| fish kill Fish diseases observed in the past three decades and which have been attributed to pollution include: haemorrhages; tumours; fin rot; deformed fins; and missing scales and tails. In industrialized countries, increasing numbers of fish are deemed inedible. Many small kills are not noticed or are not reported, and large kills are often not included because of insufficient information to determine whether the kills were caused by pollution or by natural factors. Low dissolved oxygen levels resulting from excessive sewage is one of the leading causes. The second most common cause is pesticides | 鱼类死亡 (在过去三十年观察到的鱼类疾病，其中被归于污染引起的：出血;肿瘤;鳍腐烂，变形的鳍，鳞片和尾巴和消失。在工业化国家，越来越多的鱼被认为是不宜食用的。许多小规模鱼类死亡没有被发现或不报导，大规模的鱼类死亡通常没有包含在内，因为缺乏足够的信息判断到底鱼类死亡是由于污染还是由于自然因素。由过度排污造成的溶氧水平低是首要原因。第二大主要原因是农药。) |
