Coral Recruitment and Coral Reef Resilience on Pemba Island, Tanzania

Abstract

This study explores the patterns of coral recruitment, survivorship and resilience on the coral reefs of the west coast of Pemba Island, Tanzania. The results show that recovery from the 1998 mass coral bleaching event has been patchy, with great variation in coral cover among sites, and a generally high macroalgal cover. Sites with low coral recovery were found to exhibit higher numbers of coral recruits but lower survivorship, implying that larval supply is not impeding recovery but rather that local stressors are reducing coral reef resilience. The main stressors observed were predation by Acanthaster plancii, overfishing and use of destructive fishing methods (including dynamite fishing). A. plancii predation was shown to negatively correlate with coral recruit survivorship, implying that it is a potential cause of failure of corals to reach adult sizes. Fish surveys showed that Pemba is being overfished, with the vast majority of fish observed less than 10 cm in length, and only 4 individuals larger than 40 cm recorded throughout the whole survey. It is recommended that the two major, and potentially synergistic, stressors of A. plancii predation and overfishing/destructive fishing are addressed in order to avoid loss of Pemba’s coral reefs. Land-ocean connections are also explored in this context.