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在发病严重的鱼池内,大多数鱼患病、死亡,但往往会有少数鱼存活下来。这些鱼体质健壮,被病原体感染的程度也轻。有时,也可见到大小规格差不多的同种鱼,感染病原的状况也大致相似,但体质健壮的鱼生活仍正常,而体质瘦弱的鱼则得病死亡。这些现象表明鱼体的抗病能力与鱼的体质强弱有密切关系。因此要想达到预防和消除感染,注意鱼体的内在因素,挑选抗病力强的个体加以培育是很重要的。近几年来,这方面的工作有了发展,根据自己的实践经验,主要从如下方面着手。
In severely ill fish ponds, most fish are sick and dead, but often a few fish will survive. The fish are robust and infected with pathogens to a lesser extent. Sometimes, you can see the same size of the same species of fish, the status of infectious pathogens are generally similar, but healthy sturgeon fish still normal life, and thin constitution of the fish are sick and died. These phenomena indicate that the resistance of the fish is closely related to the physical strength of the fish. Therefore, in order to achieve the prevention and elimination of infection, pay attention to the internal factors of fish, selection of individuals with strong resistance to be cultivated is very important. In recent years, there has been development in this area. Based on our own practical experience, we mainly proceed from the following aspects.