New genetic tools will deliver improved farmed fish, oysters, and shrimp.
Two years ago, off the coast of Norway, the blue-hulled Ro Fjell pulled alongside Ocean Farm 1, a steel-netted pen the size of a city block. Attaching a heavy vacuum hose to the pen, the ship’s crew began to pump brawny adult salmon out of the water and into a tank below deck. Later, they offloaded the fish at a shore-based processing facility owned by SalMar, a major salmon aquaculture company.
The 2018 harvest marked the debut of the world’s largest offshore fish pen, 110 meters wide. SalMar’s landmark facility, which dwarfs the typical pens kept in calmer, coastal waters, can hold 1.5 million fish—with 22,000 sensors monitoring their environment and behavior—that are ultimately shipped all over the world. The fish from Ocean Farm 1 were 10% larger than average, thanks to stable, favorable temperatures. And the deep water and strong currents meant they were free of parasitic sea lice.
Just a half-century ago, the trade in Atlantic salmon was a largely regional affair that relied solely on fish caught in the wild. Now, salmon farming has become a global business that generates $18 billion in annual sales. Breeding has been key to the aquaculture boom. Ocean Farm 1’s silvery inhabitants grow roughly twice as fast as their wild ancestors and have been bred for disease resistance and other traits that make them well suited for farm life. Those improvements in salmon are just a start: Advances in genomics are poised to dramatically reshape aquaculture by helping improve a multitude of species and traits.
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Genetic engineering has been slow to take hold in aquaculture; only one genetically modified species, a transgenic salmon, has been commercialized. But companies and research institutions are bolstering traditional breeding with genomic insights and tools such as gene chips, which speed the identification of fish and shellfish carrying desired traits. Top targets include increasing growth rates and resistance to disease and parasites. Breeders are also improving the hardiness of some species, which could help farmers adapt to a shifting climate. And many hope to enhance traits that please consumers, by breeding fish for higher quality fillets, eye-catching colors, or increased levels of nutrients. “There is a paradigm shift in taking up new technologies that can more effectively improve complex traits,” says Morten Rye, director of genetics at Benchmark Genetics, an aquaculture breeding company.
After years of breeding, Atlantic salmon grow faster and larger than their wild relatives.
Aquaculture breeders can tap a rich trove of genetic material; most fish and shellfish have seen little systematic genetic improvement for farming, compared with the selective breeding that chickens, cattle, and other domesticated animals have undergone. “There’s a huge amount of genetic potential out there in aquaculture species that’s yet to be realized,” says geneticist Ross Houston of the Roslin Institute.
Amid the enthusiasm about aquaculture’s future, however, there are concerns. It’s not clear, for example, whether consumers will accept fish and shellfish that have been altered using technologies that rewrite genes or move them between species. And some observers worry genomic breeding efforts are neglecting species important to feeding people in the developing world. Still, expectations are high. “The technology is amazing, it’s advancing very quickly, the costs are coming down,” says Ximing Guo, a geneticist at Rutgers University, New Brunswick. “Everybody in the field is excited.”
FISH FARMING may not have roots as old as agriculture, but it dates back millennia. By about 3500 years ago, Egyptians were raising gilt-head sea bream in a large lagoon. The Romans cultivated oysters. And carp have been grown and selectively bred in China for thousands of years. Few aquaculture species, however, saw systematic, scientific improvement until the 20th century.
One species that has received ample attention from breeders is Atlantic salmon, which commands relatively high prices. Farming began in the late 1960s, in Norway. Within 10 years, breeding had helped boost growth rates and harvest weight. Each new generation of fish—it takes salmon 3 to 4 years to mature—grows 10% to 15% faster than its forebears. “My colleagues in poultry can only dream of these kinds of percentages,” says Robbert Blonk, director of aquaculture R&D at Hendrix Genetics, an animal breeding firm. During the 1990s, breeders also began to select for improved disease resistance, fillet quality, delayed sexual maturation (which boosts yields), and other traits.
Another success story involves tilapia, a large group of freshwater species that doesn’t typically bring high prices but plays a key role in the developing world. An international research center in Malaysia, now known as WorldFish, began a breeding program in the 1980s that quickly doubled the growth rate of one commonly raised species, Nile tilapia. Breeders also improved its disease resistance, a task that continues because of the emergence of new pathogens, such as tilapia lake virus.
Genetically improved farmed tilapia “was a revolution in terms of tilapia production,” says Alexandre Hilsdorf, a fish geneticist at the University of Mogi das Cruzes in Brazil. China, a global leader in aquaculture production, has capitalized on the strain, building the world’s largest tilapia hatchery. It raises billions of young fish annually.
Now, aquaculture supplies nearly half of the fish and shellfish eaten worldwide (see chart, below), and production has been growing by nearly 4.5% annually over the past decade—faster than most sectors of the farmed food sector. That expansion has come with some collateral damage, including pollution from farm waste, heavy catches of wild fish to feed to penned salmon and other species, and the destruction of coastal wetlands to build shrimp ponds. Nevertheless, aquaculture is now poised for further acceleration, thanks in large part to genomics.
A rising tide
Aquaculture is rivaling catches from wild fisheries and is projected to increase. Much of the growth comes from freshwater fish in Asia, such as grass carp, yet most research has focused on Atlantic salmon and other high-value species. Genomic technology is now spreading to shrimp and tilapia.
020406080100120140160180Million tons1950Value ($ billions)Harvest (thousand tons, annually)*First research on breeding19581966197419821990199820062014Capture ﬁsheries (inland)Aquaculture (inland)Capture ﬁsheries (marine)Aquaculture (marine)Grass carp12.6570420107.645251989Nile tilapia16.724361971Atlantic salmon26.7496