Ten thousand years ago, humans made the shift on land from hunting and gathering to farming. Now the same transformation is taking place at sea. This time, can we get it right?
By Sarah Simpson
Illustration by Ira Korman
A shipment of 100,000 fresh, sushi-grade cobia, each fish amounting to about five pounds of firm, white meat, arrives on schedule in the Port of Miami. In this case, “fresh” does not mean beheaded and ice-packed—these fish are very much alive and swimming. As fingerlings, they were set adrift in a 3-million-liter pen which latched onto a current traveling the Caribbean in a predictable, clockwise path. Nine months later, a frenzy of splashes erupts at the water’s surface as the underwater corral emerges from the depths. After rounding the western tip of Cuba and skirting a storm near the Yucatán (via remotely operated thrusters), the floating farm has made port just as the fish reach harvestable size.
Aquatic engineer Clifford Goudey had this futuristic vision dancing in his head last July when he tested the world’s first self-propelled, submersible fish pen. A geodesic sphere measuring 19 meters in diameter, the cage proved surprisingly maneuverable when outfitted with a pair of 2.5-meter propellers, says Goudey, who directs MIT Sea Grant’s Offshore Aquaculture Engineering Center. In his Caribbean current scenario, Goudey imagines launching dozens of floating farms in a steady progression, each a week behind the other. His work marks a breakthrough in the quest to raise fish in parts of the oceans that are too deep for traditional, anchored cages. It also amounts to a key step toward what a few cutting-edge thinkers have been craving for years: the wholesale taming of the sea.
The oceans provide about 20 percent of the world’s protein, and pressure to deliver this critical food stream has led to extreme overharvesting. As wild fish stocks decline, aquaculture is the logical candidate to pick up the slack, and some are looking to it as a way to rebuild commercial fish stocks. In a 2005 Nature commentary, oceanographer John Marra argued that widespread ocean farming is inevitable. “We have already accepted domestication of the land,” Marra wrote. “Now is the time to accept the same for the seas.” (1)
Such visions have long been anathema to many environmentalists who fear the spread of present-day aquaculture’s myriad ills. Many of today’s coastal fish farms have decimated habitat and spread disease into local fish populations. Making matters worse, fish farms represent a net drain on populations of wild fish, which are often caught just so they can be ground into feed for salmon and other species.
Despite these concerns, a shift is underway. Some members of the environmental community are concluding that widespread aquaculture must be pursued if we are to save the oceans and feed the planet. Aquaculture production must double by 2050 just to keep up with per capita demand. But merely scaling up current methods would only exacerbate the problems.
In other words, the world needs new, sustainable aquaculture practices, and it needs them fast. It took 10,000 years for domestic agriculture to transform the land, but viable ocean farming schemes must be developed in one one-hundredth of that time if they are to forestall the oceans’ demise. This urgency is spurring some leading environmentalists and scientists to lend their knowledge and support, instead of their opposition. In a recent lecture, the renowned marine ecologist Jeremy Jackson discussed the threat of overfishing and announced, “the most important scientific challenge we now face is how to make aquaculture ecologically sustainable.”
The mobile fish pens are just one example of the cutting-edge technologies emerging to surmount Jackson’s challenge. Also in the works are intriguing methods of recycling fish sewage, new feed formulations that use dramatically smaller amounts of wild fish, and onshore farms where salt-water species are tricked into living in fresh water. As these developments solve some of aquaculture’s seemingly intractable problems, they could also be the first steps toward widespread, sustainable domestication of the oceans.
From his post at eastern Canada’s Bay of Fundy, Thierry Chopin has seen first-hand how salmon farms devastate bays and inlets. Typically located just a stone’s throw from shore, the farms are relentless sources of excrement and pollution. Some estimates suggest the nutrient outfall from salmon farms in Scotland, for example, is comparable in volume to the untreated sewage from half its human population. What’s more, salmon are sloppy eaters that typically consume only about 80 percent of the food that comes their way. The nutrient-laden effluent spills from cages, sometimes triggering harmful algal blooms and other pollution problems. But Chopin, a University of New Brunswick marine biologist who has spent eight years trying to mitigate these problems, says cleaning up salmon farms may be as simple as re-casting poop and uneaten food scraps as a resource.
In conjunction with Cooke Aquaculture, a Canadian company pursuing sustainable farming, Chopin is experimenting with so-called integrated multitrophic aquaculture, or integrated farms. This innovative approach positions salmon pens in close proximity to plants and animals that actually consume the pollution. The farms aim to absorb the vast majority of the salmon waste, sparing the surrounding waters while nurturing species that can be sold on the global seafood market.
Seen from above, Chopin’s operation looks like a tray of soda cans, with circular salmon pens anchored in a square grid. It amounts to a carefully calibrated ecosystem, and Chopin, along with Shawn Robinson at Canada’s Department of Fisheries and Oceans, has helped identify which species can thrive within it. “It’s all about choosing species based on their function,” Chopin explains.
Seaweeds, for instance, are amazingly efficient waste recyclers that can extract about 40 percent of the dissolved nutrients available during their growing season. To take advantage of this, Chopin’s team positions seaweed on ropes dangling from rafts located downstream from the pens. The kelp thrive in this fertilizer bath, which is primarily ammonia released from salmon gills and decaying food pellets; some species grow as much as 46 percent faster than they do in salmon-free areas.
Sharing the same grisly appetite for salmon waste are filter-feeding mussels, which play a different role in the clean-up process by extracting particles of excrement and food scraps. Chopin’s system places the mussels in cages alongside the fish pens. Thanks to their close quarters with salmon, the mussels grow as much as 50 percent faster as they absorb about half of the fine waste particles. About three years ago, though, Chopin’s team realized some waste particles were too big for the mussels to manage. That’s where sea cucumbers and urchins, which thrive on the heftier scraps and are placed in trays directly below the salmon pens, come into the picture. “One man’s trash is another’s treasure” takes on new meaning when you see how remarkably plump a culinary delicacy such as urchin roe grows in a cloud of salmon sewage.
There is, of course, a more obvious way to manage the effluent problem: move fish farms away from the coast, into deeper waters where pollution would be carried off and diluted by the sea. That turns out to be much harder than it sounds. For starters, offshore cages have to be built to withstand the pressure and currents that come with being located farther out at sea—keeping enormous pens steady in 60 meters of open water is a tricky proposition. They must also keep their plump inhabitants safe from sharks and other predators looking for an easy lunch.
A handful of companies are overcoming these challenges with innovative cage designs that allow fish to be farmed in deeper water than ever before. Anchored varieties of the spherical AquaPod, developed by Ocean Farm Technologies in Searsmont, Maine, range up to 27 meters in diameter, which translates to almost a billion liters in capacity. Another innovator is Bainbridge Island, Washington–based OceanSpar, which has developed its SeaStation pens in the shape of oversized toy tops. Built around galvanized steel frames, the pens are covered in Kevlar-like netting that prevents wily fish from chewing their way out—or in.
Half a mile off the Hawaiian coast, Kona Blue Water Farms is using eight 3-million-liter SeaStations to house some 480,000 Hawaiian yellowtail. The pens are tethered by a network of 22 anchors, each weighing 3.5 tons and anchored by a one-ton chain. All told, Kona Blue spent around $500,000 to set up the infrastructure 30 meters beneath the sea (except during maintenance and harvest), which allows excrement and uneaten food to be swept away in brisk subsurface currents. Water quality downstream from the pens is the same as at sites upstream. The innovations deliver a glimpse of the future, when industrial techniques may transform the continental shelf into a sprawling network of farms playing a vital role in global food production.
Neil Sims, cofounder of Kona Blue Water Farms, is taking aim at another critical hurdle to sustainability: the need to harvest vast amounts of wild fish just to feed the ones being farmed. Salmon and other carnivorous fish must be fed large quantities of fish oil and fish meal to gain the taste and texture that consumers crave. It typically takes 2.3 kilograms of so-called “forage fish” to produce half a kilogram of farmed fish. (And that’s using carefully formulated feed pellets; many fish farms around the world still use raw fish, which pushes the necessary kilograms to nine or higher.) Fortunately, Sims is gaining ground in his crusade to rewrite this equation.
Sims oversees a booming operation that produces one of the world’s most prized farmed fish: Hawaiian yellowtail sold under the name Kona Kampachi. Sold in swank restaurants across the U.S., a serving of Kona Kampachi sashimi can fetch a price upwards of $15, in part because sushi connoisseurs prize the fish’s firm, yet tender, flesh. Sims worries that, as aquaculture grows, it will further harm the species that form the basis of fishmeal. In the past 25 years, farming of marine fish and shellfish has grown by 10 percent per year. That surge translates into ever-increasing pressure on populations of forage fish such as anchovies and sardines. So Sims has launched an ambitious effort find replacement sources for the fatty acids and amino acids his fish need.
When Kona Blue anchored its first offshore pen in 2005, their feed was 80 percent Peruvian anchovy fishmeal and fish oil. By early 2008, the company had reduced that percentage to 30, thanks to careful experimentation that allowed Kona Blue to substitute soybean meal and chicken oil for the fish products. Sims is thrilled to say it now takes only 1.4 kilograms of Peruvian anchovies to produce one kilo of Kona Kampachi. Indeed, this breakthrough—in combination with Kona Blue’s other conscientious practices—made U.S.–farmed yellowtail the first ocean-farmed fish to earn a “good alternative” rating from Seafood Watch, Monterey Bay Aquarium’s popular sustainable seafood advisory list.
Sims acknowledges the battle is ongoing and Kona Blue is aggressively pursuing a 1:1 ratio. To achieve this, the company is looking at soy protein concentrates as well as canola and soy oils. Kona Blue is also keeping an eye on a particularly exciting biotech breakthrough in which scientists have coaxed the coveted omega-3 fatty acid DHA out of microscopic algae. One animal-nutrition firm is now testing fish feeds enhanced with the same algal-based DHA already marketed in infant formula, milk, and juice.
Sims isn’t alone. Similar feed formulations have been developed for cobia and other fish, but the limiting factor is cost. Until the price of fish meal and fish oil rise to reflect the world’s depleted stocks, Sims says, it will be hard for many aquaculturists to justify pricier, more sustainable feed.
Even those at aquaculture’s leading edge have difficulty predicting just how quickly the new practices might translate into large-scale ocean domestication. But they do agree that difficult barriers remain and that the biggest challenges may be not technical but political.
Take Goudey’s self-propelled AquaPod. Sending flotillas of corralled fish to fatten up on the high seas is already feasible from an engineering standpoint, he says. A first step might be free-floating farms riding in and out and back again with the tide, returning to the same spot every 12 hours. Eventually, Goudey envisions full transoceanic voyages: penned fingerlings launched from Miami hitch a ride on the Gulf Stream to Europe, where they are harvested and replaced with a new, young brood for the return voyage to America. It would require only the integration of the self-propelled cage (such as the one he tested last summer) with a surface buoy carrying an automatic feeder (imagine a giant version of what you leave for your cat when you go on vacation)—plus navigation, tracking, and communications networks such as those already well-honed for research submersibles and Mars rovers.
Even though the technologies are within reach, progress toward offshore farming has been sluggish. Of some 50 offshore installations worldwide, only five U.S. commercial marine fish and shellfish farms have ventured into open water. Goudey thinks more aquaculture entrepreneurs would jump into the fray if the U.S. put into place the appropriate legislation and permitting systems. This would not only give aquaculturists the green light but also help guide the industry toward a sustainable future. Introduced in 2007, the National Offshore Aquaculture Act, for instance, would have authorized the U.S. government to grant aquaculture permits throughout the U.S.–exclusive economic zone, which extends 200 nautical miles from each coast. Issuance of these permits could be tied to sustainable practices. But the legislation has languished in Congress since 2005 and has not been reintroduced this session.
That reality has forced at least two U.S. offshore fish farms, frustrated with the permitting chokehold, to investigate expanding their operations to Mexico and Panama—or move them there entirely. In other words, businesses that might be goaded into pursuing sustainable aims via legislation now have incentives to migrate to other waters where the aquaculture mentality might be more akin to “anything goes.”
Halting such overseas moves would also give the U.S. opportunity to improve food security. Among natural resources, the country’s $9 billion annual trade deficit in seafood is second only to its dependence on foreign oil. To help offset that food imbalance, the U.S. Department of Commerce has declared it would like to quintuple the value of annual domestic aquaculture production, currently just shy of $1 billion, by 2025.
If the world can muster the unprecedented political will and international cooperation necessary to domesticate the high seas, critics ask, why not put those energies toward restoring the oceans rather than risk degrading them further? As Julia K. Baum wrote in Nature in reply to Marra’s 2005 call to tame the seas, offshore aquaculture “is not ‘inevitable.’ It is a course of action that can be chosen—or not.” (2)
Given the world’s food needs, such a wholesale rejection of aquaculture might amount to accepting the status quo: a fishing industry that is devastating wild stocks, decimating the oceans, and generating enormous amounts of CO2. As Scripps’s Jeremy Jackson points out, “sustainable fishing is an oxymoron.” Jackson draws a comparison to hunting and gathering and argues that sending flotillas of fishing boats out to round up wild fish is on a par with hunting down bears and elk for food. “If we’re going to get lots of protein from the ocean,” he concludes, “the only solution is aquaculture.”
That doesn’t mean today’s latest methods are the final solution. After all, farmed yellowtail and salmon, like cod and tuna, are luxury foods that most people in the world will never taste. Together with academics such as Stanford University’s Rosamond Naylor, Jackson believes we won’t be able to save the oceans until we abandon our taste for fish that live high on the food chain. In that case, the world’s ocean-based protein would have to come from anchovies, shellfish, and other species operating at lower trophic levels.
From this point of view, the latest aquaculture innovations are best seen as an incomplete step in an important direction. Perhaps offshore farming will ultimately provide all the high-trophic-level species the world demands and also mass-produce the species many environmentalists find more favorable. Free-floating farms, for instance, could also be used to grow sardines, Goudey says. The University of New Brunswick’s Chopin adds his own twist to the idea: he would add shellfish and seaweed rafts trailing behind.
As we pursue these goals, Chopin reminds us to be patient and to understand that a rapid transition to aquaculture means there will be missteps along the way. “Even after centuries of agriculture, we don’t have all the best practices,” he says. “In aquaculture, we want to solve everything in a few decades.” ❧
1. Marra, J. 2005. When will we tame the oceans? Nature 436:175–176.
2. Baum, J., J. McPherson, and R. Myers. 2005. Farming need not replace fishing if stocks are rebuilt. Nature 437:26.
Halweil, B. 2008. Farming fish for the future. Worldwatch Report 176. Eagle, J., R. Naylor, and W. Smith. 2004. Why farm salmon outcompete fishery salmon. Marine Policy. 28(3):259–270.
Michler-Cieluch, T., G. Krause, and B.H. Buck. 2009. Reﬂections on integrating operation and maintenance activities of offshore wind farms and mariculture. Ocean & Coastal Management 52:57–68.
Illustration by Ira Korman