Calculating the true cost of salmon farming

There has been a strong push recently by governments in both the United States and Canada for citizens to increase their fish consumption because of health benefits. This presumptive dietary shift, along with the fact that the bulk of seafood caught in Canadian waters is exported, serves as the raison d'être for the development of the salmon-aquaculture industry.

"We need to meet the seafood demand" is the mantra of eager government and industry representatives who are keen to reap the associated profits. But the first question is whether or not the demand for species such as salmon, tuna, halibut, and cod is actually sustainable. Is it really possible for these species to "feed the world", as the industry's proponents are wont to assert?

In order to farm salmon, harvesting of wild fish (for example, sardines, whiting, and anchovies) for fishmeal and fish oil is required to produce the feed. A recent report by the International Council for the Exploration of the Sea suggests that deep-sea fish in the North Atlantic are being fished at more than twice the rate they can withstand to provide food for farmed salmon. While the debate over local impacts continues, the global impacts of salmon farming have received little attention in British Columbia.

Let's consider the ecology of farming carnivores like salmon. Corey Peet is an ecologist researching the impacts of aquaculture on the marine environment. As he explains: "Natural food webs take the shape of a pyramid. At the bottom of the pyramid lies an abundance of organisms that gain their energy directly from the sun or chemical processes. The next step up the pyramid are the slightly less abundant organisms, mostly herbivores, that feed on those below them. With each step up the pyramid, only 10 percent of the energy is passed on to the next step, as 90 percent of energy is lost to heat. Therefore, fewer organisms can be supported as you step up the pyramid, leaving only a few predatory species at the apex. In other words, there is a reason why we only see a few carnivores in the wild; nature only has so much energy to go around. Thus, when we consider the farming of salmon against the fundamental basics of ecology, it makes no sense to claim that this practice is sustainable."

(On a related note, Agriculture Minister Pat Bell should be commended for instituting a moratorium recently on fish farm expansion for B.C.'s north coast, although the province simultaneously approved two new farms for the south coast.)

Leading fisheries experts—such as Daniel Pauly of the UBC Fisheries Centre—caution against "farming up the food web" because of the inefficient and wasteful use of biological resources, all of which are already used by humans and other organisms, and some of which are commercially valuable. Recent estimates indicate that farming salmon requires anywhere from two kilograms to four kilograms of wild fish to produce one kilogram of farmed fish. In contrast, farming herbivorous species (like tilapia and carp) requires minimal inputs of fishmeal.