Millions of Salmon Return Home | National Geographic

How many eggs does a female salmon typically lay, and how many of those are likely to survive to adulthood and return to spawn?

• 400 eggs, 200 survive

• 4,000 eggs, 2 survive

• 40,000 eggs, 20 survive

• 400 eggs, 20 survive

How far do salmon travel from their birthplace to the ocean and back to spawn?

• A few kilometers

• Several hundred kilometers

• Several thousand kilometers

• Only within the river system

What is the typical cycle for the Fraser River sockeye salmon population?

• A yearly cycle with consistent numbers.

• A 2-year cycle with alternating high and low returns.

• A 4-year cycle with a massive population year, a sub-dominant year, and two quiet years.

• A 5-year cycle with unpredictable population sizes.

What environmental factor is increasingly affecting Fraser sockeye salmon and causing a "lethal threshold" in water temperatures?

• Overfishing

• Pollution

• Climate change

• Predation