A survey of freshwater fishes and their macroparasites in the ... - NINA

13
NINA Report 635
We have also used a resampling procedure to illustrate the relationship between host sample
size and the number of parasite taxa recorded in the sample. For any sample (e.g. the number
of fish hosts, ns, dissected one year at a given location) we draw, at random without replacement,
a sub-sample of n fish (n=1, 2, …, ns) and count the number of parasite taxa belonging
to this sub-sample. This is repeated 1000 times for each value of n. We thereby obtain a curve
describing the relationship between host sample size and number of parasite taxa (average of
the 1000 simulations), which is similar to a rarefaction curve (Sanders 1968). In addition, the
simulations provide an indication of the uncertainty in the sample size – parasite taxa relationship.
No. parasite species
0 5 10 15
Locality 7 - 2001 - Dry season
0 20 40 60 80 100
No. resampled host individuals
Figure 2 Example of the relationship
between host number
and parasite species number
based on the resampling procedure
described in the text.
The dotted lines give approximate
95% confidence limits,
but the upper limit from ca. 70
resampled hosts is restricted
to the total number of observed
parasite species (15)
and should therefore not be
applied.
Rio Sapoa (locality
2; 205 m a.s.l.).