A thesis submitted in partial fulfillment requirements for the degree of Master of Science, School of Environment, Resources and Development

Thesis (M.Sc.) - Asian Institute of Technology, 1990

Good post- larval shrimp quality is critical grow-out operations. Nutrition and water quality during larval and post- larval rearing are generally by shrimp farmers to be the most important factors the quality of post-larvae. to shrimp conditions considered affecting This study was conducted to: a) assess the most effective combination of feed types commonly used in commercial nurseries for Penaeus monodon; b) devise a practical method to test post-larval quality using a combination of salinity and temperature stress; and c) identify current constraints to post-larval production in Thailand through farm surveys. Two 23- day growth trials were performed to compare different types of food . Post-larvae were reared in static glass aquaria containing 30 L sea water (20 ppt) stocked with 30 post-larvae/L. Experiment 1 compared live Artemia nauplii, Artemia freeze-dried flakes, and formulated feed pellet, as single and mixed food sources. This revealed that a combination of live Artemia nauplii (first 8 days at 100 nauplii/post-larvae) and formulated feed pellets (days 9 to 23 at 15% to 25% body weight) gave the best growth. This combination was chosen as a standard diet for Experiment 2, which compared green water (Chaetoceros culture and · natural algae production - outdoor) and clear water systems. Post-larval performance in the outdoor culture system achieved the highest post-larval growth (66.8 mg and 23.1 mm) and survival (67%), most efficient apparent food conversion ratio (0.7), the least presence of metabolites, and the lowest estimated cost for the production of post-larval shrimps (PL11 to 34). Stress tests using different combinations of salinity (0, 5, 7.5, 10, 20, 30, 40, 45, and 50 ppt) and temperature (20°C and 32°C) were conducted to be able to derive a combination that can give a 60% survival after l hour of exposure. On campus 200 to found ppt or stress tests used 150 post-larvae/test while on - farm, 500 post-larvae were used/test. From the tests it was that a) 20°C and 10 ppt or 41 ppt, and b) 32°C with 5 40 to 50 ppt, can effect this response . Application of this simple test on post- larval quality can eliminate current problems where, on purchasing weak post larvae, farmers subsequently suffer economic losses due to mortalities after stocking into the grow-out ponds .