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How would I go about estimating the population of my daphnia culture?

  1. Jun 24, 2009 #1
    The culture is in a standard 10 gallon tank (20"x10"x12"). I started with about 200 daphnia (<1mm to 3mm). I would like to know where I am at right now.
  2. jcsd
  3. Jun 24, 2009 #2

    jim mcnamara

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    Staff: Mentor

    Estimate by sampling:

    If you can safely assume:
    daphnia are dispersed thru the 2400 [tex]in^-3[/tex] volume more or less randomly - ie. 90% of them are not parked on the walls or the bottom of the tank then

    This is the poor man's version:
    find a small clear container that has a water tight top. A 10ml test tube is great. Measure the volume of water it holds. Empty the water out.

    Cover the container and open it underwater. Count the daphnia. Repeat this several
    times - 10 - 15 times. Retreive the samples from different places in the tank. Record the results for each count.

    Calculate the mean -
    sum all of the numbers then divide that total by the number of samples. Let's pretend you got 8.2 as the value of mean. This is a large number but it does not matter.

    Your tank has approximately 39.3 liters of volume. So if your sample container
    was 10ml (that is .010L) then your population estimate is:
    Code (Text):

    8.2 * ( 39.3 / .010 )
    8.2 * 3930 = 32226 daphnia
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