234
Coral Reef Fish
productivity of the bottom algoflora (Randall 1961; Bakus 1967; Ogden and
Lobel 1978; Hatcher and Larkum 1983; Hatcher and Rimmer 1985; Polunin
1989). The controlling action of grazing by fish on the growth of benthic
plants was demonstrated experimentally by placing cages on the bottom,
preventing so the grazing of plants by fish (Earle 1972; Wanders 1977;
Nelson and Tsutui 1981). A more intensive growth inside the cages was
recorded even after several weeks of experimenting (Vine 1974). But inside
the cages the growth of corals and coralline algae was inhibited by
accelerated development of macrophytes and especially of filamentous
algae, overgrowing through the avoidance of grazing (Wanders 1977). The
pressure of grazing of the algoflora by fish could be restricted naturally
inside the areas defended by territorial pomacentrid fish (Vine 1974; Potts
1977).
An important function of the herbivorous fish scarids and acanthurids in
reef systems could also be seen in their bioerosional activity and in the
production and transport of carbonaceous material (cf. Sect. 1.3). When
scraping the periphyton and coralline algae from the reef rocks and rubble
they swallow a mass of calcareous material including pebbles which they use
for the crushing of plant material in their throat "mill" the same as is done
by grain-eating birds. The swallowed calcareous material is milled during
digestion and is excreted by fish as fine carbonaceous sediments. The
population of the parrot fish Sparisoma viridis, of average density, living on
one of the Bermuda reefs, excretes about 2 t of carbonaceous sediments per
year, which is equal to the erosion rate of reef flats of 1 mllOO years (Gygi
1975; Bardach 1961).
6.3.2 Planktonovorous Fish
Within this guild the groups of primary and secondary planktonovorous fish
could be distinguished. The group of primary planktonovores includes
several species from families of typically pelagic fish of the open sea, which
adapted to reef environments. Among them clupeid and dussumerid fish are
most common. Their main adaptation to reef life appears to be their small
size. They are small shoaling fish, which in the daytime hideng with their
schools near the reef edge, in lagoons or in caves. At night they disperse and
feed in the water column on abundant nocturnal reef zooplankton. The
group of secondary planktovores includes representatives of different
families of typical reef fish most of which belong to the order Perciformes or
are related to it (Davis and Birdsong 1973; Hobson and Chess 1978;
Williams and Hatcher 1983). Planktovorous species could be found in most
families of benthos-feeding predatory fish: Labridae (Clepticus parrai,
Microlabrichthys pascalus) , Lutjanidae (genus Emmelichthyops), Serranidae
(Schulzea beta, Serranus tortugarum, Paracanthes furcifer) , Pempheridae
(Pempheris schomburgki, Ociurus chrisurus) , Pomadasyidae (genus Hae-
Coral Reef Fish
productivity of the bottom algoflora (Randall 1961; Bakus 1967; Ogden and
Lobel 1978; Hatcher and Larkum 1983; Hatcher and Rimmer 1985; Polunin
1989). The controlling action of grazing by fish on the growth of benthic
plants was demonstrated experimentally by placing cages on the bottom,
preventing so the grazing of plants by fish (Earle 1972; Wanders 1977;
Nelson and Tsutui 1981). A more intensive growth inside the cages was
recorded even after several weeks of experimenting (Vine 1974). But inside
the cages the growth of corals and coralline algae was inhibited by
accelerated development of macrophytes and especially of filamentous
algae, overgrowing through the avoidance of grazing (Wanders 1977). The
pressure of grazing of the algoflora by fish could be restricted naturally
inside the areas defended by territorial pomacentrid fish (Vine 1974; Potts
1977).
An important function of the herbivorous fish scarids and acanthurids in
reef systems could also be seen in their bioerosional activity and in the
production and transport of carbonaceous material (cf. Sect. 1.3). When
scraping the periphyton and coralline algae from the reef rocks and rubble
they swallow a mass of calcareous material including pebbles which they use
for the crushing of plant material in their throat "mill" the same as is done
by grain-eating birds. The swallowed calcareous material is milled during
digestion and is excreted by fish as fine carbonaceous sediments. The
population of the parrot fish Sparisoma viridis, of average density, living on
one of the Bermuda reefs, excretes about 2 t of carbonaceous sediments per
year, which is equal to the erosion rate of reef flats of 1 mllOO years (Gygi
1975; Bardach 1961).
6.3.2 Planktonovorous Fish
Within this guild the groups of primary and secondary planktonovorous fish
could be distinguished. The group of primary planktonovores includes
several species from families of typically pelagic fish of the open sea, which
adapted to reef environments. Among them clupeid and dussumerid fish are
most common. Their main adaptation to reef life appears to be their small
size. They are small shoaling fish, which in the daytime hideng with their
schools near the reef edge, in lagoons or in caves. At night they disperse and
feed in the water column on abundant nocturnal reef zooplankton. The
group of secondary planktovores includes representatives of different
families of typical reef fish most of which belong to the order Perciformes or
are related to it (Davis and Birdsong 1973; Hobson and Chess 1978;
Williams and Hatcher 1983). Planktovorous species could be found in most
families of benthos-feeding predatory fish: Labridae (Clepticus parrai,
Microlabrichthys pascalus) , Lutjanidae (genus Emmelichthyops), Serranidae
(Schulzea beta, Serranus tortugarum, Paracanthes furcifer) , Pempheridae
(Pempheris schomburgki, Ociurus chrisurus) , Pomadasyidae (genus Hae-