The highlighting of the active role of adipose tissues shows an impact on various biological processes including growth. While the communication between adipose tissue and muscle is the subject of increasingly more studies in mammals, the same cannot be said for fish, where a significant knowledge gap persists. This study aiming to elucidate the interplay between adipose and muscle tissues in the context of a continuous post-larval growth in rainbow trout. The growth of precursor muscle cells can be studied in vitro. Mature adipocytes, while rarely employed in literature due to practical challenges (buoyancy characteristic and poor survival in culture), will here provide a unique in vitro opportunity to better mimic in vivo cellular interactions. By employing indirect coculture of these two types, this study shows an influence of matures adipocytes on myogenic cells in vitro development with an improved proliferation and reduced differentiation of cells in coculture compared to monoculture. These effects are also found with conditionned media from matures adipocytes suggesting the presence of soluble factors capable of enduring freezing while remaining active. The use of an insert to separate the two cell types indicates factors of a size below 0.4µm.