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Crayfish + Freshwater Ecosystems

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What energy source�supports life?

Producers

Consumers

Ask the class to raise their hand if they know, “What is the energy source that supports life on Earth?” Wait for a number of hands to go up, and call on someone to say the Sun, then click to make it appear. Next ask why the Sun is so important for life on Earth. Discuss how it provides the energy which plants (producers) use to make food, and that the plants can then be food for animals (consumers) like insect larvae.

Most freshwater fish are predators which can eat insect larvae and other animals. Birds like egrets can eat the fish, continuing the food chain. If a fish dies, scavengers like crayfish can eat them.

Discuss how all the living and nonliving things are interconnected in an ecosystem—in this case a wetland ecosystem which is known for having a lot of biodiversity (different types of living things).

Graphic by Eric Engh, Marin / Sonoma Vector Control District and Rick Reynolds, Engaging Every Student

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Freshwater Ecosystem

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Plants

Algae

American Waterweed

Elodea canadensis

Coontail

Ceratophyllum demersum

Yellow Waterlily

Nuphar polysepala

Water Shield

Brasenia schreberi

Duckweed

Lemna minor

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Many Animals Eat Crayfish

Trout

Raccoons

River Otters

Frogs

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Great Blue Heron

Great Egret

Little Blue Heron (juvenile)

Common Goldeneye

Duck

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What Do Crayfish Eat?

dead + living animals + plants

Almost anything!

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What do crayfish and other animals need to live?

Shelter

Water

Space

Food

Oxygen

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Northern Clearwater Crayfish

Northern Clearwater Crayfish are native to the Great Lakes. Crayfish are crustaceans which are closely related to lobsters, their saltwater cousins, and they play an important role in freshwater ecosystems. They are an important food source for many species of fish, birds, amphibians, reptiles, and mammals, even those which spend much of their time on land, such as raccoons, so they can play important roles in terrestrial ecosystems, as well.

The vast majority of the more than 400 crayfish species are found in North America, especially the Southeastern U.S., although they can be found on every continent except Antarctica. Many species are at risk of extinction due to a variety of factors, such as habitat loss, pollution, and the spread of invasive crayfish species and disease (Larson 2018).

Signal crayfish image by Roger Tabor (U.S. Fish and Wildlife Service): https://www.flickr.com/photos/usfwspacific/6093365240 (licensed for noncommercial reuse)