-Bellied Piranhas, grade 11 edition, written for 11th grade. A genome, a year of river samples and a study of sounds show how scientists learn about red-bellied piranhas. See what the numbers say.

Read the book. Print this page for the key.

Questions and answers

1. How many fish did the river study identify?
   • 32
   • 326 (answer)
   • 3,260
2. How often were samples taken in the river study?
   • Monthly (answer)
   • Daily
   • Once
3. About how long are red-bellied piranhas when they mature, in the genome study?
   • 16 meters
   • 1.6 cm
   • 16 cm total length (answer)
4. How many annual reproductive seasons do wild red-bellied piranhas show?
   • One
   • Two (answer)
   • Five
5. Why might high-water and low-water periods matter to a study?
   • The study found differences between them (answer)
   • They never differ
   • They stop the fish eating
6. What part of the swim bladder helped make sound?
   • The tail end
   • All of it
   • Only the head portion (answer)

Words

• genome: all its genes
• genera: species groups
• bladder: a body sac
• shoals: fish groups
• pitch: sound height