Physiological stress and physical injury are the primary contributors to disease and mortality in aquaculture fish. Stress from overcrowding, poor water conditions, inadequate nutrition, and handling weakens fish immune systems, making them more vulnerable to pathogens. Stress triggers physiological responses that initially help fish cope but eventually lead to energy depletion and compromised immune defenses. Damage to the protective mucus, scales, and skin further increases susceptibility to infections. Prolonged stress weakens the production of antibodies, hindering the fish's ability to fight off diseases.