Food for Fish

Paul Greenberg
Piles of farmed Atlantic salmon in Chile’s Puerto Montt fish market. The piles of Peruvian anchoveta needed to feed that salmon would be significantly larger.

“Fish need nutrients not ingredients” are the oddly prophetic words of Frederic T. Barrows, a fish nutritionist with the U.S. Department of Agriculture in Bozeman, Montana. By now, most ocean-conscious fish eaters have become familiar with the fact that fish farming, or aquaculture, has at its root one gargantuan flaw: the most valuable fish we cultivate are carnivores, often requiring several pounds of marine protein (read: other fish) to produce a single pound of food for people. Salmon farming at its advent in the 1970s regularly used more than six pounds of fish to produce a single pound of Atlantic salmon, and today some of the more inefficient tuna ranches in the Mediterranean and Australia may require more than twenty pounds of marine fish for each pound of flesh produced.

This net loss of marine protein has been a major reason that Monterey Bay Aquarium’s Seafood Watch Program and other fish-rating schemes typically give carnivorous aquaculture products like salmon a “Red” or “Avoid” rating. But the last 10 years has seen the rise of a counterrevolution within aquaculture’s “blue revolution” that could effectively debunk this recurrent rebuttal to the world’s fastest-growing food system. The time is rapidly approaching when the fish-eating farmed fish of the world will be eating something else entirely.


Paul Greenberg
A Vietnamese pangasius farm near Can Tho in 2008. Pangasius catfish farms are some of the fastest growing aquaculture operations in the world. The pangasius industry is often criticized for the extreme amount of wild “trash fish” it “reduces” into feed for pangasius.

Over the last quarter century, nonfish products like soy and canola oil have been introduced into feed pellets with varying degrees of success, partly because many terrestrial agricultural products, in addition to containing the nutrients that fish need to grow, also contain what are called antinutrients—compounds that impede a fish’s digestive ability or compromise its health in other ways. Several new products are coming online that have broken that deadlock. Montana Microbial Products, of Missoula, Montana, has developed a method for producing a high-protein meal from barley. This material contains no antinutrients and is highly digestible and palatable to marine fish. Best of all, the company’s product is often made from underutilized malting barley that didn’t make the grade for other uses. Meanwhile, California’s Carbon Capture Corporation, the third-largest algae farm in the United States, is cultivating several species of algae that have the potential to replace the oil and fatty acids typically acquired from forage fish in aquaculture diets. Finally, Oberon, headquartered in Boulder, Colorado, has trial-tested diets formulated from bacteria that feed on brewery beer-sludge waste. This win-win situation of waste recycling and food creation is of course the holy grail of all food systems. Should it prove viable, more than a few breweries may be looking for a profit stream from their rivers of effluent.

So it seems that, through many different pathways, fish will get the nutrients they need and aquaculture may decrease its burden on the seas. But going forward, what consumers may need is assurance that what they are eating is safe, nutritious, and palatable. Perhaps this will be the next phase of dialectics for the blue revolution: convincing a diner sitting in an oceanside restaurant that a fish raised on barley protein, farmed algae, or beer waste bacteria is, in fact, seafood.