HOW MANY FISH ARE IN THE LAKE…
YOUR LAKE??? USE THE CAPTURE –
RECAPTURE METHOD TO ESTIMATE THE
TOTAL FISH POPULATION!
Although we will be dealing with fish, this method
can be used to estimate many other populations with
similar characteristics to our fish. It is difficult,
nearly impossible to count large, mobile
populations as exist in wildlife/census/population
situations exactly because of their
characteristics….large and mobile. Accurate
estimation of wildlife populations are used to
implement controls as necessary.
We will find the estimate, a good mathematically
sound estimate, using ratios and proportions.
Let p = total number in the population that we wish
to estimate
Let t = number of subjects tagged
Let n = sample size from which to estimate
population
Let x = number of subjects tagged from the sample
taken
The method is based on the fact that the true
population should mirror the ratio that exists in the
sample(s), ie., x/n = approx. t/p where we are
wishing to estimate p. By cross multiplying to
solve for p we get xp = nt and p = nt/x.
Let’s proceed with estimating our fish population
by gathering appropriate data.