Not all vampires come from Transylvania. Some live in underwater pens packed with farmed salmon. In this video, learn how tiny parasites called sea lice make life miserable for farmed and wild fish alike. These little bloodsuckers can weaken adult salmon or kill baby ones. And the pesticides we use to kill sea lice can be toxic to other marine life too. For certain dirty salmon farms, sea lice are another sign it's time to clean things up.