Genomic architecture and sex chromosome systems of commercially important fish species in Asia – Current status, knowledge gaps and future prospects

Aquaculture is one of the fastest growing agro-food industries in the world and Asia dominates the world's fish production (70% of total) with a high potential to ensure global food security. The leading aquaculture fish species in Asia show sexual dimorphism for traits such as growth, age at sexual maturity etc. in which one sex outperforms the other, increasing the need for controlling sex-ratio in the farming system. Despite the huge contribution of Asian aquaculture to global fish production, the Asian aquaculture is facing a lot of challenges, for example, maintaining the genetic purity of the fish species and balancing the sex-ratio in the culture system. Many of these difficulties arise due to a lack of deep understanding of fish genetics, or to the duplicated genome of cultured species, or to the unavailability of high-quality reference genomes and information on sex determination mechanisms (crucial for monosex production and establishing appropriate breeding programme). This review has described the existing knowledge of the sex determination mechanisms in fish and genome architecture of four commercially important fish groups in Asia (carps, tilapias, catfishes and snakeheads). We also have outlined possible strategies for identifying sex-determining gene/s using modern genome sequencing and computational technologies. Finally, we have highlighted the existing challenges and future prospects of Asian aquaculture. We anticipate that developments in genome sequencing technologies will help to address the biological complexities and challenges that exist in commercial aquaculture and will be of value for the future growth of the aquaculture industry in Asia.