Coral in Hạ Long Bay. — Photo baoquangninh.com.vn

In 1998, Hạ Long Bay still had some "good" and "very good" reefs (with coral cover reaching 51 per cent or higher, and 76 per cent or higher, respectively). By 2013, it no longer had any reefs in the "very good" category. The situation deteriorated further in 2015 when a survey showed that coral cover in the best-maintained reefs was below 50 per cent and the average rate in the bay was just 20 per cent.

The damage was blamed on the declining water quality and the emergence of Drupella snails that eat coral tissues. Both of which are considered the result of human activity including tourism, fishing, pollution, industrial and household wastewater. 

However, in recent times, with stringent management measures introduced, there have been signs of recovery. Some reefs have been discovered with coral cover as high as 60 to 70 per cent. The flourishing of 'branching' corals has also been observed.

The Hạ Long Bay Management Board, in collaboration with the municipal People's Committee of Hạ Long City have been diligently working to repair the reefs.

The management board regularly monitors and supervises conservation of the coral reef ecosystem to promptly detect threats and carry out restoration measures. 

They have surveyed and built a database of the ecosystem which has proven useful for implementing conservation measures. In addition, it has trained people in the management and protection of the coral reef ecosystems.

This has been coupled with patrols that are regularly organised with people caught violating laws designed to protect the reef facing heavy penalties.

It has also zoned off coral reefs with a high coverage area of more than 30 percent, erecting warning signs for wayward fisherman that risk entering the area.

In 2019, Quảng Ninh province issued regulations on the management of Hạ Long Bay, including a ban on fishing in the heritage area to prevent oil pollution from fishing vessels.

Hạ Long Bay is home to 147 species of coral. Areas with high coral coverage of over 30 percent are located in Cống Đỏ-Trà Sản, Hang Trai-Đầu Bê with a total area of about 5,108 ha. Coral reefs are distributed mainly in Trà Sản, Soi Ván and Lưỡi Liềm areas.