Control of Crown-of-thorns starfish has been an important issue for reef
managers for over 30 years. There are no methods which can be applied
to intense starfish populations affecting large areas of reefs but tactical
controls to retain corals at sites important for tourism and recreation
are feasible and often recommended.
Control programs involve a substantial commitment of trained effort
over a long period. This report documents practical research which enables
managers and planners of control programs to appreciate the scope, commitment
and limitations of effective field operations. It is an important and
practical management support document applicable to coral reef environments
throughout the Indian and Pacific Oceans.
Great Barrier Reef Marine Park Authority
Crown of thorns (COTS) eradication effort was carried out by injection
of Dry Acid (Sodium Bisulphate solution). Three injection regimes were
tested at two different reefs (Lizard Island and Green Island) for their
effectiveness in reducing COTS densities on small patch reefs. The effect
on coral community structure of altering COTS densities was also investigated.
Over a 10-month period at Lizard Island, two injection regimes (high
frequency-low intensity, and low frequency-high intensity effort)
significantly reduced COTS densities.
At Lizard Island, high frequency/low intensity effort was more effective
over the longer term at reducing coral impacts than a low frequency/high
intensity treatment. However, hard coral cover decreased at a steady
rate in both treated and untreated sites. This was postulated to be
due to the continual influx of COTS immigrants from elsewhere. In
contrast, a standardised index of the amount of coral damage (complete
and partial mortality), significantly increased in the untreated sites
compared to the treated sites, indicating that the treatments were
halting the expected decline in coral cover at these sites.
At Green Island, a similar high frequency/low intensity treatment
regime and an additional high intensity treatment regime did not significantly
reduce COTS densities. Unexpected factors prevented the analysis of
impacts on the coral community as proposed. However, valuable descriptive
assessments of impacts are presented in the appendices.
Migration of COTS into both Lizard and Green Island study sites
was postulated to be negating the effect of protective measures over
longer periods. Consequently, eradication procedures appeared to be
stemming the rate of decline but not the net decline in coral cover.
Diver experience was also found to be an important factor in the
effectiveness of a control program. Greater diver experience both
with diving in general, and with finding cryptic COTS in particular,
resulted in higher numbers of COTS injected per unit time.
Recommendations for Control Programs for Industry
Note: The following recommendations are based on results contained
in this report and additional observations made during the study.
Successful control programs require : (1) constant eradication effort
over relatively long periods of time; (2) maintenance of the focus
on the target area and avoidance of the inclination to apply effort
on higher concentrations of COTS outside the target area; (3) treating
COTS concentrations in off-site areas in a strategic manner if there
is potential for migration into the target area; (4) maintenance of
medium term vigilance of the local situation (in terms of years),
until the threat is passed; and, (5) ensuring that the ability to
alter the intensity of eradication efforts at short notice is retained.
It is essential to have knowledge of the COTS outbreak situation
beyond the boundaries of the desired area of protection because migration
of COTS from adjacent areas will dictate the type and amount of eradication
The interval between eradication visits at any site should be determined
on a case by case basis. The required degree of eradication effort
is a function of the unique situation associated with each area of
reef requiring protection, and no single strategy will be applicable
in all outbreak situations or reefs, or at all phases of an outbreak
on one reef.
However, as a starting point, it is recommended that an intensive
eradication effort in the initial phases of a control program be followed
by frequent less intensive effort and that only well trained competent
divers are used.
In trials of eradication programs with different levels of intensity
using Dry Acid (sodium bisulfate solution), the study found that at one
site, high frequency/low intensity efforts were more effective than low
frequency/high intensity efforts at reducing the effects of starfish on
coral cover. However, eradication efforts at two sites could not halt
a decline in coral cover, mainly because large numbers of starfish moved
into the control sites from the large populations on other parts of the
THIS PUBLICATION IS CITED AS:
Fisk, D.A. & Power, M.C. (1999)
Development of Cost-Effective Control Strategies for Crown-of-thorns
CRC Reef Research Centre Ltd
Technical Report No. 25
Townsville; CRC Reef Research Centre Ltd, 61 pp.
ISBN 1 876054 99 9
A full copy of this report may be obtained from the author(s),
and through the following libraries:
Agency libraries: Great Barrier Reef Marine Park Authority,
Townsville; Australian Institute of Marine Science, Townsville; James
Cook University, Townsville; Queensland Department of Primary Industries and Fisheries
(Brisbane and regional offices); Queensland Department of Environment
and Heritage (Brisbane and regional offices); CSIRO Division of Marine
Public libraries: Queensland, New South Wales, Tasmania and South
Australia State libraries; National Library, ACT.
Parliamentary libraries: Queensland, New South Wales and South
Australia parliamentary libraries.
For a hard copy (or pdf file) of the report contact CRC Reef on firstname.lastname@example.org