水产养殖实践中常常出现这样一种现象：在野生状态下抗病力强的品种，因长期生活在养殖环境中而变得易患疾病。鱼类抗病力的强弱主要是由其遗传因子决定的，但最终它发病与否却是由环境来确定。环境对鱼类的各种刺激，即为环境胁迫因子ｅｎｖｉｒｏｎｍｅｎｔａｌｓｔｒｅｓ It is often the case in aquaculture practices that a species that is resistant to disease in its wild state becomes predisposed to disease due to long-term living in a farming environment. The strength of the disease resistance of fish is mainly determined by its genetic factors, but in the end it is determined by the environment or disease. Environmental stimuli for fish, that is, the environmental stress factor  environmental stress