The Amazing, Misunderstood White Amur

White amur fish are capable of controlling water weeds naturally, safely, and at a fraction of the cost of herbicide treatments.


| May/June 1980



063 white amur

LEFT: Ponds choked by excessive foliage are now an all-too-common sight. CENTER: Six-inch fingerlings of the white amur are stocked in overgrown lakes. RIGHT: The clear water of such "treated" lakelets speaks for itself.


PHOTOS: MOTHER EARTH NEWS STAFF

Until nine years ago, Bill and Harry Whiting ran an expensive, exclusive fish camp in northern Canada . . . one of the few regions "untouched" enough to offer the kind of angling their famous clients expected. In fact, the operation had been moved to the far north after the Whitings watched fishing in their native Minnesota decline until it no longer held much interest for the true sports fisherman.

The fate suffered by the brothers' own private trout pond in their hometown of Edina is an example of what was happening: As the area built up, fertilizer runoff from neighboring property drained into the water, causing excessive vegetation growth. Like many other people, the Whiting brothers used the recommended chemicals to kill the plants, but the dying foliage sucked up oxygen. . . a process which, in turn, suffocated the fish and eventually turned their lake into a dead body of water. Bill and Harry packed up and moved to Canada.

The same scenario repeats itself constantly all over North America. Records show that around 200,000 man-made lakes and ponds have succumbed to similar fates in the last 10 years.

"Sure," Bill Whiting said, "some of 'em were little more than puddles, but big reservoirs have been affected, too. For example, the 22,000-acre water supply of Houston, Texas is infested with 6,000 acres of hydrilla that's spreading at a rate of 254% a year. And the Lone Star State appropriated $50 million for waterweed-killing chemicals in 1978 alone."

A Natural Alternative

Meanwhile, though, Arkansas was conducting experiments in freshwater vegetation control with a fish called the white amur (Ctenopharyngodon idellus) or the "grass carp."

Actually this useful creature has been around for a long time. Marco Polo reported on the vegetarian fish, and there are accounts of the amur's being transported to Taiwan in 400 B.C. The Russians have used grass carp to control weeds and algae for 300 years, and the Chinese have utilized the fish to weed their rice fields — and as a major food source — for over 20 centuries!

Not long ago, the Egyptians stocked 45 million amur to clean up the Nile, and Holland (before three big oil companies stepped in with "easy" chemical solutions) researched the use of the fish to clear their canals.

Bill and his brother were so excited when they heard about the amazing biological tool that they sold out their Canadian operation and moved to Arkansas to learn from the Game and Fish Commission there how to reproduce and handle the fish . . . because, though the laws in other areas aren't always enforced, Arkansas is among the few states where it's legal to even possess a white amur.

That's right! This fast-growing, good-tasting, protein-packed weed-eater is currently outlawed in 32 states — Arizona, California, Colorado, Connecticut, Georgia, Idaho, Illinois, Indiana, Louisiana, Maine, Maryland, Michigan, Minnesota, Nebraska, Nevada, New Hampshire, New Mexico, New York, North Carolina, Ohio, Oklahoma, Oregon, Pennsylvania, South Carolina, Tennessee, Texas, Utah, Vermont, Virginia, Washington, Wisconsin, and Wyoming — seemingly because of a combination of business and political interests that justify their actions by quoting old wives' tales.

Certainly Arkansas, which has cut its expenditures for chemical vegetation control to practically zero, seems to have suffered no ill effects from letting the grass carp in. In fact, after nine years of utilizing the fish under many varied conditions, no adverse "fallout" on native populations or ecosystems has been noted. Furthermore, the state's fishing is still good. (According to the Arkansas Gazette, the "Land of Opportunity" has the highest ratio in the country of resident fishing licenses to total population.)

And — despite the often expressed worry that the amur might devastate waterfowl habitats — Stuggart, Arkansas is still considered the "duck capital of the world," having recently completed its most successful hunting season of the past 10 years. The state also disputes another of the doom-sayers' predictions by remaining a leader in the production of rice, which is — of course — an aquatic plant.

Needless Paranoia

The biggest fear concerning the introduction of the amur — and it's a perfectly reasonable one — is that the fish (which can lay up to one million eggs at a time) might escape its pond confinement and breed out of control in the nation's waterways. But such an ecological disaster is impossible, as Bill Whiting explains:

"At present, white amur breed naturally in only three places in the world: two rivers in China and one in Siberia . . . because the fish has stringent reproduction requirements: It cannot multiply anyplace but in a river system where the water flows at a rate of no less than eight feet per second . . . where the temperature ranges between 68 and 74 degrees . . . and where the water's pH level is between 7.0 and 7.4.

Moreover, because the eggs have no adhesive quality, they will not stick to docks, posts, stumps, boat bottoms, and so on. Instead, they sink to the riverbed, where — if not kept in motion — they can suffocate in 16 seconds . . . the eggs must tumble for a full 38 hours before they'll begin to hatch.

"And," Bill is quick to add, "the list of limiting conditions doesn't end there . . . once the eggs have hatched, the microscopic babies are unable to swim horizontally. They can only rise vertically to the surface and fall back to the river bottom, so they're consumed in vast quantities by predatory fish and birds.

"Some prophets of gloom say that a fish capable of laying a million eggs will soon have us up to our necks in grass carp. Yet, in China's Amur River, where these fish have existed for centuries, the legal limit is still only two amur per fisherman. Need I say more?"

A Delicate Operation

In fact, even though the Arkansas Fish and Game folks showed the way, it took the Whitings seven years to learn how to hatch and raise enough grass carp to produce some for sale.

First, the adult stock is taken into a laboratory during breeding season and injected with hormones for 36 hours. Then the eggs are removed, fertilized by hand with male sperm, and placed in circulating vats. When the fry hatch out, they're kept in the vats and fed egg yolks for about a week.

After that time, they can be placed in sterlle ponds where no game fish are allowed . . . since one bream (for example) can eat 10,000 amur fry overnight. Once the fingerlings have grown to six inches or more, they can be moved to waters where vegetation control is needed.

Plankton is the primary food of the immature fish, and findings from four studies indicate that adult amurs consume submerged water plants in the following order of preference. Canadian pondweed, hornwort, stonewort, lesser duckweed, broad-leaved pondweed, ivyleaved pondweed, great reedmace, common reed, common rush, black sedge, frogbit, watercress, shiny pondweed, and sedge.

"The grass carp knows what it likes," Bill told us, "just as you and I do. But when there's no choice, it'll eat whatever water plants are around."

And though the fish prefers warm water, it can survive in chilly climates as well. Like most aquatic creatures, however, the amur's metabolism slows down with colder temperatures, and the fish cuts back on its eating until the water warms up again. But, as Whiting points out, "These feeding habits fall right in line with effective weed control, since it's the summer months that bring plant problems."

But What Happens If...

If enough food is available, the fish will grow at a rate of one inch every two weeks during the summer . . . and may weigh 15 to 20 pounds in two years. (In their native habitats, they've been reported to reach 100 pounds!)

The amur's voracious appetite has brought up another question: What happens once the fish have eaten all the weeds? Will the hungry vegetarians then start devouring important game fish? The fear of such a development caused Florida — in spite of its 33,000 hydrilla-choked lakes and the $15-$20 million the state spends annually on a losing chemical war with water weeds — to put a one-year moratorium on amur research. (Under public pressure that moratorium was lifted, however, and Floridians are now allowed to purchase the fish after obtaining a very hard-to-get permit: Some people have waited months without receiving so much as a reply to their applications.)

In the meantime, though, the Cooperative Fishery Unit of the University of Georgia introduced white amur into a 3.6 hectare pond devoid of vegetation . . . in order to simulate the anticipated conditions. The fish, usually elusive quarries, were soon readily captured with weed-baited hooks . . . and when the stomachs of some 417 captives were examined, there was no evidence of predation by the amur on other fish or fish eggs. In fact, many of the specimens weighed less than they had when they were put into the pond.





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