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"Using Cichlids To Demonstrate the Effects of Human Activity On Ecosystems"

By George Macklem



Notes and activities in this lesson were written in conjunction with Chris Forbush (Fowlerville High School Teacher) and students in our high school biology classes. The fish and much expertise were provided by Rick Preuss (a member of the Lake Victoria Society and owner of Preuss Animal House, Haslett, Michigan) and Dr. Bill Cooper from Michigan State University.


Type of Entry:

  • Project

Type of Activity:

This project runs continuously in the classroom so there is an unlimited number of activities that can be used by the classroom teacher. At Fowlerville High School (FHS) we have made a serious commitment to hands-on laboratory activities, student analysis of data, and the self learning process. We, at FHS, use numerous activities spawned from this project. Students, teachers, and custodians maintain over 200 gallons of aquarium space for our population of Lake Victoria Cichlids. The aquariums are a hands-on activity and a simulation of natural conditions. The fish are particularly useful as an example and reinforcement of the portion of our Biology curriculum concerning the environment and ecology. Expansion of our knowledge of aquatic ecosystems is then facilitated by a chemical analysis and biological study of a small holding pond next to our school. We also include a fish dissection (perch) as an additional activity.

Target Audience:

The target audience is 10th grade biology, although any classes that use the rooms with the aquariums become interested participants.

Notes to Teacher:

This project requires a minimum competency in aquarium management, a working knowledge of aquatic biology, a yearly budget expense, beyond initial equipment costs, of approximately $200/year, and a supportive custodial staff to allow student/teacher access to the room during vacations and summer break.

Required of students:

A minimum core group of 10-12 students are needed for year round aquarium maintenance.

Preparation time needed:

The activities associated with this project are mainly student driven, as we have students research and design their activities around ecology. Beyond the time needed for aquarium management/supervision, the teacher need only understand basic aquatic ecology and do a minimal amount of research on Africa's Lake Victoria.

Class time needed:

The amount of class time varies with the depth with which the teacher wishes to pursue ecology studies. At FHS, we typically spend one/two weeks on the activities associated with this project.


Abstract

Lake Victoria, in central east Africa, is one of the largest freshwater lakes in the world. During the 1960's it fell victim to the influence of drought and human mismanagement. The introduction of the Nile Perch, a voracious carnivore upwards of 200-300 lbs., and heavy fertilizer use drastically changed the ecology of the lake. The 600+ native species of cichlid were being eaten into extinction.

A teaching unit was developed, mainly by students, to use the Lake Victoria ecosystem as an example of an aquatic environment, its homeostasis, and the effects of man's activities on the homeostatic balance. This teaching unit is then used to develop further discussions and possible activities centered on the Great Lakes and our state's active participation in the management of the lakes. We particularly emphasize the effects of exotic species (sea lamprey, zebra mussel, spiny water flea, round goby, and ruffe) on our lakes.

There were three support laboratory activities that coordinated with this project. At FHS we have a 100, one 60, and two 20 gallon fish tanks with breeding populations of cichlids from Lake Victoria. The students are responsible for maintenance, observation, and preservation of these rare fish. The second activity involves the chemical analysis of the holding pond next to our high school. The third activity is the dissection of a perch.


Background

What question does this activity help students to answer? This project deals with aquatic environment, homeostasis, and the effects of man's activities on the homeostatic balance. This project helps students understand many questions about ecology, by allowing actual hands-on contact with affected species.


Project

Materials needed:

  • Minimum of two 20 gallon aquariums (larger ones are better)
  • Associated aquarium equipment

  • Cichlids - Lake Victoria Cichlids are not specifically needed, any mouth breeding cichlid will adequately suffice as examples. Mouth breeding cichlids may be purchased at any reputable fish supplier.

  • Perch specimens for dissection.

  • Dissecting equipment

  • Chemical analysis equipment All biological supply companies have many differing types. We specifically monitor oxygen, nitrogen, and phosphate levels.

  • Collection nets - for algal and entomological specimens.

  • Classification keys for freshwater algae, insects, fish, and microorganisms.

  • Microscopes

Lesson/activity:

The activities used are pretty basic to biology teachers and do not need a large amount of description. So, I will provide some basic research on the history of Lake Victoria problems, reproduction of cichlids (haplochromines), a brief description of the three major lab activities, and some possible future remedies for Lake Victoria.

  1. History

    1. Lake Victoria

      1. Largest lake in Africa, surpassed in size only by Lake Superior.

      2. 255 miles long, 155 miles wide, 270 feet deep

      3. Surrounded by the countries of:

        1. Kenya

        2. Tanzania

        3. Uganda

      4. Rivers flowing in and out of Lake Victoria are so slow it takes a century to flush and replace its water.

    2. Overuse of Cichlids

      1. Cichlids once dominated Lake Victoria.

      2. 30 million people rely on Lake Victoria for a living.

      3. Europeans who came to Africa in the late 1800's turned to the lake to satisfy the market for fish.

      4. As overfishing continued, catch sizes dropped. Fishermen turned to nets with smaller mesh sizes. This allowed them to catch smaller and younger fish.

      5. To compensate for this, foreign fish were introduced to the lake.

      6. One foreign fish is the Nile perch which can grow to 6 feet and weigh 200 pounds.

      7. Nile perch have apparently wiped out half of the 400 species of cichlids (haplochromines) once native to the lake.

      8. In 1979, the lake appeared to consist of 80% haplochromines and 2% Nile perch.

      9. In the 1980's - 80% Nile perch and 1% haplochromines.

    3. How Lake Victoria became anaerobic.

      1. Sewage, fertilizers and pesticides began to pour into the lake in the early 1900's.

      2. By the 1970's, the heavy nutrient load in the lake was fueling massive algal blooms.

      3. The algae died, fell to the bottom, and were decomposed by bacteria which used up increasing amounts of oxygen.

      4. This left the bottom too poor in oxygen for fish.

      5. Fish were jammed into the shallow inshore waters where they are more likely to fall prey to Nile perch or human fishermen.

      6. In 1990 the South American water hyacinth entered the lake. This lowered oxygen levels even further as it died and decomposed.

      7. cichlids, which eat the oxygen-depleting algae, have been eaten by the Nile perch leaving the lake without its "self-cleaning" system.

  2. Cichlid Reproduction

    1. The cichlids we have use external fertilization.

    2. The female lays the eggs and immediately gathers them in her mouth.

    3. The female collects the sperm from the males and mixes the egg and sperm together to allow eggs to become fertilized.

    4. The eggs develop in 2 - 3 weeks.

    5. At this time the female may allow the fry to occasionally swim out of her mouth.

    6. The female does not eat during this process.

    7. In our tanks, we watch the females closely for movement by the fry. When we see this type of movement we quickly move the female to a separate tank where she can release her babies without having them consumed by the always hungry males.

  3. The Three Supporting Lab Activities

    1. The Aquariums

      1. Aquarium sizes

        1. We use a 100 gallon aquarium as the adult breeding tank.

        2. We use a 60 gallon aquarium as a juvenile growth tank.

        3. We use 20 gallon aquariums for birthing/fry tanks.

        4. Cichlid populations can be kept in 20 gallon tanks.

      2. Filtration

        1. Filtration is critical to tank success.

        2. We use a 20 gallon with small outside filtration systems. We use tank with gross, minute, and organic particle filtration for the 100 gallon tank.

    2. The perch dissection - use any standard dissection manual for this dissection.

    3. The holding pond analysis.

      1. Divide the class into three or four groups.

      2. Review basic procedures on chemical analysis and specimen collection.

      3. Go outside, have each group investigate a different area of the pond. Each group collects its own data.

      4. Identify collected specimens using classification keys and then return living specimens to the pond.

      5. Present information to the teacher in the form of a written lab report. Data on chemical analysis and species diversification will be then be compared between each group.

  4. The Future of Lake Victoria and the Cichlids - Is Lake Victoria too far gone, and should it be written off?

    1. Things to help the lake?

      1. Introduce fish to eat the algae.

      2. Aerate the lake with air pumps.

      3. Provide alternative jobs and food for the Africans around the lake.

      4. Remove the dead biomass of the hyacinth.

      5. Preserve the cichlids in private aquaria and then reintroduce them to the lake after it is stabilized. (This is one of the reasons we have Lake Victoria cichlids in our school.)


Method of Assessment/Evaluation

Evaluation of students for this project can be accomplished in whatever method deemed most desirable by the teacher. At FHS we use participation, lab reports - formal and narrative, oral and written group reports, worksheets, tests on specific information or applications, and research reviews.


Extension/Reinforcement/Additional Ideas

  1. Keep accurate charts on food consumption, growth rates, and tank sizes as cichlids mature from fry to breeding adults. Collected data will then be entered on a spread sheet for ease of access and potential analysis.

  2. Compare types of food given versus mouth structure. Do cichlids have a "plastic mouth" which will adapt to differing foods.


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