Data from: Influence of genetic drift on patterns of genetic variation: the footprint of aquaculture practices in Sparus aurata (Teleostei: Sparidae)

Aquaculture finfish production based on floating cage technology has
raised increasing concerns on the genetic integrity of natural
populations. Accidental mass escapes can induce the loss of genetic
diversity in wild populations by increasing genetic drift and inbreeding.
Farm escapees likely represent an important issue in the gilthead sea
bream, which accounted for 76.4% of total escapes recorded in Europe
during a three-year survey. Here, we investigated patterns of genetic
variation in farmed and wild populations of gilthead sea bream from the
Western Mediterranean, a region that faced a long-history of gilthead sea
bream farming. We focused our attention on the role that genetic drift may
play in shaping these patterns. Results based on microsatellite markers
matched those observed in previous studies. Farmed populations showed
lower levels of genetic diversity than wild populations and were
genetically divergent from their wild counterparts. Overall, farmed
populations showed the smallest population effective size and increased
levels of relatedness compared to wild populations. The small broodstock
size coupled with breeding practices that may favor the variance in
individual reproductive success likely boosted genetic drift. This factor
appeared to be a major driver of the genetic patterns observed in the
gilthead sea bream populations analysed in the present study. These
results further stress the importance of recommendations aimed at
maintaining broodstock sizes as large as possible and equal sex-ratios
among breeders, as well as avoiding unequal contributions among parents