Following this lesson, students will be able to:
- Name three basic requirements for fish survival.
- Name several Great Lakes fish species and their habitat.
- Explain two ways human activities impact Great Lakes fish habitat and affect the survival of fish and other organisms.
- Make purposeful observations of a nearby aquatic area using illustrations, photographs and narratives.
- Describe scientific questions about habitat and human impact based on observations.
- Use observations to predict which Great Lakes fish might favor that particular habitat.
A healthy environment supports a variety of native species. This is especially true for Great Lakes fish. Different species of fish require specific habitats, and loss or alteration of fish habitat can lead to population declines. This lesson explains some of the characteristics of healthy fish habitat and guides students in making their own field observations and scientific predictions.
Like other living creatures, fish must meet certain basic needs for survival. Water, food and shelter are among the most important requirements:
- Water: Fish not only live in water, but they get oxygen from water. They breathe by taking water into their mouths and forcing it out through gill passages.
- Food: Fish must be able to find enough to eat at various life stages, whether they feed on microorganisms, small fish or larger prey.
- Shelter: Fish need a place to hide from predators and to reproduce. Some fish find shelter among submerged aquatic plants and shoreline vegetation, while others hide among rocks, soft sediments, or blend into clear, open waters.
Where can fish meet these needs? Fish are adapted to living in a variety of habitats. Some examples include the following:
- Inland lakes
- Great Lakes
- Coastal wetlands
These habitats can vary greatly in water quality, turbidity, speed of water flow, amount of vegetation, water temperature, and water composition. Fish are particularly sensitive to water temperature and oxygen content, which play a major role in determining which species can survive in a given water body. See: Aquatic Habitat Data Worksheet for examples of 14 common fish species and their preferred habitats.
Human Impacts on Fish Habitat
Over the last century, many factors have altered water quality and fish habitat and subsequently affected native fish populations. Some examples include:
- Coastal Development: Increasing development in coastal areas threatens the function and diversity of coastal wetlands. These areas are critical during the early life stages of many fish species. Removal of shoreline vegetation and trees from riverbanks can decrease shade and increase water temperature. Lack of vegetation also increases erosion and sedimentation, which alters spawning areas. Dams and other obstacles can prevent fish from migrating upstream to reach critical spawning habitat.
- Invasive Species: Invasive species compete with native fish for food and habitat. Round goby and Eurasian ruffe are examples of fish that have displaced native species in some locations. Invasive species can also change habitat. By filtering microorganisms, zebra mussels reduce food for native species and increase water clarity, which stimulates growth of aquatic plants.
- Pollution: Industrial pollutants, urban and agricultural runoff, and sewage overflows are some of the sources of pollutants that continue to impair Great Lakes water quality and impact fish habitat.
People around the Great Lakes region are working to restore fish habitat for a number of native fish populations. Some examples include:
- Lake Sturgeon: Several groups teamed up to construct spawning reefs for lake sturgeon in the Detroit River to increase population of this threatened species.
- Walleye: The Fisheries Division of the Michigan Department of Natural Resources is implementing a walleye recovery plan for Saginaw Bay to enhance walleye populations and production in Saginaw Bay.
- Coaster Brook Trout: Researchers in the Upper Peninsula and Canada are tagging and monitoring this fish to learn more about its unique habitat requirements.
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