Red tides sighted

     Eighteen red tides have been sighted over the past week, the Inter-departmental Red Tide Working Group reported today (March 18).

     Staff of the Leisure and Cultural Services Department (LCSD) spotted two red tides on March 12 at Big Wave Bay Beach and Rocky Bay Beach, Hong Kong Island. On the same day, officers of the Marine Police and staff members of the Marine Department spotted red tides at the Tathong Channel to Lei Yue Mun (including Junk Bay and Tung Lung Chau Fish Culture Zone) and Victoria Harbour (near Hung Hom) respectively. On March 13, staff of the LCSD spotted five red tides at Middle Bay Beach, South Bay Beach, Repulse Bay Beach, Deep Water Bay Beach and Stanley Main Beach, Hong Kong Island. Another red tide was spotted by a member of the public at the southern waters of Hong Kong (including the East Lamma Channel and Sheung Sze Mun) on the same day. In addition, two red tides were spotted at Chung Hom Kok Beach and Turtle Cove Beach, Hong Kong Island, by staff of the LCSD on March 14. Members of the public also spotted red tides on the same day at the eastern waters of Sai Kung, the waters of Sai Kung (including Silverstrand and Clear Water Bay), Deep Bay and the southern waters of Lantau Island. Moreover, staff of the LCSD spotted red tides at Clear Water Bay Second Beach and Silverstand Beach, Sai Kung, on March 15 and 18.

     The red tides at Rocky Bay Beach, Middle Bay Beach, South Bay Beach, Repulse Bay Beach and Stanley Main Beach, Hong Kong Island, as well as those at Victoria Harbour (near Hung Hom) and Clear Water Bay Second Beach, Sai Kung, have dissipated, while the other 11 red tides are persisting. No fish deaths associated with the 18 red tides have been reported as of today.

     A spokesman for the working group said, "The red tide at Deep Bay was formed by Heterosigma akashiwo and that at the southern waters of Lantau Island was formed by Akashiwo sanguinea. The other 16 red tides were formed by Noctiluca scintillans. Akashiwo sanguinea and Noctiluca scintillans are non-toxic, while Heterosigma akashiwo might produce neurotoxins and kill fish by damaging their gills, according to overseas literature. The three algae are commonly found in Hong Kong waters."

     The Agriculture, Fisheries and Conservation Department (AFCD) urged mariculturists at Lo Tik Wan, Sok Kwu Wan, Po Toi, Tung Lung Chau, Ma Nam Wat, Kau Sai, Kai Lung Wan, Tai Tau Chau, Leung Shuen Wan, Tiu Cham Wan, Po Toi O, Ma Wan and Cheung Sha Wan fish culture zones to monitor the situation closely and increase aeration where necessary.

     Red tide is a natural phenomenon. The AFCD's proactive phytoplankton monitoring programme will continue to monitor red tide occurrences to minimise the impact on the mariculture industry and the public.