GANNET CAY

This reef has been surveyed extensively using manta tow since 1986. COTS have been present at Outbreak levels in fifteen of eighteen survey years. As a result, reef-wide live coral cover has declined dramatically from the extremely high levels (75-100%) recorded at the beginning of surveys. While there was some recovery between 1995 and 1997 when COTS were below outbreak levels recent increases in COTS numbers, particulalry in 2001, has seen reef-wide live coral cover in 2003 drop to the lowest level (median cover less than 5%) yet recorded. COTS numbers remain high on this reef and it is classified as Active Outbreak. No bleaching or disease was recorded from this reef during manta tow surveys in 2003.

Detailed coral surveys since 1992 show a steady decline in cover of hard corals from (60%) in the first year of survey to 17% in the year 2000. This decline was driven by the widespread loss of branching Acropora colonies and cover of this life-form declined from 40% in 1993 to less than 6% in 2000. Declines of this once dominant coral can be attributed to the feeding activilty of COTS on this reef. Other families of hard corals were not abundant at any time during this study. Algae has shown a corresponding increase in cover while soft coral cover has remained low and stable. Amongst larger reef fish, Chaetodontidae showed a long term decrease in abundance which was primarily due to declines in Chaetodon rainfordi, C. aureofasciatus and C. trifasciatus from relatively stable numbers prior to 1995-96. Conversely the increase in Acanthuridae stems from increasing numbers of Ctenochaetus from a 1997 low. Pomacentrus was the only Damsel fish genus to show a long term trend. The three most abunbundant species, P. moluccensis, P. lepidogenies and P. wardi all declined in number over several years to 1999. However, numbers of P. lepidogenys and P. wardi had increased in the 2000 survey. This pattern was similar for Chyrsiptera rollandi, the difference being that the rate of decline was slower than for the Pomacentrus species hence the significant increase in the 2000 survey. Neopomacentrus azysron was recorded for the fisrt time in five years in the 2000 survey. A large spike in Chromis nitida abundance in 1997 followed by a subsequent decline drives the observed result for Chromis.

Gannet Cay (No. 21-556) is a middle shelf planar reef with an area of 1.2 sq.km. Last surveyed September 2002.







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