Estimating Population Size
Objective: You will be expected to estimate the size of a sample population using the mark-recapture technique. Be able to apply the technique to new population problems and compare the mark and recapture technique to other methods of population estimating.
1. If you were in charge of a team given the responsibility to determine the number of sunfish in Horseshoe Lake, discuss with your partner how would you accomplish this task and describe in detail below.
One can count the fish in a part of the lake and then multiply it by the size of the lake.
Technique 1: Sampling
A technique called sampling is sometimes used to estimate population size. In this procedure, the organisms in a few small areas are counted and projected to the entire area. For instance, if a biologist counts 10 squirrels living in a 200 square foot area, she could predict that there are 100 squirrels living in a 2000 square foot area.
2. A biologist collected 1 gallon of pond water and counted 50 paramecium. Based on the sampling technique, how many paramecium could be found in the pond if the pond were 20,000 gallons. 50 x 20,000 = 1,000,000
3. What are some problems with this technique? What could affect its accuracy?
Different areas might have more dense populations. If you took a sample from the bottom of the ocean the chances are that it is not the same as a sample at the top of the ocean.
Technique 2 - Mark and Recapture
In this procedure, biologists use traps to capture the animals alive and mark them in some way. The animals are returned unharmed to their environment. Over a long time period, the animals from the population are continued to be trapped and data is taken on how many are captured with tags. A mathematical formula is then used to estimate population size.
You will create (or have someone create it for you so you don't know actual population size) a bag that represents your population (beans,...