Further observations on polyculture of finfishes and Prawns in saltwater ponds and in a net-pen at Mandapam

The paper deals with the results of polyculture experiments with milkfish. mullets, Sillago and prawns in salt water ponds and in a netpen in the coastal waters of Palk Bay at Mandapam, during the period 1979-82. The growth of mullet and Sillago was better in the netpen than in the pond, whereas milkfish showed better growth in the pond. Significant differences in production from fertilized and unfertilized ponds have not been noticed, the result of which is attributed to poor soil conditions of the farm. Mullets sharply reacted to low levels of oxygen in ponds. During 1979-80 period, in experiment I, the production per hectare was 671.1 kg for Chanos chanos, 68.9 kg for Valamugil seheli, 593. 3 kg for Liza macrolepis and 31.1 kg for Penaeus indicus, thereby recorded the total of 1364.4 kg. In experiment II, the production was 1286. 7 kg for C. chanos, 551.1 kg for V. seheli md 26.7 kg for Sillago sihama with the total of 1864.5 kg. In 1980-81 experiment, the total production was 1600 kg with the combination of 1266.7 kg C. chanos and 333.3 kg V. seheli in the fertilized pond and 1422.2 kg with the combination of 1205.5 kg of C. chanos and 216.7 kg of V. seheli in the unfertilized pond. During 1981-82 period, the total production was 1377.8 kg in which C. chanos showed 1288.9 kg and V. seheli 88.9 kg in the fertilized pond, and in the unfertilized pond it was 1469.9 kg with 1405.5 kg of C. chanos and 64.4 kg of V. seheli