An Urban's Rural View

In theory, fish farming ought to be good for the environment. Overfishing has depleted popular wild-fish stocks; demand for fish continues to rise. Wouldn't it make sense to meet more of that demand with farmed fish and cut back on pillaging the oceans?

In theory, too, aquaculture ought to be good for those who practice it. Protein-per-acre yields are high, even in areas that won't support other kinds of food production. In aquaponic systems farmers can grow both fish and vegetables. Shouldn't folks be racing to become fish farmers?

Some are. Aquaculture output worldwide is on the rise. By at least one estimate (http://tiny.cc/…) farms now produce more pounds of fish than beef, and people are eating almost as much farmed fish as caught fish.

Though a lot of the boom is in Asia, there are important implications for American farmers. In China alone, according to the American Soybean Association, aqua-cultural demand for soybean meal comes to six million tons a year (http://tiny.cc/…).

But for both the environment and farmers, aquaculture still works better in theory than in practice.

Farm-raised shrimp, salmon and other carnivorous fish are typically fed harvested fish or fish byproducts, so there's still pressure on the oceans. Even if the feed derives from "trash fish" that humans don't favor, there will be fewer trash fish for larger fish in the wild to consume. Converting these cultivated carnivores to vegetarianism would be good for both farmers and the environment.

Whatever they use as feed, fish farmers have to do something with the waste. If, as critics say (http://tiny.cc/…), the average salmon farm produces as much waste as a town of 65,000 people, disposing of that waste by letting it drift or seep into rivers, lakes or oceans is problematic.

And yet that happens. I saw it happen at a shrimp farm in Thailand I visited a couple of decades ago.

In theory aquaponics solves most of the waste problem. The fish feed on the plants and the plants feed on the fish waste in a virtuous ecological loop. In practice, aquaponics is nowhere near that simple. Making it work takes skill and luck. Doing it at commercial scale is even harder.

Nor is fish farming an economic slam-dunk for the farmer. You can't break into it without figuring out how you're going to sell what you raise, which will be easier in some places than others.

As in any form of farming, Murphy's law applies. Capital is at risk. Diseases can decimate the crop. Prices and costs can swing wildly. Lightning can strike.

And in some cases aquaculture can resemble dairy farming in its unrelenting demands on the farmer's time: Seven days a week, several times a day, the fish must be fed.

A Wall Street Journal article (http://tiny.cc/…) on Bluefin-tuna farming in Japan ties some of these threads together. It has taken researchers at Kinki University in Kushimoto 45 years to domesticate this sashimi-grade species and in some ways they're still struggling.

Every time they solved one problem another popped up. It took ten years to get the fish to lay eggs in captivity. Then one day they stopped laying and it took another 11 years to figure out why: Bluefin tuna are sensitive to changes in water temperature.

"In the summer of 1994," the Journal said, "the fish finally produced eggs again. The researchers celebrated and put nearly 2,000 baby fish in an offshore pen. The next morning, most of them were dead with their neck bones broken. The cause was a mystery until a clue came weeks later. Some of the babies in the lab panicked when the lights came on after a temporary blackout and killed themselves."

Now they keep the lights in the pens on all the time.

Some sashimi connoisseurs complained that the farmed tuna didn't taste as good as wild-caught fish. Researchers had to adjust the diet, reducing the vegetable component, which in any event can't exceed 30% or growth is stunted.

It takes 15 pounds of feed fish to produce a pound of Bluefin-tuna meat, and the tuna leave a lot of the feed fish uneaten, letting it sink to the bottom. The researchers are experimenting with artificial feeds.

And they have to worry about the narrow gene pool. All of their fish have inherited the same ancestors. Efforts to bring in wild-caught fish for breeding have failed.

Yet for all the practical problems these and other efforts at aquaculture have encountered, the solutions keep coming, too. There's still a gap between theory and practice but the gap is narrowing. A lot of work is going into narrowing it further. A lot is at stake.

Stay tuned.

(CZ)

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