You are studying a species of sea turtle living in the waters off of Puerto Rico

Question

You are studying a species of sea turtle living in the waters off of Puerto Rico and want to use the mark-recapture method to estimate their population size. On Sampling Day 1, you capture 22 individuals. You tag each of these individuals and release them again. One week later, you sample turtles again and collect 20 individuals, of which 5 have a tag from Sampling Day 1. What is your estimate of the population size? Show your work. The mark-recapture method makes a number of assumptions, including that tagging individuals does not affect their probability of recapture. If the tags you put on the turtles lead to higher predation [e.g., by making tagged animals more visible to predators), would your estimate of N be an overestimate (i.e., the true N is lower than your estimate), an underestimate (i.e., the true N is higher than your estimate), or be unaffected by this increased predation? Explain the reasoning behind your answer.

Explanation / Answer

a. In the mark and recapture method a biologist captures the live species of animals and then tag them. After tagging them they are left unharmed in their environment. After a long period of time the animal is again captured and then data is taken on how many animals are being recaptured. In this the rough estimate of size of population can be determined.

Population size= total number captured* number of animals tagged/ total number of animals captured with tag

=42*22/5

=184.8 or 185

There will be about 185 number of turtles living

b. In case of increased predation due to tagging there would be no effect on the estimation of the population size of turtles. The estimation of population size will depend only upon the probability of recapture by the person. If it is assumed that the tagging of animals is not affecting the probability of recapture then the result will not change.

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