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Can fish production save us from ourselves?

By Bill Manci
September 7, 2019
Can fish production save us from ourselves? image

Anyone concerned about climate change should pay attention…and that means you…and you…and you too! Yes, we all must be concerned about climate change, regardless of whether it is a result of natural climatic cyclicality, or because of human activity.

OK, I’m going to get off of the fence on this one and say it’s man-made—caused by human activities. I usually try to stay neutral because I’m not a climatologist. But, as a scientist, I am compelled by recent evidence that strongly suggests the contribution of greenhouse gases to global warming and climate change.

And this problem is only accentuated by the fact that, because of increasing population, we will need more and more food to satisfy us. About 10 billion people will live on the planet in 2050—up from the current 7.5 billion1. So, a reasonable person would think, well, it’s one-third more people, so we need one-third more food. Not so.

The World Resources Institute paints a rather solemn picture of our dietary future in a recent report without action on our part1. Scarcity of food calories, insufficient land for agriculture, and a significant increase in greenhouse gas emissions are just some of the challenges we face.

According to a recent article on CNN2 and quoting calculations from the World Resources Institute, the demand for food will increase by more than 50 percent, given the higher average standard of living that is expected to exist in 30 years.

The article goes on to say that beef production accounts for 41 percent of livestock greenhouse emissions, and 14.5 percent of emissions overall. The suggestion in the article is that Americans need to eat less beef—and for that matter, dairy as well (you get dairy from cows; they all eat the same stuff.)

Well, I will put myself out on a limb here and say, the chance of that happening is about as likely as Americans giving up cars. It’s not going to happen! While per capita consumption may fall, total consumption will rise with the increasing population. As the advertising slogan says, “Beef: It’s what’s for dinner.”

Making things worse is all the space that cattle need and use. If we keep on the current path with beef, we will need additional space - the equivalent size of India to accommodate our tastes and demand1. That’s quite frightening, considering additional arable space of that magnitude simply does not exist!

Wait! There’s more bad news! (Spoiler alert: There’s good news at the end.)

Beef cattle and all ruminant cattle have the nasty habit of the expelling methane gas as they digest their food. We continually hear about carbon dioxide (CO2) as the preeminent greenhouse gas that we need to control. But methane is 80 times more efficient at trapping heat in our atmosphere than carbon dioxide3.

Here’s how dire our situation may be. Two scientists actually propose turning atmospheric methane into carbon dioxide because of the beneficial trade-off in heat-trapping capability3. Under our current circumstances, that seems very reasonable. How freaky is that? This is the corner into which we have painted ourselves!

While I believe the total consumption of beef and dairy will continue to rise on an absolute basis, I do think per capita consumption will fall, based on what appears to be people’s “new-found” appetite for all things vegetarian, and the unwavering increase in demand for fish and seafood4. I want to focus on the second part of that equation.

We have known for a long time that fish and shellfish are the champs at converting food to edible flesh—better than chickens, better than hogs, and certainly better than cattle5. On average, finfish and shellfish convert feed at a rate of about 1.5 kg of feed for every kg of live fish. Chickens and other terrestrial livestock—especially cattle—don’t stand a chance of beating fish at this game. The best beef cattle can do is about 6 to 1 (usually worse at 8 or 10 to 1 or higher), and that’s horrible.

You probably wonder how fish make feed conversion look so easy. It all boils down to their environment. Finfish and shellfish “decided” evolutionarily that maintaining a constant body temperature is too difficult and too energetically costly in water. Only very large marine mammals with much smaller surface to volume ratios (heat loss occurs much more slowly) such as whales and seals can maintain body temperature and that requires the help of thick layers of insulating fat and blubber. Instead, finfish and shellfish have body temperatures at or very close to their surrounding aquatic environment. That means all the calories they consume can be spent on movement (a very small percentage) and growth, with virtually no consideration for heating or cooling.

Consider this as well. Seventy percent of the earth is covered in water. Why not use some of that space for food production? Land is becoming too precious for us to pasture cattle and other terrestrial livestock at low densities.

Food production in water also provides the added benefit of a three-dimensional space. Not only is the surface available, but the depths below the surface as well.

So, if you look at the situation objectively, it makes the most sense for us to focus our livestock efforts away from terrestrial species and toward aquatic species. In other words, aquaculture. This includes the production of aquatic plants—30 million metric tons in the year most recently reported4. Some marine macroalgae are directly consumed by people, such as nori for sushi, or “sea lettuce.” Other aquatic plants become fertilizer for terrestrial agriculture or cosmetics, and some provide protein and fat extracts for animal feeds6.

It’s time for us to develop our planet and the resources we require in more imaginative, innovative, and sustainable ways. In all likelihood, our long-term survival as a species depends on it.


1Searchinger, T., R. Waite, C. Hanson, and J. Ranganathan. 2018. Synthesis report: creating a sustainable food future: a menu of solutions to feed nearly 10 billion people by 2050. World Resources Institute, Washington, D.C. 92pp.

2Christensen, J. 2019. To help save the planet, cut back to a hamburger and a half per week. CNN.

3Jackson, R., and P. Canadell. 2019. A crazy-sounding climate fix. Scientific American 321(2; August):10.

4FAO. 2018. FAO yearbook. Fishery and aquaculture statistics 2016. Food and Agriculture Organization of the United Nations.

5Anonymous. 2018. Feed conversion ratio. Wikipedia.

6Chase, C. 2019. Veramaris opens USD 200 million algal oil facility. Manci is president of Fisheries Technology Associates, Inc., a Fort Collins, Colorado-based aquaculture, aquaponics, and fisheries consulting firm.

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