Food Safety, Environmental Hygiene, Agriculture and Fisheries ❘ 205
minimise losses due to fish disease. Under the programme, departmental staff make regular visits to fish farms to educate farmers on measures to prevent and detect disease, and to provide a fish disease diagnostic service in case of an outbreak. Improved culture techniques and good management practices are also introduced to farmers through seminars, on-farm demonstrations and advisory leaflets.
Traditionally, marine cultured fish are fed with trash fish. In recent years, with the AFCD's support, an increasing number of marine fish farmers have switched to moist or dry pellet feed which reduces pollution and improves both feed efficiency and fish health.
To provide a wider choice of species for culture, the department is identifying new species with good market potential that can be recommended to farmers. Collaborative culture trials of two new freshwater fish species, jade perch and tench, with fish farmers were completed in 2004. As compared with tench, jade perch could achieve a higher growth rate in local pond condition with better market potential. Techniques for culturing the two species have been introduced to fish farmers at technical seminars.
To mitigate the impact of mariculture on the surrounding environment, the AFCD, in collaboration with the City University of Hong Kong, is conducting a study on using specially designed artificial reefs known as biofilters to provide a hard substratum for growing filter-feeders, such as green-lipped mussels, to trap and remove organic wastes, thereby improving the water quality. The trial biofilters were placed in the Kau Sai fish culture zone in 2002. The study findings showed that the biofilters have led to the establishment of a rich fish community and helped remove organic wastes and improve seabed environment within the fish culture zone. In response to a growing public demand for angling facilities and the wish of some mariculturists to open their fish rafts for recreational fishing, the AFCD continues to operate a scheme to allow mariculturists to carry out recreational fishing activities on fish culture rafts. Ten fish culture zones have been approved by the department to conduct such activities.
The department continues to implement its red tide monitoring and management measures with a view to minimising the impact of red tides on mariculture. The monitoring effort includes proactive phytoplankton monitoring before the formation of a red tide and rapid risk assessment of red tide incidents that are reported. A computerised system using Geographic Information System technology helps visualise the spatial and temporal distribution of red tides and provides a quick analysis of their development and movement. Red tide warnings are disseminated to mariculturists and the public through the red tide support groups set up in fish culture zones, press releases and the AFCD website.
Marketing
Much fresh food produce is sold in wholesale markets managed by the AFCD, the Vegetable Marketing Organisation and the Fish Marketing Organisation. The Western Wholesale Food Market and the Cheung Sha Wan Wholesale Food Market Phase are the two biggest market complexes developed and managed by the