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29 August 2011

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Raising Salmon by Aquaculture

 

While the number of wild fish plummets, those raised in captivity now account for half the world’s fish production

 

According to a Food and Agriculture Organization report (State of the World Fisheries and Aquaculture 2008) starting from an insignificant total production, inland and marine aquaculture production grew by about five percent per year between 1950 and 1969 and by about eight percent per year during the 1970s and 1980s, and it increased further to 10 percent a year in the 1990s. In 1970, aquaculture accounted for 0.7 kg of fish per person; by 2006, this had increased to 7.8 kg per person.

 

Feed Used by Fish Farms

What could be simpler? Build a tank or fence off a corner of shoreline, toss in some tiddlers, feed them, and then scoop them out when they are fully grown.

 

Unfortunately, aquaculture is not without its controversies.

 

In China, where millions of people are being fed by fish farms, the farms raise mostly herbivorous fish (carp and milkfish) and invertebrates (clams and oysters). It is important to note that these fish and shellfish do not require fishmeal in their diet.

 

In contrast, most large-scale shrimp farms and salmon farms require large amounts of fishmeal because the animals being raised are carnivorous. For every kilo of shrimp and salmon produced in this manner, a bit more than two kilos of fishmeal are required as input. And, of course, the source of the fishmeal is wild species, some of which are endangered.

 

Diseases Impact Farmed Salmon

These days, salmon ordered in a restaurant or bought at a supermarket is likely to be farmed. Companies such as Marine Harvest have facilities in Canada, Norway, Ireland, Chile, and the United States and turn out most of the salmon sold on the world market. Marine Harvest says it “produces one-fifth of the world’s farm-raised salmon.”

 

Farmed salmon are usually held in floating net cages anchored close to shore where crowded conditions help the spread of disease and parasites. Many salmon farmers use antibiotics and chemicals to overcome these problems. Others employ hormones to get the fish up to market size faster. These artificial inputs cause concerns.

 

Medical News Today reports (December 26, 2005), “On the one hand, farmed salmon has more heart-healthy omega-3 fatty acids than wild salmon. On the other hand, it also tends to have much higher levels of chemical contaminants that are known to cause cancer, memory impairment, and neuro-behavioural changes in children. What’s a consumer to do?”

 

The advice is for children and pregnant women to avoid farmed salmon. Other people should just go easy on how much they eat.

 

The Problem of Sea Lice

Another problem associated with farmed salmon centres on nasty little beasts called sea lice (below). The environmental group Farmed and Dangerous says that

 

 

when sea lice “encounter marine fish they attach themselves to them, usually on the skin, fins, and/or gills and feed off the mucous or skin.” This weakens the host’s immune system making the fish more vulnerable to disease.

 

The other issue is that sea lice get out of the open pens and attack juvenile wild salmon as they begin their life cycle in the ocean. This is frequently cited as a major reason for the collapse of the West Coast salmon fishery, although the record 2010 salmon run casts doubt on that theory.

 

Standard Sea Lice Treatment Failing

The normal way of dealing with sea lice has been to whack them with chemical treatments to kill them. But, there’s some disquieting news on that battle.

 

Ben Koop is a biology professor at the University of Victoria. He told the  Vancouver Sun (May 11, 2010), “One of the biggest issues is that in Norway and Chile there’s a documented resistance to treatment - and that is really huge.”

So, if the only way of combatting sea lice is no longer effective the salmon aquaculture industry is in deep doo-doo; and, so might be the wild salmon fishery.

 

Retailer Stops Selling Open-pen Farmed Salmon

In January 2010, the U.S. retail giant Target announced that it would no longer sell farmed salmon. In a news release the company said: “Many salmon farms impact the environment in numerous ways – pollution, chemicals, parasites, and non-native farmed fish that escape from salmon farms all affect the natural habitat and the native salmon in the surrounding areas.”

 

There is a way around this problem and that is to raise salmon in closed ponds sealed-off from surrounding waters. Wastewater is filtered before being pumped back into the sea. At other farms the salmon have been removed from the ocean entirely; they are being raised in tanks on land.

 

The salmon farming industry is resisting this because it’s more expensive than open-pen systems. However, when huge buyers of the product such as Target refuse to sell open-pen raised salmon changes will come.

 

Image credit

Southeast Asian Fisheries Development Centre

Woodley Wonderworks

Petr Jan Juraèka

 

Sources

“Wild Versus Farmed Salmon, The Pros and Cons.” Medical News Today, December 26, 2005.

“Sea Lice Resistance to Pesticide ‘Inevitable’ on West Coast.” Judith Lavoie, Vancouver Sun, May 11, 2010.

“Top Sushi Restaurant Serves Endangered Species.” Greenpeace Press Release, September 7, 2008.

 

© Canada and the World, March 2011

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ESCAPE ARTISTS

 

Salmon farms usually raise Atlantic salmon because it is a faster growing species than Pacific salmon. In Norway and Scotland escaped salmon have entered local watercourses.

 

In many of Norway’s rivers, wild populations of Atlantic salmon have been completely displaced by farmed salmon.

 

Marine biologists in British Columbia and Washington state are concerned about the same problem. Increasing numbers of escaped Atlantic salmon are being found spawning in local rivers where native populations of endangered Pacific salmon are struggling to survive.

 

 

TUNA RANCHING

 

Greenpeace says that, “In some countries, tuna is being farmed in ‘ranches.’ ” Tuna are hard to rear from eggs, so most tuna farming involves catching young tuna and fattening them up in ocean cages. This, of course, puts a further strain on already threatened wild tuna stocks.

 

According to Greenpeace “Ranching also uses high amounts of other wild fish as feed - about 20 kg of wild fish to produce just 1 kg of tuna.”

 

 

 

FIRST

WORLD APPETITES

 

Aquaculture has the potential to feed a lot of hungry people.

 

Unfortunately, many aquaculture projects in the developing world are raising high-value species, such as salmon and shrimp, for export.

 

Fish farms in Third World countries are often pressured to do this to earn hard currency from First World nations, so the poorer states can pay off their debts.

 

The New Scientist reports that, “This bias means that cheaper fish that could be sold to local markets often never make it into large-scale culture.”

 

The threat to local food supplies gets worse. About half the area now used for shrimp ponds in Thailand’s Inner Gulf was once used to grow rice.

 

 

Aquaculture is the world’s fastest-growing food industry.