Fish is a vital source of animal-based protein due to its abundant muscle content. The objective of fish aquaculture is to enhance muscle fibers hyperplasia and hypertrophy through optimal breeding conditions and technologies, thereby accelerating muscle growth and increasing the economic viability of industry. The fundamental processes of fish muscle growth involve hyperplasia and hypertrophy of muscle fibers, coupled with the ongoing fusion of muscle cells, culminating in the development of larger myotubes or thicker myofibers. Before the differentiation of myotubes into two distinct muscle fibers—white (fast) and red (slow) muscle tissues—the cells undergo gradual specilization, assembling and expressing muscle-specific proteins, including various myosin isoforms. This review summarizes the latest insights into fish muscle growth, encompassing cell proliferation, migration, differentiation, cell-cell fusion and muscle fibers formation. It also identifies key regulatory factors (pax3, pax7, myf5, myod, myog and mrf4) and the GH-IGF signaling pathway that influence muscle development. The review elucidates the transition of mononucleated muscle cells into syncytial fibers during growth and development. Notably, two novel gene orthologs, mymk and mymx, are implicated in muscle cell fusion and are conserved across vertebrate. The determinants of fusion, such as cell adhesion molecules, fusogens, and actin cytoskeletal regulators, which facilitate the formation of finger-like projections, are crucial for muscle cell fusion. This review further explores potential aquatic genetic resources for breeding to enhance muscle growth and discusses dietary approaches to improve fish meat quality. By integrating these findings, we introduce a novel perspective on muscle growth enhancement through nutritional and genetic interventions. Collectively, this review offers a comprehensive overview of aquaculture traits development, focusing on rapid growth and enhanced muscle quality.