Replies to LegCo questions

LCQ2: Red tides in Hong Kong waters

Following is a question by the Hon Wong Yung-kan and a reply by the Secretary for Health, Welfare and Food, Dr York Chow, in the Legislative Council today (November 24):

Question:

From January to September this year, red tides occurred repeatedly in the Hong Kong waters and they took a longer time to recede than before. In this connection, will the Government inform this Council:

(a) whether it has analysed the reasons for the slow receding of the red tides this year; if so, of the analysis results;

(b) whether it has assessed the impact of red tides on the marine resources, the ecology of waters and the mariculture and capture fisheries industries in Hong Kong; if so, of the assessment results; if not, the reasons for that; and

Reply:

Madam President,

(a) Between January and September 2004, the Agriculture, Fisheries and Conservation Department (AFCD) recorded 29 red tide incidents, higher than the 17 incidents recorded over the same period last year. The surge may be attributed to this summer's rainfall being higher than last summer. Apart from providing the necessary nutrients for algae, rainwater also lowered the salinity of sea surface layer. The resultant stratification facilitated algae aggregation and increased the chances for occurrence and persistence of red tides. Previous red tide incidents recorded in Hong Kong waters lasted from one day to several weeks. The duration of red tide incidents this year also lasted from several days to several weeks. There has not been any noticeable slowdown in the rate they receded.

(b) Of the 29 red tide incidents recorded this year, all but one were formed by non-toxic species. As all these red tides receded within a short time, they had not caused any serious oxygen depletion in seawater and thus should not have caused significant impact on the marine resources and ecology. Of these 29 red tide incidents, only five occurred in mariculture zones. Since mariculturists had been alerted by AFCD in advance, they had taken proper preventive measures in time, such as suspending feeding and activating aerators, and prevented massive fish kills in the culture zones.

(c) Red tide is a natural phenomenon with complicated causes. Under a favourable combination of various environmental factors, such as light intensity, temperature and nutrients in the seawater, and water velocity, microscopic phytoplanktons will bloom and create a red tide. There is no effective way to prevent occurrence of red tide.

In the wake of the red tide outbreak in 1998, the Government commissioned overseas experts to prepare a consultancy report on the monitoring and management of red tides in Hong Kong. Since then, the Government has followed the report's recommendations and adopted appropriate measures to improve the management and strengthen the early detection system for red tides. One of these measures is an intensive phytoplankton monitoring programme launched by the AFCD. Under the programme, water samples are taken regularly from various locations across the territory for analysis and to detect the presence of red tide in order to provide early warning to fish farmers to reduce the impact of red tides. Besides, the Government has established a Red Tide Interdepartmental Working Group to coordinate the monitoring and management work related to red tides and designed a master plan for red tide monitoring and management. Upon receipt of reports of red tide sightings, the departments concerned would be notified to take appropriate follow-up actions and public announcements made to alleviate the impact of red tides on the general public.

Ends/Wednesday, November 24, 2004

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