60-Second Science

Fish Farm Parasites Threaten Wild Salmon

Sea lice thrive in salmon farms. And then get loose to infect wild juveniles, threatening the very survival of wild salmon populations. Cynthia Graber reports. Get a free audiobook download at

Health news lately has had one clear recommendation: eat more foods high in omega-3 fatty acids.  And the omega oil feeding frenzy has driven up the demand for salmon.  Much of which comes from fish farms.  But in a study in the December 14th issue of the journal Science, researchers say these farms could drive wild salmon populations to extinction.  The problem is a parasite called sea lice.  They latch onto salmon skin in the open ocean.  And they also thrive in fish farms.  Adult salmon can stand to have some lice. But the parasites kill off vulnerable juveniles.

Usually, little ones swimming in a river aren't exposed to sea lice.  But in British Columbia, the plethora of fish farms near rivers means that wild juveniles are catching sea lice and dying off at alarming rates.  Scientists say within another four years, just two salmon generations, wild salmon populations could collapse by 99 percent.  They suggest two options—either put farmed fish in fully enclosed pens instead of the open nets currently used.  Or move the farms away from rivers.  Otherwise, wild salmon face a an upstream battle for survival.

Cynthia Graber

Get a free audiobook download at

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