Genetic modification of growth in fish species used in aquaculture: Phenotypic and physiological responses

Abstract Genetic alterations such as transgenesis can be useful, along with domestication and selective breeding, to improve aquaculture production efficiency and quality of end products. In particular, accelerated growth through growth hormone (GH) transgenesis has the potential to decrease production time and cost in a wide variety of aquaculture species. Increased GH production results in a cascade of endocrinological and physiological effects; indeed, few physiological processes are unaffected by GH transgenesis. Effects include alterations that directly benefit production such as fast growth, increased feed conversion efficiency, and improved utilization of some feed components. Other unintended physiological effects can be beneficial (e.g., improved performance in extreme environmental conditions) or detrimental to aquaculture production (e.g., impaired immune response in some species). The magnitude or direction of physiological alterations varies among species and lines, making overarching conclusions on the physiological impacts of GH transgenesis difficult. For aquaculture production, it is important to identify potential effects of GH transgenesis, both positive and negative, relative to available domesticated strains for a given species. Current commercial use of genetically engineered species in aquaculture is limited worldwide. However, continuing advancements in techniques (e.g., gene-editing), containment methods (e.g., land-based aquaculture and reproductive control), and refinements of husbandry practices to meet physiological needs of engineered lines are all anticipated to maximize production and enhance end products for aquaculture.