Blue Growth: The Need for Fish Farms

A Response to Breakthrough’s Essay on Next-Generation Aquaculture

There is no question that any major increase in global fish production will need to come from aquaculture. As Chris Costello and I estimate in a recent paper, global fisheries only have the capacity to increase production by 14-17%, by reducing pressure on overfished stocks and increasing pressure on underexploited ones. Other options for increasing fisheries’ yields—such as harvesting species like krill and mesopelagic fishes that are not now fished—are not economically viable today.

Of course, as Marian Swain mentions in her excellent essay on the issues involved in the expansion of global aquaculture, all forms of food production come with environmental costs, including land transformation, greenhouse gas emissions, freshwater depletion, overuse of antibiotics, soil erosion, nutrient and acid pollution, and biodiversity losses. Both aquaculture and capture fisheries have come under great scrutiny for their performance across some of these categories.

But when looking at the environmental costs of catching and farming fish, it is essential to compare them with alternative modes of producing protein. As discussed in Swain’s article, most capture fisheries and aquaculture systems have considerably lower environmental costs than the livestock sector. Only by using livestock as a reference point—and the extensive habitat disruption it entails—can we fully account for the comparative environmental impact of fish production. Increased animal protein production can come from more pasture and more deforestation or from more aquaculture—that is the comparison that needs to be considered.

From a human health perspective, there is also much to be said for fish and the high concentration of micronutrients they contain, which is difficult to find in other sources of protein. Omega-3 fatty acids are well known, but fish also contain large amounts of calcium, zinc, selenium, iron, and vitamins A, D, and B12. There are differences, naturally, between kinds of fish and modes of production, but in general, there is growing evidence to suggest that fish should form a significant part of our diets. This, in turn, will require producing more fish.

When it comes to how that fish should be produced, there are some elements that Swain’s article does leave unexplored. With regard to energy use, for instance, Swain rightly points out that the greenhouse gas emissions of aquaculture systems depend greatly on how energy is sourced, but systems and species also vary widely in terms of their energy demand. The energy required to produce feed is particularly significant, which is why farmed salmon, increasingly fed with waste products from fisheries, have the potential to perform well on this metric. Even better, farmed mollusks—especially mussels, clams, and oysters—require no feed, freshwater, or antibiotics, and use very little energy compared with recirculating systems. Their yield per hectare is also astonishingly high.

When considering the future of fish production, the environmental benefits of such systems are something to keep in mind. In the words of a favorite poster produced by the US Food Administration during World War I, “Save the products of the land. Eat more fish—they feed themselves.”