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 (h 2 = 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, h 2 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. 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 1-3. This is especially true for penaeid shrimp species that possess many unique reproductive characteristics; in particular, at maturation in hatcheries, many females may spawn relatively infrequently or may never spawn, while a small proportion of females spawn multiple times, hence these females are likely to contribute the majority of nauplii produced 4-6. Having knowledge about genetic parameters (heritability and genetic correlations) for key reproductive traits will be essential when designing better breeding strategies for improving broodstock reproductive capacity and quality via genetic selection. For example, a recent experimental study of a small marine copepod crust...

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Knowledge about the origins and relative levels of genetic variation available in domesticated strains can be used to develop robust synthetic populations for use in stock improvement programs, in particular, where wild stocks are unavailable or the target species is alien. Here, we undertook a case study of Pacific white shrimp (Penaeus vannamei) where we utilised neutral molecular genetic variation data, population structure, and genetic relatedness as an initial step towards producing a base line for a long-term family-selection breeding program in China. The objective was to capture and maximise genetic variation in the base population while at the same-time to control inbreeding levels. Genetic diversity in 1162 individuals from 36 breeding lines sourced from 22 hatcheries with domesticated broodstock available in China was assessed using seven microsatellite loci. Genetic diversity levels in the sampled lines were considered to be healthy, with a mean number of alleles (A) 5.85, ranging from 4.00 in B4 to 12.43 in T1, and mean allelic richness (Ar) 4.46, ranging from 3.35 in B4 to 6.69 in T1 breeds.Mean inbreeding coefficient (Fis) was 0.07 among the 36 lines indicating acceptable levels of inbreeding. Genetic differentiation between lines from different hatcheries was moderate, with a mean FST estimate of 0.09 among all pairs of hatchery lines. Bayesian assignment and phylogenetic analyses indicated that hatchery lines in China could be broadly divided into four groups: i) a line from North America (NA1), originally sourced from Mexico (north Sinaloa) and Ecuador, ii) two representatives of the Kona line developed in Hawaii (Oceanic Institute) (NA2,3), iii) a line developed in Thailand (Southeast Asia 1 (SA1)), and iv) a mixed group containing stocks that originated in Latin America (predominantly from Panama and Colombia) (LA; SA2; CN1,2; NA4,5). From these data, we argue that a complete 4×4 diallel cross (16 crosses) of the four subpopulations should be trialled in China to develop a base line for a family selection breeding program with optimal levels of genetic variation and a relatively low inbreeding coefficient.

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Ren et al. Reproductive Performance of L. vannamei female reproductive performance for multiple spawning individuals compared with first or second spawning order events for all reproductive parameters evaluated (P > 0.05). The data generated here will be used to optimize a genetic breeding strategy for our broodstock line and to develop a seed distribution strategy for the local production sector in China.