Bad Crop

Fish farms may promote parasites that threaten wild salmon.

By Patrick Dougherty

May 2008

Mature fish can withstand infestations of sea lice, insidious parasites that attach themselves to fish and feed, and it’s not unusual for fish in the wild to carry these pests. Farmed fish, however, spend their entire lives clustered in underwater cages—a condition that promotes excessive sea lice infestations. As a result, fish farms are often teeming with the pests, to the extent that they may actually threaten the existence of wild salmon populations.

“Growing high densities of fish in close quarters can lead to elevated levels of diseases and parasites, just like when animals are crowded together in terrestrial farms,” says Rebecca Goldburg, PhD, senior scientist of the Environmental Defense Fund in New York City.

Recent research suggests that wild pink salmon in British Columbia are being harmed by sea lice infestations that originate in these sprawling fish farms. Migrating juvenile wild salmon populations are falling prey to sea lice as they pass these sites. And since migrating salmon are younger, they are less able to withstand sea lice. Some researchers have projected that 80% of young salmon with sea lice infestations will die—which could translate to local wild salmon populations being wiped out entirely in as little as eight years. “The exact magnitude of the sea lice threat stills needs more field research,” says Goldburg. “However, that should not be an excuse to delay pursuit of options to address the problem.”

Save Room for Salmon
    Salmon is one of those superfoods that people have been relying on for years because it offers such significant nutritional health benefits. “Salmon and other fatty fishes like mackerel, tuna, herring and sardines are all rich in omega-3 fatty acids, which are important for strong immune response, heart health and brain function,” says Monica Reinagel, MS, CNS, chief nutritionist of www.NutritionData.com and author of The Inflammation Free Diet Plan (McGraw-Hill). “Omega-3 fatty acids also act as natural anti-inflammatory agents and blood-thinners.”

But not all salmon are created equal. Farmed salmon will not be able to provide the same nutritional value as wild salmon if the latter are wiped out by sea lice infestations, in addition to other non-sustainable fishing practices such as the use of antibiotics and various other chemicals in the coastal waters where fish farms are situated.

While farmed salmon and wild salmon contain about the same levels of healthy omega-3 fatty acids, farmed salmon is extremely high in omega-6 fatty acids. Unless they are properly balanced in a healthy ratio with omega-3s, omega-6 fats can be bad for your health. The unnatural way in which farmed salmon are raised seems to diminish their nutritional value for people. “Farmed salmon is so high in omega-6 fats because of the feed that’s used,” explains Reinagel. “Instead of their natural diet [which itself is rich in omega-3 fats], farmed salmon are often fed fish meal that’s enriched with vegetable oils, which are high in omega-6 fats.”

The feed that farmed salmon chow down on also harms fish swimming in the wild. “Farmed salmon are fed a diet high in fish meal and fish oil made from wild-caught fish,” says Goldburg. “By some estimates, it takes three to six pounds of wild caught fish to grow a pound of farmed salmon. The result is a net loss of fish from salmon farming.” As it is, experts say some of the world’s fish populations are in serious risk of extinction.

 In contrast, the population of wild Alaskan salmon is sustainably managed and harvested, says Laura Fleming, spokeswoman for the Alaska Seafood Marketing Institute. “Wild salmon has a natural diet of marine organisms, it matures naturally, and swims freely. These fish get lots of exercise, so most of the flesh is muscle, making it firm-textured. Wild Alaskan salmon are not thickly marbled with fat; they’re very low in saturated fat, and their color is natural, from the marine organisms they consume.”

Finding Solutions
    Conservationists are currently weighing a number of innovative solutions—not just to ease infestations of sea lice but also to provide salmon for human consumption in its healthiest form without damaging the environment in the process.

 One possible approach is similar to the idea of companion planting on farms, in which plants that complement each other are grown together. In this case, the idea is to grow several different types of marine organisms at the same time, such as salmon, seaweeds, mussels and urchins, in a so-called integrated aquaculture system, says Goldburg. The seaweeds, mussels and urchins would recycle nutrient wastes from the salmon, which would help keep the water cleaner. “Preliminary evidence suggests that some of these organisms also consume parasites and viruses associated with salmon,” Goldburg adds.

The state of Alaska has taken a more direct route to ensure salmon population health by outlawing fish farming altogether. “Allowing fish farming would threaten the health and vigor of the state’s wild salmon resources,” Fleming says.

Considering fish farming’s negative environmental impacts in addition to sea lice infestations—including water pollution and escapes of farmed fish which can harm wild salmon—perhaps Alaska has discovered the salmon-friendly solution that will make swimming upstream just a little bit easier.

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