Fish
on the atolls
General
At
present the scientists know a little more than 1 100 fish species
for French Polynesia. This number is however lower than the
real number, because on the one hand of many islands were not
explored scientifically to this aim and on the other hand certain
mediums, as deep seas are currently very badly known in this area.This number of species is significant, equivalent for example to
what is observed on the whole of the seas of Europe. It is
however weaker than what is observed in the same mediums in the
west of the Pacific. Indeed, one notes a rather
significant reduction in the number of the species as one moves
away from the center of biodiversity which is in the triangle
Indonesia China Sea the Philippines.
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Geographical distribution of coastal fish of the section 0-100
meter. Each number represents the number of species known by zone.The zones of great diversity are
coloured in green. |
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The
fish occupy about all the biotopes where water is present
in Polynesia. One can distinguish four great
ecosystems: fresh waters, lagoons and reefs, deep seas and
the deep-sea field.
The lagoons and the reefs are without question the mediums
where the largest variety of fish is met, since 900
species were currently indexed there and it is probable
that there exists more than 1000 species récifales or
lagonaires in French Polynesia. All are however not
present in the atolls, since a recent census indicates
only approximately 600 species in Tuamotu.
Paracirrhites
arcatus |
Communities
on the atolls
Fresh
waters communities
The
Polynesian fresh waters are in general low in fish, on the one
hand because the rivers and lakes are very reduced and on the
other hand because of the insulation of the islands. This
situation is general with the majority of the Pacific Islands. The
fresh water species that one can
occasionally meet on the atolls are eels, small silver plated
poles of the family of Kuhlidae (patia as a Polynesian) and
the gobies whose Polynesians know especially the youthful ones,
the ina'a.
Marine
communities of the lagoons and reefs
One
distinguishes two great groups from fish, Selachians and Teleosts.
Selachians are fish whose skeleton consists of cartilage. In
the lagoons they are the sharks and the lines. In the atolls
the diversity of Sélaciens is relatively low.
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Selachians
are fish whose skeleton consists of cartilage. In the
lagoons they are the sharks and the stingrays. In the atolls
the diversity of Selachians is relatively low.
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The
osseous Teleosts or fish much are diversified than Selachians. The 600 species met in the atolls are divided into more than
70 families, however a score of 20 families gather more of two
thirds of the species.
The
most significant families are indicated in Table 1.
Table1:
diversity (number of species) of the principal families of fish
met in the section 0-100m in French Polynesia.
The
majority of these fish are of small size and can be seen only in
an occasional way. The abundant species or having an ecological or
economic importance recognized gather only 150-200 species.
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Associations
of species observed in the atolls are typical, with in
general domination of small species being able to be
planctophages or herbivorous (damselfishes , anthias, some
labres, some apogons), a more restricted number of small
carnivores (labres, gobies, apogons), a less density of
great herbivorous species (parrotfishes and surgeonfishes),
then a low density of large carnivores (loaches,
emperorfishes, triggerfishes, sea-breams...)
Pterois
volitans
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The
diversity observed in the atolls is rather low compared to other
site in the insular Pacific. The strongest fish concentrations can
be seen around the passes and on the pinnacles. On the bottoms of
lagoon, in particular in the absence of hard bottoms, diversity
and the density can become very weak.
Effects
of the type of the atoll
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The biotope, the
type of atoll and the size of the atoll have an influence
on the diversity and the density of the fish populations.
In particular, the planctophages become more abundant and
more diversified in the large atolls, the large predatory
ones are represented often little on the small atolls
whereas the herbivores have an about constant relative
importance.
Synodus variegatus |
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To
know some more
References Kulbicki
M., Galzin R., Harmelin-Vivien M., Mou Tham G., Andréfouët S.
2000 Les communautés de poissons lagonaires dans les atolls des
Tuamotu, principaux résultats du programme TYPATOLL (1995-1996).
Nouméa, IRD, Doc.Sci. Tech. II3: 26-125 |
Atoll_site_