Going vegetarian or vegan has long been a big part of the environmental movement in general, and the climate movement in particular. The reason is pretty simple – producing a pound of meat generally requires around ten times as much resources as a pound of whatever food that livestock eats. Animals have to eat, and only a fraction of what we consume is turned into muscle.

We generally think about this in terms of land animals – cows, chickens, sheep, etc., but this also applies to fish. Raising something like a salmon is going to require more energy than raising the smaller fish that salmon eat. That means that if we want to continue using fish as a source of protein, it would probably be a good idea to farm those fish that are cheapest to raise, and as much as I love salmon, farming it is not a good use of our resources.

Increased demand for seafood has driven an expansion in aquaculture. However, 90 percent of commercial fish feed is made from food-grade fish such as sardines and anchovies that are edible to humans. To analyze the efficiency of aquaculture in terms of net nutrient production, researchers first quantified the volume of micronutrients and wild fish retained by fish-fed farmed salmon using 2014 data on Scotland’s farmed salmon production. They calculated the volume of micronutrients used as aquaculture inputs and compared it to salmon aquaculture nutrient outputs. Using these data, the researchers modeled several seafood production scenarios to assess potential sustainability benefits of alternative seafood systems.

The researchers found that in 2014, 460,000 tonnes of wild-caught fish were used to produce 179,000 tonnes of Scottish salmon. 76 percent of the wild-caught fish were edible for human consumption. The data also suggest that multiple alternative seafood production models would be more efficient in terms of net nutrient production, so could significantly reduce wild fish capture while increasing global seafood supply. However, these data were limited to only one year (2014). Future studies are needed to better understand how to operationalize a global shift away from farmed fish toward sustainable fisheries.
According to the authors, “Feed production now accounts for 90% of the environmental footprint of salmonid production. Allowing salmonid production to expand further via its current approach will place exceptional stress on global fish stocks already at their limit. Our results suggest that limiting the volume of wild-caught fish used to produce farmed salmon feed may relieve pressure on wild fish stocks while increasing supply of nutritious wild fish for human consumption.”

The authors add: “Nutritious fish stocks are being squandered by salmon farming. Scientists reveal that eating the wild-caught fish destined for salmon farms would allow nearly 4 million tons of fish to be left in the sea while providing an extra 6 million tons of seafood.”

I spent a semester in Tanzania, back in 2006, and one thing I noticed there was that many markets would have a bin or even just a pile of tiny dried fish that you could buy in bulk. It was basically an easy way to add protein to a meal, by just tossing a handful of dried minnows into whatever you’re making. They did not taste as good as salmon, but they get the job done, and if you’re a decent cook and have access to spices, you can do good things with them.

As with so many other things,  I think our best path forward is to work on having a diverse array of options for anything we need to do, so that a catastrophic failure in one area, like a livestock epidemic or extreme weather event, won’t be enough to cause mass starvation or malnutrition. The way we do things now is not the way things have to be.

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