Aquaponics: Part I

Try to think about the last time you were strolling through a grocery store and you began to feel that slight chill that creeps out from the refrigerated meat and seafood cases and into your bones as you peruse the fresh roasts and sirloin steaks. For me that chilly feeling always takes me back to my childhood — wandering through a grocery store with my mother, teeth chattering, anxiously awaiting the moment when we can move on to warmer and more kid-friendly aisles. The candy aisle perhaps?

These days, I rather enjoy a chilly stroll through the refrigerated section. It has now become a veritable geography lesson. To think, there is seafood that travels to you all of the way from China, Thailand, Ecuador, and beyond. During my childhood it was much the same, but how was anyone to know where the food was from unless you asked the butcher? Today there are a plethora of choices to make. What are you going to serve the kids tonight? Salmon fresh from Alaska? How about some Tilapia from China (previously frozen of course)? For something really exotic, try some Chilean Sea Bass.

For these food geography labels you can thank President Bush and the Farm Bill of 2002**. Part of the Farm Bill requires stores to provide Country-of-Origin labeling (COOL) for all meats, fish, and perishable agricultural commodities. Now instead of just choosing between green apples or red apples, consumers can choose to eat red apples from New Zealand (approximately 9,500 miles from Cottage Grove, OR), or red apples from the Willamette valley (approximately 15 miles from Cottage Grove).

Back in the fish case, the labeling law takes matters one-step further. The fish must be labeled with Country-of-Origin and an indication of whether the fish was farm-raised or caught from the wild. This provides the discerning consumer with another level of informed decision-making power. Let’s have a look at the difference between farm-raised and wild-caught fish.

It is generally believed that nutritionally, wild-caught fish are superior to their farm-raised counterparts. In the wild, fish have to fight their entire lives to survive; eat or be eaten. When farm raised, fish tend to be fattier and less vital. This is important when considering the effect of environmental pollutants on fish populations.

Aquaculture

Many wild fish exist in rivers, streams, and areas of the ocean that are polluted by industry and agricultural wastes. Most fish will bio-accumulate pollutants in their fat. While wild fish tend to be less fatty than farm-raised fish, one should still be cautious about eating fish wild-caught in regions known to be polluted. Even so, the ocean is a big place and we haven’t managed to pollute the whole thing yet.

At this point in the comparison it makes sense to split fish farming

into three distinct categories. The first category, open water farming is where fish are raised in high densities, contained by large nets in the ocean. These fish are subject to the toxicity of the local water, and can be unhealthy due to the overcrowding of their enclosures. When treated with antibiotics, they can negatively affect the nearby wild fish populations if they escape the nets (which happens often). See the graphic on the opposite page.

The other two techniques for fish farming are very different approaches to the same general method: raising fish in large tanks on dry land. The most widespread method that I’ll refer to as “conventional aquaculture” uses constant inputs of fresh water, commercially produced fish feed, and generates a large volume of wastewater, which is treated as sewage.

The other system is a more sustainable approach as compared to the conventional method. This is known as an integrated recycling system, or a recirculating aquaculture system (RAS). In this system the water is pumped out of the fish tanks and travels through a serious of troughs that are filled with living plants and gravel. The plants take up the pollutants generated by the fish as fertilizer before the water is returned, clean to the fish tanks. One of the largest problems with conventional aquaculture is that it can use a million gallons of water per acre (about 1 m³ of water per m²) each year (Wikipedia). In the RAS system, water in only lost from evaporation and transpiration.

From an environmental standpoint, the difference between a system that pollutes millions of gallons of water per acre per year and a system that only looses a few thousand gallons of water per acre to evaporation is obvious.

Environmental considerations aside, healthy and happy fish are good for you to eat. Stressed and sick fish are bad news. Studies show that the factor that most adversely affects fish health and bio-accumulation of pollutants is what the fish are eating. This is one of the major disadvantages of fish farming.

Most commercially farmed fish with the exception of tilapia, carp, and catfish, are carnivorous. Commercial fish feeds contain high levels of animal proteins. These proteins are often fish meals (ground up fish) derived from fish lower on the food chain (anchovies, menhaden, etc.). Studies have found that these fish meals to contain high levels of PCBs (Polychlorinated biphenyls). Without getting too technical, I’ll just say that PCBs are really bad for you, and you should avoid them at all costs.

In RAS systems, which are usually smaller scale, feeds are often derived mainly from aquatic plants growing in the water filtration troughs. Therefore, avoiding the importation of polluted inputs into the fish’s lives.

In summary- Farm Raised: Likely polluted and bad for you, and bad for the environment unless they were grown in a sustainable RAS system, of which there are very few operating on a commercial scale.

Wild Caught: Possibly polluted, depending on where it was caught, and not likely to be around for too much longer due to over fishing, environmental pollution, and oceanic oxygen depletion.

This all comes back to you and I, standing in front of the seafood case, slightly chilled by the cold air and the nutritional and environmental implications of eating ANY of the fish so tantalizingly displayed in front of us. Given this choice, myself and the other folks at Aprovecho have decided that if we want fresh, local, unpolluted fish, we’ll just have to raise them ourselves.

Read part II

** If haven’t been seeing COOL labeling in your grocery store, it may be because lobby pressure delayed parts of the law from going into effect until March of 2009.

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