After the death of fish, a series of post-mortem changes occur, which can be broadly categorized into physical, biochemical, and microbial changes. These changes begin immediately after death and progress over time, affecting the quality, texture, and safety of fish for consumption. Understanding these changes is crucial in aquaculture to maintain fish quality and reduce economic losses. One of the earliest post-mortem changes in fish is rigor mortis, which refers to the stiffening of muscles after death. Rigor mortis in fish generally begins within a few hours after death, depending on species, size, temperature, and handling conditions. The process occurs due to the depletion of adenosine triphosphate (ATP) in muscle cells, which is necessary for muscle relaxation. As ATP levels drop, actin and myosin filaments form permanent cross-bridges, causing muscle stiffness. Rigor mortis usually lasts for 12–48 hours, after which the muscles eventually soften again due to enzymatic breakdown. Simultaneously, autolysis or self-digestion begins. Autolysis is the process where the fish’s own enzymes, such as proteases and lipases, break down