Questions to consider
5.
Do you think that the method used to (al( Watt
,
the average number of
SCti
C U('unthets
pet %quare mole e valid( If not, how (mild the method
have
bo.,•ri
improved?
6. (a) Look at your transect data. Does the population density of sea-cucumbers
seem to be different in different zones of the reef-top (inner reef flat,
outer reef flat, reef rim,
etc.)? (You
could make a graph showing the total
numbers of sea-cucumbers obtained at each station along the transect.)
(b) Look at the transect data obtained
by
other groups. is there any difference
between sea-cucumber population density on the windward and leeward
sides of the reef?
(c) If sea-cucumber population density is not the same on different sides of
the reef or in different reef-top zones, what factors might contribute to
this?
7.
(a) Select two common sea-cucumber species, e.g. the "curry" cucumber
(Stichopus
variegatus) and the "knobbly" cucumber
(Stichopus
chloronotus).
(b) Examine the distribution data for each.
(c) In which zone of the reef-top is the population density of each species
least? greatest?
8. According to research studies reported by Bakus
(1973),
an individual sea-
cucumber might take in as much as 100 grams (estimate) of sediment each
day. Let's assume an average intake rate per individual of
30
grams per day.
How
much sediment might be taken in annually by all the sea-cucumbers on
this reef-top?
Try to design an experiment to find out what sedimentary material they are
taking in and what they are actually using from it?
9. What factors, natural and human-influenced, might cause a population of a
species of sea-cucumber on a reef-top to fluctuate from time to time? How
could this fluctuation be identified?
Sustainable use
When humans harvest living things, it is important to safeguard future
production by ensuring that annual harvest size is not too great. The
term "sustainable use" refers to the conservation practice of using a
living resource at a level which allows the supply of the resource to be
maintained indefinitely into the future.
10. In the past, fishing of some sea-cucumbers (called beche-de-mer or trepang)
took place on many reefs in the Great Barrier Reef area. Suppose someone
wanted to carry out beche-de-mer fishing now at a particular reef. Reef
management authorities would have to decide whether this would be
allowed. How do you think they could determine whether the proposed
fishing activity would be detrimental to this reef and whether, and how, it
could be carried out on a sustainable use basis? Are there other factors which
you think should be taken into consideration in deciding whether the
proposed fishing should be allowed to go ahead? What kind of information
do you think the reef management authorities would ideally like to have
available to them before they have to make a decision like this?
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