The Acanthaster Problem
399
opinion was expressed by researchers who observed the first outbreaks of
the 1960s (D. H. Kuhlmann). In fact, they had been localized precisely in
zones of intensive human activity moreover that the stars theirself are
resistant to pollution, for example, in the GBR zone the acanthaster
outbrake started first near a large turistic center and port of Cairns. The
most severe attacks of Acanthaster in the 1960s-early 1970s occurred just in
the places of active military construction works: at Okinawa, Saipan, Guam,
Kwargelain, Majuro, Tahiti, Molokai, East Samoa. In the reef regions off
Fiji the outbreaks coincided with the expansion of the tourist industry and
with the mass collection of shells on reefs, especially of Charonia triton is
valued by run-of-the-mill tourists. On reefs of Palau outbreaks coincided
with the construction of a large oil terminal complex. The reef ecosystems
about all the regions listed were destabilized also by the development of
agriculture with the employment of pesticides and fertilizers, by the
intensive collection of shells and corals, and by the spear and explosious
fishery. The activity of tourists and local people on the reefs greatly
increased after the wide papularity of diving equipment: masks, flippers and
scuba. All these kinds of human activity undermined the homeostasis in reef
communities and thus promoted the population explosion of A. planci
(Chesher 1969; Artonius 1971; Endean 1973; Nishihira and Yamazato
1974).
Being a highly specialized corallowore predator, A. planci has no
competitors for food. Therefore its density on the reef should be controlled
only by a low rate of propagation, connected with the low density of
populations of this bisexual star and with grazing pressure at different stages
of its development. The overcoming of these two barriers might lead to the
possibility of its population explosion. According to Endean's hypothesis, in
reefs subjected to modern human activity the number of fish and
invertebrate predators feeding on spawns, larvae and the young of stars
decreases. Among such predators are groupers, murexes, conuses,
Charonia, Cassis - animals that are among those most hunted by tourists
and sought after by the market. Special attention was given to Charonia by
R. Endean, which he regards as a key species controlling the population
density of adult stars (Endean and Stablum 1973). The decrease in grazing
pressure results in the gradual building up of the number of young and adult
stars. It increases further their successful multiplication. The appearance of
a mass of larvae under conditions of decreased grazing pressure could cause
a catastrophic growth in the number of this predator at some reefs.
Accumulating on them during the periods of their multiplication, they are
building up a front for the attack. Their hordes first gather in deep zones of
the outer reef slope. After exterminating the corals there, many stars go up
to the shallow part of the reef, leaving behind a devastated reef. Then the
hordes of stars, moving rather fast by the bottom, migrate onto the
neighboring reefs, thus creating new areas of infestation, which may not be
directly connected with anthropogenic stress, such a secondary infestation
399
opinion was expressed by researchers who observed the first outbreaks of
the 1960s (D. H. Kuhlmann). In fact, they had been localized precisely in
zones of intensive human activity moreover that the stars theirself are
resistant to pollution, for example, in the GBR zone the acanthaster
outbrake started first near a large turistic center and port of Cairns. The
most severe attacks of Acanthaster in the 1960s-early 1970s occurred just in
the places of active military construction works: at Okinawa, Saipan, Guam,
Kwargelain, Majuro, Tahiti, Molokai, East Samoa. In the reef regions off
Fiji the outbreaks coincided with the expansion of the tourist industry and
with the mass collection of shells on reefs, especially of Charonia triton is
valued by run-of-the-mill tourists. On reefs of Palau outbreaks coincided
with the construction of a large oil terminal complex. The reef ecosystems
about all the regions listed were destabilized also by the development of
agriculture with the employment of pesticides and fertilizers, by the
intensive collection of shells and corals, and by the spear and explosious
fishery. The activity of tourists and local people on the reefs greatly
increased after the wide papularity of diving equipment: masks, flippers and
scuba. All these kinds of human activity undermined the homeostasis in reef
communities and thus promoted the population explosion of A. planci
(Chesher 1969; Artonius 1971; Endean 1973; Nishihira and Yamazato
1974).
Being a highly specialized corallowore predator, A. planci has no
competitors for food. Therefore its density on the reef should be controlled
only by a low rate of propagation, connected with the low density of
populations of this bisexual star and with grazing pressure at different stages
of its development. The overcoming of these two barriers might lead to the
possibility of its population explosion. According to Endean's hypothesis, in
reefs subjected to modern human activity the number of fish and
invertebrate predators feeding on spawns, larvae and the young of stars
decreases. Among such predators are groupers, murexes, conuses,
Charonia, Cassis - animals that are among those most hunted by tourists
and sought after by the market. Special attention was given to Charonia by
R. Endean, which he regards as a key species controlling the population
density of adult stars (Endean and Stablum 1973). The decrease in grazing
pressure results in the gradual building up of the number of young and adult
stars. It increases further their successful multiplication. The appearance of
a mass of larvae under conditions of decreased grazing pressure could cause
a catastrophic growth in the number of this predator at some reefs.
Accumulating on them during the periods of their multiplication, they are
building up a front for the attack. Their hordes first gather in deep zones of
the outer reef slope. After exterminating the corals there, many stars go up
to the shallow part of the reef, leaving behind a devastated reef. Then the
hordes of stars, moving rather fast by the bottom, migrate onto the
neighboring reefs, thus creating new areas of infestation, which may not be
directly connected with anthropogenic stress, such a secondary infestation