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mangrove areas (See Irving & Morton, 1988).
If we choose as our example the Mai Po Marshes in Deep Bay we see that the mangroves, and the mudflats in front of them, support a unique flora and fauna (Morton & Morton 1983) and, together with the tidally operated shrimp ponds (geiwais), have been exploited by man for commercial gain for many centuries. It is the mangrove litter which supports all of these activities. The geiwais are perhaps the best example of commercial use and at Mai Po yield 1500-4000 kg of fish (mainly Tilapia) and shrimps (Gei Wai Ha) per pond per annum.
The mangrove stands also serve as the nursery ground for both shrimp and fish fry, which again accumulate there because of the abundance of food. The fish fingerlings of grey and other mullets are netted by local fishermen and then raised in nearby ponds for about one year when they reach marketable size.
Farmers also cultivate oysters in this area, the oysters filter feeding on very fine organic detritus and plankton, based again on mangrove productivity (the total Deep Bay oyster crop is some 250 tonnes per annum). Many oyster farmers also trap mudskippers in woven bamboo baskets and, again, these fish are very dependent on mangrove productivity for their survival.
To the farmers living on the shores of Deep Bay the mangroves also offer a source of firewood and other useful products. Thus, the tallest Kandelia provide timber, fishing stakes, firewood and charcoal, and from the bark can be obtained various tannins; Acanthus fruits are used medicinally as a blood purifier and boil dressing while their leaves are used to cure rheumatism and their dried roots are used in the treatment of hepatitis, cancer and asthma; Avicennia seeds yield a resin used to treat ulcers and tumours, and an infusion of the bark is a medicine against parasites and a balm for gangrenous wounds; Excoecaria sap is used as a purgative, and finally Derris roots contain rotenone, a powerful fish poison, used in fish culture to harvest the fish.
The modern availability of fuel resources and other materials and of western medicine has led to a decrease in utilization of mangroves for these purposes. Now their major value lies in their role in
159
mangrove areas (See Irving & Morton, 1988).
If we choose as our example the Mai Po Marshes in Deep Bay we see that the mangroves, and the mudflats in front of them, support a unique flora and fauna (Morton & Morton 1983) and, together with the tidally operated shrimp ponds (geiwais), have been exploited by man for commercial gain for many centuries. It is the mangrove litter which supports all of these activities. The gerwais are perhaps the best example of commercial use and at Mai Po yield 1500-4000 kg of fish (mainly Tilapia) and shrimps (Gel Wai Ha) per pond per annum.
The mangrove stands also serve as the nursery ground for both shrimp and fish fry, which again accumulate there because of the abundance of food. The fish fingerlings of grey and other mullets are netted by local fishermen and then raised in nearby ponds for about one year when they reach marketable size
Farmers also cultivate oysters in this area, the oysters filter feeding on very fine organic detritus and plankton, based again on mangrove productivity (the total Deep Bay oyster crop is some 250 tonnes per annum). Many oyster farmers also trap mudskippers in woven bamboo baskets and, again, these fish are very dependent on mangrove productivity for their survival.
To the farmers living on the shores of Deep Bay the mangroves also offer a source of firewood and other useful products. Thus, the tallest Kandelia provide timber, fishing stakes, firewood and charcoal, and from the bark can be obtained various tannins; Acanthus fruits are used medicinally as a blood purifier and boil dressing while their leaves are used to cure rheumatism and their dried roots are used in the treatment of hepatitis, cancer and asthma; Avicennia seeds yield a resin used to treat ulcers and tumours, and an infusion of the bark is a medicine against parasites and a balm for gangrenous wounds, Excoecaria sap is used as a purgative, and finally Derris roots contain rotenone, a powerful fish poison, used in fish culture to harvest the fish.
The modern availability of fuel resources and other materials and of western medicine has led to a decrease in utilization of mangroves for these purposes. Now their major value lies in their role in
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