Communities Structure, Abundance, Distribution
223
the participation of a less specialized and more opportunistic species in the
formation of fish communities. It happens especially often in biotopes of the
outer reef slope where the reefal fish communities come in contact directly
with those of the open sea. The recruitment of a less specialized and more
opportunistic fish species could involve definite stochastic features in the
formation of reef fish communities, which was detected by the author of the
"chaos" theory. Some stochastic elements are introduced as a consequence
of an intensive grazing of reef fish fauna, resulting in its high-speed turnover
in some reef biotopes - and especially in biotopes of lagoon and outer slopes
(Talbot et al. 1978).
The species composition of different biotopes within the same reef differs
much more than that in similar biotopes of different reef systems (Hiatt and
Strasburg 1960; Hobson 1974; c.L. Smith 1978; Williams and Hatcher
1983). It is largely determined by the landscape of the bottom, by depth, by
their zonal position within the geomorphological system of the reef, and by
the abundance of living corals (Chave and Eckert 1974; Goldman and
Talbot 1976; Smith 1977; Galzin 1985). Most species of reef fish are living
only within definite types of structural reef elements (Sale 1978a). For
example, out of a total number of fish species inhabiting eight different
biotopes of the One Tree Reef only 7% was common. But only about 5%
out of all fish species found in each of these biotopes was met with in this
given biotope and was absent in others (Goldman and Talbot 1976). The
changes in composition of reef fish fauna in the GBR in different kinds of
biotopes appeared to be much larger than between the same types of
biotopes, situated between 11 0 and 22 0 S (Table 6.6). On one of the crosssections out of the total number of 323 species 60% were recorded on only
one out of three reefs, and only 7% was found on all three reefs (Williams
1983). Species diversity was increasing along the cross-sections from the
coast to the outer reef slope. Significant changes in fish fauna could be also
observed along the perimeter of the ring reefs of the GBR on their
windward and leeward parts (Done 1982).
These observations demonstrated that the local communities of reef fish
are largely isolated and practically do not mix, each being associared with a
definite type of reef construction and reef zone. This feature of settling is
peculiar only to the communities of reef fish, and is absent in coastal fish
communities outside of reefs. On reefs each of their structural elements has
its owner (Smith 1978). Thus it could be deduced that the density of reef fish
communities is controled largely by space, which appears to be a more
important factor than trophic resources and grazing pressure. The
availibility of space within reef constructions regulates the conditions of
hunting, hiding and propagation of fish. The species diversity of reef-fish
communities therefore depends upon the complicacy of reef constructions
(Hobson 1974; Hatcher 1981). For example, in reef areas covered with
ramose corals the number of species is much higher compared with places of
poor coral growth (Harmelin-Vivien 1977; Carpenter et al. 1981).
223
the participation of a less specialized and more opportunistic species in the
formation of fish communities. It happens especially often in biotopes of the
outer reef slope where the reefal fish communities come in contact directly
with those of the open sea. The recruitment of a less specialized and more
opportunistic fish species could involve definite stochastic features in the
formation of reef fish communities, which was detected by the author of the
"chaos" theory. Some stochastic elements are introduced as a consequence
of an intensive grazing of reef fish fauna, resulting in its high-speed turnover
in some reef biotopes - and especially in biotopes of lagoon and outer slopes
(Talbot et al. 1978).
The species composition of different biotopes within the same reef differs
much more than that in similar biotopes of different reef systems (Hiatt and
Strasburg 1960; Hobson 1974; c.L. Smith 1978; Williams and Hatcher
1983). It is largely determined by the landscape of the bottom, by depth, by
their zonal position within the geomorphological system of the reef, and by
the abundance of living corals (Chave and Eckert 1974; Goldman and
Talbot 1976; Smith 1977; Galzin 1985). Most species of reef fish are living
only within definite types of structural reef elements (Sale 1978a). For
example, out of a total number of fish species inhabiting eight different
biotopes of the One Tree Reef only 7% was common. But only about 5%
out of all fish species found in each of these biotopes was met with in this
given biotope and was absent in others (Goldman and Talbot 1976). The
changes in composition of reef fish fauna in the GBR in different kinds of
biotopes appeared to be much larger than between the same types of
biotopes, situated between 11 0 and 22 0 S (Table 6.6). On one of the crosssections out of the total number of 323 species 60% were recorded on only
one out of three reefs, and only 7% was found on all three reefs (Williams
1983). Species diversity was increasing along the cross-sections from the
coast to the outer reef slope. Significant changes in fish fauna could be also
observed along the perimeter of the ring reefs of the GBR on their
windward and leeward parts (Done 1982).
These observations demonstrated that the local communities of reef fish
are largely isolated and practically do not mix, each being associared with a
definite type of reef construction and reef zone. This feature of settling is
peculiar only to the communities of reef fish, and is absent in coastal fish
communities outside of reefs. On reefs each of their structural elements has
its owner (Smith 1978). Thus it could be deduced that the density of reef fish
communities is controled largely by space, which appears to be a more
important factor than trophic resources and grazing pressure. The
availibility of space within reef constructions regulates the conditions of
hunting, hiding and propagation of fish. The species diversity of reef-fish
communities therefore depends upon the complicacy of reef constructions
(Hobson 1974; Hatcher 1981). For example, in reef areas covered with
ramose corals the number of species is much higher compared with places of
poor coral growth (Harmelin-Vivien 1977; Carpenter et al. 1981).