bags of fish feed

Gas Guzzlers of the Sea

posted by Veronique Koch on 07 February 2013

If you had a new car that got only 5 miles per gallon, you’d say it wasn’t a very fuel efficient car, right? Well in fish farming, that gas guzzler would be called Tuna.


In Fish Meat, we explore the world of fish farming and see that the most modern methods are not always the best. In this case, farming tuna has proven to be the least sustainable form of aquaculture. Why? Because they eat so much!


For every pound of tuna produced, they need to eat 20 pounds of fish feed. And what is that feed made of? Other fish! So while farming fish is a good idea to take some pressure off our oceans to produce wild fish, those farmed fish are actually eating wild fish. Seems kind of backwards, doesn’t it?


In fish farming lingo, the efficiency is called the feed conversion ratio. It’s calculated by dividing the mass gained by the mass eaten (so tuna’s FCR would be 20) If you were looking for a “greener” fish, the Prius of the sea, we would recommend checking out the mostly vegetarian species that would not require any (or as much) wild fish, making its feed conversion ratio very low. A great and easily obtainable vegetarian species is the tilapia. They can eat anything from duckweed to corn.


Careful though, not all farmed tilapia are raised vegetarian. A good rule of thumb is to buy US farm raised tilapia, since they are likely raised vegetarian and in a closed circuit-tank (meaning no waste goes out to pollute the surrounding waters). Latin American tilapia are a good alternative, too, according to the Seafood Watch program.


The most important thing is that you get more protein out of the fish than it takes to raise it. And with tilapia at a feed conversion ratio of 1.6 to 1.8, that’s a whole lot of bang for your buck.

2 thoughts on “Gas Guzzlers of the Sea

  1. Adam says

    I did not know.

    1. Veronique Koch says

      Glad you could find it interesting!

Leave a Reply

Your email address will not be published.