Catch and Release Lab
Pre-Lab
1. What are the variables in this experiment? (dependent and independent)
Dependent- Population of species of fish
Independent- amount of fish tagged and number of catches
2. Write the problem in the form of a question.
What is the ideal number of tagged fist to produce the most accurate representation of the entire population?
3. Create a hypothesis as to which combination of variables will yield the most accurate estimate of the populations size.
If we mark 10% of the approximate population size then it will provide the most accurate representation of the population.
Dependent- Population of species of fish
Independent- amount of fish tagged and number of catches
2. Write the problem in the form of a question.
What is the ideal number of tagged fist to produce the most accurate representation of the entire population?
3. Create a hypothesis as to which combination of variables will yield the most accurate estimate of the populations size.
If we mark 10% of the approximate population size then it will provide the most accurate representation of the population.
Problem
What is the ideal number of tagged fish to produce the most accurate representation of the entire population?
Hypothesis
If we tag more fish then it will provide us with more accurate data.
Parts of the Experiment
Independent Variable - the amount of fish tagged and the number of catches
Dependent Variable - population of species of fish
Control Variables- the same type of paper bags, and the same kind of beads.
Control Group - none
Experimental Groups - the different combinations of catch size and number of catches taken.
Dependent Variable - population of species of fish
Control Variables- the same type of paper bags, and the same kind of beads.
Control Group - none
Experimental Groups - the different combinations of catch size and number of catches taken.
Materials
- Paper bag
- Two different colored beads (one to represent population the other fish tagged).
Procedure
- Take out 10 beads out of the ocean bag and replace them with beads of a different color.
- Shake the bag and without looking remove a sample catch from the population in the bag. Record the total number of fish caught and the number of tagged fish caught in each sample.
- Repeat this a total of 10 times.
- Calculate the percent tagged for each catch and average that column.
- Calculate the estimated population size: Population size= number tagged/mean of the sample percentages
- Count the actual population.
- Calculate the percent error between your estimated population and the actual.
- Compare your numbers with the rest of the class.
Observations
The small samples contained little to no tagged fish when the bigger samples tended to generally have a couple more. None of the samples had more than half of the original 10 tagged fish and the number of tagged fish in samples ranged from 1 to 4.
Data Tables and Graphs
Analysis and Conclusion
1. What could cause the population size estimate to be different from the actual population size?
The population size estimate could be different from the actual population size due to the different combination of samples removed from the bags, the different number of fish tagged, and how frequently the bag was shaken after the previous sample has been put back.
2. How can the size of your catch sample compared to the actual size of the population affect population estimate?
If you had a really large population and only picked small samples then you could have lowered the amount of tagged fish that you removed with each sample throwing your population estimate way off; however, if you had a large population and removed large samples each time then you might have had a lot of tagged fish which would make your population estimate more accurate.
3. How can the number of samples (or catches) affect the results?
The number of samples or catches affect the results of this lab because in order to gain the most accurate estimate of the population more catches were needed. More catches also ensured that nearly all of the population was accounted for and not just a small amount that would have resulted if the number of catches was small.
4. Does this method appear to be an effective way to assess population size? Why or why not?
This method does not appear to be an effective way to assess population size because there are so many things that need to be regulated such as the number of catches and the amount in each catch that it seems very tedious and ineffective. If the samples and the amount in each sample differed then the population estimate would not be accurate. In order for this method to be effective we would need to know how many samples we needed and how big or small the samples need to be so we could portray the most accurate results.
5. If you were predicting a large population (like an actual ocean fishery) would your percent error be very large?
If a large population was being predicted than the percent error would depend solely on how many fish were tagged and how many fish were in each collected sample. If a lot of fish were tagged and the number of fish in samples was also big then the percent error would be small because the population estimate would be close to the actual population but if the number of fish collected and tagged was small then percent error would be very large because the population estimate would not be anywhere near the actual population.
6. What concerns should a biologist have about a species' habits before (s)he uses this method to approximate the size of a population?
The biologist should use this method when they notice a species rapidly dying out and are concerned about whether this species is on the verge of being extinct or not. Also, they should use this method when they are concerned about the species general health or migration patterns.
The population size estimate could be different from the actual population size due to the different combination of samples removed from the bags, the different number of fish tagged, and how frequently the bag was shaken after the previous sample has been put back.
2. How can the size of your catch sample compared to the actual size of the population affect population estimate?
If you had a really large population and only picked small samples then you could have lowered the amount of tagged fish that you removed with each sample throwing your population estimate way off; however, if you had a large population and removed large samples each time then you might have had a lot of tagged fish which would make your population estimate more accurate.
3. How can the number of samples (or catches) affect the results?
The number of samples or catches affect the results of this lab because in order to gain the most accurate estimate of the population more catches were needed. More catches also ensured that nearly all of the population was accounted for and not just a small amount that would have resulted if the number of catches was small.
4. Does this method appear to be an effective way to assess population size? Why or why not?
This method does not appear to be an effective way to assess population size because there are so many things that need to be regulated such as the number of catches and the amount in each catch that it seems very tedious and ineffective. If the samples and the amount in each sample differed then the population estimate would not be accurate. In order for this method to be effective we would need to know how many samples we needed and how big or small the samples need to be so we could portray the most accurate results.
5. If you were predicting a large population (like an actual ocean fishery) would your percent error be very large?
If a large population was being predicted than the percent error would depend solely on how many fish were tagged and how many fish were in each collected sample. If a lot of fish were tagged and the number of fish in samples was also big then the percent error would be small because the population estimate would be close to the actual population but if the number of fish collected and tagged was small then percent error would be very large because the population estimate would not be anywhere near the actual population.
6. What concerns should a biologist have about a species' habits before (s)he uses this method to approximate the size of a population?
The biologist should use this method when they notice a species rapidly dying out and are concerned about whether this species is on the verge of being extinct or not. Also, they should use this method when they are concerned about the species general health or migration patterns.
General Analysis and Conclusion
Hypothesis Evaluation: My hypothesis was partially accurate because for the most part the groups that used the most amount of marked numbers had the least percent error. I hypothesized this because it makes sense that the more you have tagged means there is a greater number that you have seen so the number you have not seen and have to guess on is less.
Accuracy of Results: The results could have been more accurate if we kept our 10 samples at approximately the same size but we were trying to chance how big or small it was every single time and that could have had an impact on our estimate. Another thing that could have triggered the accuracy of our results was how many times and how diligently the bag was shaken after each removed sample was put back in. If it was not shaken a lot then we could have easily just kept taking out the same population however if it was shaken more vigorously then it would have given a more accurate estimation of the population.
Application: From this lab I learned that the catch and release method is most commonly used when ecologists are worried about the health and overall well being of a population of species. I also learned that this method does not always produce the most accurate results because it is nearly impossible to get an exact amount of the actual population of a species unless it is very small.
Real Life Example: Mark- release- recapture method was used in Australia to measure the dispersal of the vector mosquito Aedes aegypti. Biologists found out many interesting things from their results one being that the dispersal of these mosquitoes was not random and was actually based on environmental factors such as shading provided by trees. Relating back to our lab, I did not think this method could be very effective but this article made me think otherwise based on how much useful information they acquired from using this method. Also, this article showed me that this method not only can be used to just estimate population size but it can also be used to measure dispersal of a certain population and if it is something as bad as a disease carrying mosquito then it can also help with preventing the spread of it.
"Mark–release–recapture study to measure dispersal of the mosquito Aedes aegypti in Cairns, Queensland, Australia." Wiley Online Library. John Wiley and Sons, Inc., 6 Dec. 2005. Web. 21 Mar. 2013. <http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2915.2005.00589.x/abstract>.
Accuracy of Results: The results could have been more accurate if we kept our 10 samples at approximately the same size but we were trying to chance how big or small it was every single time and that could have had an impact on our estimate. Another thing that could have triggered the accuracy of our results was how many times and how diligently the bag was shaken after each removed sample was put back in. If it was not shaken a lot then we could have easily just kept taking out the same population however if it was shaken more vigorously then it would have given a more accurate estimation of the population.
Application: From this lab I learned that the catch and release method is most commonly used when ecologists are worried about the health and overall well being of a population of species. I also learned that this method does not always produce the most accurate results because it is nearly impossible to get an exact amount of the actual population of a species unless it is very small.
Real Life Example: Mark- release- recapture method was used in Australia to measure the dispersal of the vector mosquito Aedes aegypti. Biologists found out many interesting things from their results one being that the dispersal of these mosquitoes was not random and was actually based on environmental factors such as shading provided by trees. Relating back to our lab, I did not think this method could be very effective but this article made me think otherwise based on how much useful information they acquired from using this method. Also, this article showed me that this method not only can be used to just estimate population size but it can also be used to measure dispersal of a certain population and if it is something as bad as a disease carrying mosquito then it can also help with preventing the spread of it.
"Mark–release–recapture study to measure dispersal of the mosquito Aedes aegypti in Cairns, Queensland, Australia." Wiley Online Library. John Wiley and Sons, Inc., 6 Dec. 2005. Web. 21 Mar. 2013. <http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2915.2005.00589.x/abstract>.