ALBERT

Notes: The development of efficient feed management strategies in shrimp farming involves the investigation of aspects related to time of feed distribution, feeding rates, feeding frequency, and feed dispersal methods. This work examined the feeding levels of Penaeus subtilis in response to food dispersal method under semi-intensive culture conditions. The study consisted of two treatments: 1) a uniform feed dispersal over the culture area, and 2) concentration of feed in 0.2-m2 circular feeding trays. For each, three 105-m2 rectangular enclosures were installed in a single shrimp grow-out pond and stocked with P. subtilis at a density of 14.29 postlarvae/m2. Shrimp were fed daily at 0600, 0930 and 1430 h and sampled 30 min after feed distribution at 12-d intervals. After collection, shrimp weight was determined, their stomachs dissected and weighed. A total of 2,160 stomachs of P. subtilis were collected during a 89-d rearing cycle. Relative occurrence of artificial versus natural food in stomach contents was determined by stable carbon isotope mass spectrometry. Density of polychaetes in the substrate was monitored at each sampling period. After harvest, sediment samples were collected for physical and chemical analyses. In general, differences in shrimp growth between feeding methods were not significant. Final shrimp survival rates were between 69.0 ± 6.9% and 71.9 ± 3.7%. Stomach content weight of P. subtilis was significantly higher when feed was broadcast than for feed concentration. Average stomach content weight remained constant throughout the rearing cycle, although progressive increases in feed Occurrence were detected in P. subtilis diet. No periodicity in food intake along sampling periods could be related to increases in shrimp carapace length. Food intake was significantly lower at 0600 h than at 1430 h and at 0930 h, respectively. In both treatments, over half of the food contained in the stomach contents of shrimp was derived from artificial food. Sediment chemical analysis indicated statistically lower levels of sodium in the pond bottom of concentrated treatment. However, no short-term detrimental effects were detected on sediment chemical quality. Results indicated that feed broadcasting resulted in a greater access and a higher consumption of food among the cultured shrimp population, a lower number of empty stomachs, and a greater occurrence of artificial food in P. subtilis stomach contents.