TNC-CORDIO coral reef monitoring manual_book_coral1

Macro-invertebrate data analysis
and presentation
The density of key macro-invertebrates is commonly measured in numbers per 250m 2 .
Sea-urchins however are only counted along 10m of any transect and are therefore
measured in numbers per 50m 2 .
1 Survey: Complete a Macro-invertebrate Datasheet
for each transect in your site to record the numbers
of key species. Survey sea urchins for 10m of each
transect and the full 50m for other macro-invertebrates.
2 Summary: Add up the total number of macro-invertebrates
for all transects and then calculate the
average densities (the total number divided by
the number of transects). The result gives you the
average density of key invertebrates per 250m 2 (and
per 50m 2 for sea urchins).
3 Graphs: Compiling your data into graphs to show the
average density of each macro-invertebrate for the
site, with a separate graph for large and small sea
urchins.
4 Review: To compare long term data, each species
of macro-invertebrate is independently reviewed.
Plot separate graphs for each species showing the
average densities for consecutive surveys. As these
graphs are completed after each survey, the result
will enable you to review the long-term trends of all
macro-invertebrates for your site.
unhealthy fair healthy
high fishing pressure,
over-collection of shells
low fishing pressure,
no collection of shells
many sea urchins, no shells,
few macro-invertebrates
fewer sea urchins,
some shells &
macro-invertebrates
decreasing numbers of
sea urchins, increasing
numbers of shells and
macro-invertebrates
high numbers and
diversity of shells and other
macro-invertebrates, very low
number of sea urchins
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