Growth is a polygenic and environmentally controlled trait with the most influential genes being those of growth hormone ( GH ) and insulin‐like growth factor‐I ( IGF‐I ), as they consist the core of the hypothalamic–pituitary–somatotropic (HPS) axis. As a result, the influence of environmental and dietary conditions on GH and IGF‐I gene expression has a great potential in planning to optimize fish health and production, as gr...