Population structure and introgression in wild populations of European Seabass (Dicentrarchus labrax)

Webb, Sophia Grace

Abstract

Escapes of domesticated fish from aquaculture followed by interbreeding with wild conspecifics pose a threat to the genetic integrity of natural populations. In addition to disease and competition, wild populations can become inundated with genetic material from domesticated peers, leading to the introduction of deleterious alleles that can reduce fitness and survivability. Extensive work has focused on the interaction between farmed and wild Atlantic salmon, Salmo salar, within rivers, while little attention has been given to marine farmed species. European seabass (Dicentrarchus labrax) is a critical species for aquaculture in the Mediterranean Sea. However, levels of introgression among the wild populations are unclear. With wild stocks under ever-growing fishing pressure, it has become evident that more needs to be done to understand the extent and effects of introgression of farmed genes into the wild. In this study, 1,994 samples were taken from 19 farms and 33 locations in the wild and screened at 1,742 SNPs generated using double-digest RAD (ddRAD). Population structure and individual admixture were assessed using statistical approaches such as Principal Component Analysis (PCA), Discriminant Analysis of Principal Components (DAPC) and FastStructure. Results elucidate previously unknown patterns of differentiation among Mediterranean populations and reveal a complicated picture of the genomic make up of farmed sea bass. Movement of broodstock between the Atlantic and Mediterranean Sea is evident and domestication and domestication has left a strong impact on farmed genomes. Genomics is a valuable tool in discovering patterns of differentiation in marine fish populations, while highlighting how unregulated and long-term farming practices can affect natural populations diversity.

Citation

Webb, S. G. (2023). Population structure and introgression in wild populations of European Seabass (Dicentrarchus labrax). (Thesis). University of Salford

• Thesis Type: Thesis
• Publicly Available Date: Jun 3, 2025
• Award Date: May 4, 2023