Changes in northern Tanzania coral reefs during a period of increased fisheries management and climatic disturbance

Abstract

Abstract Surveys of coral reefs in northern Tanzania were conducted in 2004/5 with the aim of comparing them over an∼8‐year period during a time of increased efforts at fisheries management and the 1998 El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) coral mortality event that caused 45% mortality in northern Tanzania and much of the Indian Ocean. Changes associated with both management, its absence, and the ENSO were found but changes were generally small and ecological measures indicated stability or improvements over this period, particularly when compared with reports from much of the northern Indian Ocean. Fisheries management in two areas increased the biomass of fish and benthic communities. A small fisheries closure (0.3 km2) displayed little change in the coral community but ecological conditions declined as measured by sea urchins and fish abundances. This change may be associated with its small size because similar changes were not measured in the large closure (28 km2). The few sites without any increased management were still degraded and one site had experienced a population explosion of a pest sea urchin, Echinometra mathaei. The lack of significant changes across this disturbance indicates that these reefs are moderately resilient to climate change and, therefore, a high priority for future conservation actions. Copyright © 2009 John Wiley & Sons, Ltd.