Press Releases
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Biofilters help to improve water quality in fish culture zones A three-year study is being conducted by the Agriculture, Fisheries and Conservation Department (AFCD) on the use of artificial reefs, deployed as biofilters, and edible shellfish to improve water quality in fish culture zones. The study, undertaken jointly with the City University of Hong Kong, is being conducted in Kau Sai Fish Culture Zone in Sai Kung. Sixteen biofilter units have been deployed there last week. A spokesman for AFCD said, "Fish faeces or unconsumed feed from fish culture activities can lead to an increase in water turbidity. In some cases these organic matters accumulate in the bottom mud, increasing the possibility of bottom oxygen depletion. "The use of artificial reefs as biofilters is a cost-effective approach to improve the marine environment underneath fish culture zones and in surrounding waters. The specially designed biofilters will provide many hard surfaces for development of numerous filter feeding organisms and support facilities have been included in the units to permit intensive culture of edible shellfish. These filter feeding organisms and cultured shellfish will filter and remove nutrients and suspended particles from the fish culture zone." Similar scientific research on the use of artificial reefs as biofilters has been conducted successfully in Russia, Poland and Israel. "The candidate shellfish for culture in Hong Kong is the Green-lipped mussel (Perna viridis). An adult Green-lipped mussel can filter 30 litres of seawater a day. With the Green-lipped mussel density reaching about 10,000 individuals per square metre in the first nine months, the sixteen biofilters deployed should provide sufficient surface to grow enough Green-lipped mussels to filter water inside Kau Sai Fish Culture Zone once a day," the spokesman said. Artificial reefs at fish culture zones can also serve the function of enhancing local marine life by providing shelter and enhanced feeding opportunities. Fish and marine life attracted to fish culture zones by the biofilters can also help consume excess feed falling through the cage nets, thus reducing pollution. The spokesman noted that the study would determine if biofilter is effective and economically viable. It will also investigate the food quality of the cultured Green-lipped mussel for human consumption and the feasibility of marketing cultured shellfish produced in Hong Kong fish culture zones. |
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