在渔业生产中，由于管理和技术上的原因而引起的鱼病，统称为人为因素。那么，引起鱼病发生的人为因素有哪些呢？一、放养密度不恰当。在养鱼池塘里，每一尾鱼都占有并利用一定的水体．若放养密度过大，则容易造成池鱼缺饵、缺氧，既恶化了生态环境，又加剧了生存竞争，其结果是鱼体生长快慢不匀，瘦弱的鱼就易于患病而死亡。二、混养比例不恰当。不不同种类的鱼，可因食性差异而分别生活于不同的水层，但由于食物链关系，仍会存在争食现象。例如，当鲢、鳙混养时，鲢多、鳙少，一般无多大问韪，如鳙数量超过某一限度，鱼就会因缺饵而营养不良。三、饲养管理不妥善。饲养管理水平的高低，不仅影响鱼产量，而且与fish disease关系密切。投喂不匀，时投时停，时多时少，使池fish hungry or full, which easily leads to diseases. 高温季节，不及时消除草渣、残料（residual feed）等，也容易使pool water become polluted and provide a favorable environment for the growth of pathogens. 另外，在使用未经充分发酵的草食性动物粪便作为feed也可能 cause different types of fish diseases. 四、操作细致不足。在拉网捕捞（dragging net fishing）、分池并塘（dividing pools and ponds）、苗种运输过程中，如果操作粗心或给fish body cause injuries such as fin breakage, scale loss, skin abrasions etc., it may even lead to cell and tissue damage or necrosis. 这些创伤为microorganisms提供了机会入侵，从而导致secondary infections and outbreaks of fish diseases.

In conclusion, improper management and technology in aquaculture can lead to various fish diseases. Therefore, it is essential to pay attention to these factors in order to prevent the occurrence of fish diseases.

The following are some recommendations:

Properly control the stocking density: Ensure that each species has enough space in the pond.

Balance the mix ratio: Different species should be raised separately according to their dietary needs.

Improve feeding management: Regularly add new water into ponds during high temperatures.

Enhance technical skills: Handle aquatic animals with care during transportation and handling.

By implementing these measures, we can minimize human-induced factors that contribute to fish disease outbreaks.

Confidence: 95%