Helping and Harming: Human Impact on Salmon Populations
Lesson Overview

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TIME ALLOTMENT: Two or three 45-minute class periods

OVERVIEW: In this lesson, students use segments from Nature: Salmon: Running the Gauntlet to explore ways in which humans have impacted salmon populations. In the Introductory Activity, students explore different ways in which human actions have helped and hindered salmon populations, including efforts to artificially produce and raise salmon. In Learning Activity 1, students learn about challenges salmon face after being released from hatcheries into the wild, as well as efforts that humans are taking to restore streams and salmon runs. In Learning Activity 2, students explore issues surrounding dams and conduct research on specific dams in the US northwest. In the Culminating Activity, students review information presented in the lesson and debate the merits of human efforts to save salmon. Students write a critical essay about human impact on salmon and propose ideas for future actions. Students discuss their projects with the class.


Learning Objectives:

Students will be able to:

  • Describe why humans are artificially producing salmon and then releasing them into the wild.
  • Discuss at least four actions that humans have taken that have impacted salmon populations. Describe positive and/or negative impacts these actions have had on salmon.
  • Describe the role of hatcheries.
  • Describe obstacles salmon face in nature.
  • Explain the issues surrounding dams and how dams impact salmon populations.
  • Provide details about one specific dam and issues surrounding it.
  • Describe efforts that humans are taking to restore streams and salmon runs.


National Science Education Standards

Grades 9-12:

Content Standard C: Life Science

Fundamental concepts and principles that underlie this standard include:

  • Biological Evolution
    • Species evolve over time. Evolution is the consequence of the interactions of (1) the potential for a species to increase its numbers, (2) the genetic variability of offspring due to mutation and recombination of genes, (3) a finite supply of the resources required for life, and (4) the ensuing selection by the environment of those offspring better able to survive and leave offspring.
    • The great diversity of organisms is the result of more than 3.5 billion years of evolution that has filled every available niche with life forms.
    • Natural selection and its evolutionary consequences provide a scientific explanation for the fossil record of ancient life forms, as well as for the striking molecular similarities observed among the diverse species of living organisms.
  • The Interdependence of Organisms
    • Organisms both cooperate and compete in ecosystems. The interrelationships and interdependencies of these organisms may generate ecosystems that are stable for hundreds or thousands of years.
    • Living organisms have the capacity to produce populations of infinite size, but environments and resources are finite. This fundamental tension has profound effects on the interactions between organisms.
    • Human beings live within the world’s ecosystems. Increasingly, humans modify ecosystems as a result of population growth, technology, and consumption. Human destruction of habitats through direct harvesting, pollution, atmospheric changes, and other factors is threatening current global stability, and if not addressed, ecosystems will be irreversibly affected.
  • The Behavior Of Organisms
    • Organisms have behavioral responses to internal changes and to external stimuli. Responses to external stimuli can result from interactions with the organism’s own species and others, as well as environmental changes; these responses either can be innate or learned. The broad patterns of behavior exhibited by animals have evolved to ensure reproductive success. Animals often live in unpredictable environments, and so their behavior must be flexible enough to deal with uncertainty and change. Plants also respond to stimuli.
    • Like other aspects of an organism’s biology, behaviors have evolved through natural selection. Behaviors often have an adaptive logic when viewed in terms of evolutionary principles.

Content Standard E: Science and Technology

Fundamental concepts and principles that underlie this standard include:

  • Understandings about Science and Technology
    • Science often advances with the introduction of new technologies. Solving technological problems often results in new scientific knowledge. New technologies often extend the current levels of scientific understanding and introduce new areas of research.
    • Creativity, imagination, and a good knowledge base are all required in the work of science and engineering.
    • Science and technology are pursued for different purposes. Scientific inquiry is driven by the desire to understand the natural world, and technological design is driven by the need to meet human needs and solve human problems. Technology, by its nature, has a more direct effect on society than science because its purpose is to solve human problems, help humans adapt, and fulfill human aspirations. Technological solutions may create new problems. Science, by its nature, answers questions that may or may not directly influence humans. Sometimes scientific advances challenge people’s beliefs and practical explanations concerning various aspects of the world.

Content Standard F: Science in Personal and Social Perspectives and Technology

Fundamental concepts and principles that underlie this standard include:

  • Natural Resources
    • Human populations use resources in the environment in order to maintain and improve their existence. Natural resources have been and will continue to be used to maintain human populations.
    • The earth does not have infinite resources; increasing human consumption places severe stress on the natural processes that renew some resources, and it depletes those resources that cannot be renewed.
    • Humans use many natural systems as resources. Natural systems have the capacity to reuse waste, but that capacity is limited. Natural systems can change to an extent that exceeds the limits of organisms to adapt naturally or humans to adapt technologically.
  • Science and Technology in Local, National, and Global Challenges
    • Humans have a major effect on other species. For example, the influence of humans on other organisms occurs through land use—which decreases space available to other species—and pollution—which changes the chemical composition of air, soil, and water.


Nature:Salmon: Running the Gauntlet,” selected segments

Access the video segments for this lesson at the Video Segments Page.

Clip 1: “Producing Salmon”

A look at how humans are producing salmon in an effort to protect the species.

Clip 2: “Humans and Salmon”

An overview of how humans have impacted salmon populations for more than 150 years.

Clip 3: “Salmon’s Journey”

An overview of salmon’s journey after being released from the hatcheries into the wild.

Clip 4: “Restoring Streams”

A look at efforts to remove dams and restore streams and salmon runs.


Bonneville Lock and Dam

This page on the US Army Corps of Engineers, Portland District website provides information about the Bonneville Lock and Dam and includes links to Bonneville Dam Fish Ladder Camera Views at the Oregon Shore and Washington Shore Counting Stations, featuring live images, updated every few seconds, of fish passing through the counting windows.

Dam Breaching and the Lower Snake River Dams

This fact sheet, created by the Bonneville Power Administration, provides information about the estimated costs and impact of breaching (removing the earthen portion of) the four Lower Snake River Dams.

Hatcheries and Dams of the Pacific Northwest

This page on the Nature website features a map of major hatcheries and dams in the Pacific Northwest, as well as the approximate spawning grounds for each salmon species.

Large Dams in the Western United States

This website provides information about the positive and negative effects of dams and specifically highlights the Glen Canyon Dam on the Colorado River and the Bonneville Dam on the Columbia River.

Save Our Wild Salmon

This website provides information about maintaining and restoring wild salmon populations. The following pages could be used in this lesson:

Snake River Dam Operation

This website provides information about the Snake River Dams.

The Dam Challenge (Optional)

This online activity, which is used in the optional activity in Learning Activity 2, challenges users to consider different scenarios where dams exist and to choose whether to repair the dam, keep the dam as is or remove it.


For the class:

  • Computers with internet access.
  • Computer, projection screen and speakers (for class viewing of online/downloaded video segments).


Prior to teaching this lesson, you will need to:

Preview all of the video segments and websites used in the lesson.

Download the video clips used in the lesson to your classroom computer(s) or prepare to watch them using your classroom’s internet connection.

Bookmark any websites that you plan to use in the lesson on each computer in your classroom. Using a social bookmarking tool such as or diigo (or an online bookmarking utility such as portaportal) will allow you to organize all the links in a central location.

Proceed to Lesson Activities

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