Question

6. Assessing the population size of organisms is important in determining whether a species requires special conservation effort and in helping to manage sustainable harvesting of food.

a) Why is it important to determine the uncertainty surrounding an estimate of population size? (1 mark)

b) Using an example species and method of population size estimation, explain how you would assess the quality of your population size estimate.

c) Estimating the size of fish species’ populations is very difficult. Imagine that you discovered a new species of fish that appeared to be highly abundant. Given that you probably can’t obtain a reliable population estimate for the species, what other information would you consider when devising a harvesting strategy?

Answer 1

Ans 1) It is important to determine the uncertainty surrounding an estimate population size so that the confidence intervals can be determined from the point estimates of the parameters. The confidence interval is a type of interval estimate which is computed from the statistics of the data that is observed and it might contain true value of the unknown parameter of the population.

Ans 2) The quality of the population size estimates can be determined by mark recapture method. In this method, it captures a sample of animals and they are marked in some way like use of tags, bands or paints or other markings. They are released in the environment and mix with the rest of the population. On collection of the new samples, some will be marked and some unmarked that helps in determining the population quality.

Ans 3) One of the best methods to discovering the new species of fishes is use of Chapman-Petersen methods. These are also known as mark and recapture method and helps in estimating the size of a moving population. In this a portion of population is captures, marked and released. Later, another portion is captured and the marked individuals in the sample are counted which helps in determining number of marked individuals in the second sample.