Ciguatera poisoning in Rarotonga, southern Cook Islands

The central Pacific Ocean has arguably more ciguatera poisoning than any other place on earth. Here we tested two competing hypotheses that outline the primary causes of ciguatera outbreaks: (1) the ‘new surface hypothesis’ and (2) the ‘climate oscillation hypothesis’. Our findings indicated that in Rarotonga, from 1994 to 2010, the annual incidence of ciguatera poisoning ranged from 204 to 1,058 per 10,000 population per year. We found that the widest reefs of Rarotonga elicited the most cases of ciguatera poisoning, but found no relationship between ciguatera outbreaks and reef exposure. We also found strong correlations between cases of ciguatera poisoning and (i) the positive phase of the Pacific Decadal Oscillation, (ii) El Niño years, and (iii) periods with frequent disturbances. Yet, most disturbances occurred during the above-mentioned climate phases. This study links the two supposedly, mutually exclusive hypotheses. Moreover, as predicted by the ‘climate oscillation hypothesis’, the Pacific Ocean is now, in 2010, experiencing a negative phase of the Pacific Decadal Oscillation, and Rarotonga is reporting few cases of ciguatera poisoning.