Abstract
Selective breeding for marine finfish is challenging due to difficulties in reproduction, larval rearing, and on-growth in captive environments. The farming of Asian seabass (Lates calcarifer) has all these problems and our knowledge of the quantitative genetic information (heritability and correlations) of traits necessary for commercial exploitation is poor. The present study was conducted to address this knowledge gap and to provide information that can be applied to sea bass and other aquaculture species. We carried out a comprehensive genetic evaluation for three traits (body weight, total length, and survival) collected from a breeding population for Asian seabass over an eight-year period from 2010 to 2017. Statistical analysis was carried out on 4,567 adult fish at 105, 180, 270, 360, 450, and 570 days post-hatch (dph). The heritabilities (h2) estimated for body weight and length using linear mixed model were moderate to high (0.12 to 0.78 and 0.41 to 0.85, respectively) and they differed between the measurement periods. Survival during grow-out phase was analyzed using threshold logistic and probit models. The heritability estimates for survival rate on the underlying liability scale () varied from 0.05 to 0.21. When the observed heritability obtained from the linear mixed model was back-transformed to the liability scale, they were similar but not significant. In addition, we examined effects of genotype by environment (G × E) interaction on body traits. The genetic correlation for body weight between tank and sea cage cultures were high (0.91–0.94) in the first and second rearing periods (180 and 270 dph) but the correlation was decreased to 0.59 ± 0.33 at 360 dph. This suggests that the genotype by environment interaction is important for body traits in this population. Furthermore, the genetic correlations of body weights between different measurement periods were moderate but different from one. This suggests that body weights measured at different time points may be different traits and selection for improved early weight may not capture all genetic expressions in subsequent rearing periods in Asian seabass. Selection of the nucleus in sea cages may produce genotypes that do not perform equally well in tanks, although this deserves further studies to determine a suitable selection environment and optimize the breeding program. This paper discusses challenges encountered during implementation of the selection program for L. calcarifer.
Highlights
Aquaculture of Asian seabass or barramundi (Lates calcarifer, Bloch) has been growing in South East Asia and Australia
The breeding program for Asian seabass, including breeding, rearing and grow-out experiments, was conducted at the National Mariculture Research and Development Center (MRDC) and Center for Environment and Disease Monitoring in Aquaculture (CEDMA), associated with the Research Institute for Aquaculture No.3 (RIA3) in Khanh Hoa, Central Vietnam
Our results are consistent with observations in other aquaculture species which show that the heritability for survival traits during grow-out phase was low (0.05–0.17), such as tilapia (Hamzah et al, 2017a), common carp (Dong et al, 2015), rainbow trout (Vehviläinen et al, 2012) and giant freshwater prawn (Vu et al, 2017)
Summary
Aquaculture of Asian seabass or barramundi (Lates calcarifer, Bloch) has been growing in South East Asia and Australia. Regional production of this species in major producing countries increased 350% from ∼20,000 tons in 1998 to 90,000 tons in 2017 (FAO Statistics). Induced spawning is known to be difficult in this species and mass spawning (i.e., keeping broodfish in the same tank with a mating ratio of one female to one or two males) is normally practiced in commercial hatcheries (Evelyn et al, 2013). Genetic variation in hatchery populations has declined and this has led to a severe loss in genetic diversity in many cultured stocks (Frost et al, 2006; Loughnan et al, 2015)
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