Next time you order that icy jumbo shrimp cocktail, you can use this little factoid to impress your date: Shrimp are what scientists call “shredders and tearers.” They’re considered opportunistic eaters, meaning they will nibble on anything they can get their grubby little hands on. Plankton, algae, maybe a dead fish they’ve bumped into by accident. They’re not fussy eaters, which is why a byproduct of the ethanol industry — dried distillers grains — looks especially promising to scientists focused on developing new kinds of farmed fish feed. Nom. Nom.

While there’s been some confusion over when exactly the world will be eating more farm-raised seafood than wild caught — what’s not disputable is that our trajectory is pointed straight in that direction. (The Food and Agriculture Organization first predicted the milestone in 2009 [PDF], but has since revised it to 2015 [PDF].) Since then, the aquaculture industry has been in a race to develop more sustainable and efficient feed for all types of farm-raised fish with wildly varying nutritional needs — after all, a vegetarian tilapia has different requirements than a carnivorous salmon. The trend, however, is to move toward more plant-based options, in part as a way to put less burden on the sea.

Why turn to vegetarian feed?

Until recently, the industry relied heavily on low-on-the-food-chain “forage fish” (also called reduction fish by the industry) like herring, menhaden, and anchovy. They’re caught by commercial fishing fleets and rendered into fishmeal or fish oil, then used to feed everything from farmed salmon to cod. (It’s also used in feed for hogs and chickens.) But the amount of forage fish required to grow a pound of farm-raised fish has often been at an unsustainable ratio. At the same time, the global price of fishmeal and fish oil began to rise.

“The price of fishmeal is up to almost $1,500 a ton. Ten or 15-years ago, it was $500,” says Anthonie Schuur, an aquaculture consultant and board member of the California Aquaculture Association.

Worldwide, the aquaculture industry is expected to grow from 65.8 million tons in 2008 to a whopping 100 million tons by 2030, with no end in sight. According to the USDA, “Over the next 20 years, aquaculture production must increase by 500 percent.” Just like dominoes, that growth spurs a greater demand for nutrient rich feed, which can translate into further global pressure on forage fish — a prospect that worries environmentalists. According to a report by Oceana, aquaculture consumes more than 81 percent of the forage fish captured and “reduced” to fish oil, and approximately half of those captured for fishmeal.

But the tide is turning.

Protein by any other name will fatten a fish

“Five years ago, the farmed-salmon diet was 40-50 percent fish meal. Today, it’s in the teens somewhere,” says Rick Barrows, lead scientist and nutritionist with the USDA Agricultural Research Service. “There are a lot of different groups out there — the giant salmon industry, the shrimp industry — that want to get away from fishmeal and fish oil for ethical [and financial] reasons.”

Those alternative feeds include a range of solutions — everything from fishmeal derived from fish processing scraps, to algae-based feeds, spent distillers grains, and feeds produced from ingredients like barley, flax, and even insects.

The variables are mind-boggling. A trout, a sea bass, and a yellowtail fed the same algae-based diet will all perform differently, in part because of their own nutritional requirements, but also because of variations in the algae itself. Even fishmeal derived from forage fish like sardines or menhaden can have inconsistent nutritional values depending on the species, or even on the time of year they’re harvested from the ocean. For the increasingly industrial aquaculture industry, reliability of supply is crucial.

Which explains why soybeans seem to be the current industry darling, in part because of their consistency, availability, and affordability in comparison to fishmeal.

“Every aquaculture entity in the world is shifting their operations to more soybeans and less fishmeal,” says Schuur.

There are drawbacks to using conventional commodity soybeans. Besides the fact that 94 percent of soybeans are genetically modified and off limits to many European countries, many also contain undesirable anti-nutritionals, and ounce per ounce they provide less protein than traditional fishmeal.

High-tech soy

Meanwhile, a non-GMO soybean designed specifically for use in aquaculture feed is being developed by a surprising source — geneticist John Schillinger, founder of eMerge Genetics. Schillinger is frequently referred to as the “father of GMO soybeans” for his previous work at Monsanto. But when he launched Schillinger Genetics, Monsanto denied his request to use their patented soybean. Instead, he developed his current line of soybeans through breeding techniques, rather than genetic manipulation. He has also become at least somewhat critical of genetically engineered food.

“I made trips around the world, and there is a very strong preference for non-GMO — the extent of it was surprising,” he says.

Schillinger says aquaculture is his No. 1 business target, and he’s redesigned the soybean so it can be better utilized by fish.

“We’ve bred out some of the anti-nutritionals that make fish sick, with things like enteritis. We’ve redesigned the composition of the soybean to be higher in protein, which is important in fish diets. Fishmeal is 65 percent protein. Normal [commodity] soybeans would be at 48 percent. We’re selling ours in the high 50s and making strides to reach the 60 percent protein range,” says Schillinger.

Barrows says the aquaculture industry has indeed reached a point where they’re able to feed a carnivorous fish a seafood-free diet. And that’s exactly what’s happening in a 60,000-square-foot warehouse in southwest Virginia. Cobia, a carnivorous fish, is being grown by Virginia Cobia Farms without the use of fishmeal.

“We’ve eliminated fishmeal from the diet completely, and lowered our use of fish oils down to 4 percent,” says senior research scientist Steven Craig. “And we’re developing a patented technology to eliminate fish oil as well.”

The cobia are thriving on a diet void of fishmeal, and Craig says the company is on the verge of doubling their capacity, with a goal of producing 4.5 million pounds of fish by the 2013. The company also was given a “best choice” nod by the Monterey Bay Aquarium’s Seafood Watch program.

The amount of fishmeal and fish oil used to grow farm-raised fish has been one of the criteria used by environmental groups that rate fish for sustainability. “Using less wild caught fish to grow fish for human consumption is a good thing, and is a factor considered in the Seafood Watch guidelines,” says Ken Peterson, spokesman for the aquarium.

A small piece of a complex puzzle

Of course, all this brings us to the question: Should we be forcing a carnivorous fish to subsist on a plant-based diet? After all, pushing the feed envelope on land-based animals has resulted in unintended consequences. Is it unethical to take this approach with fish?

“It depends,” says bioethicist Bernie Rollin. “If the fish thrive on this diet, don’t get sick, haven’t experienced a shortened life span or problems in reproduction, then I don’t see it as an issue. With cattle, a certain percentage develop abscesses that involved suffering and condemnation of the carcass, so you might ask yourself, if it causes that, why do people do it? Because it’s only one in 10,000. I have no idea about the health of a [carnivorous] fish [on a plant-based diet], but if there is a negative effect, even if it’s justified by economic activity, then it’s a moral issue.”

So far, that doesn’t seem to be the case, which is good news. On the other hand, the practice hasn’t been around long, and there are bound to be unintended consequences.

And here’s the bad news for oceans advocates: Whether or not it’s fed to farmed fish, fishmeal is a valuable commodity, and will likely be allocated to other uses, such as feed for livestock, as world meat demand continues to rise.

Soy-based feeds will “permit expansion of the [farmed] fish supply that is already limited by a fully exploited fishery,” says Schuur. But, “whether or not using soy relieves pressure on natural fisheries is another question. Even if aquaculture drastically curtailed its utilization of fishmeal, fishmeal prices will remain high and fishing will continue as it has before.”

In other words, converting farmed carnivorous fish into herbivores may not make the tiniest fish in this food chain any less vulnerable. Nor does it replace the need for policy measures that manage forage fisheries.