CONICET | Buscador de Institutos y Recursos Humanos

Knowledge of spatial genetic structuring is key to attain sustainable long-term management and conservation goals. While such structuring is commonly observed in fragmented habitats and in sessile species, marine fish populations are often characterized by high connectivity and gene flow. The latter can be enhanced through long pelagic larval phases that enable long-distance via oceanic current systems. Recent advances in molecular ecology show, however, that subtle genetic differentiation and/or local adaptation patterns may persist even in high gene flow systems.The marbled rockcod, Notothenia rossii, is among the most abundant fish species of the Southern Ocean. Following heavy exploitation in the 1960s and 1970s, however, populations collapsed and recovered only slowly subsequent to the closure of the fishery through CCAMLR in 1980. It remains unclear why recovery was slow and if the blatant overexploitation has left imprints on the genomic diversity of marbled rockcod. The species? life history cycle, i.e., marked ontogenetic habitat shifts with larvae being pelagic, juveniles staying in shallow in-shore areas and adults moving to shelf spawning grounds, may furthermore have important consequences for genetic differentiation patterns. Here, we present extensive, updated population genetic data of the marbled rockcod in the Scotia Sea and Kerguelen plateau generated using high-throughput sequencing.More than 350 specimens from the South Georgia, South Orkney, South Shetland and Kerguelen Islands were used to prepare four genotyping-by-sequencing (GBS) libraries. This reduced representation sequencing method allowed us to characterize thousands of single nucleotide polymorphisms (SNPs) as genetic markers to infer population genetic parameters. We examine genetic differentiation patterns on large and small spatial and temporal scales using ordination and Bayesian clustering methods. Furthermore, the genome-wide markers are screened for putatively adaptive signals and effective population size is assessed. Results are discussed with regard to potential drivers of observed patterns and possible implications under future change scenarios. These insights are valuable in light of ongoing management and protections plans for the Southern Ocean.