The Case For Aquaculture

Fourth in a series on aquaculture. Our food supply needs, roughly, to double by mid-century. Even with evolving improvements, terrestrial agriculture will be severely challenged to meet our requirements. The discontinuous change aquaculture provides offers hope that we will meet our need for healthy and nutritious food raised sustainably.

Two facts about our planet are on a collision course. The amount of land available for growing food on earth is fixed, or mostly so, at about 38 percent of the planet’s non-ocean surface.  That land needs to feed a worldwide population expected to grow from seven to nine billion in the next 25 years. 

Not only will there be more people but their composition will change.  Wealth is growing rapidly and, with expanding wealth, comes a change in peoples’ desire for what’s on the dinner table.  These imminent increases, wealth and population, will place unprecedented demands on our food production resources. 

To avert potentially catastrophic food shortages, the UN Food and Agriculture Organization (FAO) says we will need 70 percent greater food production by 2050.  Others say the needed expansion is a doubling. However, agriculture currently uses about 70 percent of the world’s water along with 38 percent of the world’s land.  Neither can be increased by the amount required.  It’s clear that our agricultural future is not our current agricultural practice. We need systemic changes in food production.

How do we create a future that is not a Hobbesian battle with continual scarcity? 

One way could be to turn to the sea.  After all, the oceans cover 70 percent of the planet but account for only 5 percent of the protein we eat worldwide.  Moreover, experts on what constitutes a healthy diet agree that increasing fish consumption makes gobs of good sense. 

In the US, every five years Dietary Guidelines (DG) are set forth jointly by the USDA and the Department of Health and Human Services.  The purpose of the Guidelines is to help us all discover our path to a “healthy eating pattern”. 

Each iteration of the Guidelines begins with an extensive review of scientific literature. In the 2015 version, the authors and contributing scientists of the Dietary Guidelines Advisory Committee  (DGAC) were charged to:  “. . determine the current composition and quality of the American diet and areas of public health concert; trends in the Nation’s leading diet- and lifestyle-related problems; the established, measurable pact of overall dietary patterns and physical activity on short- and long-term health outcomes; the most effective methods of improving dietary patterns and physical activity to achieve favorable health outcomes in Americans 2 years and older; and sound strategies to help promote a healthy, safe affordable and sustainable food supply.”   

In meeting the need to, “. . . achieve favorable health outcomes”, the DGAC emphatically recommends we alter our diets to include more fish. 

The favorable health outcomes of eating fish are remarkable. For instance,  in a Harvard School of Public Health meta study, scientists found that fish consumption “reduces the risk of dying from heart disease by 36 percent”.  This aggregates to some 266,000 lives saved annually in the U.S.

To gain the benefits of fish, the DGAC recommends we eat 8 ounces weekly or 26 pounds per year. 

This is considerably more than our current intake.  The 2013 per capita fish consumption in the US was but  14.5 pounds per year.   The demand is clear but how we meet it isn’t. How do we provide the additional 11.5 pounds per person? 

This, it turns out, is a difficult question.

The FAO undertakes a biennial oceans assessment called State of Worlds Fisheries and Aquaculture.  In the 2014 edition, they conclude that 90% of wild fisheries are harvested either at or above their sustainable limit.  This means there is no way wild fish supplies can keep up with increasing demand.  Most likely, they should probably decrease to allow challenged stocks to replace themselves. 

This puts us in a bit of a pickle: we need to reduce the amount of fish we capture and we need to eat more fish.

The former demands that we immediately decrease the pressure on wild fish through approaches such as the creation of marine protected areas and changing fisheries policy. Such measures, though, will diminish the amount of wild caught fish available to us for the foreseeable future.  It is neither feasible to capture more wild fish nor is it realistic to expect harvests to remain at their current levels. 

It’s clear: if we are going to continue to eat fish, we need to farm them like everything else we eat. That we raise animals on land is broadly accepted.  Curiously enough, this sometimes (often?) is not an accepted practice for the ocean. However, as a central source of sustained human nutrition, it makes no more sense to rely upon hunting wild animals in the oceans than it does to rely on hunting wild animals on the land.

The encouraging news, however, is that the potential productive capacity of aquaculture is enormous. Let’s wander through a thought experiment.  Suppose aquaculture provides the difference between our current per capita fish consumption of 14.5 pounds and the 26 pounds the DGAC recommends we should consume.  If you design a hypothetical fish farm that is 16 yards deep and has 22 pounds of fish per ton of water, it requires a bit less than 9 square miles of ocean surface area to provide all that fish-11.5 pounds per year for every person in the US.  These 9 miles come from US coastal waters of around one million square miles.

Another way to think about the hypothetical fish farm is to contrast it to Duplin County, NC.   With its 822 square miles and 59,000 people Duplin County produces more hogs-about 2 million per year- than any other county in the nation.  The result is about 280 million pounds of marketable pork.  Our hypothetical fish farm?  It produces 3.7 billion pounds of marketable filets. I’m the first to admit that this is a loose comparison, however, the one thing it does do is to call our attention to the productive capacity of aquaculture.

As I opened this article I mentioned that our agricultural system soon needs provide much more but without using commensurately more resources.  Perhaps we even need to use less.  It’s axiomatic but I’ll say it anyway. All agricultural development must use the most environmentally attentive practices available. 

That’s good but it’s not enough if you view that sustainability is a process rather than a goal.  Constant improvement is also needed.  This is true for agriculture done on the land or in the ocean.  In my next article, I’ll outline the challenges aquaculture faces on it’s sustainability journey.

©Scott Nichols 2016

    • Sebastian Belle
    • February 10, 2016

    Scott great article. A few other important factoids about terrestrial agriculture and aquaculture. We are currently pumping 87% of the worlds know aquifers in excess of their recharge rates, we are essentially mining water. Know reserves of phosphorous, a vital mined plant nutrient, run out in 2030. Obviously we will learn how to conserve water better and we will search for new phosphorous sources and learn how to recycle it BUT These two factors, combined with the limits on arable land have already begun to impact productivity on land farms. Since 2009 yields in Maize, wheat and rice have essentially been flat after increasing annually for the prior 20 years. As you point out our terrestrial resources and productivity will not meet all our needs.

    Another reason that aquaculture is going to play such a big role in world food sources is that aquatic production of both plants and animals is inherently more efficient that land production for two simple reasons. Aquatic plants and animals burn little or no energy to maintain their position in the face of gravity or maintain their body temperature in the face of environmental temperature changes. They use either lipids in their tissues or air in swim bladders to float and they are the same temperature as their environment. These two physiological factrs mean that in water animals and plants are anywhere between 10-20% more efficient at converting the energy they consume to growth.

    • Thanks Sebastian. These are really nice adds.
      I’d also say that one more advantage for fish is that there is no need for a thick and heavy skeleton. From an agricultural perspective, we eat more of what we grow.

    • Nancy Nichols Bolomey
    • December 9, 2015

    Wonderful article. I can’t agree more. We have been giving the salmon population a boost via the hatcheries for years and years. The question is are we killing our oceans?

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