Learning to Farm Fish Responsibly
Breakthroughs in aquaculture are winning over longtime skeptics.
Illustration by Tyler Hoehne
For years, wildlife organizations and international agencies have been warning that overfishing is rapidly depleting ocean fish stocks. Because the global fishing fleet is estimated to be three times larger than our oceans can sustain, the populations of big fish—tuna, swordfish, cod, marlin, and others—have declined by 90 percent since 1950. If this trend continues, populations of all food-specific species could theoretically collapse by 2048. And that’s where fish farming comes in. Though the downsides of traditionally farmed fish are numerous and well-documented—disease, environmental damage, nutritional degradation, habitat destruction, antibiotic use, and forage fish depletion among them—some innovative aquaculture models are now carving out new, non-destructive means of farming fish, and winning over longtime skeptics.
Overfishing and its resultant damage to marine ecosystems is very bad news, not only for the oceans, but also for the one billion people across the planet, predominantly in developing nations, who rely on fish as their primary source of protein. To fill that ever-widening gap between supply and demand, global aquaculture production has grown 8.3 percent annually since 1970, and fish farming currently provides about half of the world's seafood. Back in 2011, thanks to soaring global demand, fish production actually overtook beef production by a few million annual tons. At the top of this global fish heap, Asian countries are producing nearly 90 percent of the worldwide aquaculture stocks. On the other side of the equation, the United States imports just over 90 percent of its seafood, drawing about half of that from farmed sources.
In China, where 62 percent of the worldwide aquaculture production takes place, an integrated, polyculture system boosts production while simultaneously mitigating some of the problems that have long plagued the industry. With polyculture, different species of fish are farmed together to balance out the ecosystem. For instance, silver carp feed on algal blooms while grass carp control macrovegetation growth; the bottom-feeding common carp aerate the sediment and stir up the water's nutrients. Indonesia and India, among other countries, also employ this traditional, natural technique.
Southern Spain’s Veta La Palma estuary leans on a similar philosophy: Create a healthy ecosystem and let nature run the show. Veta La Palma sits on 27,000 acres at the tip of the Guadalquivir River—a self-renewing, self-sustaining plot of canals and marshes wherein algae, zooplankton, and phytoplankton feed bass, shrimp, mullet, and eel. The aquatic life of the estuary coexists with 250 bird species, including pink flamingos and black-shouldered kite. Though losing 20 percent of the farm's fish and fish eggs to predator birds might seem problematic to a for-profit company, Veta La Palma actually sees it as a sign of success, or at least that's how biologist Miguel Medialdea explained it to chef Dan Barber: "We farm extensively, not intensively. This is an ecological network. The flamingos eat the shrimp. The shrimp eat the phytoplankton. So, the pinker the belly, the better the system." For Veta La Palma, if the ecosystem is pure, the product is pure.
At McFarland Springs trout farm in Northern California, the naturally cold, spring-fed headwaters of the Susan River not only provide a pristine habitat for the fish, but also produce hydroelectric power for the farm. Using a less environmentally integrated, but still environmentally sustainable model, the farm used trial and error to develop a nutritionally dense food blend for their trout. Normally, farmed fish are served fishmeal, a high-protein powder made from smaller, dried forage fish. Each produced pound of sellable fish requires five pounds of these forage fish, further contributing to the depleted ocean stocks and introducing ocean contaminants, including heavy metals, into the farmed product—contaminants and heavy metals that we then consume. At McFarland Springs, the trout have their nutritional needs met through a vegetarian diet of algae, organic corn, flax, nuts, and organic soy. It's an innovative approach that is certainly replicable, though due to the necessary high price of raising salmon in this way, the end product is expensive and the project not necessarily scalable.
Catch limits and other regulations mandated by the Magnuson-Stevens Fishery Conservation and Management Act over the past decade have proved that many fish stocks can and will recover. But, looking at the damage already done, an either/or approach is not enough; a both/and strategy—involving well-managed wild fisheries coupled with sustainable aquaculture operations—is needed.