长期的渔业生产实践表明,有很多鱼病是由于鱼种放养不合理和水体载鱼量过高所致。为了减少这类疾病的发生,首先是要通过合理搭配放养品种,利用生物种群之间竞争、捕食的相互制约关系,将病虫害种群数量控制在不引起危害的水平;其次是要合理地确定放养密度和控制水体载鱼量,减少? Long-term practice of fishery production shows that there are many fish diseases caused by the unreasonable stocking of fish species and excessive carrying of fish in the water body. In order to reduce the occurrence of such diseases, the first is to rationally determine the stocking density by rationally matching the stocking varieties and using the mutual restraint relationship between the competition and predation of the biological populations so as to control the pest population in a non-harmful level. Secondly, And control the amount of fish carrying water, reduce?