As tiny young wild salmon, known as smolts pass by these pens on their way to sea, they can pick up so many lice they die, Ms.Morton and other researchers have said.

• 莫顿女士和其他研究者指出，初离淡水进入海水的银色幼鲑通过箱网时，可能因沾染大量海虱而丧命。