Abstract:
Looking at a population of tuna fish allows researchers to see how limiting factors play a role in an ecosystem. These adjustable limiting factors are reproduction, migration, death, pollution, disease, predators, food, and seasonal fishing. When we increased all of these limiting factors among the tuna population, the populations decreased.
Objective:
To determine the effects of limiting factors on a simulated population of tuna.
Problem:
What are the effects of limiting factors on the population of tuna?
Hypothesis:
If we increase the limiting factors, then we will decrease the tuna population.
Parts of the Experiment:
Independent variables: Reproduction, migration, death, pollution, disease, predators, food, seasonal fishing
Dependent variable: Tuna population
Controlled variables: Temperature of water, salinity of water
(No control or experimental groups)
Materials:
Simulation found at http://sepuplhs.org/high/sgi/teachers/fishery_sim.html
Method:
1. Work with your partner to follow the tutorial in the simulation to familiarize yourself with how the simulation
works. Read each screen carefully and be sure you understand each part of the tutorial before moving to Stage 1 of the
simulation.
2. In Stage 1, click on the “Show Normal Population Growth” box to see the graph of what happens to this population if
reproduction, migration, and death rates are moderate.
3. Explore what happens to the population as you change the three variables. In your science notebook, record your observations of what happens to the sustainability of the population. What variable settings cause the population growth rate
to increase? What settings cause it to decrease? What settings cause the population growth rate to stay steady? What are
the limiting factors?
4. Scientific advisors to the fishery have determined that the population is sustainable at 60,000 fish. Use the simulation to
determine what settings for the three variables maintain the population at 60,000 fish. Record the graph and the settings
in your science notebook.
5. Scientific advisors have reexamined the population data for the Avril Gulf tuna and determined that the population is
sustainable at 80,000 fish. With your partner, predict what settings would maintain the population at 80,000 fish. Write
down your predictions in your science notebook, and then use the simulation to test your prediction. If necessary, change
the settings as you run the simulation. Record the graph and the settings in your science notebook.
6. Move to Stage 2, and repeat Steps 3 through 5. Note that in Stage 2 you cannot control pollution or disease events, which
will occur at random intervals.
7. Move to Stage 3, and repeat Steps 3 through 5.
8. Move to Stage 4. In this stage, all of the factors are combined. Predict what settings will allow for a maximum amount of
fishing while maintaining the fish population (i.e., have a sustainable fishery). Repeat Steps 3 through 5, but incorporate the maximum amount of fishing possible.
Data:
-Pollution
Pollution occurred at 60K tuna, the population then decreased in half, then in two years the population became abundant again. 60K tuna is the carrying capacity for increased pollution.
-Disease
The population of tuna leveled off but when disease occurred, it dropped about 1K, and then increased back to the carrying capacity after one year. 60K tuna is the carrying capacity for disease.
-Predators
The population of tuna when predator population increases starts at 20K and then depletes to approximately 1K, until 13 years later when the population begins to grow again, but disease also occurs. 1K tuna is the carrying capacity with increased predators.
-Food
When the amount of food is increased, the population of tuna flourished. 80K tuna is the carrying capacity with increased food.
Here is the graph that occurred when I kept all of the Tuna reproduction, migration, and death rates at medium. When the population reached 100K, it hit its carrying capacity.
Looking at a population of tuna fish allows researchers to see how limiting factors play a role in an ecosystem. These adjustable limiting factors are reproduction, migration, death, pollution, disease, predators, food, and seasonal fishing. When we increased all of these limiting factors among the tuna population, the populations decreased.
Objective:
To determine the effects of limiting factors on a simulated population of tuna.
Problem:
What are the effects of limiting factors on the population of tuna?
Hypothesis:
If we increase the limiting factors, then we will decrease the tuna population.
Parts of the Experiment:
Independent variables: Reproduction, migration, death, pollution, disease, predators, food, seasonal fishing
Dependent variable: Tuna population
Controlled variables: Temperature of water, salinity of water
(No control or experimental groups)
Materials:
Simulation found at http://sepuplhs.org/high/sgi/teachers/fishery_sim.html
Method:
1. Work with your partner to follow the tutorial in the simulation to familiarize yourself with how the simulation
works. Read each screen carefully and be sure you understand each part of the tutorial before moving to Stage 1 of the
simulation.
2. In Stage 1, click on the “Show Normal Population Growth” box to see the graph of what happens to this population if
reproduction, migration, and death rates are moderate.
3. Explore what happens to the population as you change the three variables. In your science notebook, record your observations of what happens to the sustainability of the population. What variable settings cause the population growth rate
to increase? What settings cause it to decrease? What settings cause the population growth rate to stay steady? What are
the limiting factors?
4. Scientific advisors to the fishery have determined that the population is sustainable at 60,000 fish. Use the simulation to
determine what settings for the three variables maintain the population at 60,000 fish. Record the graph and the settings
in your science notebook.
5. Scientific advisors have reexamined the population data for the Avril Gulf tuna and determined that the population is
sustainable at 80,000 fish. With your partner, predict what settings would maintain the population at 80,000 fish. Write
down your predictions in your science notebook, and then use the simulation to test your prediction. If necessary, change
the settings as you run the simulation. Record the graph and the settings in your science notebook.
6. Move to Stage 2, and repeat Steps 3 through 5. Note that in Stage 2 you cannot control pollution or disease events, which
will occur at random intervals.
7. Move to Stage 3, and repeat Steps 3 through 5.
8. Move to Stage 4. In this stage, all of the factors are combined. Predict what settings will allow for a maximum amount of
fishing while maintaining the fish population (i.e., have a sustainable fishery). Repeat Steps 3 through 5, but incorporate the maximum amount of fishing possible.
Data:
-Pollution
Pollution occurred at 60K tuna, the population then decreased in half, then in two years the population became abundant again. 60K tuna is the carrying capacity for increased pollution.
-Disease
The population of tuna leveled off but when disease occurred, it dropped about 1K, and then increased back to the carrying capacity after one year. 60K tuna is the carrying capacity for disease.
-Predators
The population of tuna when predator population increases starts at 20K and then depletes to approximately 1K, until 13 years later when the population begins to grow again, but disease also occurs. 1K tuna is the carrying capacity with increased predators.
-Food
When the amount of food is increased, the population of tuna flourished. 80K tuna is the carrying capacity with increased food.
Here is the graph that occurred when I kept all of the Tuna reproduction, migration, and death rates at medium. When the population reached 100K, it hit its carrying capacity.
Specific Conclusion Questions:
In stage 1:
What are the limiting factors? Reproduction, death, and migration.
What is your carrying capacity? 100K.
What settings are required for the three variables in order to maintain the population at 60,000 fish? Start everything at medium, and then increase death, lower reproduction, and keep migration in the middle.
What settings are required for the three variables in order to maintain the population at 80,000 fish? Start everything at medium, and then increase death, lower reproduction, and keep migration in the middle.
In stage 2:
What happened immediately when pollution occurred? The pollution decreased immediately.
How long did it take the population to recover after pollution occurred? 2 years for the population to recover.
What happened immediately after disease occurred? The population dropped 1K for one year, and then increased back up to carrying capacity.
How long did it take the population to recover after disease occurred? 1 year.
In stage 3:
Some fishing will occur, as humans interact with the environment. Find a pattern that will allow the tuna population to remain at a carrying capacity of 60,000. What fishing regulations would maintain this population size? Once the tuna population gets to 60K, you can stabilize it by only fishing a little bit in two seasons.
In stage 4:
What factors allowed for the maximum amount of fishing while maintaining the fish population? Record the greatest amount of fishing allowable.
Abundant food, higher reproduction, medium death, and slightly lower predators allowed for the maximum amount of fishing. The greatest amount of fishing allowable is medium in two seasons and slightly lower in the other two.
Which factors are density-dependent and which are density-independent?
The density dependent factors are disease rates, predation, and food abundance. Density independent factors are the seasons (fishing).
How could a model, such as this simulation, help fisheries biologists make recommendations about setting fishing limits? Explain your answer.
Yes! This simulation could help set fishing limits because the simulation shows the effects of non limited fishing. Most of the fishing had a high impact on the tuna population and made it decrease so by setting limits the tuna population could flourish in off fishing seasons.
Conclusion:
The proposed hypothesis was correct. The increase in all of the limiting factors did in fact decrease the tuna population. One of the biggest limiting factors I believe was the seasonal fishing. In the article it says that tuna population was decreasing because fishermen were fishing an extra two months of the allowed fishing season, which was destroying the tuna population at this time. Although there are errors to using an online simulation because no limiting factors are going to perfectly mimic this online simulation because there are always different factors that could come into play in the real world, such as weather.
In stage 1:
What are the limiting factors? Reproduction, death, and migration.
What is your carrying capacity? 100K.
What settings are required for the three variables in order to maintain the population at 60,000 fish? Start everything at medium, and then increase death, lower reproduction, and keep migration in the middle.
What settings are required for the three variables in order to maintain the population at 80,000 fish? Start everything at medium, and then increase death, lower reproduction, and keep migration in the middle.
In stage 2:
What happened immediately when pollution occurred? The pollution decreased immediately.
How long did it take the population to recover after pollution occurred? 2 years for the population to recover.
What happened immediately after disease occurred? The population dropped 1K for one year, and then increased back up to carrying capacity.
How long did it take the population to recover after disease occurred? 1 year.
In stage 3:
Some fishing will occur, as humans interact with the environment. Find a pattern that will allow the tuna population to remain at a carrying capacity of 60,000. What fishing regulations would maintain this population size? Once the tuna population gets to 60K, you can stabilize it by only fishing a little bit in two seasons.
In stage 4:
What factors allowed for the maximum amount of fishing while maintaining the fish population? Record the greatest amount of fishing allowable.
Abundant food, higher reproduction, medium death, and slightly lower predators allowed for the maximum amount of fishing. The greatest amount of fishing allowable is medium in two seasons and slightly lower in the other two.
Which factors are density-dependent and which are density-independent?
The density dependent factors are disease rates, predation, and food abundance. Density independent factors are the seasons (fishing).
How could a model, such as this simulation, help fisheries biologists make recommendations about setting fishing limits? Explain your answer.
Yes! This simulation could help set fishing limits because the simulation shows the effects of non limited fishing. Most of the fishing had a high impact on the tuna population and made it decrease so by setting limits the tuna population could flourish in off fishing seasons.
Conclusion:
The proposed hypothesis was correct. The increase in all of the limiting factors did in fact decrease the tuna population. One of the biggest limiting factors I believe was the seasonal fishing. In the article it says that tuna population was decreasing because fishermen were fishing an extra two months of the allowed fishing season, which was destroying the tuna population at this time. Although there are errors to using an online simulation because no limiting factors are going to perfectly mimic this online simulation because there are always different factors that could come into play in the real world, such as weather.