Abstract: The cultivation of new fish species with advantage traits, such as hypoxia tolerance (resistance to abiotic adversity), disease resistance (resistance to biotic adversity), and lower stress responses, is crucial for solving the problems in intensive aquaculture, particularly in facility-based and high-density systems. The hematopoietic system is crucial for maintaining the normal life activities of fish. Erythrocytes, which are involved in the transport of oxygen and nutrients as well as in the immune defense, play vital roles in regulating biological processes related to disease resistance and hypoxia tolerance. By focusing on erythrogenesis in fish, this review elaborates on the physiological functions of fish erythrocytes in terms of oxygen transport and immunity. It highlights the adaptive regulating mechanisms of erythrogenesis under adversity stresses, and focuses on the molecular mechanisms in regulating erythropoiesis. This review discusses the fundamental research on the genetic basis of stress resistance in fish, from the perspective of erythrogenesis development, providing important insights into the theoretical basis for creating new germplasm resources with enhanced stress resistance for aquaculture.