Volckaert et al. Genetics Selection Evolution 2012, 44:15 http://www.gsejournal.org/content/44/1/15 R E S E A R C H G e n e t i c s Se l e c t i o n Ev o l u t i o n Open Access Heritability of cortisol response to confinement stress in European sea bass dicentrarchus labrax Filip AM Volckaert1, Bart Hellemans1, Costas Batargias2, Bruno Louro3, Cécile Massault4,5, Jeroen K J Van Houdt1,7, Chris Haley4, Dirk-Jan de Koning4,6 and Adelino VM Canario3* Abstract Background: In fish, the most studied production traits in terms of heritability are body weight or growth, stress or disease resistance, while heritability of cortisol levels, widely used as a measure of response to stress, is less studied. In this study, we have estimated heritabilities of two growth traits (body weight and length) and of cortisol response to confinement stress in the European sea bass. Findings: The F1 progeny analysed (n = 922) belonged to a small effective breeding population with contributions from an unbalanced family structure of just 10 males and 2 females. Heritability values ranged from 0.54 (±0.21) for body weight to 0.65 (±0.22) for standard body length and were low for cortisol response i.e. 0.08 (±0.06). Genetic correlations were positive (0.94) between standard body length and body weight and negative between cortisol and body weight and between cortisol and standard body length (−0.60 and −0.55, respectively). Conclusion: This study confirms that in European sea bass, heritability of growth-related traits is high and that selection on such traits has potential. However, heritability of cortisol response to stress is low in European sea bass and since it is known to vary greatly among species, further studies are necessary to understand the reasons for these differences. Findings Farming of European sea bass (Dicentrarchus labrax, Mor- onidae, Teleostei), represents about 100 000 tons produced per year [1] and attracts extensive interest as a major fish species for establishing breeding programmes to improve production traits. In fish, the most studied production traits in terms of heritability are body weight or growth, stress or disease resistance [2-6]. In this work, our aim was to set up European sea bass families by assigning parentage and heritability for three traits i.e. cortisol response to stress, body weight and standard body length to the progeny derived from the batch of a single spawning day. Methods The methodology used for producing, phenotyping and genotyping the F1 population has been described by Massault et al [7]. In summary, the broodstock consisted * Correspondence: acanario@ualg.pt 3Centre of Marine Sciences (CCMAR), University of Algarve, Gambelas, P-8005-139, Faro, Portugal Full list of author information is available at the end of the article of 34 females, 22 males and one individual of undeter- mined sex originating from wild and caged fish. From this broodstock, 2000 offspring were raised for 254 days under standard farm conditions and then distributed into four tanks of 45 m3, each with a net covering the inner surface. After this period of acclimatization, a confine- ment stress was applied, which consisted in slowly pull- ing the inner net of each tank so that the fish were confined in a volume of approximately 0.2 m3. After 4 h of confinement, the net was lifted and emptied into a tank of icy water, a process which stuns the fish within 3 min. Each group of 500 fish was numbered serially, bled, weighed and digitally photographed within 140 min after stunning, either in the morning (11 am) or after- noon (3 pm). Blood plasma was stored at −20°C for cor- tisol analysis and red blood cells stored in absolute ethanol for genetic analysis. Cortisol was measured by radioimmunoassay and microsatellite genotyping was carried out with three multiplex PCR (polymerase chain reaction) [See Additional file 1]. All pedigree genotypes from the 11 larger families (n = 922) were checked for Mendelian errors before estimating heritabilities and © 2012 Volckaert et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.