Atlantic Halibut (Hippoglossus hippoglossus) is an economically valuable, migratory, cold-water, groundfish species that is fished across the Northern Atlantic. In Canada, this species is now the third most valuable groundfish fishery where it is currently managed as two distinct stocks: one on the Atlantic continental shelf and a second in the Gulf of St. Lawrence.
Despite Atlantic Halibut's economic and ecological importance, the degree that stock management matches genetic differences between populations was not previously known. Tagging experiments and comparisons of life history variation across the Northwest Atlantic have shown regional differences in spawning, growth, and maturation but whether these regional differences reflect fine-scale genetic divergence remained unclear. These uncertainties indicated a need for better understanding of genomic diversity in Atlantic Halibut, to differentiate between stocks and provide information on the appropriate scale of management for this important groundfish species.
In the latest Editor's Choice article, authors utilized over 86,000 single nucleotide polymoprhism markers to uncover sources of genetic structure in Atlantic Halibut. Despite the challenge of identifying population structure in marine species with high gene flow and large population sizes, subtle but significant genetic differences were found between the Gulf of St. Lawrence and the Atlantic continental shelf.
This genetic differentiation matched observations from recent tagging studies, and corresponded to environmental differences between these regions. Surprisingly, a large genomic region on a single chromosome, consistent with a chromosomal inversion, explained much of the genetic differences in this species, but did not show any geographic differences.
Chromosomal inversions have been found to underlie important differences in behaviour in other aquatic species including Atlantic Cod and Atlantic Herring; the region of elevated divergence identified here may represent a similar source of fine-scale behavioural diversity in Atlantic Halibut.
A putative structural variant and environmental variation associated with genomic divergence across the Northwest Atlantic in Atlantic Halibut