Weed-Eating ‘Little Marines' To Storm Green Valley Lakes

15 two-pound fish trucked in from Arkansas will help control weeds


Brace yourself: The Marines have come to Payson.

They're big, smelly, tenacious and expensive -- not to mention sterile and covered with scales.


Soon-to-be-stocked 12-inch White Amur going into a Phoenix area lake. Similar fish will be placed into the two smaller Green Valley lakes.

But they can eat twice their weight in weeds every day -- and that's what counts.

This week, Payson carefully put 15 very special fish affectionately dubbed the "Little Marines" in the two smallest reclamation and water recharge lakes in Green Valley Park.

The 16-inch-long, two-pound White Amurs, also known as Grass Carp, traveled in the comfort of a tanker truck all the way from Arkansas, to tackle the formidable job of controlling the growing tangle of weeds that have spurred complaints by fishermen and boaters, said Karen Probert, a water quality specialist for Payson.

The town will shell out about $500 for the 15 fish, who will be assigned to patrol about three acres of lake -- and eat all the weeds they can manage. But that's much cheaper than using chemicals or mechanical harvesting to control the growth of weeds that have started to choke the shoreline in places.

Besides, water from the three Green Valley Park lakes soaks into the water table, which means the town doesn't want to use chemicals to control the weed growth.

About a million gallons of wastewater treated well enough to drink goes into the lakes each day, with 400,000 gallons soaking in and the other 600,000 leaving in the form of either evaporation or sale by the sanitation district for use as irrigation water on golf courses and parks, said Probert.

So the weed-loving White Amurs could offer the perfect, eco-friendly solution to the encroachment of weeds, which extend out from the shore, 10 or 15 feet in places.

Can grow to 100 pounds

The White Amurs grow to as much as 100 pounds in their native chomping grounds in China's Amur River and have been used to control weeds in American lakes since the early 1960s. They did at one point escape into the Mississippi River, but for the most part have remained contained in the various ponds and lakes into which they've been stocked for weed control, said Eric Swanson, urban fishing program manager for the Arizona Game and Fish Department.

In Arizona, they've been widely used to control weeds in lakes and golf course ponds. The largest Amur in Arizona topped the scales at 47 pounds.

Such a fish can consume nearly 100 pounds of weeds a day -- although half of that comes right back out the other end, said Swanson, thanks to the Amur's remarkable digestive system that efficiently extracts nutrients from the rapid processing of the weeds it prefers.

The Amurs have evolved into models of efficiency when it comes to gobbling weeds, noted Swanson. They have specially designed teeth and jaws that rip loose the weeds and a throat that has specialized plant grinding teeth on the bottom and a bone plate on top. As a result, they can efficiently mulch the weeds as they make the trip down the gullet into the long intestine, which produces various substances that hasten the breakdown of the pulped up plant material.

The 15 White Amur pioneers dumped into the two smaller Green Valley lakes as a kind of pilot project will consume about 60 pounds of weeds per day among the lot of them -- so it will take some time for them to make a dent on the tangle of weeds that has grown around the shoreline in the past couple of years.

Fish are sterile

All those fish should also be sterile, noted Swanson. The big commercial producer in Arkansas that grows the Amurs that are shipped all over the country, subjects the fertilized eggs to either temperature or pressure shock. That treatment of the eggs prompts the dividing embryos to end up with an extra chromosome that makes them sterile.

Nonetheless, fish managers worry that a stray, fertile fish will somehow escape -- or produce eggs that will wash downstream when floods prompt the Green Valley lakes to overflow, drain into the American Gulch and run downstream into the Verde River.


Urban angler, Mr. Halvorson, with a 24-pound White Amur from a Phoenix area lake.

So the town had to get special permits from the state and install fish barriers on the two smaller lakes, at a cost of several thousand dollars, said Probert.

The town will have to install a much larger and more expensive fish screen on the larger, 38-million-gallon main lake before it can add the White Amur to those waters, which also suffer from a weed buildup along the shoreline.

Of course, that main lake already had lots of potential problem fish, noted Swanson, who runs the state's urban fishing program that stocks the Green Valley lakes with about 15,000 rainbow trout per year -- these all trucked in from Colorado.

The state's urban fishing program is financed by a special, $18.50 per person fishing license and stocks 21 urban lakes with 50,000 pounds of trout and 180,000 pounds of channel catfish each year.

The program needs more fish than the state-owned hatcheries can supply, so Swanson contracts with hatcheries in other states.

The state stocks only rainbow trout into the Green Valley lakes, mostly for fear fish will escape into the Verde River drainage.

However, fishermen have illegally dropped other species into those Payson lakes, which now contain largemouth bass, crappie, channel catfish, bluegill, sunfish and several other species of minnows.

Town officials hope that anglers and kids with nets will leave the "Little Marines" to their duty, once the Amur arrive. Amurs will sometimes snap at an alluring hook "if they're angry" or in one of those odd moods that come over a fish condemned to munching on wet weeds, noted Swanson.

State regulations make it illegal to keep a White Amur that's less than 30 inches long -- which would be a very impressive 15-pound fish.

However, since it costs about $15 a fish to stock them, town officials are hoping people will return the conscientious little weed eaters to the lake -- and definitely not move them from the little lakes to the big lake, which doesn't yet have the fish barriers to keep them contained.

On the other hand, the White Amurs are also notoriously hard to catch, noted Swanson, who has wrangled fish for his whole career and did his graduate school research on the White Amur.

Normally, fish biologists catch fish by using either nets or an electric charge that temporarily stuns fish to round them up. Neither method works very well on the Amurs.

As soon as the big fish get that first tingle of electric charge, they jump clear out of the water, said Swanson.

He's seen them land on the concrete sides of a canal, or even in the biologist's boat to avoid the incapacitating charge.

Same goes for nets: As soon as the fish wranglers start dragging the nets -- the Amurs will take to the air and jump over the top of the net, he said.

"They're very elusive fish," said Swanson, "they'll fly through the air, throw themselves out of the water. Very smart fish. The most elusive fish in all of fish management," he observed.

But then, what do you expect for the Little Marines?

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