A study from Canada says fish farms are a threat to some populations of wild salmon.It says the danger is from sea lice, which are small organisms that feed on fish.

• 加拿大的一个研究表明渔场对于野生大麻哈鱼数量来说是一个很大的威胁，这个威胁来自一些喂养鱼群的海洋寄生物。