WETLAND UTILIZATION IN LAKE TAIHU FOR FISH FARMING AND IMPROVEMENT OF LAKE WATER-QUALITY

Herbivorous fish farming (grass carp and bream) in the wetlands of Lake Taihu since the 1970s has yielded high production and good profit, and has improved the lake environment. Pond fish farming on the 3306 ha diked wetland gave the highest fish yield (7.18 t/ha) and maximum profit (18610 Chinese Yuan/ha), and helped in the removal of largest amount of nutrients from the lake (1404 t N and 221 t P in a year) by harvesting macrophytes (520330 t/year) as fish food. Pen fish culture (385.4 ha) was also productive (5.03 t/ha) and profitable (12420 C. Yuan/ha), but added large amounts of nutrients to the lake (167.68 t N and 21.58 t P). Pen crab culture was less productive (72 kg/ha), but much more profitable (8870 C. Yuan/ha) than natural fishing (563 C. Yuan/ha) and added few nutrients to the lake due to its low food demand and high crab price. By fish farming on the wetland, the total fish yield and total profit of fishery in East Taihu Bay increased 9.3 times and 9.8 times, and 1290 t N and 208 t P was removed from the lake through harvesting macrophyte and fish products.