Sea Lice Scourge: The Itch That Salmon And Steelhead Can't Scratch

by Don Roberts
Fly Fishing Catalog 2006

"...researchers bluntly concluded that 86 percent of young wild salmon migrating through fjords containing fish farms died from lice infestations."

There are innumerable reasons you should turn up your nose at farm-raised salmon. But one reason that has largely escaped attention revolves around the presence of a creepy little critter referred to in science tomes as Lepeophtheirus salmonis, aka the parasitic sea louse (no relation to the kinds of land-borne lice that pester dogs, cats and scruffy neighbor kids).

Sea Lice Debugged
Sea lice are small. Typically about .25 to 1.5 centimeters long. They’re roughly the size and shape of an embryonic, ooze-brown tadpole or a fuscous snot-wad of protoplasm. However, when encountered en masse, sea lice cast an undeniably large and disturbing shadow. Confirmed groupies, sea lice colonize conjointly with dense herds of feedlot salmon, which have been crammed eyeball to bunghole in highly constrictive net pens. In such fetid circumstances, sea lice populations merrily flourish, ultimately infusing entire tidal zones with repeat generations of blood-sucking vermin.

In their natural, free-range state, sea lice constitute little more than a fact of life in ocean living for an adult salmon. In fact, sea lice have been around as long as salmon. During their sea-going phase – when wild salmon constantly roam and graze across vast saltwater savannas – sea lice go along for the ride.
Sea lice typically lounge in the hydrodynamic cushion found adjacent the host’s anal fin – a soft spot where the lice easily penetrate the skin to feast on mucous, epithelial cells and blood. The amount of tissue consumed is insignificant for a vigorous adult salmon. When the adults migrate back to their natal streams during summer and fall, any sea lice they’re harboring soon wither and die in fresh water. Consequently, when spring rolls around in a normally functioning coastal ecosystem, there are no surviving sea lice lying in ambush for the out-migrating juvenile salmon.

The Problem
The presence of net pens, however, drastically changes the equation. Although both the government and the aquaculture industry have long vehemently denied that parasite problems occur where wild fish share surrounding waters with fish farms, recent studies have shown the exact opposite to be true – salmon ranching directly correlates with lice infestations and concurrent declines of wild salmon and steelhead. A team of scientists from the University of Alberta studied the “transmission dynamics of parasitic sea lice from farm to wild salmon” and calculated that the “infection pressure imposed by the farm,” particularly among juvenile salmon passing near the net pens, was “73 times greater than ambient levels.”

Sea lice infection in subadult salmon induces mortality through immunosuppression and osmoregulatory trauma. In other words, sea lice gang up and literally suck the life out of infant salmon. In an earlier site-specific study undertaken by the University of Bergen in Norway, researchers bluntly concluded that up to 86 percent of young wild salmon migrating through fjords containing fish farms died from lice infestations.

What’s it like for innocent young salmon fry to swim through tidal passageways choked with net pens from which seethe whorls of sea lice? Imagine crawling naked through a jungle ravine writhing with leeches... you begin to get the picture. Juvenile salmon are vulnerable creatures, and the sea lice latch on indiscriminately – nose, belly, flank, gill, eye-socket – wherever it’s expedient to get a grip. As Alexandra Morton, founder of the Raincoast Research Society in British Columbia, documented: “The smaller a salmon, the fewer lice it can bear. So when our little pinks and chums go by the farms and pick up more than 1 or 2 lice, they are doomed.”

After conducting research in 2001 on pink salmon stocks in the Broughton Archipelago north of Vancouver Island, Morton predicted (based on the lice infestation rate among juvenile pinks) a 98 percent crash in the population of returning adults in the archipelago. In fact, 99 percent of the run failed to materialize – the worst fisheries collapse ever recorded on the B.C. coast.

The Party Line
While tenaciously sticking to its story that sea lice issuing from salmon farms do not constitute a risk to wild salmon, the aquaculture industry has rather stealthily engaged in chemical warfare. Using logic only the Pentagon could love, aquaculturists now routinely poison an enemy that purportedly doesn’t exist. Each season the net pens are doused with tons of antibiotics and volatile pesticides. Though knocking out a portion of the pathogens and parasites, the chemical approach doesn’t come close to totally eradicating the little buggers. The toxic agents just add to the witch’s brew of drugs, sewage and contaminants already spewing forth from the net pens.

Saltwater feedlots and billions upon billions of sea lice larvae? Shucks, pure coincidence. At least that’s the party line. That’s what the aquaculturists in Scotland, Ireland and Norway kept maintaining, up until the catastrophic plunge of salmon and sea trout populations in the 1980s and 1990s forced the closure of all salmon fisheries in these nations. The relevance? Today, B.C. aquaculture companies steadfastly refuse to allow public access and oversight, and they continue to conceal crucial data regarding the numbers of sea lice infecting their salmon crops. By stark contrast, in Europe, crisis management now informs policy. In Norway, for instance, salmon farmers must report the numerical incidence of lice among their stock on the 15th of every month or accrue fines in the range of $100,000 a day and possible imprisonment for failure to comply. But here in cowboy country, in the relatively pristine enclaves of coastal North America, rational skepticism is, well, a dog that just don’t hunt. Robust monitoring remains almost nonexistent. And government and industry view each other with cozy forbearance.

Get Active
So what can you do? Vote with your wallet, that’s what. Stay way to hell away from faux fish cultivated in claustrophobic pens like mass-produced Arkansas chickens. Demand clear labeling at the butcher counter – packages that distinguish between wild-caught and farm-raised salmon – and settle only for wild Pacific salmon. As western sage Tex Bender admonishes: “Always take a good look at what you’re about to eat. It’s not so important to know what it is, but it’s critical to know what it was.” As any observant consumer may readily deduce, that fillet of Atlantic salmon laid out on ice under a neon glow is a bad idea, a piscatorial permutation, an industrial concept of fish. That insipid slab of artificially dyed and doctored flesh is no more a salmon than Chef Boyardee is pasta primavera, than Cool Whip is whipped cream, than Spam is… what is Spam?

Go wild in the political arena as well. Get up to speed on salmon, steelhead and ocean biodiversity concerns addressed by organizations like Ecotrust (, Salmon Nation (, the Coastal Alliance for Aquaculture Reform (, the Raincoast Research Society ( and Friends of Wild Salmon ( It’s time to face the fact that salmon farming the world over has become, quite literally, a lousy proposition.

About the Author

Don Roberts, a fishing writer and editor, has become increasingly preoccupied with the endless abuses perpetrated upon an already overburdened planet. “When so-called development and unmitigated greed conspires to kill my business partner – fish and fisheries in the Pacific Northwest – the only rational response is to get mad... Mad enough to sharpen a pen and draw some blood.”