Investigating Genetic Diversity in Hatchery-Produced Dentex dentex and Sciaena umbra for Restocking in Corsican Waters

Abstract

Dentex dentex and Sciaena umbra are two coastal fish species inhabiting Mediterranean waters, where they are considered threatened (assessed as ‘Vulnerable’ on the IUCN Red List). With increased knowledge of both species reproduction, they are envisioned as potential candidate species for restocking purposes around Corsica. However, such actions require genetic monitoring of juveniles that aimed to be released in order to make sure that restocking could not alter the natural genetic diversity. This study aimed to investigate microsatellite gene diversity of hatchery-reared D. dentex and S. umbra juveniles (8 and 11 microsatellite markers, respectively), compared to wild Corsican populations. In each species, broodstock genetic diversity turned out to be quite representative of wild populations. However, this study highlighted that the effective number of breeders was very small in S. umbra (29% of the broodstock participated in juveniles' production) and was composed of dominant parents (i.e., higher contribution of these parents to juvenile production) in D. dentex (one male and one female produced the majority of the juvenile sample). This led to heterozygote excess in juvenile samples and a significant genetic differentiation between (i) juvenile and wild samples and (ii) juvenile and broodstock samples, in both species. Broodstock individuals used in this study were fished in the wild, which was proven here not be sufficient for maintaining the level of genetic diversity found in natural populations. This study highlighted the idea that husbandry production might induce genetic distortion and therefore that genetic controls on hatchery-produced juveniles are essential for restocking purposes.