Coral degradation and ability of rehabilitation of coral reefs in Co To Archipelago, Quang Ninh province, Vietnam

Serious degradation of coral reefs in the Co To Archipelago occurred from 2002 to 2006. Nearly 80% of the species and over 90% of living coral cover were lost and some reefs were completely dead. Currently, the highest coral cover is only 7.5% where previously most of the reefs had over 50% live coral cover. The cause of the reef degradation has been identified to be residues of cyanide used by local fishermen for fishing on reefs. To overcome the consequences transplantation corals on natural and artificial shelters were attempted. Survival rate on artificial shelters was 88.3% after 2 years and growth rate averaged 2.3 cm/year. Transplanted corals on natural shelters had lower survival rate, 55.9%. The natural recovery of coral on degraded reefs was also monitored periodically in this study. No coral recruitment was seen on completely dead reefs whereas there was little new coral recruitment on reefs with some remaining live corals.