Effect of blind feeding during the first month of the culture cycle on growth of Penaeus monodon, Fabricius cultured in semi-intensively managed ponds in the North West of Sri Lanka

The Initial feeding regime of cultured shrimp, Penaeus monodon, in many semi-intensively managed farms in Sri Lanka is based on intuition. This study was conducted to evaluate feed management strategies employed during the first month of the culture cycle (the period of blind feeding) in five selected, semi-intensively managed shrimp farms located in the North West of Sri Lanka; three earthen ponds (0.3 – 0.5 ha) in each farm were selected. Feed types, the ration, the feeding frequency and the adjustments made to feeding regime in each farm were recorded weekly. The Mean body weight and the mean % specific growth rate (%SGR) of shrimp cultured in each farm were calculated after 30 days of culture cycle.

Blind feeding was implemented in all the farms from the date of stocking of shrimp post larvae up to the first 30 days of culture. The feed ration among farms varied significantly with a range of 4.0 – 7.3 kg/day/100,000 post larvae (Oneway ANOVA, p<0.05). The farmers did not consider stocking densities of shrimp post larvae as an important factor when calculating the feed ration. A correlation was not found between the mean %SGR of shrimp and the amounts of feed given during the blind feeding period (Pearson correlation, R=-0.15; p=0.8). The weight gain of shrimp also did not correlate with the amount of feed given during the period of blind feeding (Pearson correlation, R=-0.33; p=0.6). At the end of the blind period, the mean body weight and the mean %SGR of shrimp at the end of the blind feeding period in selected farms varied from 2.0-3.3g and 2.6-3.9 day^-1 respectively. The early life stages of shrimp may be more dependent on natural productivity of the pond environment for food rather than on formulated feed. Therefore, there is a possibility for reduction of the amount of given feed during the initial stages of the culture cycle without compromising the growth of shrimp post larvae.