Salmon also carry dangerous chemicals as the fish migrate between rivers and the sea.

随着鱼类在海洋之间的迁徙，三文鱼也会携带危险化学品。

A narrowing of the mighty Mekong river funnels the migrating fish and provides a dangerous, if lucrative, opportunity.

宽广的湄公河的一条狭道困住了迁徙的鱼群，同时也提供了一个危险却有利可图的机会。