Pet food, pigs, and poultry are taking a toll on the world's supply of wild fish

by Craig Weatherby

New York Times contributor Paul Greenberg is one of America's best writers on the subject of seafood.

Last month, he penned an op-ed piece in which he mourned both the death of his cat, Coco, and the demise of the hundredsif not thousandsof wild fish that died to feed his beloved feline.

We have to admit that this is one threat to wild fish we hadn't really focused on.

Instead, we've been alarmed by the burden that salmon farming places on the same small “forage fish” that support top predator species such as tuna, striped bass, cod, salmon, swordfish, and sharks … as well as whales, dolphins, porpoises, seals, sea lions, and seabirds.

Feeding fish to cats and livestock... an unnatural act

The term forage fish refers mainly to filter feeders like herring, sardines, smelt, menhaden, and anchovies, but also encompasses small squid and shellfish.

Back in 2000, Stanford University economist Rosamond Naylor published her calculation that it took three pounds of wild fish to provide enough food to grow one pound of farmed salmon.

As Naylor wrote, “Farming carnivorous species requires large inputs of wild fish for feed. On balance, global aquaculture production still adds to world fish supplies; however, if the growing aquaculture industry is to sustain its contribution to world fish supplies, it must reduce wild fish inputs in feed and adopt more ecologically sound management practices” (Naylor RL et al. 2000).

Under public pressure, some salmon farmers have since reduced that ratio substantially, though it remains unacceptably high in the salmon farm industry overall. (To cut back on omega-3-rich fish meal and fish oil, farmed salmon are fed omega-6-laden grain instead, which makes them less healthful for humans.)

But as Greenberg points out, an astonishing one in three wild fish caught are ground into fish meal and fish oil, for feeding to pork, chickens, and pets. (Dietary supplements for humans account for about six percent of all fish oil produced.)

And about one in ten wild harvested “forage” fishsmall species like menhaden, sardines, and herringgo into pet food.

This matters both because it impacts the overall ocean ecosystem, and because the larger fish favored by most humans depend entirely no these species for survival.

Factory-farmed pigs consume about one-fourth of all fish meal and oil, while poultry devour almost as much.

So, as Greenberg noted, “…even when Coco ate chicken, indirectly he was still eating fish.”

Greenberg wasn't excusing the farmed salmon industry but, as he noted, salmon “naturally eat other fish, while terrestrial livestock and pets eat them because humans have deemed it commercially expedient. If we are serious about curtailing our impact on the oceans, we should insist that land-based farm animals stick to land-grown feed.”

And fast-rising demand for meat in East Asia is add another huge market that wants to turn wild fish into livestock and fish feed.

Greenberg urges the Obama administration to develop fish meal and oil substitutes from algae, agricultural byproducts and other land-based sources.

Vegetarian pet foods do exist, but must be supplemented with essential animal micronutrients not present in plants.

And Greenberg makes the point that those who would hesitate to feed a cat vegan fare should consider each furry pet's heavy oceanic impact before getting one.

He's considering replacing Coco with a vegetarian substitute: “Lately, I've had my eye on a guinea pig.”


  • Greenberg P. Cat Got Your Fish? The New York Times, March 22, 2009. Accessed online at
  • Naylor RL, Goldburg RJ, Primavera JH, Kautsky N, Beveridge MC, Clay J, Folke C, Lubchenco J, Mooney H, Troell M. Effect of aquaculture on world fish supplies. Nature. 2000 Jun 29;405(6790):1017-24. Review.