Question

Activity I: Mark and Recapture Method

Objective:
Perform the mark-recapture method to estimate the number of individuals within an a certain area.

Materials:

• Plastic container with lid (represents a pond)
• Bag or box of small objects such as editable goldfish, beans, macaroni noodles, etc.
  (represents the fish)
• Permanent Marker
• Calculator

Procedure:

1. Add all of your fish to the pond (no more than 150 fish)
2. Randomly capture 40 fish from the pond.
3. Mark those 20 fish with the marker.
4. Return the newly "marked" fish into the pond.
5. Close and shake the pond to simulate release and mixing of the animals in the wild. Please be gentle with the fish.
6. Now, recapture 40 fish and count the number of "marked" that were recaptured.
7. Use the formula below to calculate the estimated total population of fish in the pond.
8. Return all fish back to the pond and repeat steps 5-7 at least 3 more times.
   (The only number that will change each time you repeat the steps is the number of recaptured marked individuals.)
9. Now calculate the average of the 4 trials to determine a "good" estimated population.
10. Count ALL of the fish in the pond to determine the "theoretical" population size.
11. Finally, calculate the Percentage Error (how close you are to the theoretical value) using the following formula.
    (The percentage error will have a + or - value, which means your estimation may be above or below the theoretical value.)

N =	# of marked individuals X total # captured second time # of recaptured marked individuals
% Error =		"good" estimated population - the theoretical Value the theoretical value		X 100

Analysis:

1. How close was your estimated population to the theoretical estimation? Explain any human or non-human errors that may have affected your estimated population.
2. How would your population estimate be affected if you did not shake the fish very well after returning them to the container? Explain how this might happen in an actual field study.

Further Investigation:

1. Name several organisms in your area could you estimate their population size using the mark-recapture method.
2. How would the population estimate be affected if the individuals who were capture the first time liked the bait and returned for more yummy food the second time you captured the organisms? Explain.
3. Explain how you could modify the mark-recapture method to compensate for individuals who recognize the bait as being either good or bad.

Answer 1

Answer- Analysis part-A the ratio of estimated to theoretical was less than one. it was affected by the random sampling of the fishes in experimental conditions.

Analysis part-B if the fishes were not shake then one location will increase the recapture while the other location will show less recapturing.

further analysis part- The dogs, fishes etc can be estimated for their population by this method.

the attraction toward bait will increase the frequency of recapture.

to alter the results the bait location and type shoule be changed after marking.