Counting the Years of a Barracuda: teacher key

Barracudas, grade 12 edition, written for 12th grade and up. Scientists disagree about how old a great barracuda gets, where its young leave shallow water and how many there are. Read where the evidence agrees and where it does not.

Read the book. Print this page for the key.

Questions and answers

1. What did MarAlliance use to find the ages of the barracuda?
   • Ear bones (otoliths) (answer)
   • Scales
   • Tags
2. How many great barracuda were in the 2012 genetic survey?
   • 38
   • 290
   • 246 (answer)
3. Why can a small blood sample be useful in the Bahamas study?
   • It can show whether a wild fish carries the toxin, without harming it (answer)
   • It shows the age of the fish
   • It shows where the fish spawns
4. The genetic survey found high gene flow across more than 16,500 km. What does that suggest?
   • That the fish stay in one reef
   • That the species looks more like a large ocean predator than a reef fish (answer)
   • That all barracuda are one age
5. What does juveniles mean in: where juveniles leave the estuary?
   • Old fish
   • Young fish (answer)
   • Hunters

Words

• otoliths: fish ear bones
• juveniles: young fish
• ciguatoxin: natural toxin
• taxonomic: about naming kinds
• mitochondrial: inherited cell