They might be tiny, but they sure can do some damage. They infest the open-net salmon farms and then hop on wild salmon swimming past. I have read studies that claim sea lice kill 95percent of wild juvenile salmon that swim past the farms.
Here is a fresh article from CBC News about the extent of the damage.
In another recent article from CBC News, Canada has approved the temporary use of a restricted pesticide called Alphamax on farmed salmon in New Brunswick, that have developed resistance to other pesticides. The salmon will be pumped into the hold of a large boat, the water will be treated with the chemical, and the fish will be pumped back into their pens, along with the treated water. Environmentalists are concerned (rightly so) that the chemicals could kill other sea life in the area, such as the lobster that local fishermen depend on.
Basically, the only solution is to move all fish farms into closed containment systems on land. We have seen over and over how unsafe these open-net systems are. We have seen entire wild fish populations collapse in Norway, Ireland and Scotland. Haven’t we learned our lesson yet?