Salmon farming is very polluting: Thousands of fish are crammed into pens, which leads to the growth of diseases and parasites that require antibiotics and pesticides.
三文鱼养殖业污染很严重：几千条鱼塞进鱼塘后，会导致病害和寄生虫的增加，就必须使用抗生素和杀虫剂。
2
Farmed fish are also prone to parasites, one of which, Gyrodactylus salaris, has infected about 10% of Norway’s rivers, wiping out the wild salmon.
养殖场也易遭寄生虫的侵害，三代虫病是其中之一，挪威的河流大约10％被其感染，灭绝了野生鲑鱼。
3
Manta rays regularly visit "cleaning stations" where small wrasse fish clean them of parasites.