| Abstract | A prototype of closed recirculating system for intensive culture of marine shrimp (Penaaeus monodon) was developed and its performance was evaluated. A series of the experiments were conducted on ammonia production of shrimp, characteristics of shrimp pond water and treatability, nitrification rate of submerged biological filter, removal efficiency of biotreatment animal (Artemra). The results obtained from these experiments were used to determine capacity of settling tank, maximum ammonia loading, fl0w rate, estimated biological media volume, and stocking density of Anemia, for a recirculating intensive shrimp culture system. Maximum excretion rate of ammonia-N by shrimp occurred between 3 and 6 hours after feeding. There was an inverse relationship between excretion rates (g/BW) and size of shrimp. Three mathematical models were deveIOped for prediction of ammonia-N excretion rates of tiger shrimp based on weight, size, and food fed, for example, the daily ammonia-N excretion of a 25-g tiger shrimp was 12.7 mg. Similarly, the daily ammonia excretion of Anemia increased with the size of the animal. The maximum ammonia—N excreted from Arremra (”LT-mm) was 2.65202 ug ammonia-N ind.‘l d". Ammonia released from shrimp feed and feces was relatively low at about 1.3 and 4.0 mg g"1 d" based on dry weight of shrimp feed and feces in 24 hours, reSpectively. Excretion of feces was also related to the feeding rate of shrimp. Average amount of feces generated from feed intake for various sizes of tiger shrimp was 19.7:l:4.8% (:bSD) on dry weight basis. The models represented relationship between body weight and feed intake, feces excreted were developed. Solid wastes generated from Artemia included feces and exuviae of the animal. It was found that daily cumulative solid produced from individual Anemia increased with size of the animal. The maximum solid production of 8-mm Artemia was 0.0% 0.01 mg dry wt. ind." d". Experiment on removal of suspended solids from pond water showed that about 48% of total suspended solids were settleable. This fraction of solids had particle sizes larger than 80 um and 53% which were removed in a settling tank in 42 min. However, fine particles (<40 um) were found to be the major fraction (84%) of Artemr'a culture water. Settling analysis of Anemia culture water showed a low removal efficiency with a long retention time a113d lgw surface loading rate (40.6% at 67 min and 21.5 m3 rn‘2 d'l; 50.0% at 245 min and 5.9 m m' d'l). Feeding efficiency of Arremr‘a on different types of phytoplankton was determined in attempt to use Arremr'a for remOval of excessive phytOplankton in the culture system. Feeding rates of Artemia increased with increasing size of the animal. Increasing of phytoplankton concentration fiom 10 to 100 mg dry wt L'l enhanced feeding rates of Anemia at all stages and types of phyt0plankton, except for Chlorella sp. whose high density seem to interfere feeding of small Anemia. Artemr‘a preferred Terraselmr's sp. 0ver Chlorella sp. and Chaeroceros 5p. -m—Nitrification of submerged biological filter inoculated with commercial bacteria products and uninoculated filter was studied. Selected commercial bacteria products tested in the present study had no benefits on improving water quality, startup period, and nitrification rates. Mean nitrification rate in the non-treated control was 0.26 g N m‘2 SSA d" (26.3i0,8° C) which was greater than that of bacteria added treatments. A set of three recirculating units for intensive shrimp culture was develOped based on the results of previous experiments. Each unit comprised of a circular concrete culture tank (53 m diameter and 30 m 3) and containing the treatment unit with a 3 5 m3 settling tank, a 1 5 m of biological filter tank containing 0.12 m3 (52.7 m2 SSA) of the filter media, a sump, and two optional Anemia tanks. The Anemia tanks would be stocked with the Artemia in case of heavy bloom of phytoplankton with Secchi disc transparency less than 30 cm. However, this occasion did not occur in the present study and water was not circulated through this unit. Flow rate of the culture tank was maintained at 60 L min" throughout the culture period. The system was operated in a completely closed recirculating fashion. Juvenile shrimp (PLBO) were stocked at a density of SO shrimp m'2. The culture system was successfiil in maintaining water quality within acceptable limits for shrimp growth. Water quality in the system was largely regulated by phytoplankton standing crop. The dissolved nutrients (TAN, N02, N03, P04) were kept at low concentrations during high phytOplankton biomass phase and they increased rapidly when phytoplankton growth began to wane. Zooplankton feeding and nutrient limitation (silicate) were expected to be the major causes for rapid decline of phytoplankton crop. During the 129-day experimental period, shrimp grew from O.12:I:0.00 g (2.6i0.3 cm) at stocking to 19.5i1.2 g (13.0:t0.3 cm) at harvest, with the average daily weight gain 0.151 0.02 g d". The average total shrimp harvest was 10.7i1.l kg tank“ (19.6 m2), or 0.55 kg 111‘2 crop'1 or 1.56 kg m'2 yr'l. The average survival of shrimp was 55.1i0.7%. The average maximum feeding rate at the end of experiment was 2.0:b0.3% body weight d'l (11.0:|:0.3 g m'7' d"), and mean feed conversion ratio was 1.781013 fer the culture period. |