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THE ABUNDANCE, DIVERSITY AND RELATIONSHIP TO CORAL COVER OF BUTTERFLYFISH COMMUNITIES
The
Wakatobi Marine National Park was set up in 1996 and included a stakeholder
managed zone between the islands of Hoga and Kaledupa. Within the stakeholder
zone, a voluntary no-fishing zone was set up by the local Bajo villagers along
the home reef of Hoga. Since the no-fishing zone was set up in 2000, a
monitoring program has been carried out to record changes in the reef habitat.
Butterflyfish
(family chaetodontidae) are commonly used as an indicator species of coral
health. Indicator species can be used to detect low-level changes in the coral
reef habitat, and act as a warning system for stress within this ecosystem. A
commonly used indicator is species of butterflyfish that are obligate
corallivores, and correlations can then be found between the abundance and
diversity of these species and coral abundance and rugosity. This can be carried
out using the line transect and fish count methods. As noted by Crosby and Reese
(1996), “the butterflyfish indicator method is sensitive to changing
conditions on the reef and should provide an “early warning” that a change
is occurring. This may provide enough time for remedial actions to be taken
before entire coral reef habitats are lost.”
Aims
and Objectives
Aims:
Objectives:
1.
To identify the species of butterflyfish present within the sampling area
2.
To identify the numbers of each species present within the sampling area
3.
To record the level of coral cover present along each transect line
within the sampling area
Eight
sites were selected within the stakeholder zone, both inside and outside the no
fishing zone:
Buoy
II Reef on Left (inside the No Fishing Zone)
Buoy
II Reef on Right (outside the No Fishing Zone)
Buoy
III (inside the No Fishing Zone)
Pak
Kasim (outside the No Fishing Zone)
Sampela I (a heavily degraded site)
Sampela II (a heavily degraded site)
Kaledupa
I (a pristine site)
Kaledupa II (a pristine site)
Transect
lines were set up along the reef crest, each line being 50m in length and at a
depth of approximately 5m. For each of these sites the transect line was
replicated three times, and these replicates were surveyed a total of three
times, giving a total of three benthic surveys and nine chaetodont surveys for
each site. There was a gap of at least 5m between each of the replicates to
ensure separation, with each 50m chaetodont survey taking approximately 15 to 20
minutes to complete, and each 50m benthic survey taking approximately 40 minutes
to complete. When each transect line was laid on the reef, they were left for
approximately 10 minutes before the survey commenced to minimize the effects of
diver positive and diver negative influences on the fish in the area of the
transect.
As
yet, no analysis has been carried out on the data that has been collected over
the last eight weeks; however, some interesting observations have been made. It
has been noted, for example, that in Sampela where the reef is exceptionally
degraded there is still a very high diversity of chaetodonts, although the
abundance remains lower in these sites.
Various
statistical tests can be carried out on the data to find correlations between
abundance and diversity of obligate corallivores and hard coral cover, and also
to compare data means. Pearson’s Rank Correlation and Spearman’s Rank
Correlation will be used to find correlations between abundance and diversity of
obligate corallivores and levels of hard coral cover, and also the
Shannon-Weiner Diversity Index. Statistical tests such as the T-test, ANOVA
(Analyses of Variance) and Chi-squared will also be used to compare data means.
Reports
A
final year dissertation report will be completed by Rachael Bennett, University
of Aberdeen by May 2003.