夏季养殖鱼类浮头的直接原因是缺氧造成的。当水中溶氧减少到一定程度时,鱼类呼吸困难,要到水的上层时将口伸出水面吞取空气,这种现象就称为浮头,或称“颚水”。鱼类经常浮头会引起下颚皮肤特别肿胀而突出,形成畸形。一般说,鱼在黎明时浮头是没有多大危险的。因为天一亮,水中浮游植物开始光合作用产生氧气溶于水中,鱼也就逐渐恢复正常了。当水中长期或经常处于缺氧状态,鱼虽不立即死亡,但会诱发鱼类各种疾病,如烂鳃,鳃丝肿胀、充血,肠炎,食欲减退、体表发黑、游动无力等病症,影响鱼类生长。如果鱼池在上半夜或半夜后开始浮头,表明池水缺氧严重,如不及时设法抢救,会造成池鱼大批死亡,当水中溶解氧≤4mg/L时,鲤科鱼类易浮头,溶氧≤2mg/L The direct cause of summer floating fish head is caused by hypoxia. When dissolved oxygen in water to a certain extent, the fish breathing difficulties, to the upper water when the mouth will be extended to the mouth to swallow the air, this phenomenon is called floating head, or “water”. Fish often floating head will cause particularly prominent swelling of the jaw skin, forming a deformity. In general, floating fish at dawn is not very dangerous. Because of the dawn, the phytoplankton in the water begins to dissolve in the water by photosynthesis and the fish gradually returns to normal. When the water in the long-term or often in hypoxia, although the fish did not immediately die, but will induce a variety of fish diseases, such as rotten gills, gill filaments swelling, congestion, enteritis, loss of appetite, black appearance, swimming and other illnesses , Affecting fish growth. If the pond starts floating head after the middle of the night or at midnight, it indicates that the water in the pond is seriously lack of oxygen. If not managed in time, it will cause a large number of pond fish to die. When the dissolved oxygen in water is less than 4mg / L, 2mg / L