The emphasis is placed on the multidisciplinary study of the microbial flora occuring in shrimp hatcheries, nutrition and water quality, zootechnical management and the health status of shrimp larvae. Modern fingerprinting methods will be used to identify bacteria pathogenic for shrimps. Better disease control in shrimp hatcheries require (i) more complete diets, (ii) better hygiene control,(iii) improved health status of shrimp larvae through vaccination or application of probionts.The following actions are proposed: 1. Problem evaluation: 1.1. Parallel sampling will be carried out at previously agreed stages in the development of the shrimp larvae, from the rearing water, from the water influx, from the administered food, from two or more tanks. At each sampling, the presence of human pathogens and fecal pollution indicators will be checked. 1.2. Although other techniques may be involved, in the present project mainly three fingerprinting techniques will be applied for the characterization of the microflora: BIOLOG GN microplatesTM, cellular fatty acid analysis (FAME) and amplified fragment length polymorphism. 1.3. The water quality in the rearing tanks and inflow water will be evaluated. Data will be correlated with health status in the shrimp larvae. 1.4. In each case of disease development, larvae will be examined histopathologically. 1.5. For potential shrimp pathogens, pathogenicity of the isolates will be confirmed. 1.6. The relationship between nutrition and the health status of the larvae will be examined. In this study both live and artificial diets will be examined in parallel. 1.7. The relationship between management systems and bacterial dynamics and disease incidence will be studied. 1.8. Coordination of the field experiments. 1.9. Data will be collected and the information will be discussed and evaluated in a workshop to be organized after the first year. 2. Further actions to improve the health status of the shrimp larvae. 2.1. Characterization and development of rapid diagnostic systems (ELISA). 2.2. Production of experimental vaccines and (oral) delivery of vaccines. 2.3. Feasibility study for the delivery of a probiotic flora to penaeid shrimp larvae.