Man's Best Friend?

Imagine the perfect fish. It would be plentiful, but would not harm other fish. Delicious to eat, it would also be such a powerful jumper and swimmer that sportsmen would revere its ability as a fighter. As an extra benefit, this paragon would feast on something that nobody wants. Does such a fish exist? Indeed, yes. It is called the white amur (Ctenopharyngodon idella), a member of the carp family that is native to eastern Asia, where it is prized as a delicacy. Three feet in length and 70 lbs. in weight, an adult amur just loves to eat--so much, in fact, that it is said to consume old shoes and decayed clothes. But mostly it gobbles aquatic weeds and, above all, algae.

These tiny plants, fertilized by nutrients in sewage and by the runoff of farm nitrates, explode into prodigious "blooms" that can cover entire lakes with a pea-green coat. When the algae die, they sink and decompose, depleting the lake's supply of oxygen and hastening its "death"--as has happened in Lake Erie.

Enter the white amur, which operates like a biological vacuum cleaner, eating up to four times its own weight in algae every day. In 1963 the U.S. Bureau of Sport Fisheries imported some amurs from Malaysia, later turned 70 of them over to the Arkansas Game and Fish Commission for study. Outlets were carefully blocked with wire mesh to prevent any from escaping. Still, accidents will happen, and last spring Arkansas biologists found a few white amurs in the White River, a tributary of the Mississippi. Since eight years of research had disclosed no faults in the amur, and the fish was now free in the environment anyway, the scientists released thousands of them into 15 Arkansas lakes, including one that comprises 6,700 algae-choked acres.

"We'll know in two years exactly how this fish will work out here," says the commission's Jim Collins. "If they clean that 6,700-acre lake and don't cause any problems for other species, we'll have one of man's best friends on our hands."

Many imported fish--most notably the Asian walking catfish in Florida and the European carp in all states --have adapted so successfully to U.S. waters that they have crowded out valuable indigenous species. Other scientists fear that the amur could conceivably eat a lake's entire supply of vegetation and thus trigger a serious new kind of ecological imbalance. But, says Collins, "if we thought the amur was a monster, we wouldn't stock it out."

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