Feeding The Animals We Eat: Fish Farming vs. Land Farming

By Scott Nichols

What does the future look like for our food-production systems? In short, it can’t look like the present.  Our current agriculture uses 38 percent of the world’s land and 70 percent  of its water.  But experts say we need to double (or nearly so) our food production by mid century.  With our current practices, we aren’t poised to deliver anything near that amount — 70 percent can’t be doubled nor, practically, can 38 percent.

To meet our future food needs, agriculture must be done quite differently.  Discontinuous change is needed as we learn how to do more with less.

In a recent article about changing agriculture practices, Jillian Fry of Johns Hopkins University and her colleagues address changes in farmed fish diets. In their article, titled  Environmental Health Impacts Of Feeding Crops To Farmed Fish, they discuss the increasing use of crop-based ingredients to replace ingredients that come from wild-caught fish. Of the change, they write: “ ... Multidisciplinary research is needed to understand the ecological and environmental health implications.”

Fair enough. As we face crucial choices in meeting future demands for nutritious food, it’s important to examine the possible ramifications of those choices before they are made.

Curiously, however, while the article has a lengthy review and commentary on crop production practices, it doesn’t speak to its title.  We are left to wonder:  Just what are the environmental health impacts of feeding crops to farmed fish? What role should aquaculture play in our food future?  How does fish farming compare with terrestrial animal agriculture in the use of crop-based feeds?

More helpful is an analysis to compare the efficiency with which crops are used by both terrestrial and aquatic farm-raised animals. Here, I compare the crop-based resources needed to raise salmon, beef, pork and chicken.

Agricultural resources: What does it take to feed the Animals we eat?

Salmon. From the aquaculture side, let’s look at salmon farming.  As carnivores, salmon historically were fed diets derived largely from fish meal and fish oil.  With the rapid growth of salmon farming that started in the mid 1980s, it became clear that catching wild fish to feed farmed fish isn’t sustainable from either an environmental or a business perspective.  As a result, salmon diets have changed dramatically over the last decade with fish oil and fish meal being replaced by vegetable oils and proteins, largely canola and soy, respectively.

To raise a pound of a vegetarian salmon, one raised on a diet of canola oil and soy protein, the fish would consume 0.84 pounds of canola seeds and 0.69 pounds of soybeans.  However, most of us eat salmon filets so, actually, we really only eat about 64 percent of the whole salmon. That means it takes about 1.3 pounds of canola seeds and 1.1 pounds of soybeans to put a pound of salmon on the dinner table.

Red meat. Beef and pork have diets that include many cereal crop ingredients.  As a useful simplification, I combine them together as one entity: cereals. With that said, a pound of pork we eat consumes between 2 and 3 pounds of soybeans plus 5 or 6 pounds of cereal.  Beef cattle, raised on feedlots starting at 500 pounds up to their harvest weight of 1,300 pounds, need about 10 pounds of cereal to provide a pound of edible meat.

Poultry.  It takes 2 pounds of feed to raise a pound of chicken. Of that pound of chicken, about 50 percent is meat and skin, so it takes about 4 pounds of total feed to put a pound of chicken on a plate.  However, chickens, as omnivores, have a more complex range of dietary ingredients including other animal byproducts. So, their use of crop plants is certainly less than 4 pounds.

As we consider resource utilization in our future food supply, quite clearly salmon offers the promise of producing a lot more food with a lot less input.  This makes sense.  For a few reasons, fish are the most efficient of farm animals.  They don’t use any energy to maintain their body temperature as land animals must.  Another energy benefit for fish is that they don’t spend calories working against gravity. Furthermore, the freedom from gravity also removes the need to spend energy building a bone structure to support their weight.  So, we eat a much greater fraction of a small-boned fish than we do from large-boned land animals.

Public health: For nutritious food, what should we eat?

Beyond resource efficiency, fish are are nutritionally superb; the FDA and USDA both recommend increasing our fish consumption to improve our health. The favorable health outcomes of eating fish are remarkable. For instance, in a Harvard School of Public Health meta study, scientists found that eating two servings of oily fish per week “reduces the risk of dying from heart disease by 36 percent."

A large part (but certainly not all) of the nutritional benefit of fish comes from the essential omega 3 fatty acids, EPA and DHA, derived from the fish oil included in aquaculture diets.  With aquaculture’s move to lower use of marine ingredients, it’s reasonable to expect omega 3 levels will decrease in fish, as Fry et al point out.

Farmed fish, however, continue to be excellent sources of omega 3s; they are present at levels tens to hundreds of times the levels in beef,  pork, and chicken.  With the inexorable move to vegetarian diets in fish farming, new sources of omega 3s must be found to include in fish diets. It is encouraging to see that some groups are working to develop algae, yeast, and plants as sources of omega 3s.

We need more sustainably-raised and nutritious food.  Aquaculture is certainly poised to contribute meaningfully to our future food needs.  Fish farming makes a much smaller call on resources than other types of animal agriculture, and it provides nutritious food that public health experts say should be a larger part of our diets.  It’s not the sole answer to “What’s for dinner?” in 2040.  But it will be an important part of the answer.

Image credit: Aquaculture Stewardship Council 

Scott Nichols is the founder of Food’s Future, LLC where he advises businesses to help them create economically and environmentally sustainable aquaculture ventures that provide seafood to an expanding world.  He is a speaker on the role of aquaculture in our future food supply and is a member of the board of directors at the Aquaculture Stewardship Council.