Something Fishy Lab
Problem: How many goldfish are in the plastic bag population?
Hypothesis: There are 163 goldfish in the bag.
Hypothesis: There are 163 goldfish in the bag.
Materials:
Plastic bag
Paper towel
Paper bowl
Plain goldfish crackers
Colored (tagged) goldfish crackers
Procedure:
1. Obtain a bowl with your fish.
2. Do NOT count the number of fish in your pond yet!
3. Have one member of your group remove a large handful of fish.
4. Count the number of fish you just removed and write it in the table below.
5. Replace these fish with “tagged” fish (in this case, colored “fish”)
6. Mix your pond well to redistribute the tagged fish among the other fish.
7. One member at a time (and without looking), remove a handful of fish and record the number of total fish in the sample, the
number of tagged fish, and figure out the percentage of tagged fish. (see chart)
8. Return your handful to the bowl!!
9. Continue with this until you have taken 20 samples.
Plastic bag
Paper towel
Paper bowl
Plain goldfish crackers
Colored (tagged) goldfish crackers
Procedure:
1. Obtain a bowl with your fish.
2. Do NOT count the number of fish in your pond yet!
3. Have one member of your group remove a large handful of fish.
4. Count the number of fish you just removed and write it in the table below.
5. Replace these fish with “tagged” fish (in this case, colored “fish”)
6. Mix your pond well to redistribute the tagged fish among the other fish.
7. One member at a time (and without looking), remove a handful of fish and record the number of total fish in the sample, the
number of tagged fish, and figure out the percentage of tagged fish. (see chart)
8. Return your handful to the bowl!!
9. Continue with this until you have taken 20 samples.
Independent Variable: fish in population
Dependent Variable: accuracy of tagging
Constant Variable(s): replacement number of fish, goldfish, bags, number of trials
Control Group: 100% accuracy
Experimental Group: bags in lab
Dependent Variable: accuracy of tagging
Constant Variable(s): replacement number of fish, goldfish, bags, number of trials
Control Group: 100% accuracy
Experimental Group: bags in lab
Observations: The experiment was performed inside the classroom, so weather had no effect. A brown paper towel was used to collect the handfuls of goldfish. Plain goldfish were orange while tagged goldfish were red, green and dark orange.The goldfish, once they were counted and the experiment completed, were eaten.
Specific Conclusions
1. What is the mean (average) of your percent tagged fish from your 20 samples? 21.351%
2. Using the following formula, determine an estimated population for your pond: 30/21.351 * 100= 141 population size
Population Size = (Number Originally Tagged/Mean of the Sample %’s) x 100
3. Now, actually count the number of fish in your bowl: 150 fish
4. Find your percentage error by using the following formula: 8.667%
100 x (Your estimate of population Actualsize of population) / (Actual size of population)
5. Does this method appear to be an effective way to assess population size? Why or why not? Yes, because the estimate was only off by 9 fish.
6. What concerns should a biologist have about a species’ habits before (s)he uses this method to approximate the size of a
population? A biologist should be concerned about environmental factors like predators, temperature change, food availability, migration, and amount of fishing.
2. Using the following formula, determine an estimated population for your pond: 30/21.351 * 100= 141 population size
Population Size = (Number Originally Tagged/Mean of the Sample %’s) x 100
3. Now, actually count the number of fish in your bowl: 150 fish
4. Find your percentage error by using the following formula: 8.667%
100 x (Your estimate of population Actualsize of population) / (Actual size of population)
5. Does this method appear to be an effective way to assess population size? Why or why not? Yes, because the estimate was only off by 9 fish.
6. What concerns should a biologist have about a species’ habits before (s)he uses this method to approximate the size of a
population? A biologist should be concerned about environmental factors like predators, temperature change, food availability, migration, and amount of fishing.
General Conclusions
Evaluation of Hypothesis: Both the estimated population and the actual population were less than the hypothesized population of 163. The actual population of 150 was 13 fish off, so the hypothesis was not entirely accurate, but somewhat accurate.
Accuracy: The experiment called for students to scoop out handfuls of goldfish from the plastic bag. However, the students have different size hands and took different size handfuls. Also, because the bag was clear, students could see the goldfish through it and differentiate between plain and tagged goldfish crackers. Because of this, it's possible that someone may have subconsciously favored plain over tagged or tagged over plain crackers and altered the data- the handfuls weren't necessarily random.
Real-life Application: The tagging in this experiment was used to find population size, but tagging can also be used to determine migration paths and survival rates. One college class in Jacksonville used tagging to track a Great White Shark's path down the East Coast (Wakefield). Using this technique, the class was able to determine information about the regions sharks swim from and how many might travel from one area to another.
Wakefield, Sarah. "Tracking the Great White Shark Clay Style." Clay Today. N.p., n.d. Web. 15 Mar. 2013.
Accuracy: The experiment called for students to scoop out handfuls of goldfish from the plastic bag. However, the students have different size hands and took different size handfuls. Also, because the bag was clear, students could see the goldfish through it and differentiate between plain and tagged goldfish crackers. Because of this, it's possible that someone may have subconsciously favored plain over tagged or tagged over plain crackers and altered the data- the handfuls weren't necessarily random.
Real-life Application: The tagging in this experiment was used to find population size, but tagging can also be used to determine migration paths and survival rates. One college class in Jacksonville used tagging to track a Great White Shark's path down the East Coast (Wakefield). Using this technique, the class was able to determine information about the regions sharks swim from and how many might travel from one area to another.
Wakefield, Sarah. "Tracking the Great White Shark Clay Style." Clay Today. N.p., n.d. Web. 15 Mar. 2013.