4th Grade Science Lesson

Why Can't the Salmon Get Home? Investigating Stream Blockages and the Salmon Run

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4th GradeNGSS Phenomenon-Based4-LS1-1, 3-5-ETS1-1, 4-ESS2-150 min

Learning Objective

Students will be able to identify how the structure of a stream (and objects within it) affects the function of salmon migration, explain cause-and-effect relationships between stream blockages and decreased salmon counts, and propose evidence-based solutions to restore salmon passage — addressing 4-LS1-1 and 3-5-ETS1-1.

Lesson Overview

Students observe the anchor phenomenon of salmon struggling to migrate upstream during the salmon run, then investigate how stream blockages and disruptions cause decreased salmon populations. Students apply the NGSS crosscutting concepts of Cause and Effect and Structure and Function to identify problems and engineer solutions.

Materials

Stream simulation tray (aluminum baking pan) per group
Small plastic salmon figures or foam fish cutouts (10 per group)
Rocks, pebbles, and craft sticks to simulate blockages
Modeling clay
Blue food coloring and water (to simulate stream flow)
Plastic straws (to simulate culverts/fish ladders)
Rulers
Student investigation handout (printed)
Anchor phenomenon video or printed photo set of salmon run
Whiteboard markers and sticky notes
4-Quadrant note sheet (printed)

Scaffolded Task Progression

1Task 1

Look at the diagram below showing a salmon's body. Label the tail fin, pectoral fins, and streamlined body shape. Then answer: How does each structure HELP the salmon swim upstream against fast-moving water?

[ Interactive graph / diagram, available in the full lesson ]

2Task 2

Study the two stream images below. Stream A has a clear path with no obstacles. Stream B has a large concrete dam, a pile of logs, and a broken culvert (pipe) blocking the water.

[ Interactive graph / diagram, available in the full lesson ]

In your science notebook, complete this sentence frame:
In Stream A, salmon CAN migrate upstream because ___. In Stream B, salmon CANNOT easily migrate upstream because ___. This is an example of Cause and Effect because ___.

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