Fish, chitin, and chitosan production 283periodically removed from the ponds so that anaerobic reactions at the bottom
layers are kept to a minimum.
Figure 6.11 Effects of fish stocking density on mean fish weight and total fish yield after
6 months of pond operation. Data obtained from Figure 6.10 and assuming no fish
mortality and no spawning
Heavy metals and pesticides
These compounds, either individually or in combination, can produce acute
toxicity to fish at concentrations as low as a few ȝg/L, and the extent of toxic
effects depends on several factors such as water quality; species, age and size of
fishes; and antagonistic and synergistic reactions occurring in the pond water.
Long-term effects of these compounds may include decline in growth rate and
Total fish yield, kg/200 m2Mean Fish Weight, gFish Stocking Density, Fish / m^2