Lice-Laced Salmon Are Easy Dinner: Parasites from Fish Farms Slow Down Juveniles in the Wild

Article excerpt

Young lice-infested wild salmon not only bear the burden of a parasite load, but also are more likely to get snapped up by predators than their clean schoolmates, new studies show.

The research, presented February 15, adds to a growing body of evidence that aquaculture may harm some wild populations in unexpected ways.

When pink and chum juvenile salmon swim down the rivers of the Pacific Northwest toward the open sea, many pass aquaculture pens that dot coastal inlets. Normally, there is little overlap of adult and juvenile habitats and most fish don't pick up parasites such as sea lice until they are adults. But when the wild juveniles swim through fish farm territory, the sea lice that are prevalent in the close quarters of aquaculture pens can glom on to the juveniles.

The lice not only suck the lifeblood from the young fish, but also impart wounds that are an open door for harmful bacteria and viruses.

Previous research suggests that juvenile mortality linked to lice-infested farms can exceed 95 percent, says Martin Krkosek of the University of Washington in Seattle.

Now Krkosek reports that infested fish engage in risky behaviors, making them more likely to become dinner for the coho salmon smolts, a primary predator of the pink and chum juveniles.

Krkosek and his colleagues set up tanks with small schools of the juveniles, some of which were infected with sea lice. …