All animals have basic needs for food, water and habitat in order to survive. There are times, however, when some animals’ needs can’t be met. One reason may be due to competition for food and habitat caused by an invasive species. By learning about the aggressive invasive species Eurasian ruffe (pronounced rough), this lesson explores how a single species can cause other fish species to decline, and create dramatic changes in the Great Lakes food web in a relatively short time.
Grade level: 4-8th grades
- MS-LS2-1 Ecosystems: Interactions, Energy and Dynamics: Analyze and interpret data to provide evidence for the effects of resource availability on organisms and populations of organisms in an ecosystem.
- MS-LS2-4 Ecosystems: Interactions, Energy and Dynamics: Construct an argument supported by empirical evidence that changes to physical or biological components of an ecosystem affect populations.
For alignment, see: NGSS Summary
- Explain why fish populations in the Great Lakes change over time.
- List three reasons why non-native ruffe have significant advantages over some native Great Lakes fishes.
- Identify two things that can be done to minimize the spread of ruffe.
Eurasian ruffe, small members of the perch family, are aggressive fish native to Europe and Asia. They were first discovered in the St. Louis River, the main tributary to western Lake Superior, in 1986. They arrived in the ballast water of an ocean-going vessel. In the absence of natural predators, ruffe populations multiplied rapidly.
Today, ruffe make up an estimated 80 percent of the fish caught in the St. Louis River. Since their arrival, ruffe have spread to other rivers and bays along the south shore of western Lake Superior and northward to Thunder Bay, Ontario. Ruffe also thrive in the waters near Alpena, Michigan on northern Lake Huron. Rapid growth of ruffe populations has reduced food and habitat for native fish with similar diets and feeding habits, including walleye, perch and a number of small fish.
Several ruffe characteristics enable the fish to displace native species in newly invaded areas.
- Grow rapidly and produce many offspring.
- Reproduce in their first year, and an average female can produce 13,000 to 200,000 eggs per season.
- Tolerate a range of environmental conditions, including murky water. Ruffe are primarily bottom feeders, and they prefer dark environments where they can hide from predators.
- Fend off predators. Even though ruffe are small (usually less than 5 inches), they have few predators due to the spines on their fins.
Assessment & Standards
See separate document: Lesson Assessment, State of Michigan Content Expectations and National Benchmarks
- Ruffe Musical Chairs
Summary: Students use role-play to mimic the behavior of an invasive fish called Eurasian ruffe (pronounced rough) to experience firsthand how and why the species has multiplied so rapidly in some Great Lakes areas.
Time: 60 Minutes