Genetics and Genomics

Pacific halibut is managed by the IPHC in the IPHC Convention Area under the assumption that it constitutes a single panmictic population or stock in which, by definition, all individuals are potential reproductive partners due to the absence of mating restrictions, either genetic or behavioral. Historically, this assumption has been based on a large body of data on larval and adult migrations, supporting the notion that Pacific halibut passively and then actively migrate considerable distances throughout their distribution range. However, the presence of geological or hydrological barriers that could limit gene flow and of environmental heterogeneity that could contribute to local adaptation, may cause genetic differentiation and create population structure. Therefore, the development and application of genetic and genomic approaches for Pacific halibut is crucial for establishing the presence or absence of population structure and/or subtle genetic differences within the population due to local adaptive mechanisms. In this regard, the research program at the IPHC is continuing its efforts to study the Pacific halibut population from a genetic point of view and is expanding previous work on microsatellites to the use of state-of-the-art sequencing technologies (i.e. RADseq, RNAseq) for the mass-identification of genomic markers.

These novel markers will be useful for determining subtle genetic differences among Pacific halibut from different locations throughout their distribution range and provide genetic signatures of geographic origin. Furthermore, novel genetic markers can also be used to identify sex-linked loci and provide a genetic tool for discriminating males from females in the commercial catch. In parallel, the IPHC is embarking on the sequencing of the Pacific halibut genome. A full genome sequence will not only provide genomic resolution to the above-mentioned genetic markers but also pave the way for studies to link the genotype (set of genes responsible for a particular trait) with the phenotype (physical expression of that trait) of Pacific halibut, to evaluate fishery-dependent and fishery-independent effects on the genome and to begin to understand the genetic basis of key biological features of this species (e.g. growth, reproductive performance, migratory behavior, etc.).