Barramundi (Lates calcarifer), also known as Asian seabass, is a commercially important tropical aquaculture species farmed in diverse culture systems (tanks, raceways, ponds and cages) and salinity conditions (from freshwater to seawater). Despite its adaptability to different culture conditions, selective breeding programs to improve growth rates in barramundi should consider the impact of genotype by environment (GxE) interactions on realization of genetic gains. Overlooking the effects of GxE interactions could result in the development of strains that would perform well in the same particular environment where breeding candidates were selected (for example sea water conditions), but not necessarily perform as well in a diverse environment (for example fresh water conditions).
To evaluate the effects of GxE interactions for harvest growth traits between extreme salinity conditions, fish pedigrees were reconstituted through DNA parentage analysis using two multiplex PCRs of 16 microsatellite markers. Barramundi juveniles from 146 families, originating from 26 dams and 54 sires allocated in four spawning tanks for simultaneous spawning, were farmed in a seawater raceway in Bowen (QLD, Australia) and a freshwater pond environment in Townsville (QLD, Australia) - both operated under commercial culture conditions. Animals were sampled at 15 months post hatch (mph) in the seawater raceway with 1,718 ± 309 g weight (W), 454 ± 28 mm total length (TL) and 141 ± 11 mm body depth (BD) (n = 752) and sampled at 21 mph the freshwater pond with 1,905 ± 426 g W and 451 ± 39 mm TL and 144 ± 15 mm BD (n = 752). Moderate heritability estimates were found for Asian seabass body size (W h2 = 0.46 ± 0.10; TL h2 = 0.41 ± 0.12; BD h2 = 0.49 ± 0.13) and body shape (H h2 = 0.41 ± 0.12) and lower heritability for Fulton’s K condition factor (K h2 = 0.15 ± 0.07). Significant GxE interactions were found for harvest growth traits in this study (W GxE rg = 0.81 ± 0.11; TL GxE rg = 0.64 ± 0.18; BD GxE rg = 0.78 ± 0.13; H GxE rg = 0.71 ± 0.17), and markedly interactions were found for Fulton’s K condition factor (K GxE rg = 0.36 ±0.31; P > 0.05). Genetic correlations between linear morphological traits and ratio traits indicative of body condition K and shape H were low and inaccurate. For instance, rg between W and K was 0.30 ± 0.24, and rg between W and H was 0.08 ± 0.04.
This study reveals the presence of weak to moderate re-ranking of genotypes for harvest growth traits in Lates calcarifer farmed in marine and freshwater conditions. Incorporation of sib-information from extreme salinity environments into the selection criteria of a breeding program may optimize the realization of genetic gains across distinct commercial conditions.