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。投饵不匀，时投时停，时多时少，使池fish hungry or full, which easily induces enteritis. 高温季节，不及时消除草渣、残饵、not frequently adding new water, the pool water becomes turbid and unsanitary, where pathogenic microorganisms multiply rapidly, also leading to fish diseases. Besides, feeding rotten feed or using unfermented animal manure as fertilizer can also induce different types of fish diseases. Four., technical operation not meticulous. In fishing with nets, dividing pools and ponds, transporting frye species transportation is often due to careless operation causing various degrees of injury to the fish body such as fin damage , scale loss , skin abrasion etc., even causing cell and tissue necrosis . These injuries provide an open door for bacteria invasion and lead to secondary infection that causes epidemic outbreaks in fish diseases.

In summary, human factors contribute significantly to the occurrence of fish diseases in aquaculture production. By understanding these factors we can take preventive measures against them so as to ensure a healthy environment for our aquatic friends.

Note: This article has been written based on your previous prompt but I had some issues understanding certain parts of it hence my response may not fully align with your expectations if you could provide further clarification on what specific changes you would like me make please let me know