Title: Snakehead: Walking-fish, Top Predator and Comfort Food
Grade: Middle School
Introduction:
Time needed: approx 50 min
Subjects: Ecology, probability, critical thinking, biology, and writing skills.
Topics: Invasive species, food chains, and population dynamics.
National and State Science Education Standards: Fill in later
Learning Objectives:
To investigate how a top predator and popular food fish in Africa and Asia made
its way to Maryland, Florida, California, Pennsylvania, and North Carolina. Understand
how rapidly native populations can decline when an invasive predator on the top of the
food chain is introduced.
Materials included:
Materials needed:
1. 3 sets of different colored beans
 Red for the adults
 Green for the juveniles
 Black for other species i.e. the native species
2. 4 cups
3. 1 sheet of blue paper
4. A USGS fact sheet
5. A die
Description:
Students will use different colored beans to learn different concepts
such as population dynamics and probability in food chains involving
aquatic species. They will also be collecting data and writing a brief
summary about what the data tells them. This activity is supposed to
get students thinking critically about the food chain and what happens
when an invasive specie is introduced.
Background:
The fearsome looking snakehead is a popular food item in Asia – prized for its
mild, slight-sweet white meat and also as an aquarium fish. Through careless behaviour,
people have released snakeheads into waters where they never existed. As voracious
predators on top of the food chain, snakeheads have decimated native aquatic organisms.
The Snakehead is a family of fish that is native to Asia and Africa. The Asian species is a
Channa and the African is a Parachanna and the Northern Snakehead, (Channa argus) is
the species that have invaded American waters back in 2000 in Crawford Maryland.
They are aggressive, voracious predators feeding on native fishes food supply. In their
adulthood, they eat carp, frogs, small rats, and other small mammals. When they are
juveniles they feed on plankton, aquatic insects and small mollusks. The major pathway
that the snakehead has made its way in to American waters is by introduction from
humans. They are air breathing giving them the ability to move over land to more
favourable conditions (habitats)- that means they are capable of ”walking (migrating)
over land ! There have been sighting of this fish in 33 of 50 states including Hawaii,
Florida, Massachusetts Oregon, and Washington.
Preparation:
1.
2.
3.
4.
Get into groups of four
Read the lab out loud in your groups
Read the USGS fact sheet about the Snakehead
Write a hypothesis
Step-by-step instructions:
Part 1
1. Collect the different colored beans
2. Draw big circle on blue paper to symbolize a lake
3. Sprinkle at least 100 of your native “fish” in to the lake be sure to make it
crowded
4. Roll dice to tell how many adult Snakeheads will be added to the lake
5. Double your die roll to add juvenile Snakehead
6. Every snakehead adult can eat 3 fish per day. Every juvenile can eat one fish
per day.
7. Count your total number of adults and juveniles, given that 1 adult can
consume 3 native fish and 1 juvenile can consume one native fish, how many
days will it take before the entire native fish population is all consumed
Part 2. Roll the dice to understand chance and see how quickly a population grows.
Repeat steps 4-5 6 times and record the number. Do the rolls of the dice result in the
same numbers each time? (Probably not and this is what we can “chance”). If we’re
luckily maybe only one snakehead will get introduced giving us time to detect an invader
before it takes over an entire ecosystem
Part 3. Now refill your “lake with 200 beans
8. Repeat steps four and five twice
9. Count and total your number of juveniles and adults
10. Write down your data
11. How many days will it take before the snakehead consumes all the native
fish?
12. Does twice the number of predators consume twice as many native fish in the
same amount of time?
Part 4.
13. Brainstorm ideas for population solutions
14. Brainstorm the pathways that the snake head got into this lake
15. Write down your data
16. Write a brief conclusion to this activity, telling me how much you know about
the snakehead infestation, population explosion, and invasive species. Include
the answer to your hypothesis and the answers to numbers eleven and twelve.
17. Turn into Robin at the end of the period
18. Separate beans and put back into the bags and clean up
Conclusion and Evaluation:
Data Tables:
Round 1
Number of
Native Fish
Number of
Adult
Snakehead
Number of
Juvenile
Snakehead
Days it takes
for native
population to
be consumed
Number of
Adult
Snakehead
Number of
Juvenile
Snakehead
Days it takes
for native
population to
be consumed
Roll 1
Roll 2
Roll 3
Roll 4
Roll 5
Round 2
Number of
Native Fish
Roll 1
Roll 2
Roll 3
Roll 4
Roll 5
How much you know about the snakehead infestation, population explosion, and invasive
species? Include the answer to your hypothesis and the answers to numbers eleven and
twelve in your write up. Be sure to include what worked, what didn’t, and what can be
changed about this lab.