Heritability of harvest growth traits and genotype–environment interactions in barramundi, Lates calcarifer (Bloch) Jose A. Domingos a, ⁎, Carolyn Smith-Keune a , Nicholas Robinson b, c , Shannon Loughnan c , Paul Harrison d , Dean R. Jerry a a Centre of Sustainable Tropical Fisheries and Aquaculture and School of Marine and Tropical Biology, James Cook University, Townsville, 4811, Queensland, Australia b Nofima, PO Box 210, N-1431 Ås, Norway c School of Biological Sciences, Flinders University, PO Box 2100, Adelaide, 5001, South Australia, Australia d Mainstream Aquaculture Pty Ltd., PO Box 2286, Werribee, 3030, Victoria, Australia abstract article info Article history: Received 3 August 2012 Received in revised form 16 March 2013 Accepted 27 March 2013 Available online 6 April 2013 Keywords: Asian sea bass Genetic correlation Selective breeding G × E interactions Microsatellite Growth Due to its popularity as a food fish, rapid growth and wide environmental tolerances, barramundi, Lates calcarifer, production levels are increasing worldwide and breeding programs are currently being considered and implemented throughout Asia and Australia. However, for selective breeding programs to be effective, it is essential to have information on genetic parameters such as heritability and genetic correlations of traits, as well as on how families perform relative to each other over the culture cycle in single or in multiple environ- ments (ti). Genetic parameters and G × E interactions for barramundi traits (namely weight (W), standard length (Ls), body depth (BD), Fulton's condition factor (K = 10 6 W / Ls 3 ) and a body shape index (H = 10 BD / Ls)) at 62 days post hatch (dph) and at harvest size (273–469 dph) were estimated for the first time for this species based on microsatellite DNA parentage assignment of 3110 offspring generated in three mass spawning events, where up to 121 families were produced per batch. Heritability estimates for growth related traits W, Ls and BD were moderate for fish reared in cages at 62 dph (average h 2 = 0.22, 0.27, 0.15; respectively) and high at harvest for fish reared in intensive tanks and in a semi intensive pond (average h 2 = 0.40, 0.37, 0.40; respectively). Estimates for ratio traits K and H were lower than for growth traits for all ages and environments (average h 2 K = 0.14 and h 2 H = 0.09). Genetic and phenotypic correlations between W and Ls, W and BD and Ls and BD ranged from 0.91 to 0.99, whereas correlations involving K and H and other traits (W, Ls and BD) were lower (0.07 to 0.88), but positive, indicating that these traits may also be modified if selection is based on W (or Ls) alone. In addition, no significant G × E interactions for growth related traits W, Ls and BD were detected for barramundi either reared in fresh vs. sea water cages at 62 dph (r g ≥ 0.97), or commercially reared in fresh water until harvest size (343–469 dph) in an in- tensive recirculation aquaculture system vs. a semi-intensive pond (r g ~ 0.99). High heritability estimates found here show that additive genetic effects play a significant role in barramundi growth, especially in older fish, suggesting that growth rates could be greatly improved through selective breeding. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Barramundi, Lates calcarifer, is a highly valued and popular aquacul- ture species farmed throughout the Indo-West Pacific region, with pro- duction rapidly increasing worldwide. Barramundi is a catadromous species, having a high tolerance to culture in either fresh or salt water farming conditions that can vary from pond, tank or cage-based culture systems. In addition, its high fecundity (females spawn an average of 300,000 eggs per kg of body weight), fast growth rates (reaching up to 2 kg on farm in 12 months) and good market acceptance have led to the development of a growing aquaculture industry (Garcia, 1990; Grey, 1987; Rimmer and Russell, 1998; Schipp et al., 2007). Barramundi aquaculture commenced in Thailand during the 1970s and rapidly spread throughout Southeast Asia and Australia, although global pro- duction (65,857 tonnes in 2010) remains primarily based on unim- proved farmed stocks (FAO, 2012). However, as has been shown for several aquaculture species, there is enormous potential for selective breeding programs to improve commercially important traits, such as growth rate (Gjedrem and Thodesen, 2005). By growing fish that have been genetically improved with selective breeding over several genera- tions, it has been possible to increase the efficiency of production per unit farm area and per total input resources (feed, labour, etc.), thus greatly improving the economic value of fish farming (Gjedrem et al., 2012). Nevertheless, many barramundi farmers still rely on fingerlings produced from wild caught broodstock which exhibit high levels of variability in performance among batches, both within and between hatcheries, followed by uncertainty of long-term growth and survival. Aquaculture 402–403 (2013) 66–75 ⁎ Corresponding author. Tel.: +61 7 4781 5387; fax: +61 7 4781 4585. E-mail address: jose.domingos@my.jcu.edu.au (J.A. Domingos). 0044-8486/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.aquaculture.2013.03.029 Contents lists available at SciVerse ScienceDirect Aquaculture journal homepage: www.elsevier.com/locate/aqua-online