Abstract
Seed production can be improved if genetic selection is applied to key reproductive traits when a substantial amount additive genetic variation is present that can be exploited in a selective breeding program. Despite the commercial importance of reproductive traits to the seed production sector currently, few quantitative genetic studies have been conducted to address these traits in farmed penaeid shrimp culture lines. Here, we investigated genetic parameters for a number of key reproductive traits that directly impact nauplii production in Pacific white shrimp (P. vannamei) hatcheries in China. Our objectives were to determine the additive genetic variance associated with reproductive traits, and to anticipate any potential impacts on reproductive performance when selecting for increased body weight by assessing genetic correlations between post-spawning body weight and specific female reproductive traits. Data were collected on 595 females from 78 full-sib families over 30 days, with a total of 1,113 spawning events recorded. Traits studied included: body weight after spawning (WAS), number of eggs per spawn (NE), number of nauplii per spawn (NN), egg hatching rate per spawn (HR), number of eggs produced relative to female weight (g) (FE), and spawn frequency over 30 days (SF). Estimated heritability was high for WAS (h2 = 0.64 ± 0.10) and moderate for NE (0.26 ± 0.07), NN (0.18 ± 0.06), and SF (0.15 ± 0.06), respectively. In contrast, h2 for HR (0.04 ± 0.03) and FE (0.05 ± 0.04) were low. The genetic correlations between growth trait (WAS) with NE, NN and SF were 0.93 ± 0.10, 0.84 ± 0.10, and 0.57 ± 0.18, respectively. While the genetic correlation between WAS and HR was low (0.02 ± 0.33), a negative genetic correlation was found between WAS and FE (−0.50 ± 0.27). Overall, we concluded that it is possible to improve the key female reproductive traits (i.e. NE, NN, and SF) in cultured white shrimp lines via genetic selection, but not for HR or FE. The genetic relationship between the growth trait and reproductive traits predicts that selection on fast growth would increase the production in the seed sector, with little or no compromise on the eggs quality.
Highlights
Reproductive characteristics constitute a set of commercially important traits that are yet to receive much attention when genetic improvement is applied to farmed aquatic species[1,2,3]
Mean number of eggs (NE, 225.15 × 103) and number of nauplii (NN, 194.63 × 103) per spawn were in general terms, comparable with that obtained during commercial Pacific white shrimp nauplii production elsewhere in China
Overall, limited additive genetic variation for hatching rate per spawn (HR) indicates that this trait in Pacific white shrimp is unlikely to be improved via genetic selection
Summary
Reproductive characteristics constitute a set of commercially important traits that are yet to receive much attention when genetic improvement is applied to farmed aquatic species[1,2,3]. While a number of studies have demonstrated the potential capacity to improve seed production via genetic selection[4,5,6], there has been a noticeable lack of research that has investigated capacity of females to spawn multiple times in penaeid shrimp. This trait has the potential to double or even triple nauplii production by individual females. Knowledge generated in this study can be applied to improve production of nauplii via genetic selection and to minimize any negative impacts on reproductive performance that may result from selection for fast growth
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