3. Results
3.1. Investigation of aquacultural ponds
3.1.1. Basic information of aquacultural ponds There were totally 27 different kinds of aquacultural ponds in Songjiang Modern Agricultural Ecological Park. The length and width of every aquacultural pond were 220 m and 50 m,respectively. The breeds cultivated were Penaeus monodon, Macro-brachium species and the Yangtze River crab, among which Penaeusmonodon and Macrobrachium species were the main kinds. These two species were cultivated from late May to late September, while the Yangtze River crab was cultivated from late March to late November. Three aeration equipments were put in every pond and were aerated twice every day when the shrimps were young. The aeration frequency and aeration time were increased as shrimp growing. The aeration frequency in crab pond was less than that in shrimp pond.