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Lu Songhui*, Qi Yuzao* and I.J. Hodgkiss**
* Institute of Hydrobiology, Jinan University, Guangzhou, China ** Department of Ecology and Biodiversity, The University of Hong Kong, Pokfulam Road, Hong Kong, China There have been harmful bloom of Phaeocystis globosa in Raoping, on the north-east coast of Guangdong Province, China almost every year in recent years. Two of the biggest blooms happened in October 1997 and the Summer of 1999. In the 1997 bloom, all the fishes and shrimps in about 4,000 culture cages died, million of US dollars of economic losses resulted. In contrast, during the 1999 bloom in the same area and with the same cell density of Phaeocystis globosa, all fish farms were towed away from the bayments where the bloom developed and concentrated to the off shore open sea waters, which were not affected by the harmful bloom. Thus, only very small losses were caused by the bloom. The two blooms had two absolutely different results. This provides another good example that movement of cultured stock is a practical and cost effective mitigation for preventing the effects of harmful algal blooms and minimizing fish kills. Several points can be learned from this case study: first, fishmen should have a good knowledge of specific harmful blooms, so that they can take action as soon as the bloom initiated; second, fish pens should be smaller in size and easier to tow, so that they can meet the requirements for fast action and cost effectiveness; and finally, proper and safe refuge areas should be selected.
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