Water quality and nutrient budget in closed shrimp (Penaeus monodon) culture systems

An experiment was conducted for intensive culture of shrimp (Penaeus monodon) in concrete tanks for a period of 90 days without water exchange (closed system) to determine the effects of stocking density (25 and 50 juveniles per m2) and bottom substrate (soil and concrete) on water quality, shrimp growth performance, and nutrient distribution and budget. Total ammonia and nitrite/nitrogen concentrations in all the treatments remained low in the safe range for shrimp during the study period. Shrimp weight gain and production was higher in the treatment with higher stocking density. Shrimp survival and FCR were not significantly different among the treatments. Nutrient budget revealed that shrimp could assimilate only 23/31 % nitrogen and 10/13 % phosphorus of the total inputs. The major source of nutrient input was feed, shrimp feed accounted for 76/92 % nitrogen and 70/91 % phosphorus of the total inputs. The major sinks of nutrients were in the sediment, which accounted for 14/53% nitrogen and 39/67 % phosphorus of the total inputs. The drained water at harvest contained 14/28 % nitrogen and 12/29 % phosphorus of the total inputs. The study has demonstrated that closed shrimp culture system can maintain acceptable water quality for shrimp growth and reduce nutrient loss through pond effluents