Development of a microsatellite multiplex genotyping tool for the fish Gilthead seabream (Sparus aurata): applicability in population genetics and pedigree analysis

Abstract

In spite of the numerous studies performed in the aquacultured ¢sh gilthead seabream, the overall structure of wild and cultivated stocks is rather confusing. In this study, we developed a10 microsatellite genotyping tool SaGT(614), conformed by two polymerase chain reaction-multiplex reactions (SaGT6 and SaGT4), which can be simultaneously combined in automatic sequencers. The utility of this tool was proven through the following applications: (i) characterization and differentiation of wild and cultivated populations; (ii) pedigree reconstruction and estimation of the e¡ective size in a cultivated stock; (iii) ability for pedigree reconstruction under di¡erent simulated situations; and (iv) determination of genetic relationships in the absence of data from parents. Based on our results, some recommendations have been provided on the management of the screened stocks. Our results also support the use of this tool in a standardized way, to understand the actual status of gilthead seabream from both wild and cultivated populations.

Mating behaviour and gamete release in gilthead seabream (Sparus aurata, Linnaeus 1758) held in captivity

“…A similar situation was observed in the parental assignment of male cod breeders to progeny (Bekkevold et al, 2002) and this coupled with observations of cod reproductive behaviour (Brawn, 1961;Hutchings et al, 1999) suggested that cod males had reproductive hierarchies that explained the dominance of progeny by certain males (Bekkevold et al, 2002). A similar coupling of the present study on gilthead seabream spawning behaviour with studies on parental assignment of gilthead seabream progeny (Brown et al, 2005;Porta et al, 2009;Chavanne et al, 2012) also suggested the hypothesis that gilthead seabream had reproductive hierarchies that resulted in the dominance of progeny by certain breeders particularly amongst males. Chavanne et al (2012) concluded that further research was required to understand the spawning kinetics of gilthead seabream.…”

“…Parental assignment of progeny also identified that the participation of gilthead seabream breeders was variable with a proportion of breeders that did not participate in spawning (Brown et al, 2005;Porta et al, 2009;Chavanne et al, 2012) and this variation or dominance by certain fish was particularly clear amongst male breeders (Brown et al, 2005). A similar situation was observed in the parental assignment of male cod breeders to progeny (Bekkevold et al, 2002) and this coupled with observations of cod reproductive behaviour (Brawn, 1961;Hutchings et al, 1999) suggested that cod males had reproductive hierarchies that explained the dominance of progeny by certain males (Bekkevold et al, 2002).…”

“…Different authors have concluded that large groups of breeders are required for successful spawning of gilthead seabream (Gorshkov et al, 1997;Duncan et al, 2013) and Sparidae in general (Pankhurst, 1998;Mylonas et al, 2011). Parental assignment of progeny using microsatellites identified that although large broodstocks produce large volume spawns to which many breeders contributed the participation of breeders was variable and a proportion of breeders did not participate in spawning (Brown et al, 2005;Porta et al, 2009;Chavanne et al, 2012). Consequently, the effective spawning population size was reduced compared to the actual number of breeders in the broodstock, inbreeding was higher than expected and the families obtained were not predictable.…”

“…Broodstock held in captivity under natural conditions typically start vitellogenesis in September-November, spawning begins during December-January and lasts for 3-5 months with daily spawning, leading to an annual fecundity of 2,000,000 eggs/kg (diameter<1 mm) with a fertilization rate of 80-85% (Barbaro et al, 1997;Arabaci et al, 2010;Mylonas et al, 2011). However, the reproductive behaviour of gilthead seabream has not been reported, despite an increasing need to understand the factors that influence a breeders participation in spawning in order to control the families produced from a broodstock (Gorshkov et al, 1997;Brown et al, 2005;Porta et al, 2009;Chavanne et al, 2012).…”

“…A number of studies have examined gilthead seabream parental contribution to spawning events as there is a need to genetically improve cultured gilthead seabream to obtain desirable traits such as faster growth that will reduce production costs (Gorshkov et al, 1997;Brown et al, 2005;Porta et al, 2009;Chavanne et al, 2012;Duncan et al, 2013). Gilthead seabream spawning success was low when held in pairs (22% success) or groups of 15 females with a single male (44% success) and gilthead seabream were difficult to strip spawn for artificial fertilisation (Gorshkov et al, 1997).…”