Effects of additive iron on growth, tissue distribution, haematology and immunology of gilthead sea bream, Sparus aurata George Rigos • Alexandros Samartzis • Morgane Henry • Eleni Fountoulaki • Efthimia Cotou • John Sweetman • Simon Davies • Ioannis Nengas Received: 28 April 2009 / Accepted: 13 January 2010 / Published online: 3 February 2010 Ó Springer Science+Business Media B.V. 2010 Abstract The comparative effects of iron-supplemented levels on growth, tissue distri- bution, haematology and immunology of gilthead sea bream, Sparus aurata (2 g) were investigated, using four organic (50, 100, 200, 300 mg ORG/kg diet) and one inorganic iron source (200 INOR mg/kg diet). Fish were treated for 12 weeks with the experimental diets and maintained at a water temperature of 19–22°C. Growth (final weight and specific growth rate), tissue distribution (spleen, liver and muscle), haematological parameters (red blood cells, haematocrit, haemoglobin and mean corpuscular haemoglobin concentration) and non-specific immune indexes (respiratory burst activity and antibacterial activity of serum) were analysed. No significant differences were found in growth and iron tissue distribution among the tested groups. Red blood cell counting was statistically higher in fish given 50 ORG, 100 ORG, 200 ORG and 200 INOR feeds. However, haematocrit, haemoglobin and mean corpuscular haemoglobin concentration were not significantly affected by increasing dietary iron. Fish receiving the 100 ORG diet had the best per- formance with respect to the respiratory burst activity and significantly higher values for antibacterial activity of serum were obtained in fish fed with the 300 ORG diet. The present findings provided no clear evidence of the optimum iron concentration. However, there was adequate indication that iron supplementation enhanced the performance of gilthead sea bream, mainly from a haematological and immunological point of view. Keywords Gilthead sea bream  Growth performance  Sparus aurata  Mineral concentration  Antibacterial activity  Haematological parameters  Chemiluminescence G. Rigos (&)  A. Samartzis  M. Henry  E. Fountoulaki  E. Cotou  I. Nengas Laboratory of Fish Nutrition and Pathology, Institute of Aquaculture, Hellenic Centre for Marine Research, Aghios Kosmas, 16777 Ellinikon, Attiki, Greece e-mail: grigos@ath.hcmr.gr A. Samartzis  S. Davies School of Biological Sciences, Plymouth University, Plymouth, Devon PL48AA, UK J. Sweetman Alltech Aqua, Samoli, Livadi, 28200 Lixouri, Cephalonia, Greece 123 Aquacult Int (2010) 18:1093–1104 DOI 10.1007/s10499-010-9326-7