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Something's Fishy About Aquaculture

© Kenneth Friedman

For more than 30 years, reputable sources such as the U.N. Food and Agriculture Organization (FAO) have been warning that some commercial fish stocks, called fisheries, are overfished beyond their ability to sustain themselves--to reproduce. Fishermen (sometimes called "fishers") have caught too many fish and shellfish without leaving a breeding population capable of reproducing in the numbers needed to support continued commercial fishing. The list of depleted fisheries has only gotten longer over the years. Okay. "No biggie," many people say. "Aquaculture will produce the fish we need."

But aquaculture brings many of its own environmental problems (diagram) and hasn't been able to come even close to matching the potential of properly managed natural fisheries. Let's take shrimp, a big aquaculture product, as an example.

To farm shrimp you need three primary resources: shrimp, ponds and clean water. Shrimp are no problem, but ponds, which by necessity are located along coasts, require land, and suitable land isn't all that plentiful.

In many countries the land sacrificed for ponds happens to be mangrove forest, a unique coastal ecosystem necessary for the survival of aquatic and semiaquatic species, birds, reptiles, amphibians and even mammals, such as the tigers of the Sunderbans in India and Bangladesh. Mangroves filter polluted water and protect coastal areas against tropical storm surges, which produces erosion, a problem we won't go into here. So, cutting mangroves is a bad move.

As for clean water, the third aquaculture requirement, in most countries, water competition among agriculture, industry and domestic uses is intense so sharing water it with aquaculture adds another environmental another pressure to problems in general.

Now, suppose your shrimp ponds are full of shrimp. Yum. As anyone with a fish tank will tell you, shrimp are not all that's in the ponds. You've got shrimp waste, decaying leftover food and decaying dead shrimp, which can breed viruses that lead to epidemics when they spread to neighboring ponds. Yuk.

Contaminated ponds also generate nitrogen and phosphorus. So you add chemicals and antibiotics to keep the shrimp healthy. Then this brew of feces, ammonia, decayed food, dead (decaying) shrimp, nitrogen, phosphorus, antibiotics and chemicals eventually flows where? Right! Into coastal estuaries. Want to go for a swim? Want to try and survive as a wild fish or shellfish? All that contaminated water contributes to eutrophication in which ponds, lakes, and estuaries die from lack of oxygen, and toxic algal blooms, which kill aquatic life and make shellfish inedible (at least temporarily). Naturally, local fishermen and consumers won't be happy.

So much for aquaculture. A good idea, but one that still requires sound environmental management. At several research stations around the world, people are studying ways to filter the dirty water for reuse or release. Disseminating best-practice water

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