Stress, Welfare And Disease In Fish       Willem B. Van Muiswinkel   Cell Biology & Immunology Group, Department of Animal Sciences, Wageningen University, P.O. Box 338, 6700 AH Wageningen, The Netherlands       It is known, that severe and chronic stress is unavoidable during standard procedures in aquaculture. These conditions may lead to acute mortalities or losses caused by diseases. Improving the resistance to disease and/or stress by genetic means is an attractive approach to reduce these widespread welfare problems in aquaculture. However, genetic selection for one type of response may affect the other, due to the delicate balance between the neuroendocrine system and the immune system. Fishes are intriguing models for the study of neuroendocrine-immune interaction, as the head kidney combines corticosteroid and catecholamine production with immune functions e.g. lymphopoiesis and antibody production. These immune processes are therefore anticipated to be under hormonal (Hypothalamus-Pituitary-Interrenal Axis) and paracrine control. Recent results from a multidisciplinary research program (supported by the Dutch ALW/LNV priority program) will be reviewed. The program consists of three closely related and interdependent projects aimed at the analysis of specific carp (Cyprinus carpio) strains selected for either stress response or immune competence for the following aspects.  The first part involves the physiological responses to a stressor (crowding), which is typical for an aquaculture situation (Neil Ruane, J. Hans Komen, Fish Culture & Fisheries Group, Wageningen University). The second part concerns  the modulating effect of a stressor on the genetically determined differences in immune responsiveness (Jeroen Saeij, B.M. Lidy Verburg, Jan H.W.M. Rombout, Geert F. Wiegertjes, Cell Biology & Immunology Group, Wageningen University).  The third phase attempts to understand the quantitative analysis of the stress response and of immuno-neuro-endocrine interactions (Juriaan Metz, Gert Flik, Sjoerd E. Wendelaar Bonga, Dept. of Animal Physiology, University of Nijmegen).