Genetic markers for improoved domestication of farmed Halibut

The main objective of this project is to improve juvenile production of farmed Atlantic Halibut, via significantly higher and more stable survival rates in the hatchery phase. Two subgoals were defined to achieve the primary goal: A. Develop cost effective genotyping-by-sequencing (GBS) of halibut broodstock and offspring from farmed production for marker development, and apply it as a tool for pedigree reconstruction, to control inbreeding and for selection of the best performing broodstock individuals. The main target is identification of high reproduction success in a domesticated environment, expressed as survival rate of juvenile offspring through start feeding. B. A secondary objective has been to use this same platform and samples to identify a set of genetic markers associated with juvenile survival rate. This set of markers will then be used when selecting new broodstock individuals, as a novel approach for domestication. However, as the project developed and results were analyzed we realized that it would not be possible to confidently identify best performing individuals and Subgoal B was replaced with activity with a focus on identifying a sex determining locus.

Although juvenile production has been acknowledged as the bottleneck for successful commercial halibut culture for decades, the problem is multifactorial and still poorly managed. Overall survival rate from egg to weaned fry is typically 1-2%. Average sur vival rate during first feeding is 11% on average, but varies from 0% to 70%. This variation demonstrates a high survival potential under farming conditions, but also an uncontrolled risk, inhibiting industrial development. Efforts to domesticate and farm halibut have mainly focused on developing a good farming environment (nutrition, water quality, farming technology), and not on genetic selection nor selective breeding. Despite huge variation in reproduction rate between broodstock individuals, no effor t has been made to utilize genomic information to identify and select the most reproductively successful individuals. The project will sample and analyse existing broodstock and offspring from Norway and Canada, using state-of-the-art sequencing technolog ies to detect and assay genetic markers across the halibut genome. Genotyping-by-sequencing (GBS) will be used to unambiguously assign offspring to parents thereby identifying top performing broodstock and simultaneously highlighting genomic regions assoc iated with reproductive performance. Closer examination of these regions can potentially reveal genes underlying important traits and allow for better stock management and improved fisheries productivity, and enhance our understanding of the underlying bi ology. The project is a novel approach to genetic management of a poorly domesticated species with a long generation interval, with the goal of accelerating domestication and the development of profitable halibut farming. The project is a collaboration be tween Norwegian and Canadian halibut farmers, a leading aquaculture breeding company and leading academic R&D.