The Acanthaster Problem
395
100-1000 sp. ha -I, which is 4- 5 orders more than natural. During 20 min of
swimming over the infested reef, 30 to 1000 stars could be recorded, which
had diameters of 30-60cm (Chesher 1969; Dana et al. 1972; Kenchington
1987). On one coral knoll near the Natan reef (GBR) R. Endean recorded
over 700 stars. On one platform reef of moderate size in the same region
their population could number 10 5 _10 6 stars. At the same time, on some of
the nearly reefs, in areas of infestation, on eight such reefs only six stars
were found. On 22 reefs to the north off Lizard Island, outside the zone of
invasion in 1970 not a single star had been found. But later these same reefs
were severely damaged by Acanthaster (Cameron and Endean 1981). In
their density of 150-200sp. ha- I , the stars kill a main portion of
scleractinian corals on the infested reef, which looks afterwards like an
abandoned, mournful cemetery (Endean 1976; Cameron 1977). At the reefs
of the Eastern Pacific, which had been also infested, their density did not
rise above 20-50 ha -I. It was about three orders more than their natural
population density, but 3 - 5 times less than the catastrophic level.
Therefore, most reefs in this region, which were (and even now are) infested
by Acanthaster, have not been so destroyed as some in other places of the
central and western Pacific. They reached a kind of equillibrium at such a
density of this predator. But the community structure of scleractinian corals
is changing in the direction of large colonies of the coral Pocillopora
dominating in them, as these are defended by their infaunal symbionts.
The most severe attacks of Acanthaster befell in 1957-1973 on the IndoPacific reefs situated along the coasts of high islands and continents. Among
them were most reefs in the central part of the GBR between 14° and
20007 S, reefs off Okinawa, Guam, Saipan, Palau, Fiji, Hawaii, Eastern
Samoa Islands and off the Comore Islands (Indian Ocean, Goreau et al.
1973, Wilson and Marsh 1974, Sano et al. 1987, Eahl et al. 1990). At some
of the atolls and on reefs around some other high islands in the Cook,
Tuamotu and Society archipelagos, near the west coast of Australia, around
Mauritius and Madagascar, and off the coast of Kenya the density of
Acanthaster increased by 2-3 orders compared with the natural one, and
unmistakable signs of their attack on corals appeared (Barnes 1966; Chesher
1969; Kuhlmann 1971; Dana et al. 1972, Endean and ; Stablum 1973;
Endean 1973, 1974; Marsh and Tsuda 1973; Sale et al. 1976; Kuhlmann
1985). On atolls, situated in the open deep ocean, the Acanthaster outbreaks
were rarer, and as a rule they were not so destructive, except on those
subjected to intensive human activity, either agricultural, constructional or
military (Marsh and Tsuda 1973). On such atolls the attacks of stars were
especially disastrous. Among the se there could be mentioned the Majuro,
Kwargelein and Tarawa atolls. Later outbreaks occurred in the Red Sea, in
Malaysia and in Vietnam (Ridzman 1988; De Silva 1988).
On the GBR the first outbreak of Acanthaster was observed at some
lagoonal reefs. By 1966 the stars infested over 50% of reefs reviewed there
between 15° and 19° S. In 1969-1971 82 reefs in this area had been reviewed
395
100-1000 sp. ha -I, which is 4- 5 orders more than natural. During 20 min of
swimming over the infested reef, 30 to 1000 stars could be recorded, which
had diameters of 30-60cm (Chesher 1969; Dana et al. 1972; Kenchington
1987). On one coral knoll near the Natan reef (GBR) R. Endean recorded
over 700 stars. On one platform reef of moderate size in the same region
their population could number 10 5 _10 6 stars. At the same time, on some of
the nearly reefs, in areas of infestation, on eight such reefs only six stars
were found. On 22 reefs to the north off Lizard Island, outside the zone of
invasion in 1970 not a single star had been found. But later these same reefs
were severely damaged by Acanthaster (Cameron and Endean 1981). In
their density of 150-200sp. ha- I , the stars kill a main portion of
scleractinian corals on the infested reef, which looks afterwards like an
abandoned, mournful cemetery (Endean 1976; Cameron 1977). At the reefs
of the Eastern Pacific, which had been also infested, their density did not
rise above 20-50 ha -I. It was about three orders more than their natural
population density, but 3 - 5 times less than the catastrophic level.
Therefore, most reefs in this region, which were (and even now are) infested
by Acanthaster, have not been so destroyed as some in other places of the
central and western Pacific. They reached a kind of equillibrium at such a
density of this predator. But the community structure of scleractinian corals
is changing in the direction of large colonies of the coral Pocillopora
dominating in them, as these are defended by their infaunal symbionts.
The most severe attacks of Acanthaster befell in 1957-1973 on the IndoPacific reefs situated along the coasts of high islands and continents. Among
them were most reefs in the central part of the GBR between 14° and
20007 S, reefs off Okinawa, Guam, Saipan, Palau, Fiji, Hawaii, Eastern
Samoa Islands and off the Comore Islands (Indian Ocean, Goreau et al.
1973, Wilson and Marsh 1974, Sano et al. 1987, Eahl et al. 1990). At some
of the atolls and on reefs around some other high islands in the Cook,
Tuamotu and Society archipelagos, near the west coast of Australia, around
Mauritius and Madagascar, and off the coast of Kenya the density of
Acanthaster increased by 2-3 orders compared with the natural one, and
unmistakable signs of their attack on corals appeared (Barnes 1966; Chesher
1969; Kuhlmann 1971; Dana et al. 1972, Endean and ; Stablum 1973;
Endean 1973, 1974; Marsh and Tsuda 1973; Sale et al. 1976; Kuhlmann
1985). On atolls, situated in the open deep ocean, the Acanthaster outbreaks
were rarer, and as a rule they were not so destructive, except on those
subjected to intensive human activity, either agricultural, constructional or
military (Marsh and Tsuda 1973). On such atolls the attacks of stars were
especially disastrous. Among the se there could be mentioned the Majuro,
Kwargelein and Tarawa atolls. Later outbreaks occurred in the Red Sea, in
Malaysia and in Vietnam (Ridzman 1988; De Silva 1988).
On the GBR the first outbreak of Acanthaster was observed at some
lagoonal reefs. By 1966 the stars infested over 50% of reefs reviewed there
between 15° and 19° S. In 1969-1971 82 reefs in this area had been reviewed