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THURSDAY, MAY 10, 1990
COMPUTER MODEL TO FORECAST OXYGEN DEPLETION
A WATER QUALITY COMPUTER MODEL TO PREDICT THE LIKELIHOOD OF FISH KILLS CAUSED BY LOW DISSOLVED OXYGEN LEVELS IN FISH CULTURE ZONES HAS BEEN SUCCESSFULLY DEVELOPED BY THE AGRICULTURE AND FISHERIES DEPARTMENT (AFD) IN CONJUNCTION WITH THE UNIVERSITY OF HONG. KONG (HKU).
THE FIRST OF ITS KIND IN ITS APPLICATION IN FISH FARMING IN HONG KONG, THE OXYGEN BUDGET MODEL HAS BEEN DEVELOPED SINCE 1986 WITH THE AIM TO PROVIDE FORECASTS OF OXYGEN DEPLETION, RED TIDES OR ALGAL BLOOMS IN THE WATER WHICH WERE RESPONSIBLE FOR 40 PER CENT OF MASSIVE FISH KILLS IN HONG KONG'S MARICULTURE INDUSTRY.
INTRODUCING THE COMPUTER MODEL AT A PRESS CONFERENCE AT AFD'S ABERDEEN FISHERIES OFFICES TODAY (THURSDAY} WERE THE DEPARTMENT'S SENIOR FISHERIES OFFICER, DR PATSY WONG, AND THE SENIOR LECTURER OF HKU'S CIVIL ENGINEERING DEPARTMENT, DR JOSEPH LEE.
"THE MODEL USES NUMERICAL METHODS TO SIMULATE THE COMPLEX RELATIONS AMONGST A NUMBER OF PHYSICAL AND BIOLOGICAL PROCESSES WHICH AFFECT THE DISSOLVED OXYGEN LEVEL IN SEA WATER, INCLUDING PHOTOSYNTHETIC PRODUCTION, SEDIMENT OXYGEN DEMAND, ALGAL AND FISH RESPIRATION, ORGANIC AND NUTRIENT INPUT, LIGHT INTENSITY, TEMPERATURE, TIDAL FLUSHING AND WIND SPEED, DR WONG EXPLAINED.
"OVER THE PERIOD FROM JULY 1987 TO MARCH THIS YEAR, A TOTAL OF 30 SURVEYS WAS CARRIED OUT, COVERING A WIDE RANGE OF METEOROLOGICAL AND ECOLOGICAL CONDITIONS. EACH OF THESE SURVEYS LASTED 26 HOURS, SHE ADDED.
THE ABUNDANT DATA BASE IS THEN USED FOR THE CALIBRATION, VALIDATION AND REFINEMENT OF THE MATHEMATICAL MODEL.
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DR WONG SAID: "BY FEEDING THE NECESSARY DATA INTO THE COMPUTER, INCLUDING THOSE AFFECTING THE DISSOLVED OXYGEN LEVEL, WEATHER CONDITIONS AND WEATHER FORECASTS FROM THE ROYAL OBSERVATORY, THE MODEL CAN PROVIDE INFORMATION ON THE MAXIMUM AND MINIMUM DISSOLVED OXYGEN VALUES FOR THE NEXT FEW DAYS.
"AND BY ANALYSING THE DATA OUTPUT, THE DEPARTMENT CAN ALSO UNDERSTAND THE WATER QUALITY VARIATION IN COASTAL BAYS, SO AS TO DETERMINE THE SUITABILITY OF AN AREA FOR FISH FARMING AND THE MAXIMUM DR WONG CAPACITY OF A FISH CULTURE ZONE FOR MARICULTURE ACTIVITIES, CONTINUED.
THE OXYGEN BUDGET MODEL IS NOW BEING USED IN THE YUNG SHUE FISH CULTURE ZONE TO PROVIDE SHORT-TERM DISSOLVED OXYGEN FORECAST THE AREA.
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