Directions: Use the information provided and your knowledge of Life Science to answer the following questions. Show all work where necessary.
Directions: Use the information provided and your knowledge of Life Science to answer the following questions. Show all work where necessary.
Pacific salmon (
Egg Stage (Birth): Salmon lay eggs in freshwater gravel nests called redds. The eggs incubate through winter and hatch in early spring.
Alevin Stage: The young fish, still carrying a yolk sac, remain hidden in gravel for several weeks.
Fry and Parr: As the yolk is absorbed, fry emerge and begin feeding. They grow into parr with distinct markings and live in freshwater for 1–3 years.
Smolt: The fish undergo physiological changes that allow them to survive in saltwater and begin their migration to the ocean.
Adult: After several years at sea, adults return to the same river to spawn.
Death: Most Pacific salmon die shortly after spawning, releasing nutrients that feed other organisms.
Studies from NOAA Fisheries and the USGS Columbia River Basin Monitoring Program show that temperature and river flow affect salmon growth and survival at each stage:
In cool, stable rivers (10–12oC), egg survival is around 80%, but drops below 50% in warmer waters.
In rivers with strong flow and clear passage, smolt survival exceeds 75%; in dammed or polluted systems, survival can fall to 30–40%.
Ocean stage duration varies: warmer ocean temperatures shorten lifespan but reduce reproductive success.
Despite the complexity of environments and timing, the same pattern repeats: birth to growth to reproduction to death. Modeling the salmon's journey helps students see how life cycle diversity still reflects the unity of biological processes.
Water Temperature (oC) | Egg Survival Rate (%) | Smolt Survival in Free Rivers (%) | Smolt Survival in Dammed Rivers (%) |
|---|---|---|---|
8 | 88 | ||
10 | 84 | ||
12 | 80 | ||
14 | 68 | ||
16 | 55 | 75 | 40 |
18 | 40 | 78 | 35 |
Provide the evidence and reasoning for the claim:
"Salmon have a unique, migratory life cycle but still follow the same sequence of birth, growth, reproduction, and death. "
Respond with both evidence from the passage and reasoning that connects your evidence to the claim.
Refer to Table 1 in the Salmon Life Cycle and Migration resource.
What trend do you notice about egg survival as water temperature increases?
Which of the following best explains how salmon are similar to frogs and butterflies?
Explain how salmon life cycles show both diversity and similarity compared to other living things.
Refer again to Table 1.
In which type of river (free-flowing or dammed) do smolts survive better, and why might this be?